Vegetable Crop Insects – July 6, 2012

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

Lima Beans
Be sure to scout fields for leafhoppers, spider mites as well as plant bugs and stink bugs. As soon as pin pods are present, be sure to watch carefully for plant bug and stinkbug adults and nymphs. As a general guideline, treatment should be considered if you find 15 adults and/or nymphs per 50 sweeps. The higher rates of labeled products will be needed if stinkbugs are the predominant insect present.

Melons
Continue to scout all melons for aphids, cucumber beetles, and spider mites. The first beet armyworm (BAW) larvae have been detected in melon fields. As a reminder, both cucumber beetles and beet armyworm feed on rinds. Since BAW are difficult to control, be sure to select a material that is labeled for beet armyworm (BAW) on melons such as Coragen, Avaunt, Intrepid, Radiant, Synapse/Belt or Vetica. The pyrethroids will not provide effective BAW control.

Peppers
As soon as the first flowers can be found, be sure to consider a corn borer treatment. Depending on local corn borer trap catches, sprays should be applied on a 7 to 10-day schedule once pepper fruit is ¼ – ½ inch in diameter. Be sure to check local moth catches in your area by calling the Crop Pest Hotline (instate: 800-345-7544; out of state: 302-831-8851) or visiting our website at: http://ag.udel.edu/extension/IPM/traps/latestblt.html. You will also need to consider a treatment for pepper maggot. Beet armyworm larvae can be found in fields and can quickly defoliate plants. Be sure to use a material that provides beet armyworm control — the pyrethroids will not effectively control this insect.

Potatoes
Continue to scout fields for Colorado potato beetle (CPB), aphids and leafhoppers. Controls will be needed for green peach aphids if you find 2 aphids per leaf during bloom and 4 aphids per leaf post bloom. This threshold increases to 10 per leaf at 2 weeks from vine death/kill. If melon aphids are found, the threshold should be reduced by half.

Snap Beans
Continue to scout for leafhopper and thrips activity in seedling stage beans. We are seeing a significant increase in leafhopper activity in seedling stage beans. Sprays will be needed for corn borer at the bud and pin stages on processing beans. As earworm trap catches increase, an earworm spray will also be needed at the pin stage. Additional sprays may be needed after the pin spray on processing beans. Since trap catches can change quickly, be sure to check our website for the most recent trap catches and information on how to use this information to make a treatment decision in processing snap beans after bloom (http://ag.udel.edu/extension/IPM/traps/latestblt.html and http://ag.udel.edu/extension/IPM/thresh/snapbeanecbthresh.html). Once pins are present on fresh market snap beans and corn borer trap catches are above 2 per night, a 7-10 day schedule should be maintained for corn borer control.

Sweet Corn
Continue to sample all fields from the whorl through pre-tassel stage for corn borers, corn earworms and fall armyworm. We have started to see an increase in fall armyworm damage in whorl stage corn. A treatment should be considered when 12-15% of the plants are infested. Since fall armyworm feeds deep in the whorls, sprays should be directed into the whorls and multiple applications are often needed to achieve control. The first silk sprays will be needed for earworm as soon as ear shanks are visible. Be sure 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).

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