کاهش خسارت خشکسالی در گندم دیم

تولیدات کتان ارگانیک Organic Cotton Production   متن کامل مقاله برای دانلود در ادامه مطلب  خلاصه                                           Abstract   Cotton sold as "organic" must be grown according to the federal guidelines for organic crop production. Soil fertility practices that meet organic certification standards typically include crop rotation, cover cropping, animal manure additions, and use of naturally occurring rock powders. Weed management is accomplished by a combination of cultivation, flame weeding, and other cultural practices. A wide variety of insects attack cotton. Management options include trap cropping, strip cropping, and managing border vegetation to encourage high populations of native beneficials. Certain biopesticides using bacteria, viruses, and fungal insect pathogens are available as insect control tools. We discuss specific insect management strategies for cutworm, cotton bollworm, tobacco budworm, pink bollworm, armyworm, loopers, thrips, fleahoppers, lygus bugs, aphids, whitefly, spider mite, and boll weevil. Seedling disease, soil disease, and foliar disease management is also discussed. Pre-harvest defoliation methods that meet organic certification are mostly limited to citric acid, flamers and frost. The publication concludes with sections on marketing organic cotton and the economics and profitability of organic cotton production  تولیدات       Introduction   Organic cotton has provided significant price premiums for growers willing to meet the many challenges inherent in its production without the aid of conventional pesticides and commercial fertilizers. Growing organic cotton is demanding, but with commitment, experience, and determination, it can be done. This publication covers the major steps in organic production of cotton. It covers soil fertility, weed control options, and alternative pest controls for the many insect problems that plague cotton. Finally, marketing of organic cotton is discussed as well.   Organic cotton acreage declined 18% from 2000 to 2001 in the seven states where most of it is grown. (Marquardt, 2002) Most of this decline came from one large organic cotton farmer in New Mexico who lost it all to drought and withdrew from organic cotton farming altogether. A total of 11,459 acres of either certified organic or transitional organic cotton was produced in 2001. Texas produced the most organic cotton – 8,338 acres – with Arizona and California being the next two highest producing states.   World production of organic cotton amounts to 6,000 tons of fiber annually, or about 0.03% of global cotton production. Turkey produces the most at 29%, with the U.S. being second at 27% and India third at 17%. (Ton, 2002) Demand for organic cotton is highest in Europe (about 3,500 tons or 58% of the total) and the U.S. (about 2000 tons or 33%) (Ton, 2002). Demand in the U.S. increased at an annual rate of 22% between 1996 and 2000. (Organic Trade Association, 2001; cited by Ton, 2002) نگاهی بر تولیدات ارگانیکOverview of Organic Production   Growing cotton organically entails using cultural practices, natural fertilizers, and biological controls rather than synthetic fertilizers and pesticides. A systems approach to organic production involves the integration of many practices (cover crops, strip cropping, grazing, crop rotation, etc.) into a larger system. Through good soil and biodiversity management, farms can become increasingly self-sufficient in fertility, while pest problems are diminished, and some pests are even controlled outright. A diverse rotation, using legumes and other cover crops, is at the heart of good humus and biodiversity management in an organic cropping system. Cotton, for example, would be but one of several crops an organic farmer would grow. For more complete coverage of general organic crop production, we recommend the ATTRA publication Organic Crop Production Overview. Throughout this publication, we use examples from conventional farming that illustrate principles relevant to organic cotton production.     In order to market a crop as "organic," a grower must be certified through a third party. This process involves several on-farm inspections and paying a certification fee. More on this subject can be found in the ATTRA publication Organic Farm Certification and The National Organic Program. Applicants for certification are encouraged to become familiar with provisions of the Final Rule posted on the USDA's National Organic Program Web site.   Organic production begins with organically grown seed. If certified organic seed cannot be located, untreated seed may be used as long as it is not derived from genetically modified plants. Most certifiers will accept proof that growers have tried unsuccessfully to buy organic material from at least three different suppliers as evidence of unavailability. Federal organic regulations also address composting and the use of raw manures. These may have implications for cotton production when used as fertilizer.   متن کامل مقاله برای دانلود در ادامه مطلب     دانلود مقاله بصورت پی دی اف   دانلود ترجمه مقاله       خلاصه                                           Abstract   Cotton sold as "organic" must be grown according to the federal guidelines for organic crop production. Soil fertility practices that meet organic certification standards typically include crop rotation, cover cropping, animal manure additions, and use of naturally occurring rock powders. Weed management is accomplished by a combination of cultivation, flame weeding, and other cultural practices. A wide variety of insects attack cotton. Management options include trap cropping, strip cropping, and managing border vegetation to encourage high populations of native beneficials. Certain biopesticides using bacteria, viruses, and fungal insect pathogens are available as insect control tools. We discuss specific insect management strategies for cutworm, cotton bollworm, tobacco budworm, pink bollworm, armyworm, loopers, thrips, fleahoppers, lygus bugs, aphids, whitefly, spider mite, and boll weevil. Seedling disease, soil disease, and foliar disease management is also discussed. Pre-harvest defoliation methods that meet organic certification are mostly limited to citric acid, flamers and frost. The publication concludes with sections on marketing organic cotton and the economics and profitability of organic cotton production  تولیدات       Introduction   Organic cotton has provided significant price premiums for growers willing to meet the many challenges inherent in its production without the aid of conventional pesticides and commercial fertilizers. Growing organic cotton is demanding, but with commitment, experience, and determination, it can be done. This publication covers the major steps in organic production of cotton. It covers soil fertility, weed control options, and alternative pest controls for the many insect problems that plague cotton. Finally, marketing of organic cotton is discussed as well.   Organic cotton acreage declined 18% from 2000 to 2001 in the seven states where most of it is grown. (Marquardt, 2002) Most of this decline came from one large organic cotton farmer in New Mexico who lost it all to drought and withdrew from organic cotton farming altogether. A total of 11,459 acres of either certified organic or transitional organic cotton was produced in 2001. Texas produced the most organic cotton – 8,338 acres – with Arizona and California being the next two highest producing states.   