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Commercial Horticulture > Comm Hort Blog > Posts > Cabbage Insect Pest Management: Recent lessons from field studies

Cabbages are popular among open field and high tunnel crop producers during fall. While insect pests in open field are moderated by temperature changes and other weather parameters, crops grown in high tunnels are highly vulnerable to caterpillars that favor the hot and humid environment. This report is based on open field cabbage (small-plot) research but results are applicable to high tunnel and conventional producers who can benefit from the use of bioinsecticides for early season pest management.

Insect pests to look for: In Alabama, cole crops are at high risk from many species of caterpillars like cabbage butterflies (http://tinyurl.com/mhnzvj4), cross-stripped cabbageworms, diamondback moths, and cabbage loopers. We have seen instances where two or three pest species may occur at once due to favorable environment. A good prevention strategy is to minimize weed pressure and crop residue (sanitation). To learn more about insect pests of cole crops and hands-on scouting techniques, contact the Chilton County Extension Office and register for the upcoming Extension event on December 4 starting at 1 p.m. For more information about the event, contact Regional Ext. Agent Gary Gray, (334) 539-2128, graygar@aces.edu.
 Xentari 10-30-14.jpg
Lessons learned in alternative pest management: We established cabbage plots in Clanton with the objective of evaluating weekly treatment of Bacillus thuringiensis species aizawai (Xentari ®) for reducing cabbageworm feeding on leaves and minimizing product contamination. Month-long observations on cabbages have provided some fascinating insight regarding the potential of alternative insecticides. Take a look at the four photos here that show progression of insect damage due to cabbage butterflies from October-November 2014 (click to enlarge photos). Weather in October (mild temperature and dry condition) was excellent for the cabbageworms resulting in over 50% damage to untreated cabbage plants in check plots.  Xentari weekly sprays under those weather conditions kept leaf feeding at or below 10% on average resulting in very good looking produce. We have seen similar effectiveness of Xentari in tomato test plots at various pest pressures.  In short, the lessons learned were:Xentari 11-07-14.jpg

·         Cabbageworm onset is indicated by flight of the butterflies and leaf feeding can be dramatic within few days after egg hatch. Prevent movement of caterpillars from outer leaves to the center head of cabbage by timely intervention.
·         Bt treatments must start at the first symptoms of leaf scarring when caterpillars are small and most susceptible to the treatment. Remember, Bt paralyzes insect gut rapidly after ingestion but eventual death of the host may take several days.
·         At least one weekly spray for several weeks can provide protection to old and new plant parts (since Bt does not translocate after application). If you get a period of heavy rainfall, apply Bt slightly ahead of the warm weather that may follow.Xentari 11-14-14.jpg

·         We also observed early planted cabbage to be a trap crop for cabbageworms resulting in much lower population of caterpillars in new plantings. Trap crops of cabbage (or collards) may work to distract the butterflies in laying eggs there; caterpillars in the trap crop can be destroyed with conventional chemical or alternative insecticides.
 
For more information about Bt and other alternative insecticides, visit the Alabama Vegetable IPM website www.aces.edu/go/87 where you can find IPM training modules, publications, and presentations for self-paced learning. Don’t forget to register and attend the upcoming vegetable crop production meetings for hands-on IPM training suitable for large and small farms. Stay in touch with your Regional Extension Agent for accurate insect pest identification and scouting updates for correct decision making.Xentari 11-21-14.jpg

 
Article by Ayanava Majumdar (Ext. Entomologist), Gary Gray (REA), and James Pitts (Director, Chilton REC)

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