Vegetable Crop Insect Scouting

David Owens, Extension Entomologist; owensd@udel.edu

Lima Beans
Be on the lookout for corn earworm and beet armyworm. Earworm thresholds are 1 larvae per 6 row-ft. Beet armyworm are defoliators, pre pod defoliation thresholds are 20% defoliation. Non-pyrethroid options for worm management include Radiant and Blackhawk (group 5 insecticides), Intrepid (group 18; should target small worms), Coragen (group 28), and Lannate (group 1A).

Watermelon
Beet armyworm were observed feeding on pigweed last week in a watermelon field. Beet armyworm prefer pigweed over just about anything else and will defoliate it first. Adult moths lay egg masses on pigweed leaves. When the eggs hatch, larvae will disperse by hanging on a silk thread until a passing breeze catches them. Other larvae will remain on the plant and defoliate it. If you see larvae on pigweed, there’s a chance that they are in the main crop as well. In watermelon, they will aggressively feed on the rinds. Beet armyworm are resistant to pyrethroids, including a worm specific product will aid in control. Examples include Coragen, Harvanta, Radiant, Intrepid, and Avaunt.

Sweet Corn
This year’s moth flight has begun earlier than usual. Insecticide vial testing is resuming, and results will be in next week’s edition of WCU. Fall armyworm are also quite active. A recent sweet corn test in Georgetown was harvested and a sizeable proportion of larvae in ears were fall armyworms. This species will also infest whorls. Large worms developing in whorls are fairly well protected by frass accumulation. Worms will be pushed out of whorls with the developing tassel, but these worms will then go to the side of the developing ear and bore in through the husk. If a pre-silk treatment is needed, Radiant and Avaunt (indoxacarb) are good options. Avaunt is not labeled for use during or after silking. Diamides will also do a good job but watch label restrictions on the amount of product that can be used. We have a limited number of applications we can make of diamide containing products, and this depends on the product and rate used.

Traps are checked on Mondays and Thursdays, trapping data is posted by the next morning on our website:

https://agdev.anr.udel.edu/trap/trap.php. Moth counts from Thursday are as follows:

Trap Location BLT – CEW Pheromone CEW
3 nights total catch
Dover 4 85
Harrington 1 21
Milford 7 123
Rising Sun 6 83
Wyoming 2 56
Bridgeville 2 84
Concord 5 62
Georgetown 6 106
Greenwood 1  
Laurel 7 87
Seaford 2 52
Trap Pond 7 4
Lewes 5 128

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