World production of organic cotton amounts to 6,000 tons of fiber annually, or about 0.03% of global cotton production. Turkey produces the most at 29%, with the U.S. being second at 27% and India third at 17%. (Ton, 2002) Demand for organic cotton is highest in Europe (about 3,500 tons or 58% of the total) and the U.S. (about 2000 tons or 33%) (Ton, 2002). Demand in the U.S. increased at an annual rate of 22% between 1996 and 2000. (Organic Trade Association, 2001; cited by Ton, 2002) نگاهی بر تولیدات ارگانیکOverview of Organic Production   Growing cotton organically entails using cultural practices, natural fertilizers, and biological controls rather than synthetic fertilizers and pesticides. A systems approach to organic production involves the integration of many practices (cover crops, strip cropping, grazing, crop rotation, etc.) into a larger system. Through good soil and biodiversity management, farms can become increasingly self-sufficient in fertility, while pest problems are diminished, and some pests are even controlled outright. A diverse rotation, using legumes and other cover crops, is at the heart of good humus and biodiversity management in an organic cropping system. Cotton, for example, would be but one of several crops an organic farmer would grow. For more complete coverage of general organic crop production, we recommend the ATTRA publication Organic Crop Production Overview. Throughout this publication, we use examples from conventional farming that illustrate principles relevant to organic cotton production.     In order to market a crop as "organic," a grower must be certified through a third party. This process involves several on-farm inspections and paying a certification fee. More on this subject can be found in the ATTRA publication Organic Farm Certification and The National Organic Program. Applicants for certification are encouraged to become familiar with provisions of the Final Rule posted on the USDA's National Organic Program Web site.   Organic production begins with organically grown seed. If certified organic seed cannot be located, untreated seed may be used as long as it is not derived from genetically modified plants. Most certifiers will accept proof that growers have tried unsuccessfully to buy organic material from at least three different suppliers as evidence of unavailability. Federal organic regulations also address composting and the use of raw manures. These may have implications for cotton production when used as fertilizer.     Soil Fertility   Mineral nutrition of crops in organic systems comes from proper management of soil organisms that are responsible for releasing nutrients. Rather than feeding plants with fertilizer, organic farmers feed the soil and let the soil organisms feed the plants. The biological activity in the soil can be likened to a digestive process whereby organic food sources are applied to the soil and then digested by soil organisms to release nutrients for the crop. Soil mineral levels are built up through the application of animal manure, compost, soluble rock powders, and deep-rooted cover crops that bring up nutrients from deep within the soil. Plant nutrition is supplemented with foliar fertilization in some situations. Soil fertility, levels of organic matter, minerals, pH, and other measurements can be monitored with regular soil tests. The overall cropping sequence fosters a system in which a previous crop provides fertility benefits to a subsequent crop - such as a legume cover crop providing nitrogen to a following corn crop. Much more detailed soil-fertility information is available in these ATTRA publications: Sustainable Soil Management, Manures for Organic Crop Production, Sustainable Management of Soil-Borne Plant Diseases, and Sources of Organic Fertilizers and Amendments. Crop Rotation   Crop rotation is a traditional agricultural practice involving the sequencing of different crops on farm fields; it is considered fundamental to successful organic farming. Rotations are a planned approach to diversifying the whole farm system both economically and biologically, bringing diversity to each field over time.   Rotations can benefit the farm in several ways. Planned rotations are one of the most effective means of breaking many insect pest and plant disease cycles in the soil. Likewise, many problem weeds are suppressed by the nature and timing of different cultural practices. Rotations also affect the fertility of the soil in significant ways. The inclusion of forage legumes, in particular, may serve as the primary source of nitrogen for subsequent crops.   Rotation is an important means of controlling a number of cotton pests, including nematodes. Even basic corn-cotton rotations have been found effective in reducing some species of nematodes. (Anon., 1993) A minimum of two years planted to non-host species is the standard recommendation.   A long-term cotton study at Auburn, Alabama, showed that using winter annual legumes produced cotton yields equivalent to those grown using fertilizer nitrogen. The study found an 11% yield increase for a 2-year cotton-legume-corn rotation compared to continuous cotton grown with legumes each year. Adding conventional nitrogen fertilizer boosted the two-year rotation cotton lint yields in this study another 79 pounds per acre. A three-year rotation of cotton-vetch, corn-rye (fertilized with 60 pounds of conventional N/acre), followed by soybeans, produced about the same cotton yields as the two-year rotation. (Mitchell, 1988) Cover Cropping   Cover crops are crops grown to provide soil cover and erosion protection. At the same time, cover cropping may accomplish a number of other objectives, including providing nitrogen to the subsequent cotton crop when tilled into the soil, improving tilth by adding organic matter, and serving as a catch crop when planted to reduce nutrient leaching following a main crop.   Fast, dense-growing cover crops are sometimes used to suppress problem weeds as a "smother crop" or allelopathic cover. The mere presence of most cover crops reduces the competition from weeds. Sometimes crops are no-till planted into such covers. If the cover crop is not killed, it is referred to as a "living mulch." Some cover crops that have been used successfully for weed suppression include small grains (particularly grain rye), several brassica species, hairy vetch, and forage sorghums.   For the humid Cotton Belt, crimson clover, field peas, and hairy vetch are excellent winter cover crops for nitrogen production. Also, a mixture of hairy vetch and rye works well for overall biomass production. When flowering, these provide nectar and pollen as alternate food for beneficials. Hairy vetch is noted for its dense spring cover and weed suppression. Cereal rye provides an enormous amount of biomass to the soil and is known to attract and shelter beneficial insects. It also suppresses germination of small-seeded weeds when left as a mulch cover on the soil surface. Natural allelopathic chemicals leach from the rye residue and inhibit weed germination for about 30-60 days. (Daar, 1986) Weed suppression effectively ends once the rye residue is incorporated. Weed suppression has made rye attractive as a cover crop/mulch in no-till and ridgetill systems. Mowing or a burn-down herbicide is often used in conventional systems to kill the rye cover crop so that no-till plantings of field crops can be established. An effective organic no-till system for cotton has yet to be developed, but early indications are that it will be. For more information on the potential for organic no-till, see the ATTRA publication Pursuing Conservation Tillage Systems for Organic Crop Production, which discusses progress in this area. It is important to mow rye at the flowering stage when the anthers are extended, and pollen falls from the seed heads when shaken. If mowing is done earlier, the rye simply grows back. As allelopathic weed suppression subsides, a no-till cultivator may be used for weed control. This is not a proven system for organic cotton production but only presented here as food for thought about the development of future organic no-till systems.   