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This is a pest alert for producers with leafy greens or cole crops in open field or high tunnel.
There have been plenty of imported cabbageworms or cabbage butterflies (Pieris rapae) flying around in our research plots and producer fields scouted. This is a major pest of cole crops and the butterfly is active at day time – unlike cabbage loopers and diamondback moths that are active at dusk. Cabbageworm butterflies are white or yellowish with black spots on the wings. Watch this video (http://youtu.be/2--JZgcZsgU) to see the identification characteristics and flight pattern of the cabbageworm. If you look carefully and follow the butterfly around, you can probably find foot-ball shaped eggs on the top or bottom of the leaves (see photo). A good hand-held magnifying glass is excellent for scouting. Each female butterfly is capable of laying 50-100 eggs over several days. Cabbageworm larvae are velvety green and usually feed close to major leaf veins. If not controlled, the cabbageworms can destroy foliage along with caterpillars of the other pest species.
Early season management of butterflies and moth by physical exclusion: Small producers and gardeners can use very light shade cloth (woven fabric) or Superlight Insect Barrier (fabric) to keep the butterflies and moths away and minimize egg laying on desirable crop/s. Superlight insect fabric (Gardensalive.com) allows over 85% light penetration and traps heat for faster crop production if you are behind in planting. For shade cloth, use the widest opening available, say, 30% or less shading. Take the fabric/shade cloth off if the plants get too big. If you decide to use physical exclusion tactics, make sure to periodically check inside to remove any unwanted pests or weeds for optimum of crop production. High tunnel producers can install 30% or lower shade cloth on the sides to prevent entry of pest butterflies/moths (net house strategy).
Collards can act as trap crops for some of these pests. Plant collards in outside rows and slightly earlier than the main crop to enhance trap crop effectiveness. Make sure to apply synthetic or approved organic insecticides to kill multiple pest species at once. Monitoring and timely use of insecticide on trap crop can enhance beneficial insect populations in the main crop.
Conventional producers have a wide selection of products to choose from after confirming the presence of eggs or caterpillars on the crop. Good knock-down chemicals ae flubendiamide (Belt), spinetoram (Radiant) and Bacillus thuringiensis (Xentari). Stay away from use of harsh synthetic pyrethroids that can drastically reduce beneficial insect populations. Stop using the products once the pest is under control. Check the insecticide label and any precautions for best results.
Organic producers should first think about prevention (physical exclusion) and alternative pest management strategies (trap crops) rather than insecticidal control – although some organic insecticides are extremely effective as well. Use Bt product (Xentari or Dipel), pyrethrin (PyGanic), or spinosad (Entrust or Monterey product) when the caterpillars are small. Rotate insecticides and stop using them once pest pressures are down. Ensure proper coverage of plants and repeat spraying as needed to prevent caterpillar outbreak. While Bt products are pest-specific, pyrethrin and spinosad have broad action.
While scouting cole crops, also watch for aphids on the underside of leaves (see photo, image courtesy: Colorado State Univ.). Aphids are a major cause of crop contamination and they can be difficult to control in an outbreak. The migrating adult aphids has wings and appears as a small dot on the back of the leaves. Don’t let aphids escape your attention and mark the hot-spots for insecticidal or manual removal when the clusters are small. Large number of aphids are extremely difficult to control with approved organic insecticides – they will slow down with repeated use of neem oil and/or paraffinic oil-based products. However, conservation of natural enemies (lady beetles, lacewings, etc.) is one of the most sustainable ways of managing aphids. Conventional producers should shift to using or incorporating selective insecticides like pymetrozine (Fulfill) in their spray schedule rather than repeated applications of synthetic pyrethroids. Stop using organic or conventional products once the pest populations have crashed.
For further information about vegetable IPM tactics, visit the Alabama Vegetable IPM website www.aces.edu/go/87. Use your smartphone to take pictures or collects an insect sample for proper identification. To learn more about alternative pest management strategies or conventional IPM please attend Extension educational events near you. Subscribe to the IPM newsletter using the website linked above and stay abreast with latest happenings around the state.
Disclaimer: Mention of product names is only for example only – names do not indicate endorsement of those products or the company by ACES or this author. Always read the insecticide label because it is the LAW!!
Ext. Entomologist and State SARE Coordinator
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