Meet The Pickleworm

Cucumbers and other cucurbits beware—this munchy pest could take out your crop.

by Kevin Fogle
PHOTO: Forest Starr and Kim Starr

Who has been munching on your cucurbits? Well, there are certainly many possible suspects, but if you live in the Gulf Coast states or along the East Coast between Connecticut and Florida, the culprit just might be pickleworms.

What a great common name. The pickleworm gets its name from one of its favored food sources: the cucumber. Although cucumbers are a major food source for pickleworms, a whole host of other cucurbits entice this hungry caterpillar. Summer squash, cantaloupe, pumpkin, butternut squash, turban squash and, to a lesser degree, watermelon are all delicious snacks for this pest, which tunnels into the crops’ flowers and fruits. Severe infestation can destroy entire crops, but even lesser populations can ruin the edibility of fruits (through fruit drop and fruit deformation), resulting in lower yields.

Try To Spot The Pickleworm

Gardeners are unlikely to ever encounter the adult moths, which are only active at night. They’re quite small with a wingspan that only reaches about 1¼ inches wide. The upper sides of the wings are distinctively marked with a brown border surrounding a yellowish area in the center of that has some attractive iridescence. The rear of the pickleworm moth abdomen features an unusually large broom-like tuft of hairs that can help identify this species. The pickleworm only overwinters in southern tip of Florida and in southernmost Texas. The wide feeding range of this species is due to migrations of the adult moths who travel north during warm months, laying eggs near suitable food sources, which include your cucumbers.

Eggs are laid near the flowers or fruit of host plants and emerge in a few days. The first instar of the pickleworm larva tends to feed on the exterior of flowers or fruit before quickly tunneling into the fruit or blossom. It will change colors as it develops and is not commonly spotted because it feeds inside the blossom or fruit. A mature larva reaches only about 1/2 inch long and has a brown head and greenish-yellow body. Earlier instars are often lighter-colored with dark spots that disappear as the caterpillar reaches maturity.

Stop The Pickleworm

Because the pickleworm is an internal feeding caterpillar, it is challenging to use traditional organic pest solutions that contain Bt (Bacillus thuringiensis). Instead, the best solution to prevent damage by pickleworms is to plan ahead by planting your squash and cucumbers as early as feasible in your region so that your first harvest is completed or on-going when the first pickleworms emerge or arrive in your region. This is especially important for gardens found outside of the overwintering range of this insect. Also, many cucurbits are somewhat resistant to pickleworms, so if this pest is a regular issue in your region, focus on planting those species and varieties. Talk to your local extension agent about pickleworm-resistant cucurbits that are successful in your area.

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