In addition to producing nitrogen, cover crops often provide excellent habitat for predatory and parasitic insects and spiders. Some good insectary plants often used as cover crops include alfalfa, buckwheat, sweet clover, vetch, red clover, white clover, mustards, and cowpeas. Migration of beneficials from the cover crop to the main crop is sometimes associated with the post-bloom period of the cover crop. In these instances, mowing the cover crops in alternate strips may facilitate their movement, while the remaining strips continue to provide refuge for other beneficial species. Sickle-bar mowers are less disruptive to beneficials than flail mowers, rotary mowers, and mower conditioners with crimpers.   Long-term cotton cover-crop studies have also been done in Louisiana (Millhollon and Melville, 1991) and Arkansas. (Scott, 1990) The Arkansas study spanned 17 years, from 1973 to 1988. Cotton grown after winter cover crops of rye + hairy vetch produced an average of 234 pounds more seed cotton per acre than a control treatment of winter fallow. Cotton following pure vetch showed a 129-pound increase, while yields after rye + crimson clover had a 72-pound yield improvement.   In the long-term Louisiana study, cotton yields declined for the first nine years when cover crops were used, but increased steadily thereafter. In the final four years of the study, cotton yields were 360 pounds-per-acre higher following vetch, compared to fallow + 60 pounds of fertilizer N per acre. Averaged over the 30-year study period, the highest cotton yields followed wheat + 60 pounds of fertilizer N, hairy vetch alone, common vetch alone, or vetch + 40 pounds of N. For additional information on cover crops, see the ATTRA publication Overview of Cover Crops and Green Manures.   Back to top Weed Management   Cotton germinates at a soil temperature of 61° F at a depth of about 2 inches. With planting delayed until the soil temperature reaches 66°, the crop emerges rapidly and uniformly and is more vigorous (Head and Williams, 1996), giving it a competitive edge on weeds. The delay in operations also allows additional growth of winter cover crops where used. The downside of this strategy may include risks of increased damage from certain insect pests such as boll weevil, tobacco budworm, and cotton bollworm. Cultivation   Tillage and cultivation are the traditional means of weed management for organic crops. Some specific tillage guidelines and techniques for weed management include the following: Preplant tillage. Where weeds such as johnsongrass are a problem, spring-tooth harrows and similar tools can be effective in catching and pulling the rhizomes to the soil surface, where they desiccate and die. Disking, by contrast, trends to cut and distribute rhizomes and may make the stand even denser.   Blind tillage. Blind cultivation employs finger weeders, tine harrows, or rotary hoes during the pre-emergent and early post-emergent phase. These implements are run at relatively high speeds (6 mph plus) across the entire field, including directly over, but in the same direction as, the rows. The large-seeded crops like corn, soybeans or sunflower survive with minimal damage, while small-seeded weeds are easily uprooted and killed. Post-emergent blind tillage should be done in the hottest part of the day when crop plants are less turgid, to avoid excessive damage. Rotary hoes, not harrows, should be used if the soil is crusted or too trashy. Seeding rates should be increased 5-10% to compensate for losses in blind cultivation. (Anon., 1991; Doll, 1988)   Inter-row cultivation. When annual weeds are the concern, cultivation is best kept as shallow as possible to bring as few weed seeds as possible near the soil surface. Where perennial, rhizomaceous weeds are a problem, the shovels set furthest from the crop row may be set deeper on the first cultivation to bring rhizomes to the surface. Tines are more effective than sweeps or duck feet for extracting rhizomes. Later cultivations should have all shovels set shallow to avoid excessive pruning of crop roots. Earliest cultivations should avoid throwing soil toward the crop row. This places new weed seed into the crop row where it may germinate before the crop canopy can shade it out. As the crop canopy develops, soil should be thrown into the crop row to cover emerging weeds.   Inter-row cultivation is best timed to catch weeds as they are germinating - as soon as possible after rain or irrigation, once the soil has dried enough to avoid compaction or surface crusting. Flame Weeding   Prior to the 1950s, before modern herbicides became available, flame weeders were used in the U.S. to control weeds in cotton, sugar cane, grain sorghum, corn, and orchards. Interest in flame weeding has resurfaced in recent years with rising herbicide costs. Weeds are most susceptible to flame heat when they are young seedlings 1-2 inches tall or in the 3-5 leaf stage. Risk of damaging the cotton plants diminishes as the cotton grows and forms a bark on the stem. Broadleaf weeds are more susceptible to flaming than grasses. Grass seedlings develop a protective sheath around the growing tip when they are about 1 inch tall. (Drlik, 1994) Consequently, repeated flamings may be necessary on grassy weeds for effective control. Searing the plant is much more successful than charring. Excessive burning of the weeds often stimulates the roots and encourages regrowth, in addition to using more fuel.   Preplant flaming has commonly been referred to as the stale seedbed technique. Prepared seedbeds are flamed after the first flush of weeds has sprouted. Cotton planting follows the flaming without any further disturbance to the seedbed. Assuming adequate moisture and soil temperature, germination should occur within two weeks. Note that a fine-to-slightly-compacted seedbed will germinate a much larger number of weeds.   Costs associated with flame weeding can vary. Flamers have been built for $1,200 for an 8-row unit (Anon., 1993a) and for as much as $1,520 for a 12-row unit. (Houtsma, 1991) Commercial kits cost around $1900 for an eight-row from Thermal Weed Control Systems. These kits do not include hoses, a tank, or a tool bar. It is more cost-effective to pick these items up locally from a gas dealer or salvage operation. An Arkansas cotton grower uses a "water shield" to help protect the cotton plants, but still feels flaming should be delayed until the crop has developed a woody bark on the stem. (Vestal, 1992) Adapting flame technology requires careful implementation. Thermal Weed Control Systems (TWCS), Inc. of Neillsville, Wisconsin, and Flame Engineering, Inc. (FEI), of Lacrosse, Kansas, are two flame-weeding companies that can provide technical assistance and equipment. LP gas usage depends on ground speed but generally runs from 8-10 gallons per acre, according to sources at Thermal Weed Control. For an overview of weed management strategies and options for agronomic crops, please see the ATTRA publication Principles of Sustainable Weed Management for Croplands.   