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    Save the Date: Perennial Plant Society’s 30th Plant Sale is April 4, 2020, 9 a.m. – 1 p.m. at the new Expo 3 Building at The Fairgrounds Nashville. Here’s where you can find the newest varieties of perennials, shrubs, vines and annuals from local growers, along with long-time, never-fail favorites, ready for spring planting. Learn more at the PPS website.

     

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Stinkbugs, harlequin bugs plague late-summer gardens

There are flat, brightly colored bugs all over my cabbage and broccoli plants right now. What are they? Are they harmful? How can I get rid of them?
Harlequin bug copy

What you see plaguing your plants are, no doubt, harlequin bugs, and yes, they are harmful to your plants in the brassica family – broccoli, greens, cabbage turnips and kale. This time of year, the bugs you see are probably the adults. They use piercing mouth parts to extract the juices from all parts of the plants, and heavy infestations can cause severe damage – you may see discolored spots on the plants. The leaves of young plants may wilt and die, and mature plants will become stunted.

Getting rid of them can be a challenge. Toxic Free NC, A website devoted to non-toxic solutions to pest problems, suggests removing them by hand if there are only a few (drop them into a bucket of soapy water), or if there are large numbers and you are willing to sacrifice the plants they have damaged, trap them in large garbage bags, seal the bags and let them bake in the sun for a few days.

It’s always good to encourage the natural predators of damaging insects to visit the garden. Praying mantises eat harlequin bugs and other stinkbugs, so if you see them around, don’t shoo them off. There are parasitic flies and wasps that are among stinkbugs’ natural predators, and birds, spiders and toads also enjoy them as a food source.

As a last resort, Toxic Free NC suggests insecticides that are approved for organic farms, such as rotenone, pyrethrin, Neem oil and insecticidal soap. Note that these products can be harmful, so be sure to follow label directions and use as little as possible. These insecticides can also kill the bugs you want to keep, so spray only in the morning or late evening when those insects may be less active. Insecticides are most effective on the pests in the younger larval or nymph stages. The adult bugs are resistant to sprays.

To prevent the bugs from finding your plants in the first place, Toxic Free NC suggests using lightweight floating row covers over your brassica crops, making sure the edges are weighted so the bugs can’t get to the plants. It also helps to control weeds in the garden, as stinkbugs are attracted by weedy areas in or near the garden, they advise.

A sticky hackberry situation

QUESTION: We have a question regarding one of our large hackberry trees. It’s covered with little white flying bugs and the leaves have a sticky residue. What causes this and is there something that we can do about it?

Asian wooly hackberry aphids are a nuisance, but won't harm the trees.

Asian wooly hackberry aphids are a nuisance, but won’t harm the trees.

The bugs you are seeing are called Asian wooly hackberry aphids, and they seem to make an appearance about this time every year. They feed exclusively on hackberry trees, and like all aphids, they feed by piercing the leaves and extracting the juice. The sticky residue is what they excrete after feeding on the leaves, a substance called honeydew. Another byproduct you may notice is a black mold that grows on the honeydew, which is called sooty mold.The aphids apparently do not do enough damage to harm the tree, they are just a nuisance, mostly in late summer and early fall when their population grows due to the many generations that have been produced. If it’s a nuisance you can’t tolerate for some reason, there is a systemic insecticide product that is said to be effective in controlling aphids, but it would not do anything to solve this year’s population. There are several brands available, but the main ingredient is a chemical called imidacloprid, and it should be applied to the ground around the tree in early spring, where it will be taken up via the tree’s vascular system into the leaves.

Not much, then, can be done about this year’s population of hackberry aphids. Hose off the cars, the deck, the lawn furniture and anything under the trees that are sticky from the honeydew, and take comfort in the knowledge that they are a temporary annoyance, and will be gone in a few weeks.