Large Holes in A Wilting Cucumber Vine
Pickleworms and melon fly larvae have similar characteristics and both go after the cucurbits. The melon flies stick the thin skins of the young fruit and deposit their eggs and the moths lay their eggs on the plants. I've found both types of larvae inside the fruit but the pickle worms also tunnel into the vines.
The section of cucumber vine above was wilting and when I looked closer I saw the holes where the larvae had tunneled inside.
A Pickleworm Inside the Vine
I broke this vine horizontally at the holes and tore it open vertically and found the pickleworm munching it's way down inside the vine. The small green pickleworm was about 3/4 inch long.
A Better Look at the Pickleworm
The green larvae were the most prevalent but I've found larvae that were translucent white with black spots and larvae that were reddish brown. With the exception of the coloration, the larvae had very similar characteristics.
There may be several moths responsible for these terrible pests. I've read that they have a preference for summer squash. In my garden, they seem to do the most damage to the zucchini - they actually massacre the blossoming portion of the plant.
Pickleworm Damage to a Young Squash
(A pickleworm is boring another hole in the blossom end)
Even though the squash above was covered by a paper bag, a pickleworm crawled down the vine and tunneled holes into the fruit.
Melon flies and pickleworms are a problem in Kihei predominately during the spring and summer. From April through September I put white paper lunch bags around the pollinated female cucurbits to protect the fruit. White and brown paper lunch bags are avalable at WalMart.
Bt and spinosad are recommended products to use for pickleworms in an organic garden. I haven't tried either product and I'm not convinced that Bt is truly safe.
Following is a link with additional information and product recommendations for pickleworms. http://www.gardeners.com/on/demandware.store/Sites-Gardeners-Site/default/Page-Show?cid=5293&utm_term=PDD
If the pickleworms become a serious problem, parthenocarpic varieties of cucumbers and zucchini can be grown under light row covers. These are F1 hybrid cucumber seeds that produce only female flowers and don't require pollination. These types of seeds are commonly grown in greenhouses. Johnny's Select Seeds offers a variety of parthenocarpic cucumber and zucchini seeds. http://www.johnnyseeds.com/