We call them diamondback moths because they have a row of diamond shapes on their back like the infamous rattlesnake. They don’t have a venomous bite, but collectively, their caterpillar stage will take a big bite out of your greens (brassica) crop.
They are very small, green, blending into the leaf veins, and you may totally miss them until your greens are riddled with holes. They are very difficult to control and may be resistant to some of the products many farmers use for caterpillar control.
This spring, we are having an awful infestation of early-season diamondback caterpillar on brassicas like collards and cabbage, most likely due to the overwintering on brassicas like radish in cover crops. When these cover crops are terminated for summer cropping, these insects, and other insects like yellow-margined beetles, invade vegetable production fields. Thank goodness that yellow-margined beetles like sandy soils and are not typically a problem in the Pee Dee.
Don’t get me wrong. I appreciate the use of cover crops. They have improved row-crop production tremendously, keep down erosion, and improve the soil, but they should be selected properly, and sometimes they act as homes for problems in vegetable crops.
Also, cover crops containing brassicas should not be used in vegetable production fields because they increase diseases like bacterial soft rot and sclerotinia, which are tremendous problems in all types of vegetable crops.
I believe bacterial soft rot is one of the few diseases for which no chemical control is listed in our Southeast Vegetable Crop Handbook. In fact, last week I asked a plant pathologist how to control it and he said, “Disk them up.” Disking them up, rotation and bottom plowing are forms of sanitation and are excellent ways to control bacterial soft rot, but they cannot be employed in the middle of the crop season. Sclerotinia is what I call “a white mold on steroids” which can totally devour many types of vegetable crops. I call sclerotinia a disease “that keeps on giving” because it produces a survival structure that looks like a black bean that can stay in the soil, destroy healthy crops and be a real pain in the butt for many years.
An ag supplier just asked me to give him a simple cookbook recipe for growing vegetables like the one we have for peanuts. Vegetables are not row crops, folks; they are very hard, complex and intensive to grow, but our “Southeast Vegetable Crop Handbook” is the best we have. I will be getting some 2021 handbooks in a few days to give out to farmers.