Handling a Scourge of Cucumber Beetles

Striped cucumber beetle on zucchini


Zucchini are notoriously prolific. I have grown to appreciate the abundance a single hill of plants can provide, and look forward to them as much as any garden vegetable. Unfortunately, I have had some bad luck over the years. Last time I tried to grow them, squash vine borers killed all the plants outright. This summer I am fighting another annoying, if less fatal, scourge: cucumber beetles.

Nibbled zucchini plantsWhere they came from in such numbers, I do not know. The adults hibernate in the soil and emerge in the spring. I have not seen any vegetable gardens in the immediate neighbourhood to account for this plague. However, Backyard Bounty, the local community-supported agriculture program, has fields not far away. I understand they use floating row covers to keep these pests away.

There are two species. The ones invading my garden are adult striped cucumber beetles. They will attack all members of the cucurbit family: cucumbers, melons, squash and pumpkins. They are ignoring the nearby acorn squash in favour of the more vigorous zucchini.

The Integrated Pest Management site at University of Connecticut recommends delaying seeding until the last week of June, protecting young plants with floating row covers, removing the covers in time for pollination, and rotating the crop to a distant field. None of this helps my already-infested plants. Unfortunately the adults are highly mobile and lay their eggs in the soil, guaranteeing another crop of cucumber beetles next spring.

The best remedial strategy for a small crop such as this is hand-picking. The bugs are fairly sensitive and agile. As soon as you lift a leaf they will try to make their escape using one of two manoeuvres: dropping or flying. If they fly they are virtually impossible to catch, although I read somewhere that a vacuum cleaner will do the trick.

They are easiest to pick if I go into the garden not long after sunrise when it is still in shade and the air is cool. Under those conditions the sluggish beetles usually drop. If they fall on the dirt they can be hard to catch, especially if they run under the zucchini branches or crawl into loose soil. Fortunately these zucchini were seeded directly through a hole in cardboard when I established this permaculture-style garden. Most of the cardboard remains intact, so the bugs can easily be pressed or pinched with a fingernail.

First zucchini fruitYesterday morning I found an even more efficient method. I peered under the leaves to find a group of beetles, placed one hand underneath, then touched the leaf. All the beetles would drop conveniently into my hand and I could squish them all at once.

I do not know how effective this will prove in the long run. Every morning I kill as many striped cucumber beetles as I can find, but next day a new army arrives from somewhere, attacking young and old leaves indiscriminately.

“Once feeding begins, beetles use an aggregation pheromone to call others to an acceptable food source,” says University of Connecticut. Great. I should try the vacuum cleaner.

I have seen (and squished) plenty of mating pairs. The larva will set up shop in the soil and begin feeding on the roots. They carry a bacterial wilt in their guts, which is bound to affect any seedlings next spring.

However, the plants seem to be holding their own so far. The growing tips remain unscathed. So do several embryonic fruit beginning to form. The largest one shown here is the size of my thumb. We may have a glut of zucchini after all. I hope so. I am grateful for any challenge that draws me into a more intimate, cooperative relationship with the plants that feed us.

3 thoughts on “Handling a Scourge of Cucumber Beetles

  1. I’m surprised that you didn’t have a problem with squash borer this year. I’ve found that the only way I can avoid it is through a combination of tin foil on the vine and late planting (July). How did you avoid svb this year?

    1. It was just luck, I guess. I had trouble with squash borer one year at a different location, but so far I haven’t had any here. The local CSA uses floating row covers to keep cucumber beetles off the vines until pollination time. Presumably that would work for borers, too.

  2. In my area, the season for squash borer and pollination probably overlaps. So there’d be no row covers when the borers are active. That’s why I plant later in the summer to disrupt the cycle. Row covers might work as well or even better than tin foil on the vines. It probably would help with striped cucumber beetle, too.

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