Pickleworms! With a name like that, I had to learn more.
Pickleworms (Diaphania nitidalis) are serious pests of squash, cucumbers, melons, and other cucurbits. Mostly found in the southern United States, these pests are poised to expand their range. It can’t hurt to know what to watch for, right?
Pickleworm moths have triangular, iridescent brown wings with white edges and a yellow stripe. When light shines on these wings, they look metallic blue. Their legs and tail segment are white and the tail ends with a tuft of bristles called hairpencils. The wingspan is just a little more than one inch wide.
Caterpillars start out thin and white with black spots. As they grow and feed, they lose those spots and turn more of an opaque green. Spherical to flattened eggs are extremely small. They start out white but turn yellow in a day or so.
These moths are only active at night. Each adult female lays 300 to 400 tiny pickleworm eggs in small clusters on new buds, and flowers, and shoots. These tender plant tissues make the perfect meal for pickleworm caterpillars, who eat voraciously for two weeks, going through five instars. Then they curl themselves up in dead leaves where they pupate for 8 to 10 days and turn copper-colored. There can be up to four generations each year.
Pickleworms cannot handle extreme cold (yet), so winter weather often takes care of the problem for some regions. Pickleworms have several natural predators, such as soldier beetles and ground beetles, but these predators cannot eliminate the problem. Bacillus thuringiensis (Bt) can be used but is only marginally effective because of where these pests feed and hide. Pickleworm moths are not attracted to light and there are no pheromone traps available, so what’s a gardener to do?
Commercial growers facing pickleworm damage must resort to preventative sprays of insecticides. These sprays can also kill the honey bees needed to pollinate cucurbit crops. It’s a dilemma.
If pickleworms are a problem in your garden, you can buy Steinernema carpocapsae. These are parasitic nematodes that love to eat pickleworm larvae. Also, because these moths only fly at night and honeybees generally pollinate during the day, you can cover your cucurbits each evening with row covers and uncover them each morning.
I know it means more work, but those delicious cantaloupes and chocolate zucchini cake are worth protecting. And nobody wants wormy pickles.
You can grow a surprising amount of food in your own yard. Ask me how!
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