Back to top Insect Management Practices   Biological and cultural insect control involves understanding the ecology of the surrounding agricultural systems and the cotton field and making adjustments to production methods that complement the natural system to our benefit. To realize the full benefits of a biological approach we need to move beyond asking how to kill bugs and ask the larger question: Why do we have bugs in our cotton fields in the first place?   In a nutshell, we invite pest problems by planting large expanses of a single susceptible crop. When cotton is the only food available, bugs are going to eat cotton. When we have a more diverse farmscape involving many types of plants and animals, the likelihood of severe pest outbreaks diminishes. For more information on farmscaping, see the ATTRA publication Farmscaping to Enhance Biological Control.   Many types of insects feed on cotton plants and threaten yields. Proper identification of these pests as well as their natural enemies is the first step in successful management of pests. State Extension services typically have Internet-based information that can help with pest and beneficial insect identification. Once the pest is properly identified, a scouting program with regular monitoring can help determine the pest pressures and the densities of beneficial insects. When pest pressures reach the economically-damaging threshold, control actions become necessary. If biological controls are to be used, they must be started before the pests reach critical levels. That is why monitoring is so important.   The use of beneficial insect habitats along crop field borders has shown to increase the presence of beneficial insects. These habitats provide shelter, pollen and nectar sources, and refuge if the fields are treated with a pesticide. In the event you are releasing purchased beneficial insects, these field-edge habitats will encourage the beneficials to remain and continue their lifecycle in that location, helping reduce the pest population. Some pests may also inhabit the field-edge habitats; therefore, these habitats should be monitored along with the crop field. For additional information, see ATTRA publications Biointensive Integrated Pest Management and Farmscaping to Enhance Biological Control.   Though not completely organic, the Sustainable Cotton Project's BASIC program (Biological Agriculture Systems in Cotton) offers California growers strategies designed to save money and reduce the need for pesticides, chemical fertilizers, and water. The BASIC program utilized the following strategies in their 2002 program that showed a 73% reduction in pesticide use over the Fresno County average. (Figure 1) In Figure 1, the "enrolled acreage" had the free monitoring, habitat plantings, and insect releases provided to them. "Basic growers" had implemented the principles on their own fields but without the direct involvement of the basic program staff. Regular IPM, intensive monitoring, beneficials, and beneficial habitat can reduce pesticide use whether you are organic or conventional. For pesticide use questions or analysis questions, contact Max Stevenson at: [email protected].       Figure 1: Pesticide reductions resulting from the BASIC program in California     1. Intensive Monitoring Fields enrolled in the program were monitored weekly. Monitoring included an overall picture of the field and the local conditions, the levels of pests and beneficials, farmscape observations, the status of the adjacent beneficial habitat, and any unusual sightings or areas for concern. Farmers were given a copy of the monitoring form, and the overall results were published bi-weekly in a newsletter.   2. Strip Cutting of Alfalfa Intercropped with Cotton One of the "best management practices" promoted by the BASIC program has been the strip cutting of alfalfa. This practice prevents the immigration of certain species at harvest time and keeps one of the main cotton pests, Lygus hesperus, from moving out of the alfalfa (its preferred host) into the adjacent cotton. BASIC field staff and mentor growers were also able to provide technical support for growers wanting to implement a system of strip cutting.   3. Bezzerides Weed Cultivator A Bezzerides cultivator was tried by a BASIC grower during the 2002 season. The cultivator works in the planted row where conventional cultivators can't reach. Traditionally, this is the area where chemical herbicides are used to eliminate competing weeds. The trial was not considered a success, since the cultivator also removes cotton plants along with the weeds, and the growers who tested the equipment felt that it was not significantly better than their existing cultivators.   4. Beneficial Habitat Planting Seventy percent of the growers enrolled in the 2002 BASIC program planted beneficial habitat adjacent to their enrolled fields. The habitat was intended to attract and hold naturally occurring beneficials. The remaining thirty percent of the enrolled fields were adjacent to alfalfa fields where strip cutting was practiced.   5. Beneficial Insect Releases Releases of beneficial insects were also utilized during the growing season. Thousands of lace- wings and predatory mites were released to augment the naturally occurring insects. When growers see a pest problem starting to develop in their fields they want fast action and so will often turn to a chemical spray. Releasing insects helped them feel like something was being done, while the natural enemies took over the pest control.   For additional information on the Sustainable Cotton Project or the BASIC program, contact Marcia Gibbs at [email protected], or see the Web site. Trap Cropping   A trap crop is planted specifically to attract pest insects. It is then sprayed with some type of insecticide, in conventional management, or left to detain the pests from the cotton crop, or the entire trap crop is tilled under to kill the pest insects. Early-sown cotton has been used as a boll-weevil trap crop. Using fall-planted-cotton trap crops to reduce the number of over-wintering boll weevils was first proposed as early as the late 1800s. (Javaid and Joshi, 1995) Both early and fall cotton trap crops are effective at attracting boll weevil adults and can be enhanced by adding pheromones such as GrandlureTM to the trap crop. The concentrated weevils can then be killed with organically accepted insecticides, which are limited to a few botanicals and biologicals. Crop consultants James and Larry Chiles were able to reduce the cost of boll weevil control by 30% using trap crops of early and late-planted cotton. Even with the cost reduction, they were able to maintain good yields of 1000 to 1200 pounds per acre. They planted a trap crop of cotton in early April, 30 days before the normal cotton planting time, and a late-planted trap crop on August 10. A weevil attractant pheromone was used to lure boll weevils to the cotton trap crops. The trap crops were sprayed for weevils whenever populations were high. This technique reduced the number of early emergent weevils infesting the main crop and reduced the number of weevils overwintering to attack the next year's crop. In a Mississippi study, Laster and Furr (1972) showed sesame (Sesamum indicum) to be more attractive than cotton to the cotton bollworm. Robinson et al. (1972) reported more predators on sorghum than on cotton in his Oklahoma strip cropping study. Lygus bug may also be kept out of cotton by using nearby alfalfa as a trap crop. Unmowed or strip-mowed alfalfa is preferred by that pest over cotton. (Grossman, 1988) Strip Cropping   Strip cropping takes place when harvest-width strips of two or three crops are planted in the same field. The most common strip crop grown with cotton is alfalfa. Increasing the diversity of crops increases stability in the field, resulting in fewer pest problems, due to natural biological controls. Crop rotation is one means of introducing diversity over time. Strip intercropping creates biodiversity in space.   