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What’s bugging your plants?

The squash vine borer moth lays eggs at the base of plants in the squash family. Photo courtesy John Obermeyer/Purdue University

Sometimes veggies that you’ve grown for several years don’t do as well as you expect. A reader wants to know why her squash, melon and peppers are not doing well, even though they were planted as always. “The fruit begins to set and then plants die,” wrote C.K.B. of Mooresville.

Here are some things to consider when dealing with any vegetable or annual plant that doesn’t seem to be doing well.

  • How many years have the same plants been planted in the same place? Rotate vegetable crops and annuals annually, or at least every two years. Planting the same thing in the same place year after year can lead to a build up of insects or diseases that affect susceptible plants.
  • If the fruit starts to dry up or turn brown or black on the blossom end, it’s likely blossom end rot. This is a condition (not a disease or insect), caused by irregular watering. We’ve had a lot of rain, which could contribute to this problem.
  • If the flowers form but the fruit does not, the plants are not being pollinated. A lack of bees and other pollinators, weather that’s too hot or too wet and other environmental factors are likely causes. Hand pollination, using a paint brush to move pollen from male squash and melon flowers to female flowers, is an option.
  • Squash vine borer could be a culprit on the squash and melon. This larva develops in the stems, causing them to die. Examine stems close to the base of the plant. The adult looks a bit like a wasp and it flies around during the day, making detection a bit easier. It lays eggs at the base of plants in the squash family. The eggs hatch and the borers move into the stems.

The squash vine borer burrows into the plant, disrupting the flow of water and other nutrients. Photo courtesy Cliff Sadof/Purdue University

Once the borer is in the stem, an insecticide is ineffective. The best control is to slit the stem lengthwise and dig out the insect, which looks like a whitish-gray grub. Preventative insecticides can be used, such as spinosad, an organic product. These are usually applied on the stems, especially at the base of the plant. Always read and follow the label directions.

Holey leaves

A lot of people think slugs cause the holes in the leaves of sweet potato vines (Ipomoea batatas) and morning glories (I. purpurea). Instead, the damage is likely the work of golden tortoise beetle, also called gold bug (Charidotella sexpunctata). Whenever I hear that, I think of Richard Scarry’s Cars and Trucks and Things that Go, which I loved reading with my son, learning the names of objects and  hunting for that elusive gold bug.

This beetle is about ¼ inch long. Usually, no treatment is needed because there are many predatory insects that will do the job for us, including parasitic (nonstinging) wasps, shield bugs, damsel bugs and others. This is a case of allowing Mother Nature to do her job.

A beetle, not slugs or snails, is responsible for the holes in sweet potato vines. (C) Jo Ellen Meyers Sharp

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