Project on Sustainable Cotton Production

During the years of 1995 until present we have been engaged in a project directed toward developing a systems approach for pest management for cotton in Georgia and the southeastern USA. Due to the recent eradication of the boll weevil from this region, the overall use of insecticides has dropped dramatically and cotton production has made a major resurgence. It is clear that the boll weevil was a classic primary pest and early season treatments for the weevil was evoking outbreaks of other pests that now can be typically kept under natural control through ecologically sound management. The cotton system can serve as a model for similar programs for other crops. The project involves cooperative, on-farm studies with several growers, local University of Georgia extension agents, NRCS representatives, and private agricultural consultants, along with a multidisciplinary team of scientists and collaboration with the Georgia Cotton Commission. The use of cover crops and conservation tillage practices are used to foster natural enemy/ pest balances as well as to reduce erosion and promote better soil quality. Interventions with therapeutics are minimized and are based on comprehensive monitoring programs and the premise that they do cause ripples and should only be used sparingly as short-term back-ups to the inherent strengths. The results thus far have been highly encouraging in terms of net profits, sustainable pest management systems, and conservation of soil and other natural resources (#58 Lewis et al., 1997, #49 Stapel et al., 1998). It is clear that in order to fully develop these approaches, we must invest in research to better understand the multiple interactions among the crops habitat and associated organisms and landscape ecology principles.

Project Objectives
Rather than 'dissecting' key pests out of the system for study by themselves, we propose to develop an IPM approach that deals with the natural enemy/pest complex as components of an overall system, with the following main objectives:
1) Habitat Management: Use of cover crops such as vetch, winter grains and crimson clover combined with conservation tillage to improve soil quality and fertility, provide alternate habitats, and increase stability in the cotton agroecosystem. This will also help decrease the amount of soil erosion, run-off, and nutrient leaching.
2) Crop Attributes: Use of improved varieties and agronomic practices (planting dates, fertilization practices, etc.) combined with management of the surrounding habitat to help attract natural enemies.
3) Treatment Thresholds: Develop more precise treatment guidelines that include not only the pest numbers but also consider natural enemy densities. This component also focuses on pest and natural enemy biology, and on timing of treatments.
4) Therapeutics: Use of 'soft' materials that target the key pest while causing minimum disruption of the agroecosystem. Also considers indirect sublethal effects such as reduced fecundity, behavioral disruptions, etc.
5) Economics: Help make cotton more sustainable by reducing energy, equipment, pesticide, fertilizer and labor input costs, and by maximizing yields and net returns.

Twelve fields in four Georgia counties in the Piedmont, Coastal Plain, and Deep Sand regions were monitored. Seven of the fields were conservation-tilled with a winter cover crop, and five of the fields were conventional-tilled. The two Piedmont sites, located in Morgan county, included a 10 ha conservation-tilled field with a canola cover crop and a nearby 4 ha conventional-tilled field. The two Deep Sand sites, located in Decatur county, were an 11 ha conservation-tilled field with a rye cover crop and adjacent, a 7 ha conventional-tilled field. The remaining eight fields were all located in the Coastal Plain region. The Jenkins county site was a 10 ha field with a rye cover crop. In Spring two strips of buckwheat was planted; the site in nearby Burke county was a 12 ha conventional-tilled field. The other six fields were all located in Coffee county. Four of the sites were conservation-tilled fields with cover crops, including a 3 ha field with Crimson clover, a 15 ha field with a wheat/rye mixture, a 6 ha field with a mixture of Crimson clover and rye and a 10 ha field with rye. Two sites were conventional-tilled fields of 10 and 15 ha.

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The use of wheat/rye and Crimson Clover as cover crops in the early cotton season in South Georgia. Cover crops prevent soil erosion and help support beneficial insects in the field. In fields with cover crops cotton is later planted with minimum tillage equipment.

Most of the field work involved monitoring pest and beneficial insect populations on a weekly basis. We compared the population development of both groups of insects in conservational and conventional tillage systems. The table below shows the different sampling methods we used to monitor insects and which groups of beneficial and pest insects we mainly focussed on. Results Cotton Project.

 

Beneficial Insects
Pitfall Trap Sampling





 

Whole Plant Sampling


Spiders
Centipedes
Staphylinidae (6 spp.)
Ciccindellidae (2 spp.)
Carabidae (17 spp.)
Earwigs (Dermapterae)
Ants

Parasitoids (Hymenopterae, 10 spp.)
Coccinellidae
Hoverflies (Syrphidae)
Big eyed bugs (Geocoris spp, 2 spp.)
Lacewings (Chrysopidae, Hemerobiidae)
Damsel bugs (Nabidae)
Assasin bugs (Reduviidae)
Minute Pirate bugs (Anthocoridae)
Ant-like flower beetles (Anthicidae)
Predacious stinkbugs (Asopinae)
Ant

Pest Insects
Whole Plant Sampling


Tobacco Budworm (Heliothis virescens)
Corn Earworm (Helicoverpa zea)
Beet Armyworm (Spodoptera exigua)
Cabbage Looper (Trichoplusia ni)
Thrips
Aphids
Tarnished Plant Bugs (Lygus lineolaris)
Stinkbugs (Pentatomidae)


Damsel bugs (Nabidae)

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Damsel bugs have a slender body (lenght 3-10 mm). These insects are predaceous on many different insects including aphids and caterpillars. They are commonly found throughout the USA.

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Assasin bugs (Reduviidae)

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Most adult and juvenile reduviids are predaceous on other insects and their color varies from blackish/brown to bright red.

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Spiders

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Parasitoids

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A large variety of insects exist that are parasites of other insects. Some parasitoids are wasp-like (Hymenoptera) and others look more like flies (Diptera). Also the size is variable from less than 1 mm to more than 1 cm. Generally, parasitoids lay one or more eggs in or on the host insect or egg. The offspring lives either inside or outside the living host and feeds on host body fluid and tissue. When the juvenile parasitoids mature the host will eventually die.

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Big eyed bugs (Geocoris spp)

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The big eyed bugs are partly predaceous. Both young and adult individuals attack many insect species and their eggs.

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Ground Beetles (Carabidae)

Ground beetles are commonly found under ground cover and are especially active at night.They move fast and seldom fly. Nearly all of these beetles are predaceaous on other beneficials, which makes them highly beneficial.The genus Calosoma (on the photo) is one of the largest and most colorful ground beetles that feed mostly on caterpillars.

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Corn Earworm (Helicoverpa zea) and Beet Armyworm (Spodoptera exigua)

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Both larvae of these noctuid moths can be very harmful to crops, such as cotton, corn and tobacco. Younger stages of the corn earworm feed on young leaves and terminals of plants. Later stages become typical fruit feeders damaging cotton squares and bolls. Beet Armyworms are leaf feeders that have become a serious secondairy pest because of their high tolerance of many insecticides.

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Coccinellidae

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Adult and larval stages of these lady beetles are predaceous and feed mainly on aphids, but they will also feed on young instars of caterpillars when given the opportunity. Lady beetle larvae look different than the adults as shown in the top left photo.

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Lacewings (Chrysopidae, Hemerobiidae)

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Minute Pirate bugs (Anthocoridae)

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Rove Beetles (Staphylinidae)

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Hoverflies (Syrphidae)

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Tiger Beetle (Ciccindellidae)

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Tarnished Plant Bug (Miridae)

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Predacious Stinkbugs (Asopinae)

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