I have noticed holes in the leaves of my petunia plants and other flowers planted recently. A friend said it was probably snails or slugs. I have also noticed holes in the roots of my early planted radishes. How can I control these pests?
Yes, the culprit chewing leaves of your new flowers is probably snails or slugs. Root maggots cause the damage in radishes and other root vegetables.
Snails and slugs feed on the leaves of all flowers and vegetables. They are probably feeding on your perennial flowers also, but the damage is less noticeable because they are larger plants. Slugs and snails feed at night and hide in the soil in the daytime.
Two types of baits are available. Baits containing metaldehyde are the cheapest. Baits with iron phosphate are a little more expensive but are safe for use around pets and wildlife. Deadline is another effective control which poisons slugs if they cross a line of pesticide. Saucers of beer placed around plants have also proven somewhat effective. The slugs are attracted to the beer, they crawl into the saucers and drown.
Root maggots are the larvae of flies that lay their eggs on the soil around root vegetables such as radish, turnip and beet. Adult flies start laying eggs as soon as new seedlings or transplants appear. They are best controlled by placing pesticides on the ground where seeds or transplants are planted. Granular Sevin has been recommended for years, but I prefer two organic materials. Diatomaceous earth is a naturally occurring material which is very effective. Spinosad is a newer organic insecticide which is effective against all kinds of chewing insects.
A little later in the spring, cabbage family vegetables including broccoli, cauliflower and Brussels sprouts will be attacked by cabbage worms which feed on the leaves and flower buds. You may notice small white moths flying from plant to plant laying their eggs. In addition to Spinosad, another organic insecticide sold as Thluricide or Dipel was developed specifically for this pest.
Both root maggots and cabbage worms can be prevented by covering plants with insect barrier row covers. They are a thinner version of row covers used to stimulate faster growth of heat-loving vegetables like tomatoes. They prevent the maggot flies and cabbage moths from reaching the plants with their eggs.
