Cucurbits come in all shapes and sizes and are extremely versatile vegetables. Some of the common cucurbits include the various types of squash, such as yellow, acorn, spaghetti and zucchini squash, plus pumpkins, watermelons and cucumbers. Many of these are grown very easily in the home garden, with just a few plants producing more than a single family generally consumes. In north Florida, fall cucurbits should be planted from July through September. Most of the fall-harvested cucurbits should already be planted by now but if you haven’t had time to get anything out you can still put in some of the squash such as yellow squash or zucchini, yielding harvest in as little as 40 to 50 days.

Now, if you’ve already planted some, it’s likely you’ve started to see the pests moving in. While growing these in the spring can be done relatively pest-free, it’s not the same in the fall. Pest populations usually increase throughout the summer and peak during the fall until cooling temperatures knock them back. Melon aphids, squash bugs, silverleaf whiteflies, cucumber beetles and the “worms” … rindworms, pickleworms and melonworms; UF/IFAS has guide on these common pests at https://edis.ifas.ufl.edu/in168. While all of these pests can potentially cause significant damage, what I’ve been seeing the most out in the garden right now are the “worms.” No, these aren’t really worms though; they are moth larvae.

What we call rindworms are actually several species, most commonly the cabbage looper or the beet armyworm. These larvae often feed on the stems and foliage of cucurbits but they get their name from their tendency to feed on the surface. While this can significantly reduce the marketability of a harvest, in general the damage is not significant  and the harvest is still usable. The damage caused by the other two moth larvae is a bit harsher, however. Both pickleworm and the melonworm larvae will feed voraciously on cucurbits, squash in particular. In large agricultural production systems, these are considered minor pests that can be controlled relatively easily with pesticide applications, but in the home garden they can quickly devastate small plantings. In these sites, regular scouting is critical and should be done at least every few days. I’ll discuss a bit about the damage these two pests cause and then some simple scouting methods before we get into a few control options.

The pickleworm larvae can be best identified young; they go through five molts before they pupate into adults. The first through fourth instars (that’s what we call each stage as they molt and grow) are a nearly white to light green color with distinct rows of black spots along the length of their bodies, the final instar loses those dots. While they will attack a range of squash, the summer squash are their preferred hosts and are most heavily damaged. These larvae really like to feed on flower buds and fruits. They often move from flower to flower, destroying any chance of production. Fruit that does set is fed upon readily. On the exterior of fruit small entrance holes can be found with frass exuding, inside the larvae are feeding heavily. Sometimes the damaged portions of the fruit can be cut off but fungal and bacterial pathogens often take hold as well and the fruit begins to rot; when fruit is not present, pickleworms will occasionally feed within vines as well.

The melonworm (this is what I’ve been seeing the most of lately), also goes through a total of five instars; they can be identified by two white stripes on their backs following the length of their bodies. The melonworms have a different feeding strategy, while they can also be found causing similar damage as the pickleworms, they are more often found feeding on the foliage. Melonworms will feed heavily on the foliage, leaving only the veins leaving a type of damage called skeletonization.

To scout for these pests, look for initial signs of damage, paying particular attention to blossoms and young foliage. For the blossoms, inspect for entry holes and exuded frass; you can also lightly open the flowers and look for the larvae inside. On foliage, inspect the underside for signs of yellow egg clusters or larvae, they will often be found within loose webbing near leaf veins. As the adults are night-flying, they are much harder to scout for. The best way to manage these pests is to grow early in the spring — populations usually don’t start to move into north Florida until June — but now in the fall avoidance is not an option. If you find larvae in a small planting, quickly remove the damaged blossoms or manually squish them. You can often utilize row covers but be sure to remove them during the day so the flowers can be pollinated. Growing a variety of cultivars is another great method; not all cultivars are as attractive, so having the variety will ensure a few are less affected. Using squash or large flowered pumpkins can be used to pull moths away from cantaloupes and watermelons. At times you may consider pesticide applications; due to the pickleworm’s internal feeding behavior pesticides are not as effective (particularly those depending on residual activity) but the melonworm can be controlled well. Along with a few conventional pesticide choices, botanical neem oil and the biological insecticide Bacillus thuringiensis are very effective as well.

As always, scout regularly for best results. Have more horticulture questions? Feel free to reach out to the Master Gardener Volunteers at your local county extension office. Contact information for your county can be found at https://sfyl.ifas.ufl.edu/find-your-local-office/.

Chris Kerr is an environmental horticulture agent with the Duval County Extension Service and the University of Florida/IFAS.