Pickle Worms

Pickle worms are a yellow white caterpillar with black spots growing as large as 2cm. As they age they become green or brown with brown heads. 

Pickle worm larvae ( top left)-NC Cooperative Extension Service, Young Larvae (top right)-Clemson University, Older Larvae(bottom)-Clemson University

Description 
The adult is a nocturnal moth and are black with a yellowish white band on each wing. They have slender bodies with hairy scales on their abdomens. They are found in most parts of Southeastern United States and as far as Northern New York as well.

Adult moth-NC Cooperative Extension Service

Lifecycle
A pupae hibernates in rolled leaves and emerge in spring as an adult moth. Moths mate and lay eggs on hairy parts of the host plant. The eggs hatch and larvae feed on curcubits. There can be as many as 4 generations per year.

Damage on squash (top left), Larvae inside squash (top right)-photos NC Cooperative Extension Service, Damaged squash (bottom)-photo Ohio State University

Diet and Damage
Squash is the favourite of these pests but they also eat watermelon, cantaloupe and cucumbers. They bore small holes in stems, buds & fruit and eat the insides. Once they are inside the fruit feeding, fruit is seldom edible. These guys are a major problem when they are not controlled. Be sure to burn your dead crops that have been damaged by the larvae. This will kill any eggs that may have be laid. Mounds of greenish pile are found near infected fruit and that is the first sign you should treat your plants.

Control
1) Bt or Soap Sprays
At the first sign of the pest spray with Bt. Adults can be killed with insecticidal soap.
2) Plant Squash
Since squash is their favourite plant. Use a special spot for squash to attract them there. Control the pest on the plant and it will prevent an outbreak on your other veggies.
3) Rowcovers
Rowcovers can be used in late May and early June as this is when the moths first appear.
4) Keep your Garden Free of Debris
Adults lay their eggs in rolled leaves and garden debris so eliminating the waste from your immediate garden is a benefit.
5) Plan Your Crop Harvest
If you have this pest try to plant early varieties of cucumbers and squash since the problem with larva begins in late May early June. Rotate your crops every year.