Vegetable Crop Insects – August 17, 2012

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

The potential for significant populations of corn earworm, beet armyworm and in some cases soybean loopers remains high in fall vegetable crops statewide. Moths can be found laying eggs in fields so you may need to scout fields at least twice a week as well as check local trap catches on our website for corn earworm and corn borer (http://ag.udel.edu/extension/IPM/traps/latestblt.html) or call the Crop Pest Hotline in state: (800) 345-7544; out of state: (302) 831-8851.

Cole Crops
Continue to sample for cabbage looper, diamondback larvae, beet armyworm, fall armyworm and Harlequin bug. Although the pyrethroids will provide control of Harlequin bugs they are not effective on beet armyworm or diamondback. Be sure to scout and select controls options based on the complex of insects present in the field.

Lima Beans
Continue to scout for stink bugs, lygus bugs and corn earworm. A treatment will be needed if you find one corn earworm larvae per 6 ft-of-row. With the increase in local corn earworm catches we are starting to see a significant increase in larval populations. We have also found soybean loopers in lima bean fields. Remember that they are a migratory pest, difficult to control and pyrethroid resistance has been documented in states to our south. The Belt SC, Besiege and Lannate labels list soybean looper or looper species control on the label. Be sure to check the label for rates, restrictions (including plant back/rotational crop restrictions) and days from last application to harvest.

Melons
Continue to scout all melons for aphids, cucumber beetles, and spider mites. We continue to see a significant increase in aphid populations. Treatments should be applied before populations explode and leaf curling occurs.

Peppers
At this time of year, corn borer, corn earworm, beet armyworm and fall armyworm are all potential problems in peppers. So be sure to select the material that will control the complex of insects present in the field. Be sure to check local moth catches in your area by calling the Crop Pest Hotline (in state: 800-345-7544; out of state: 302-831-8851) or our webpage at http://ag.udel.edu/extension/IPM/traps/latestblt.html. We continue to see aphid populations increasing, especially in fields where pyrethroids have been used on a weekly basis. Labeled materials are only effective if applied before populations explode.

Snap Beans
With the high trap catches, you will need to consider a treatment for both corn borer and corn earworm. You should also watch for beet armyworms and soybean loopers. Sprays are needed at the bud and pin stages on processing beans for worm control. With the diversity of worm pest that may be present in fields, be sure to scout fields and select materials that will control the complex of insects present. You will need to check our website for the most recent trap catches to help decide on the spray interval between the pin stage and harvest for processing snap beans (http://ag.udel.edu/extension/IPM/traps/latestblt.html and http://ag.udel.edu/extension/IPM/thresh/snapbeanecbthresh.html).

We have also observed an increase in whitefly populations. Be sure to check the Vegetable Crop Recommendations for materials labeled for whitefly control on snap beans (http://ag.udel.edu/extension/vegprogram/pdf/Beans.pdf).

Spinach
As the earliest planted spinach emerges from the ground, be sure to watch for webworms and beet armyworms. Both moths are active at this time and controls need to be applied when worms are small and before they have moved deep into the hearts of the plants. We are starting to see an increase in beet armyworm populations being found in all vegetable crops – so it will also be important to select a material that will provide beet armyworm control. As a reminder, the pyrethroids have not provided effective beet armyworm control in past years. Since webworm populations are generally heavier during hot, dry seasons, it is important to apply controls before any webbing occurs. Remember that both insects can produce webbing on the plants. Generally, at least 2 applications are needed to achieve control of webworms and beet armyworm.

Sweet Corn
With the continued high corn earworm trap catches, be sure that a spray is applied as soon as ear shanks are visible on plants. If fall armyworms are present in the whorl, you will need multiple whorl sprays for this insect before the ear shank spray to achieve effective control and to prevent larvae from dropping into the ear zone. Once fields are silking, you will need to check both blacklight and pheromone trap catches for silk spray schedules since the spray schedules can quickly change. Trap catches are generally updated on Tuesday and Friday mornings (http://ag.udel.edu/extension/IPM/traps/latestblt.html and http://ag.udel.edu/extension/IPM/thresh/silkspraythresh.html). You can also call the Crop Pest Hotline (in state: 800-345-7544; out of state: 302-831-8851). Be sure to check all labels for days to harvest and maximum amount allowed per acre.

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