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Wasps on grapes

Bob Dluzen
Special to The Detroit News

The major task in the garden recently was starting our grape harvest.

We have two types of grapes; concord, which we use for juice to make jelly; and an unknown seedless table grape variety that has a thin skin and wonderful flavor.

The seedless variety usually ripens about two weeks before the concords, so those were the ones we picked last week.

I’ve been checking them nearly every day for the past two weeks to determine when they would be ready to harvest.

Changing color from green to pink was the first but by no means the only clue. The color change only told me it was time to keep a closer eye on them. It is their taste that is the determining factor. Even though they were red, they were still tart for some time after the color change.

Last week they finally developed their full sweetness.

The grapes are quite a bit smaller than the ones you find in the produce department but are much sweeter.

Since animals will eat grapes way before they’re palatable enough for people, I covered the vines with netting weeks ago to keep the birds and mammals from reaching them.The netting could not, however, stop an assortment of insects from enjoying the sweet crop. Among the insect visitors I encountered were sap beetles, corn rootworm beetles, earwigs, several species of flies, hornets, small spiders and yellow jackets.

Most of the insects showed up for the prodigious amounts of sugary juice inside the grapes. The spiders were there just hanging out and hunting insects.

Curiously, even though there are honey bee hives close by, I’ve never seen honey bees feeding on these grapes. There are plenty of reports out there of honey bees damaging grapes much like the other social insects.

Of all the insect visitors, the ones I was most wary of were the yellow jackets and hornets. In the summer, when they are building up the number of individuals in their nest, protein in the form of other insects is their preferred food. This time of year, they look for sources of carbohydrates to forage, and grapes are full of carbs.

Yellow jackets hollow out each grape leaving only the skin.

The other insects I saw were looking for carbs too, but they don’t sting. It’s very easy to get stung by a yellow jacket or hornet when dozens of them are buzzing around the grapes you are trying to pick.

The best way I’ve found to avoid stings is to harvest very early in the morning, preferably shortly after dawn at first light. At that time the yellow jackets and hornets are inactive and most are still back at their hive. The cool morning temperatures will keep them close to home, allowing you a window of opportunity to get your grapes harvested.

By 9 or 10 a.m., the sun usually warms them up to the point where they will begin flying and foraging for the day. That’s the time I stop and wait to begin again the next morning.

This solution only works if you have a small number of vines that can be harvested in a few days before they become over-ripe.

Some growers with acres of grapes also have to deal with those stinging insects during harvest. They are trying all kinds of solutions to alleviate their problem. But that is beyond the scope of this blog.

Night harvesting could be the solution they are looking for, since the yellow jackets would  be tucked away in their hives during the nighttime hours. There would be very few insects around to sting workers. That may prove to be a viable, low-tech solution for them.

Even if you don’t consider yourself a morning person, you will find it worthwhile to get up early. It will only be for a few mornings until the grapes are harvested.