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Friday, April 13, 2012

Potato Beetles

Adult potato beetle.

Ozarks Gardening
Copyright 2012, Jim Long

The Colorado potato beetle is a major pest throughout most of North America. It was first recognized as a pest in 1859 in potato fields in Colorado. The beetle had previously only grazed on buffalo bur, a distant potato relative. But when pioneers who moved West, began planting large fields of potatoes, the beetle adapted to the increased food supply. In the wild, the beetle had to travel up to a quarter mile to find buffalo bur plants, but with the new fields of one crop, the potato, it had only to hop from plant to plant. By the mid-1870s, the potato beetle had expanded its range (at the rate of 85 miles a year),  all the way to the East Coast.

The arrival of the potato beetle caused farmers and gardeners to search for ways to control the bug. An infestation of potato beetles could wipe out hundreds of acres of potatoes in ten days. There were all sorts of inventions, mixtures and unsuccessful attempts at finding a solution. It was only by accident that a gardener who was painting his house, and probably in frustration at the beetles, threw the remains of his house paint on beetle-infested plants. The bugs died! The ingredients in the paint included something called, “Paris green,” an inorganic compound that was commonly used in wall paper, artists’ paints and house paint. Soon chemical companies were providing Paris green to farmers, to be mix with water or dust directly on to the plants. Within three or four years the beetles developed immunity to the poison and lead arsenic was added. Both compounds are highly toxic to other insects including ones that are beneficial in the garden, as well as dangerous to birds, wildlife and most specifically, to the humans who dusted or sprayed the plants (and to those who ate the potatoes later).
Potato beetle larvae, eating leaves.

The cycle continues to this day, with chemical companies readjusting their formulas about every three years as the beetles continue to evolve resistance. One method that large-production potato growers use, is to use an assortment of different pesticides, week by week as the season goes along, trying to stay ahead of the beetles’ adaptations and resistance to the other formulas. Today we know how dangerous lead arsenic and French green compounds were, but many of the newer formulas may prove to be as dangerous.
Larvae cluster together and devour leaves, sections at a time.

Home gardeners can easily prevent potato beetles from being a problem. My method of early planting of potatoes in late January to early February, always misses the emergence of the beetle. By the time I’m digging my potatoes, the beetle is just hatching out and searching for potato plants. But gardeners who planted later, combined with the abnormally early season, will likely experience potato beetles. In small numbers they don’t pose a problem and it’s easy to pick the beetles off by hand and drop them into a bucket of soapy water. Spraying isn’t necessary. To prevent them becoming a pest, be sure to plant potatoes early in the year next season.

Happy gardening!

Monday, April 2, 2012

Tent Caterpillars Pitch Their Tents

Tent caterpillar tent.

Tent caterpillars have hatched and you’ll see them in saplings everywhere. My father hated these wooly pests and his method was to twist up a newspaper real tight, light it and set the tent-webs ablaze. The caterpillars would fall out, escaping the blaze.
Caterpillar eating a young leaf.

Tent caterpillars are only mildly harmful. They will devour the young leaves on the tree where they have pitched their tent, occasionally they’ll travel far enough to eat leaves on a neighboring small tree, but generally they stay on the tree with their tent.
The caterpillars live in a community and travel in groups to eat.

The the eggs which become the caterpillars were laid by a moth the previous fall, and their hatching is timed so they hatch just as the young, tender leaves are beginning to appear. Once the leaves get larger, the caterpillars have quit eating and gone dormant.

Tent caterpillars are social, going about their daily habits in groups. Appearing in early spring when the weather is much cooler, the tents are built in layers. When the night is cold, the caterpillars all move into a group in one of the inner chambers of the silk web where the temperature can remain as much as 50 degrees warmer than the outside air. They venture to the outer layers in the sunlight as the temperature warms, then during the day they travel in groups into the limbs for feeding. By evening, as the air cools, the caterpillars move back into the web.
Rain crow, or American cuckoo, is a natural predator of tent caterpillars.

The American cuckooo, also known as the rain crow, is the natural predator of tent caterpillars. Cuckoo populations have been on the decline over the past decades due to loss of woods habitat as land is cleared for more farms and house development. (To hear the sound of the American cuckoo, or rain crow, click here for an audio clip).
Bacillus, sold under the brand name of Thuriside.

Setting the web ablaze may be satisfying, but it can also damage the branches of the tree. A less harmful method is to the spray tree foliage with a Bt mix (Bacillus thurenginsis, the same organic control we use for cabbage loopers and other caterpillar pests). It’s non-toxic and not harmful to other insects. They have to eat and digest it for it to work, so spraying the leaves of the tree is helpful.

Tent caterpillars look messy but they don’t do a lot of serious damage. They prefer wild cherry, persimmon or fruit trees and seldom move far from the tree where their tent is located. While it may look like they are spreading to other trees, those are usually completely different colonies where other moths have laid their eggs.

Caterpillars grow fast and typically complete their development in seven to eight weeks. They leave their tree and move to the ground or under the eaves of buildings to spin their cocoons. About fourteen days later the moth emerges and begins laying eggs for the following spring.

Happy spring (or is that summer?)