Strip cropping cotton fields with alfalfa generally increases beneficial arthropod populations. Among the most notable are carabid beetles that prey on cutworms and armyworms. (Grossman, 1989) Alfalfa has been found to be one of the best crops for attracting and retaining beneficial insects. Strip-cutting alfalfa (i.e., cutting only half of the crop in alternating strips at any one time) maintains two growth stages in the crop; consequently, some beneficial habitat is available at all times. In some cases alfalfa is mixed with another legume and a grass.   In a conventional cotton management study, Stern (1969) interplanted 300-500 foot cotton strips and 20-foot wide alfalfa strips to compare pest control needs with monoculture cotton. The intercropped field required only one insecticide application, while the monoculture cotton had to be sprayed four times. The practice was abandoned in this specific case, however, due to modifications to irrigation systems and extra labor to cut alfalfa, which did not compensate for the reduced pesticide costs.   Dr. Sharad Phatak of the University of Georgia has been working with conventional cotton growers in Georgia testing a strip-cropping method (Yancy, 1994). Phatak finds that planting cotton into strip-killed crimson clover improves soil health, cuts tillage costs, and allows him to grow cotton without any insecticides and only 30 pounds of commercial nitrogen fertilizer per acre. Working with Phatak, farmer Benny Johnson reported saving at least $120/acre on his 16-acre clover-system test plot. There were no insect problems in the trial acres, while beet armyworms and whiteflies were infesting nearby cotton and required 8 to 12 sprayings. This system may have some applicability in an organic cotton system. In the study, cotton intercropped with crimson clover yielded 5,564 pounds of seed cotton per acre, compared with 1,666 pounds of seed cotton in the rest of the field (Yancy, 1994). Boll counts were 30 per plant with crimson clover and 11 without it. Phatak identified up to 15 different kinds of beneficial insects in these strip-planted plots.   Phatak used a crimson clover seeding rate of 15-pounds per acre that produced around 60 pounds of nitrogen per acre by spring. By late spring, beneficial insects were active in the cover crop. At that time, 6- to 12-inch planting strips were killed with RoundupTM herbicide (not allowed in an organic system). Fifteen to 20 days later the strips were lightly tilled and the cotton planted. The cover crop in the row-middles was left growing to maintain beneficial insect habitat. Even early-season thrips, which can be a problem following cover crops, were limited or prevented by beneficial insects in this system. When the clover is past the bloom stage and less desirable for beneficials, they move readily onto the cotton. The timing coincides with a period when cotton is most vulnerable to insect pests. Following cotton defoliation, the beneficials hibernate in adjacent non-crop areas.   Phatak emphasizes that switching to a whole-farm focus while reducing off-farm inputs is not simple. It requires planning, management, and several years to implement on a large scale. It is just as important to increase and maintain organic matter, which stimulates beneficial soil microorganisms. Managing Border Vegetation   Weedy borders are particularly infamous as sources of insect pests. Current recommendations suggest mowing them prior to establishment of cotton. Mowing after weeds have formed flower buds will tend to drive plant bugs into the cotton field. (Layton, 1996)   Grassy weed species harbor lepidopterous pests generally. A specific weed, wild geranium, is an important spring host of tobacco budworm and should be discouraged in border areas.   More diverse field borders with habitat plant species support some crop pests but also sustain beneficial insects that prey on pest populations, particularly during non-crop seasons. Managing the vegetation in these areas as habitat for beneficial insects counterbalances the threat from insect pests. The strategy entails planting or otherwise encouraging the growth of plants that provide alternative food sources (nectar, pollen, alternate prey), moisture, shelter, and perching sites preferred by beneficials. Plant species that are aggressive and invasive, or are known hosts to major crop diseases or insect pests, should be avoided. Descriptions of crops, cover crops, and wild plants that are known to attract certain beneficial insects and information on designing landscapes to attract beneficial organisms can be found in ATTRA publication Farmscaping to Enhance Biological Control. Natural Disease Organisms as Pest Control   A naturally occurring fungal disease of aphids is known to occur under conditions of high infestation. In Mississippi, this historically occurs between July 10 and 25. (Layton, 1996) Fungal diseases commonly attack and suppress populations of lepidopterous pests, most notably the cabbage looper and beet armyworm. Suppression of these pests by natural disease organisms is encouraged by developing dense crop canopies, which also assists in weed control. However, these are also conditions that encourage plant diseases and may not be desirable where cotton diseases are rampant. Early Crop Maturation   Early maturing crops are more likely to escape damage from late-season infestations of boll weevil, tobacco budworm, cotton bollworm, armyworms, loopers, and other pests. The use of short-season cotton is the most obvious means of doing this. Excessive nitrogen use, late irrigation, and excessive stand density can result in delayed maturity and increased exposure to these pests, and should be avoided. (Layton, 1996)   Back to top Biopesticides   B.t. (Bacillus thuringiensis) is a naturally occurring bacteria that produces a toxin effective in controlling many caterpillars. The toxin causes paralysis of the worm's digestive tract. Worms may continue to live for some hours after ingestion, but will not continue to feed. B.t. strains have been formulated into a number of commercial products under various trade names. B.t. degrades rapidly in sunlight, requiring careful timing or repeated applications.   B.t. must be ingested in sufficient amounts by the caterpillar to be effective. Consequently, an understanding of the feeding habits of the pests is necessary, so that proper formulations are used and timing of applications is optimal. Spray formulations are most effective against armyworms and those species feeding on exposed leaf surfaces. B.t. sprays are very effective against tobacco budworm and moderately effective against cotton bollworm. (Layton, 1996) Because of their feeding habits, granular bait formulations are more effective for control of cutworms. Careful inspection of specific product labels will assure that the product has been formulated for the pest to be controlled.   