Vegetable Crop Insect Scouting

David Owens, Extension Entomologist,

Cole Crops
In Georgetown, we have seen a bit of an uptick in both diamondback moth and cross striped worm activity recently. Other pests of note include green peach aphid, cabbage aphid, beet armyworm and corn earworm. Corn earworm only occasionally gets into cabbage, but when it does, it is extremely damaging to the growing point. Diamondback moth, corn earworm, and beet armyworm are all resistant to pyrethroids. Parasitic wasp activity, especially on diamondback moth and imported cabbageworm, can sometimes be extremely high which is another reason to avoid pyrethroids as much as possible. Thresholds during vegetative stages are 30% infested plants, but once cupping in cabbages begins, thresholds drop to 15% and then 5%. The exception to this is cross striped worms which have a lower threshold because they are voracious and feed in groups. Cross striped egg masses look like fish scales on the underside of leaves.

Continue regular worm applications. My untreated tomatoes in Georgetown are getting torn up severely by corn earworm. Spider mites seem to be making a bit of a resurgence with the hot weather, but if you are within a couple of weeks of terminating a planting, odds are you can outrun this late season uptick.

Legume Vegetables
Continue monitoring for corn earworm and soybean looper. Loopers can cause direct damage to lima bean pods, while in other legumes they tend to be defoliators only. Corn earworm moths have been very active over the last 3 weeks and worm damage is fairly easy to find in plots without protection. Remember, corn earworm control with pyrethroids alone is inconsistent at best. Also monitor for stink bug activity. If both pests need to be controlled in the same field, consider using bifenthrin in as a tank mix partner with a worm material, or using the premix product Elevest. If the only stink bugs present are green stink bugs, Besiege should do a good job at its higher rates.

Sweet Corn
With hot weather, consider a 2/3-day spray schedule. Moth activity, although a little bit less than last week, remains quite high. We just harvested a plot at Georgetown that was treated every 3 days and I have never seen so much damage following a Besiege/pyrethroid rotation. There are sites that blacklight traps indicate may benefit from being on a flat 2 day schedule (35 or more moths per week/ 5 per night).

Thursday trap counts are as follows:

Trap Location BLT – CEW Pheromone CEW
3 nights total catch
Dover 8 165
Harrington 5 81
Milford/Canterbury 14 97
Rising Sun 21 73
Wyoming 13 63
Bridgeville/Redden 4 31
Concord 10 51
Georgetown 5 55
Woodenhawk 6 79
Laurel 17 86

Be on the lookout for green peach aphid and beet armyworm. Both pests are resistant to pyrethroids. There are several good options for aphids, including products with worm activity such as cyantraniliprole, Torac, and the organophosphates, especially if tank mixed with a pyrethroid. However, such a combination is going to completely destroy natural enemies.

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