Rusty Patched Bumblebee

Be careful using insecticides in your garden. Even the organically approved insecticides can kill honeybees.

Every year there is more and more concern for bees, this year in Minnesota, the Rusty Patch Bumblebee! This is a good thing!

With that in mind, a quick primer on insecticides: to dust or not to dust — that is the question. Considerations are: how soon will I want to eat from this dusted plant, and am I also killing beneficial insects like ladybugs and bees?

Even most of the organically approved insecticides will kill honeybees like Sabadilla and Pyrethrins. Before you spray or dust, you need to determine if you actually have an insect issue.

Have you identified who they are? Identification is critical to getting the right product for the job. Most of our insect trouble makers can only be treated at one stage of their life. That is why repeated applications are often necessary.

For example, while you are dusting the adult Cucumber Beetle, the eggs they just laid in the soil will soon be hatching and later becoming adults – more dust. Horticultural oils and soaps kill insects by smothering through a direct contact spray. There are several ways to minimize the damage from insecticides to beneficial insects.

It is possible to gently fan off bees – usually only a few on a plant, and then spray your group of slower moving aphids for instance. Even DE (diatomaceous earth) a mineral-bearing insecticide can desiccate good insects.

Also, spray towards evening, when bees are usually not present. Many of the problem insects are very mobile, flitting from plant to plant. Try dusting only one third of your bean or melon plants instead of all of them, eventually the dusted plants will be visited by the target insect. Avoid dusting near the flowers of plants like squash for instance, where the bees will be visiting. Most of the insect damage done to squash plants is on the leaves or the main stem by the Squash Vine Borer.

One of my tricks is to heavily dust a potted, sacrificial vine plant like a squash. Then you can move it throughout the garden, changing its location daily. If you have a small garden, no need to move it around.

The Mexican Bean Beetle is usually one of the first garden pests to show itself. The adults feast on bean plants for two weeks before laying their eggs, so get them before they lay eggs!

How about crop rotation to minimize insect issues?

If you have a garden that is under 50-by-50 ft., rotating really doesn’t help. Many of our problem insects fly so moving a plant 50 feet doesn’t deter them. Rotating crops out of production for a year or two would be more effective.

For instance, the Colorado Potato Beetle can be devastating to potato plants. Plants from the same family (nightshade) are also destroyed by the CPB — tomatoes and peppers. Avoid these plants for a year or more and the problem insects may move on.

Now, if your neighbor close by has the same issue, try to get on a rotating schedule together. Squash plants, pumpkins and zucchini can all be attacked by the Squash Vine Borer. If this guy is a problem again, avoid growing them for a year. The SVB is a native insect troublemaker so they may find you again, but growing every other year, your troubles may be reduced.

The single piece of advice to limit insect issues (for many of you I know this is an often-repeated statement) stop tilling in your garden plant debris or composting on site!

Rake off the dead, diseased infested, insect laden plants and bring to your local compost site. There, piles are turned and plants break down and insects die and proper temps are achieved to kill off some of the disease pathogens.

Our first outdoor market will be at the Best Buy parking lot on Adams Street May 2, 8 a.m. to noon and does plan to open on time! You can also follow the Mankato Farmer’s Market information on our Facebook page.

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