Foliar sprays of chlorothalonil can be used to control this problem. Begin applications at the first sign of the disease and repeat in 10 to 14 days. Q. Some of my young broccoli plants are stunted, weak-looking and covered by small, green bugs. A. Aphids, or plant lice, are sometimes a real problem on broccoli and other members of the cabbage family. They are easy to control with insecticides such as malathion or diazinon.
Early control is necessary because aphids reproduce rapidly.
These are probably loopers, imported cabbage worms, or perhaps broccoli head worms. Regardless of the type worm, they can be controlled with a product containing Bacillus thuringiensis . This is a biological-type insecticide which controls most types of worms. This material must be eaten by the worm and activated by the gut of the worm which is alkaline. This takes 2 to 3 days which means worms are not killed immediately.