Squash pollinators versus cucumber beetle spraying

[simy1]

This year for the first time I have been using Rotenone regularly in my garden. I am fairly happy with the results. The brassica are unblemished by cabbageworms, and huge. I sprayed the base of the zucchini, and so far there is no sign of vine borers. Both used to be a regular occurrence in the past.

But all my cucumbers (4) and all the winter quash (3) show signs of bacterial wilt. Soon zucchini, melons and watermelons may follow. I sprayed them irregularly, for fear of killing pollinators. Indeed some of the melons have only one fruit, and the zucchini and string beans have gone through a dry period, so I may have done something bad. Last week I used a paintbrush to pollinate things by hand. I inspected the cuke flowers two days ago and I found a cucumber beetle (striped) every second flower.

The cukes are fairly advanced in the disease but they have all produced their share. The winter squash are still going through the all male flowers period, barely show signs, but I suspect I will lose the crop (as well as 80 sqft of garden use, they are huge plants). No signs yet in the other plants. I wonder how others manage cuke beetles, specially during blooming.

[TQ]

Rotenone provides good insect control but will do nothing for leaf diseases.

Next year, rotate your crops, plant resistant varieties, mulch to inhibit splashing rain water from spreading soil-borne diseases, and maintain a weekly fungicide spray routine.

[Pat Kiewicz]

I finally gave up on being virtuous and a started spraying my peppers with malathion (to combat pepper maggots). I also hit the bases of my squash plants with it, too. Not so much sign of squash borers.

The recent stretches of hot, humid weather (with the very warm nights) didn't help...

Downy mildew is the big worry for cucurbits in Michigan this summer:

was even mentioned in the Detroit Free Press.)

Winter squash usually tolerates bacterial wilt pretty well. It's cucumbers and melons that inevitably die from it.

I gave up on growing melons and only grow cukes that don't require pollination in a large screened-in box. I just was not willing to spray as often with as potent an insecticide as would be required. Probably the safest thing (bee-wise) would be a synthetic pyrethrin sprayed in the late evening or *at night* but you pretty much have to hit the beetles with it directly. Even one beetle feeding on a plant can infect it with wilt.

The most often recommended and potent pyrethroid formulations are restricted use pesticides, brand names Ambush and Pounce. Commercial growers also use Admire (active ingredient, Imidacloprid) as a soil drench. It's a systemic insecticide, chemically kin to nicotine.

I used to use a product called Adios which is carbaryl encapsulated with cucurbitacin, which acts as a bait. The beetles would feed on the grains of Adios and die. I don't know what happened to this product but since I haven't able to get it any more, I wasn't able to keep the beetles from spreading bacterial wilt and so gave up growing melons.

[simy1]

I doubt this will help. I don't know of cukes resistant to bacterial wilt, I rotate the squash, I mulch heavily, and bacteria are not fungi. It is bacterial wilt.

[simy1]

Thanks for your reply Pat. Spraying the base of zucchini is probably an efficient use of pesticides. Knowing the life cycle of borers,I really only had to do it three times, once because of heavy rain. And it is a minimal amount.

By this you mean the pollination stops under these conditions. But the lull was before the 90+ weather. It must have been me. I will spray at dusk from now on.

I have not seen it. My summer garden is sandy, dry, and windswept. Manured, mulched, and dripped it produces, but not a good place for any type mildew.

Interestingly, the cukes are keeling over but the melons (first year of growing) are unaffected. One early variety, Passport, will clearly be able to finish a few melons even if it starts wilting tomorrow. I wonder if it takes a while for the beetles to find a new vegetable.

So even for you they can't be beat without a major effort. I will google it and see what transpires.

[simy1]

I looked up some sites and the following seemed the best to me

attra.ncat.org/attra-pub/cucumberbeetle.html

It turns out that I have been reasonably lucky. Right now I am growing the green melon Passport, which is early, and is also listed as #8 out of ten in beetle attraction. I have always grown Gold Rush zucchini, because they are substantially earlier than regular zucchini, and because they are yellow and easy to spot in the jungle. Gold Rush, too, scores at the bottom as far as zucchini are concerned. I have grown some winter squash, which are mostly unattractive. The site lists watermelon as not sensistive to bacterial wilt.

I have to wonder if all these years the cukes have not acted as trap crops for me and spared me further damage. In fact, by planting year after year the ultra early County Fair (whose flavor I prefer over three other varieties I have tried), I may have had a good combination of trapping by having a early plant up, and decent crops in early July before the disease prevailed (and incidentally before other non-greens crops are ready).

Clearly from now on I will select only cucurbita that score well on the attraction list. The site does list Adios.