HNPV (Heliothis nuclear polyhedrosis virus) is a commercially produced disease organism that attacks budworms and bollworms. It has less of a track record in the Southeast than B.t., but based on preliminary observations it appears to be a viable biological pesticide. (Steinkraus et al., 1992; Anon., 1996) When using any biopesticide, be certain the formulation is cleared for use in organic production.   Beauveria bassiana is an insect-disease causing fungus that has been formulated and is available commercially. It works on several insect larvae, including cutworms and budworms. It works best during periods of high humidity. More on this natural control method can be found below in the Specific Insect Management Strategies section. Insecticidal Soap   Evolved from a traditional organic gardening technique, insecticidal soaps control insect pests by penetrating the cuticle and causing cell membranes to collapse and leak, resulting in dehydration. Several commercial formulations of insecticidal soap have been successfully used to control aphids, spider mites, white flies, thrips, leaf hoppers, plant bugs, and other pests. Soaps have limited effects on chewing pests such as beetles or caterpillars. Applied as sprays, these biodegradable soaps work by contact only and require excellent coverage to be fully effective. (Harmony Farm, 1996; Ellis and Bradley, 1992)   Insecticidal soaps will kill many beneficial insects and must be used with that in mind. Phytotoxicity has also been demonstrated, particularly on crops with thin cuticles. (Ellis and Bradley, 1992) Different varieties of cotton will have different plant characteristics. Therefore, it is advisable to test the soap solution on your plants on a small strip to determine whether any harm will result. Avoid application of soap during the heat of the day, because the plant is then under extreme stress, and you want the soap to remain on the plant as long as possible, not evaporate rapidly. Late day applications will stay on the plant longer, increasing the chances of contact with target pests. Water hardness will affect the efficacy of soap, because calcium, iron, and magnesium will precipitate the fatty acids and make the soap useless against the target insects. The best way to determine how well your water will work is the soap-jar test. Let a jar full of your spray solution sit for 20 minutes, then look for precipitates in the soapy-water solution. Product labeling must be studied to determine suitability to crop and pest in each particular state and region.   Back to Top Specific Insect Management Strategies Cutworms   Cutworms wreak havoc during seedling establishment in many cotton-growing areas. Cutworm species include the variegated cutworm, Peridroma saucia; black cutworm, Agrotis ipsilon; granulate cutworm, Feltia subterranea; and army cutworm, Euxoa auxiliaris. They are active at night, feeding and chewing through the stems of the seedlings. In the day they burrow underground or under clods to avoid detection. To inspect for cutworms, dig around the damaged areas during the day or come out at night with a flashlight to catch the culprits in the act. Problem areas are usually found near field borders and in weedier areas.   Cutworms have many predators and parasites that can help control their numbers. Some of these parasites and predators can be purchased or harnessed naturally through planting or conserving habitat for them.   Understanding the biology of beneficial organisms is imperative in order to use them effectively as pest control agents. For example, insect parasitic nematodes like Steinerema carpocapsae or insect-infecting fungi like Beauveria bassiana require adequate humidity to be effective. Other predators include spiders, minute pirate bugs, damsel bugs, and lacewing larvae. Birds also prey on cutworms, so do not assume that the birds in the field are causing the seedling damage.   If natural pesticide applications are necessary, choose one that is least disruptive to the natural enemies. The application of a rolled oats with molasses bait containing Bacillus thuringiensis or nighttime spraying of Bacillus thuringiensis is effective. Again, early detection and application during the early developmental stages of the larvae (first and second instar) make these biorational pesticides more effective. Pheromone traps will indicate when mating flights are occurring, and through degree-day calculations one can estimate egg laying and hatching. For information on degree-day calculations contact your local Extension agent.   Thyme oil serves as a toxicant, insect growth regulator, and antifeedant to cutworms. (Hummelbrunner and Isman, 2001) Mock lime or Chinese rice flower bush, Aglaia odorata, inhibits larval growth and is insecticidal to the cutworms Peridroma saucia and Spodoptera litura. (Janprasert et al.,1993) No commercial products using tyme oil, mock lime, or Chinese rice flower are known to us at this time. Azadirachtin, the active ingredient in neem, has similar effects on various insects and is used in the form of neem cakes to control soil pests in India. Certis USA produces Neemix Botanical Insecticide. Its active ingredient, Azadirachtin, is registered for cutworm, looper, armyworm, bollworm, whitefly, and aphid control on cotton. Cotton bollworm and tobacco budworm   The tobacco budworm, Heliothus virescens, and cotton bollworm, Heliothus zea or Helicoverpa armigera, attack cotton in similar ways, damaging bolls, squares, and blooms, and feeding on plant terminal buds, causing branching that delays maturity. On mature damaged bolls, one finds holes with excrement or frass surrounding the boll. These holes provide entry to secondary organisms that can cause decay. Besides cotton, other bollworm hosts include alfalfa, beans, corn, peanuts, sorghum, soybeans, peppers, sweet potatoes, tobacco, and tomatoes. Wild hosts include toadflax, deergrass, beggarweed, groundcherry, geranium, and sowthistle. In feeding preference tests, 67% of females preferred common sowthistle, about 5% preferred cotton, and 28% did not discriminate. Common sowthistle was also the most preferred by newly hatched larvae among the five host plant types presented in a multiple-choice test. (Gu and Walter, 1999) This suggests some possible management strategies using sowthistle as a trap crop.   This bollworm "complex" has many natural enemies that can be harnessed through the use of beneficial habitats or purchased from insectaries. Generalist predators such as assassin bugs, bigeyed bugs, damsel bugs, minute pirate bugs, lacewing larvae, collops beetles, and spiders will feed on the eggs of bollworm or on the larvae that are in early stages of development. Parasites like the wasps Trichogramma spp., Chelonus texanus, and Hyposoter exiguae, and the parasitic fly Archytas apicifer, parasitize eggs, larvae and pupae. These groups of natural enemies are usually enough to keep bollworms below economically damaging thresholds. In conventional fields where broad-spectrum insecticides are used, these natural enemies are so depleted that continuous spraying is required to keep bollworms and other pests in check.   Cultural practices that keep bollworm numbers down include managing the cotton field to obtain an early harvest and avoiding over-fertilizing or over-watering. Tillage significantly lowers bollworm populations by disrupting emergence from the overwintering stage. Minimum tillage operations may favor bollworm populations, except in the South, where minimum tillage favors fire ant colonization. (Monks and Patterson, no date) Fire ants are effective predators of many cotton pests, including bollworm.   