We have all fought the squash bug and lost the battle. This bug is the most serious enemy of our growing successful squash and pumpkin in the USA. The squash bug is only found from Canada to South America. Both adults and nymphs damage plants by sucking juices out of the leaves. The leaves then lose nutrients and water, become speckled, then yellow, then brown, and finally, the plant totally wilts. The squash bug also injects a toxin that expedites the plant's withering and death.
The squash bug has an ongoing life cycle. The adults we failed to eliminate last season will pass the winter under whatever shelter they can find - leaves, boards, stones, or debris. They will re-emerge as soon as the weather warms up (yes, just about the time those vulnerable baby squash plants are emerging). The adults mate soon after re-emerging and begin laying eggs in groups of a dozen or more. These eggs hatch in 10-14 days, and it only takes these new nymphs 4-6 weeks to reach maturity. So, all stages can be observed simultaneously throughout the season. How in the world do we control these multiplying monsters?
Let's just say that planning for control begins way before you plant the first seed. The very first line of defense includes several Systemic Strategies. Sanitation is a key measure. If adults over-winter under debris, get rid of all those hiding places. Next, plan to plant this year's crop where no squash or pumpkin grew last year; rotate your crops. While the bugs are quite capable of traveling, rotating and planting a little later will delay a bug population build-up. Companion planting is also worth a try, using repellent plants that deter the squash bug. They include catnip, tansy, radishes, nasturtiums, marigolds, bee balm and mint.
The second line of defense is Mechanical and Physical Strategies. The use of tightly secured barriers, such as floating row covers physically exclude the pests and prevent them from reaching the squash plants in large numbers. The covers can stay on until just before the female flowers appear. This is not labor intensive, and starts you out ahead of the war games. Another physical strategy is the use of kaolin clay products. Sprayed on the plants regularly at least every two weeks it forms a light-colored protective coating believed to deter the squash bug. Last season, I gave it a try. I sprayed half of my squash crop (both summer and winter) with kaolin and left the other half unsprayed. The results were measured daily by inspecting all leaves and counting (and removing) the number of squash bugs found in each area. While the method is definitely labor intensive (mixing and spraying every two weeks to cover new growth), I found 2/3 less squash bugs inhabiting the Kaolin covered plants. However, if I hadn't found and removed them by vigilant inspections, how much would they have multiplied?
The third line of defense is the Material Strategy. This includes biologicals and botanicals, such as sabodella, insecticide soaps and neem oil. Success with these is most effective on the nymphs. Once the adult bug emerges, this line of defense is not very effective.
Let me add my own suggestion to what all the experts have suggested: Vigilance. Checking under all the leaves each day will reward you with finding and removing the first line of adults, busily mating. Get rid of these, and their life's production cycle is interrupted,. With all these defense options to be tried, I wish you a great squash growing season!