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Pests

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Nematodes
Steve Gschmeissner/Science Source courtesy NPR

An image, from a scanning electron micrograph, of Heterorhabditis megidis nematode worms (colored blue). These parasitic worms harbor a bacteria that repels mosquitoes.

Pests. Is there a gardener on the planet who hasn’t had to deal with pests? This past year, both of Cooperative Extension’s demonstration and experimental sites were plagued with rabbits. Sweet little cotton-tailed bunnies, who can devastate a planting in short order. I used to think bunnies were cute, but there is nothing like seeing your experiments chewed up to change your mind. Also your garden. Some people pointed out that the damage might be from rats, but I cannot deal with that thought.

Anyway, pests can be four-legged bunnies, or six-legged insects. With insects, though, most of the damage is usually done by the hungry offspring. With grapes, there’s a leaf skeletonizer, which strips a leaf of its green tissue, until only the veins remain. You never see just one; they march across the leaf in military columns. A skeletonizer’s the brightly colored caterpillar of a drab grey moth about the size of a nickel.

If you grow tomatoes or peppers, you’ve likely seen a large green creature with a horn at one end – giving it the name “hornworm”. When I first saw a picture of a hornworm, I was convinced it was photoshopped. How could a caterpillar be over three inches long with a half-inch diameter?  However, when I saw the devastation they could wreak on a plant overnight, I understood. It takes a lot of food to get so big. When they develop into adults, they become large, attractive sphinx moths. Unfortunately, these moths are pollinators, so they’re not all bad.

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Among the best things to control any of these caterpillars is Bt, a bacterial toxin that doesn’t hurt us. Commercial products are available in nurseries and home stores.

We might love to see and hear birds, but they’re pests if you have the silly desire to harvest fruit from your fruit trees. Many birds have a tendency to poke holes in fruit as they test for ripeness. I’ve given up on grapes after the year when I saw a mockingbird ignoring the bird netting I’d put up, and devouring my beautiful Thompson seedless. Aside from bird netting, you might try hanging shiny objects in the trees. I use old CDs, so my garden looks oddly like Christmas. That’s moderately effective.

All these things are visible to the unaided eye, so at least it’s possible to pick them off or chase them away. Some things aren’t so simple, and this past year, we had big problems with a soil borne villain.

Nematodes are microscopic round worms. Actually, they’re not all microscopic; the one that attacks whales grows up to 10 feet long. I’m so glad I don’t have to deal with that.  There are so many nematodes in soil that a half cup might contain a thousand nematodes. Most of them, thank goodness, are only around to eat the dead stuff, as well as bacteria and fungi.

Not all nematodes cause problems, but those that do cause serious problems indeed. The one we most worry about is the infamous “Root Knot Nematode”. The name comes from the appearance of the roots – when you pull an infested plant out of the soil, the root system looks clubbed and swollen, as if one took all the roots and tied them together.

Sadly, tomatoes are among their favorite foods, although they will attack almost anything – even trees.

Plants that’ve been infected’ll show any number of symptoms, like wilting as the day gets warmer, or just not growing well with no obvious explanation. If you take it out of the planting bed, you’ll see those mangled roots.

The best way to deal with these scoundrels is first, look for plants that say “nematode resistant”. If your garden’s already infected, you can try growing French marigolds, solarizing the beds, or finding a product that claims to kill them. Adding compost to the soil may also help, since compost may introduce critters that can control them. Besides, compost is always a good idea.  

 

For KNPR’s Desert Bloom, this is Dr. Angela O’Callaghan of the University of Nevada Cooperative Extension.

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