For sprays of Bacillus thuringiensis (B.t.) to be effective, they need to be timed so that the bollworm larva is in its early stages of development (first or second instar). Night spraying will prolong the exposure to the B.t., since ultraviolet rays of the sun break it down. The use of Beauveria bassiana as a biopesticide can be effective against bollworm only when temperature and humidity requirements are met. Research from China indicates that the ideal temperature and humidity for high bollworm kill using Beauveria bassiana is 77°F with humidity between 70-95%. Mortality drastically decreased when humidity dropped below 70%. (Sun et al., 2001) Nuclear polyhedrosis virus, another biopesticide, is a disease-causing virus for use on the bollworm complex and is available commercially in a product called Gemstar LCTM from Certis USA. Azadirachtin, the principal active ingredient in many neem-based products, also shows promise as a growth regulator and anti-feedant against the cotton bollworm. (Murugan et al., 1998) Pink bollworm   Pink bollworm, Pectinophora gossypiella - or pinkies, as they are commonly called - is a significant cotton pest in the Southwest. They have also been found in Texas, Oklahoma, Arkansas, and Florida. Pinkies damage cotton by feeding on buds and flowers and on developing seeds and lint in bolls. Under dry conditions, no measurable yield reduction occurs until 25 to 30% of the bolls are infested; at this level the infested bolls have more than one larva. With high humidity, it takes only one or two larvae to destroy an entire boll, because damaged bolls are vulnerable to infection by fungi that cause boll rot. (Rude, 1984) Damaged bolls will have a pimple or wart that develops around the hole where pinkies have entered. Unlike cotton bollworm or tobacco budworm, pinkies do not deposit frass or feces at the base of the entrance hole.   Cultural practices to reduce pink bollworm numbers consist of ceasing irrigation sooner than normal, early crop harvest, shredding crop residue after harvest, plowdown of cotton residue to six inches, and winter irrigation if cotton will follow cotton on the same field (not a wise practice in organic production). Okra and kenaf are alternate hosts to pink bollworm and must also be eliminated from an area. These techniques are used in area-wide eradication efforts. Area-wide sterile release programs through the Animal and Plant Health Inspection Service (APHIS) of the USDA is a biological control method also used in eradication efforts.   Pink bollworm eggs are very small, making them susceptible to many natural enemies, including mites, spiders, minute pirate bugs, damsel bugs, bigeyed bugs, and lacewing larvae. A number of parasitic wasps such as Trichogramma bactrae, Microchelonus blackburni, Bracon platynotae, and Apanteles ornone attack pink bollworm. Studies have shown that the use of the insect-feeding nematodes Steinernema riobravis and S. carpocapsae on pink bollworm larvae in the fields achieved a larval mortality rate of 53 to 79%. (Gouge et al., 1997)   The success of insect-killing fungi like Beauveria bassiana depends on the timing of the application to correlate with hatching and early stages of development of the pink bollworm, as well as optimum humidity for the fungi to infect.   Other strategies to reduce pink bollworm populations include the use of mating pheromone disruptors. Several products, such as Biolures®, Checkmate®, Frustrate®, and PB Rope®, are available in the U.S. Pink bollworm mating disruption trials recorded higher yields (1864 pounds/acre) than control fields with no mating disruption (1450 lbs/acre). (Gouge et al., 1997) Armyworms   Beet armyworm, Spodoptera exigua, and fall armyworm, Spodoptera frugiperda, can both feed on cotton and on rare occasions cause yield reductions. Beet armyworms can cause yield reductions in cotton if populations are high enough near the end of the season. Armyworms hatch in clusters, with the small worms spreading through the plant over time, feeding on leaves, squares, flowers, and bolls. They skeletonize leaves and bracts, trailing frass and spinning small webs as they go. The egg clusters are covered with white cottony webbing, making them easy to spot. Outbreaks are attributed to favorable weather conditions and the killing off of natural enemies.   Natural enemies are assassin bugs, damsel bugs, bigeyed bugs, lacewing larvae, spiders, the parasitic flies Archytas apicifer and Lespesia archippivora, and the parasitic wasps Trichogramma spp., Hyposoter exiguae, Chelonus insularis, and Cotesia marginiventris.   Nuclear polyhedrosis virus is a disease-producing virus that infects beet armyworm. It is available in the product Spod-X LC (Certis). Bacillus thuringiensis on young worms is effective if application is thorough. Laboratory and greenhouse tests showed that caffeine boosted the effectiveness of the B.t. against armyworms up to 900 percent. (Morris, 1995) Its use is most promising against pests that are weakly susceptible to B.t. itself. Recipe: dissolve 13 ounces pure caffeine in water; add the solution to 100 gallons of standard B.t. spray; apply as usual. (Morris, 1995) Caffeine can be obtained from most chemical-supply houses and is also available in pill form from most pharmacies. Organic growers interested in this approach should ask their certifying agency about the appropriateness of this treatment in a certified organic system.   Many other crops are hosts to armyworms, as are the weeds mullen, purslane, Russian thistle, crabgrass, johnsongrass, morning glory, lambsquarters, nettleleaf goosefoot, and pigweed. These last three are preferred hosts that can serve as indicators of the populations or be managed as trap crops. Loopers   The cabbage looper, Trichoplusia, feeds on leaf areas between veins causing a net-like appearance but rarely cause significant damage, because natural enemies control them. If the enemies are lacking in number, severe defoliation of cotton plants by loopers may cause problems with boll maturation. Defoliation before bolls mature can reduce yields drastically.   Loopers feed on all the crucifers, crops and weeds, and on melons, celery, cucumbers, beans, lettuces, peas, peppers, potatoes, spinach, squash, sweet potatoes, and tomatoes. Other hosts include some flowers, like stocks and snapdragons, and tobacco. Some weed hosts include lambsquarters, dandelion, and curly dock.   