Squash bugs and cucumber beetles (both spotted and striped) are in full swing this time of year on your cucurbit crops. We no longer have to worry about flowers developing into harvestable fruits, so it is a time that you need to think strategically about insect pest damage thresholds in relation to the decision to spray. Here are some suggestions that I can offer to help with the process:
Squash bugs are piercing-sucking pests that contain phytotoxins in their saliva, meaning that when they feed on the plant they can cause damage locally to those cells which results in cell death. What you will see is crumpling yellow and brown leaves. Sometimes they will feed directly on the developing fruits as well, leaving sunken discolored scars which can impact quality and create entry points for pathogen infection. If you are a home or market gardener, you will still be able to harvest your pumpkins if the damage is restricted to the vines but they will not look good. If you have a pumpkin patch that you open to the public for picking you likely want to keep those vines looking good and therefore would be more inclined to treat this pest. They are tough to kill with insecticides. Regardless of the product you use, timing is key. The small nymphs are easier to kill compared to the adults (Figure 1). They are often on the underside of the leaves so coverage is crucial and you should consider incorporating a sticker/spreader when making the application.
Figure 1. Squash bug nymphs.
Cucumber beetles, both spotted (Figure 2) and striped (Figure 3), will congregate in the beautiful large flowers that are present on pumpkin vines. They identify these flowers as a great site to meet and mingle for mating, hence the large aggregations that can be found. Their presence in the flowers is not damaging but they can feed on the fruits which will cause damage to the rind.
Figure 2. Spotted cucumber beetles
Figure 3. Striped cucumber beetles
If you are treating for cucumber beetles or squash bugs you need to be on alert for aphid outbreaks (Figure 4) that tend to result a few weeks later. This is because the chemicals used to knock down the beetle and squash bug pests also knock down the natural enemies that are keeping the aphids in check. To minimize these non-target effects careful selection of the active ingredient in the pesticide and timing of applications to maximize impact on the pest are your best practices. Below is a table of product active ingredient, IRAC code and pests they are labeled for. The list is not comprehensive. Always refer to the product label for specific crop and pest designations as well as mixing instructions. The label is the law.
Figure 4. Aphids on a pumpkin leaf
1IRAC is the insecticide resistance action code designated for each active ingredient based on the mode of action for the product. To maintain the efficacy of products you should rotate your applications among different IRAC groups.