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Temporary Pest Exclusion

The demand for organic crop production has seen a historic rise in recent years. This increasing demand means there is a need for more farmers to produce organic vegetables at a reasonable cost, while also being environmental sustainable. For these producers, insect pest management is one of the aspects where they must watch their costs and also consider the environmental impact of their management strategies. Luckily, there are several integrated pest management (IPM) practices that can help producers do both.

Pest Exclusion Systems

Vegetable production in the Southeast is risky, with insect pests threatening crops from seedling to harvest. In fact, according to surveys of specialty crop producers, potential crop losses from pest feeding averages 55 percent. Crop contamination from insect excrement and other factors can also affect farm profits. These are referred to as the yield-limiting and yield-reducing factors, which all depend on how the crop is managed.  IPM practices, such as pest exclusion, can help with these factors.

Pest exclusion is based on the practice of blocking insects physically from reaching their host plants and is often over looked by producers. Moths and large pests, such as stink bugs or leaffooted bugs, can be good targets of a well-designed pest exclusion system, especially on small acres with intensive vegetable production. There are two types of pest exclusion systems; temporary and permanent.

  • Temporary, or time-limited, systems are suitable for early season pest management to protect seedlings.
  • Permanent pest exclusion systems are a more intense use of pest exclusion fabric that provides season-long crop protection in high tunnels. This is called the high tunnel pest exclusion (HTPE) system, which is being intensively evaluated at 14 farm locations across Alabama.

Benefits

There are several benefits of using pest exclusion system in organic vegetable production.

  • Short-term or season-long pest reduction.
  • Variable cost depending on material and design of the system.
  • Minimal training for implementation.
  • Growth and season extension from use of insect barrier fabric.
  • Overall reduction in the use of biorational insecticides with increase in natural enemy activity.

Note that not all crops and varieties may lend themselves to pest exclusion system. Contact the Alabama Extension commercial horticulture regional agent in your area before making a major purchase decision. It is recommended that pest exclusion systems be integrated with the use of insect monitoring systems or traps and natural enemies for practicing true IPM.

 

Comparison of Temporary and Permanent Pest Exclusion Systems


Temporary Pest Exclusion SystemPermanent Pest Exclusion System
Example MaterialsPolyester fabric. Super-Lite Insect Barrier, Agrofabric Pro-19, Proteknet, and other products.
Polyester mesh. Fruit protection bags and mosquito netting (figure 1).
Shade cloth-based systems (high tunnel pest exclusion systems) (figures 2a and 2b). Other fine materials, including thrips netting, can be used for building net houses (sealed structures for high value crop production, figure 4).
SuitabilitySmall farms and vegetable gardens. Most materials allow majority of light and rain penetration without excessive retention of heat. Suitable for high tunnel vegetable production over multiple years.
Target Insect PestsVery effective in significantly reducing aphids, flea beetles, grasshoppers (early season insect pests), cabbage butterflies, fruitworm, and armyworm moths. Can be used to reduce early establishment of squash vine borers and squash bugs.Very effective in significantly reducing large insects like hornworms, armyworm/looper/fruitworm moths, and leaffooted bugs when using a 50 percent shade cloth. Will also slow down squash vine borers for cucurbit production. Will not stop small insects like aphids, whiteflies, or flea beetles.
Best PracticesUse the insect barrier fabric over one or more crop rows immediately after planting on low frames or hoops. All sides must be sealed to prevent insect entry. Keep the fabric from touching the plants, so insect mouthparts don’t reach through the barrier. For insect pollinated crops, roll the fabric over the frame when needed and cover at night to keep moths out. Always remove weeds and practice sanitation to reduce insect buildup. Fruit protection bags can be used to bag individual fruits.A 40 or 50 percent shade cloth based HTPE system has been studied extensively in Alabama. Shade cloth must be installed tightly on the side and end walls, using clamps, nuts, and bolts (figure 5). Shade cloth purchased from Poly-Tex (MN) for demonstrations come with seams and grommets which make installation very easy. It is best to grow transplants in the same high tunnels where crops will be planted to avoid accidental introduction of pests. Reduce traffic inside the netted high tunnel and keep the structure closed as much as possible. Farmers facing issues with aphids and other small insects can also use Super-Lite barrier additionally for a short time period.
Ease of MaintenanceBased on studies in Alabama, Super-Lite Insect Barrier and Agrofabric Pro-19 are very delicate fabric that needs regular up-keep. Straight line winds can be very damaging to the fabric.Shade cloths are strong woven materials that can be stretched. It is easier to repair shade cloth wear-and-tear.
MovabilityFabric can be put over a chicken-wire frame or plastic/metal hoops and secured to a wooden base (figure 3).Most high tunnels are not movable. HTPE system is tightly installed all around the structure and kept in place year-round for multiple crops.
ReusabilitySome fabric is very delicate and may not last long for reuse (Super-Lite). Other materials, like Proteknet and hoops sold by vendors, can be used multiple years.Shade cloth based pest exclusion system can last many years and be very cost-effective. Farmer can also use Super-Lite barrier under a high tunnel for deflecting small insects. This extends the life of light fabric.
Nontarget EffectsInsect barrier fabric excludes natural enemies like lady beetles and lacewings. These natural enemies can be purchased and released under the fabric for controlling any accidental infestation of aphids or caterpillars. If insect barrier fabric is not used late in the season, then crop pollination is not an issue.In laboratory and field studies across Alabama, HTPE systems with 40 or 50 percent shade cloth will not affect lady beetles but can slow down lacewings due to their large wings. Lacewings and lady beetles can be introduced as needed inside netted tunnels for effective control of small insects, like aphids and whiteflies, that are regular occurrences in high tunnel crops. Bees and small sized insect pollinators are active inside netted tunnels with 40 or 50 percent shade cloth. A net house that uses fine materials like Proteknet or mosquito nets may block pollinators. Use bumble bee boxes in such instances.
DisadvantagesUse of dense fabric in high heat may promote disease.A 50 percent shade cloth may slow down air movement that can be corrected by installing a fan or fans.
CostHighly variable. Super-Lite Insect Barrier fabric is low cost ($10+ online) and available in various sizes. Proteknet is much more expensive product that comes in rolls with separate shipping cost. Cost of a permanent HTPE system with 40 and 50 percent shade cloth that has been tested at 14 farm locations range from 26 to 50 cents per square foot. Additional cost of wooden baseboards and clamps varies by region.
Training VideosTemporary Pest Exclusion System

Low-cost Net Houses for Community Gardens and Urban Farms
Introduction to High Tunnel Pest Exclusion

High Tunnel Pest Exclusion System for Stopping Leaffooted Bugs

 

More Information

To stay in touch with agriculture research and pest alerts, subscribe to the Alabama IPM Communicator Newsletter. Use the Organic Vegetable IPM slide chart for additional recommendations for common vegetable insect pests. Check out the Alabama Beginning Farmer Program for more articles on basics fruit and vegetable production systems. Contact a commercial horticulture regional Extension agent near you for assistance.

Additional Resources

 

Funding agencies: This research has been funded by the USDA Sustainable Agriculture Research and Education program, USDA NIFA CPPM, and the Alabama Department of Agriculture’s Specialty Crops Block Grant since 2011. Intensive on-farm education programs for new and beginning farmers has been funded by two grants from the USDA BFRD and SARE On-farm grants program.

Trade and brand names used are given for information purposes only. No guarantee, endorsement, or discrimination among comparable products is intended or implied by the Alabama Cooperative Extension System.

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