Natural enemies are assassin bugs, bigeyed bugs, damsel bugs, minute pirate bugs, lacewing larvae, spiders, and numerous parasitic wasps, such as Trichogramma pretiosum, Hyposoter exiguae, Copidosoma truncatellum, and Microplitis brassicae. The parasitic fly Voria ruralis also contributes to looper control. Trichoplusia ni NPV (nuclear polyhedrosis virus) sometimes is responsible for sudden looper population decline, especially after rainfall. Bacillus thuringiensis is effective when the problem is detected early. Thrips   Thrips damage seedlings by rasping and sucking the surface cells of developing leaves, resulting in twisted and distorted young leaves. They are rarely a problem and are usually kept in check by minute pirate bugs, parasitic wasps, predacious mites, and other thrips. The western flower thrip can be a beneficial insect when it feeds on spider mites on a full-grown plant. The bean thrip, Caliothrips fasciatus, feeds on older cotton leaves and sometimes causes defoliation. Insecticidal soap is the least toxic pesticide for thrips but should not be applied on hot sunny days because it may burn the plants. Research has demonstrated that cotton varieties with hairy leaves are less injured by thrips than smooth-leaf varieties. (Muegge et al., 2001)   Wayne Parramore of Coolidge, Georgia, strip crops cotton into lupine, providing him with nitrogen, soil erosion control, and a beneficial insect habitat to control thrips. (Dirnberger, 1995) When the lupine is 36 inches tall, a strip is tilled 14 inches across the seedbed. A Brown plow in front of the tractor with a rotovator in the back exposes the center strip, warming it up for the planting of cotton. The remaining lupine is host to aphids, thrips, and their natural enemies. It prevents weeds and grasses from growing up and it reduces soil erosion. The remainder of lupine that is tilled in later provides a second shot of nitrogen to the cotton. The Parramores report that strip tilled cotton-lupine required only two insecticide applications. They later determined that they could have done without the second spraying in the lupine field, based on a check-plot comparison. Neighboring conventional fields took five spray applications.   In Parramore's own words:   "By having these crop strips in my field, I have insects evenly distributed - nonbeneficials feeding beneficials. Now when the cotton gets big enough for the legume to die, where are the beneficials gonna be? They're not going to be all around the edges of the field and slowly come across the field; they're all over the field already. They're in the middle where lupine is still growing inches away from cotton plants. We're looking at a savings and increase in production of approximately $184.50 per acre."   Fleahoppers   The cotton fleahopper, Pseudatomoscelis seriatus, is a small bug measuring about 1/8 inch, with black specks covering its yellowish-green body. The whitemarked fleahopper, Spanagonicus albofasciatus, is the same size and resembles the predatory minute pirate bug, Orius sp. and Anthocoris sp. Fleahoppers cause damage by stinging the squares, which then drop from the plant, reducing yields. In 1999 the cotton fleahopper was the most damaging insect in cotton, responsible for nearly a third of the total reduction in yield caused by all insect pests in the U.S. Total U.S. insect losses represented more than two million bales that year. (Williams et al., 2000) Fleahopper infestations usually occur in fields near weedy and uncultivated ground or near weedy borders. Some of these weeds, like false ragweed, Parthenium hysterophorus, wooly croton or goatweed, Croton capitatus, and horsemint, Monarda punctata, release volatile compounds that have been shown to be preferred by fleahoppers over cotton. (Beerwinkle and Marshall, 1999) Once the weeds start to mature and dry out, the pests will move to the cotton. This information can help with monitoring and establishing a trap crop system. Natural enemies of fleahoppers include assassin bugs, bigeyed bugs, damsel bugs, lacewing larvae, and spiders. A study done in east Texas showed that spiders were three times better than insects as predators of the cotton fleahopper. (Sterling et al., 1992) Lygus or tarnished plant bug   These bugs are represented by the species Lygus hesperus, L. elisus, L. desertinus, and L. lineolaris. The first three species are found in the Southwest, and L. lineolaris is found in the rest of the cotton belt. They pierce stems and suck plant juices, causing damage to flower buds (squares), young bolls, and terminal buds. Because almost any plant that produces a seed head can be a lygus host, this pest has a wide range. Cotton is not the preferred host of lygus, but once the surrounding vegetation starts to dry up, they will move into irrigated cotton and feed on succulent plant parts. Alfalfa is a preferred host to lygus and can be grown in strip intercrops with cotton to assist in lygus control. The classic habitat manipulation system where alfalfa is strip harvested or where borders are left uncut demonstrates that lygus can be kept away from cotton during critical square formation. The alfalfa also harbors numerous natural enemies of lygus, keeping their populations in check. These natural enemies include the tiny wasp Anaphes iole, which parasitizes lygus eggs, and predators like damsel bugs, bigeyed bugs, assassin bugs, lacewing larvae, and spiders. If lygus populations are reaching economically damaging levels, then a pesticide application is warranted. Check with your organic certifier to determine which pesticides are allowed. Botanical insecticides such as pyrethrum, sabadilla, and rotenone are options but may be prohibitively expensive. Insecticidal soaps can reduce the lygus nymph population. Keep in mind that these treatments will also affect the natural enemies and may cause secondary outbreaks of pests like aphids and mites. Boll weevil   The boll weevil, Anthonomus grandis, is considered by some as the primary deterrent to growing cotton organically. In weevil eradication zones, the boll weevil may be less of a concern. Conventional controls consist of applying pesticides to target the adults when they start feeding and laying eggs. For organic systems, using this approach with organically accepted pesticides would be too costly and only moderately effective.   The use of short-season cotton may be part of an overall strategy to control boll weevils with little or no sprayed insecticides. The objective of short-season cotton is to escape significant damage caused by the second generation of weevils, through early fruiting and harvest. For this to occur, the population of first generation weevils must also be low. Crop residue management and field sanitation is essential. Destruction of cotton stalks soon after harvest has long been recognized as a useful practice for reducing the number of overwintering weevils. (Sterling et al., 1989)   Early harvest, sanitation, and immediate plowdown are strategies that keep the overwintering populations low for the following season. In order for these strategies to be effective, they must be practiced by all cotton growers in an area. Any volunteer cotton plants that are missed can be the source of infestation for the following crop season.   The boll weevil has two effective insect parasites, Bracon mellitor and Catolaccus grandis. Bracon mellitor occurs naturally in North America and can contribute to boll weevil control if conditions are favorable and suitable habitats are available.   Catolaccus grandis is originally from tropical Mexico but has been effective in controlling boll weevils in augmentative releases done in USDA cooperative studies. The researchers achieved from 70 to 90% boll weevil parasitism. (King et al., 1995) Releases began on July 19 at 350 females per acre per week over a nine-week period. The objective was to suppress or eliminate weevil reproduction in six organic cotton fields. Similar work done in Brazil resulted in Catolaccus grandis inflicting significant mortality on third instar weevils. The use of augmentative releases of C. grandis has a very high potential for supplementing and enhancing available technology for suppressing boll weevil populations. (Ramalho et al., 2000) Catolaccus grandis is currently not commercially available.   Other alternative methods used by organic cotton growers in Texas against the boll weevil are pyrethrum used with diatomaceous earth, garlic oil and fish emulsion as repellants, and pheromone traps for early detection. Aphids   Aphid problems    ادامه درپست بعدی