Wherever potatoes are grown, the Colorado Potato Beetle is sure to appear. Many gardeners are asking for advice on how to control the CPB. Remember the YARA-GRCG Garden Guidelines require all gardeners to use environmentally friendly methods of weed and pest control so please be prepared to provide information about products used to avoid any misunderstandings or penalties.

Colorado potato beetle females are very prolific; they can lay as many as 800 eggs. The eggs are yellow to orange, and are about 1.5 mm long. They are usually deposited in batches of about 30 on the underside of host leaves. Development of all life stages depends on temperature. After 4–15 days, the eggs hatch into reddish-brown larvae with humped backs and two rows of dark brown spots on either side. They feed on the leaves. Larvae progress through four distinct growth stages (instars). First instars are about 1.5 mm long; the fourth is about 8 mm long. The larvae in the accompanying picture are third instars. The first through third instars each last about 2–3 days; the fourth, 4–7 days. Upon reaching full size, each fourth instar spends an additional several days as a non-feeding prepupa, which can be recognized by its inactivity and lighter coloration. The prepupae drop to the soil and burrow to a depth of several inches, then pupate. Depending on temperature, light-regime and host quality, the adults may emerge in a few weeks to continue the life cycle, or enter diapause and delay emergence until spring.

Preferred Control Method

Grow Regina’s preferred method of CPB control is to hand pick the beetles and crush the eggs on the leaf. In fact, it is probably the most efficient method of controlling the CPB. If you are sweamish about touching the bugs, wear a pair of gloves or just remove the whole leaf. We suggest carrying a bottle with a little javex or soapy water to store the bugs in while you pick. Although potato is its preferred food source, this beetle will eat almost anything available, especially tomato, eggplant, and peppers. It is important to check all your plants daily and remember to look under the leaf.

Other Methods

Sticky Traps

Put sticky traps under them and then they shake the plant and they will fall off into the sticky trap. If you don’t want to buy one you could use honey or molasses on a cardboard piece.

Wheat Bran

Spray potato plants with water and dust with wheat bran. A potato bug will eat the bran, which will swell inside the bug and cause death.

Crop Rotation

Don’t grow potatoes in the same spot year after year. Since the adults overwinter in the soil of the previous years’ potato patch, all you’re doing if you plant in the same spot again next year is giving the adults convenient access to your plants. They’ll pick a potato plant, find a mate, and go about laying eggs. If they’re going to try to devour your crop, at least make them work for it a little!

Companion Planting

A number of herbs and herbal extracts are also reputed to repel or inhibit CPB, though research has been far from thorough. Among the plants believed to have some effect are: sage, hemp, flax, horseradish, garlic, eggplant, snap beans, nightshade, oak extract, wild potato and citrus oils.

Floating Row Covers

CPB can be excluded from crops with the use of “floating row covers,” a thin fabric spun from a synthetic material. The product allows air and moisture to travel through it, while preventing pest species access to the plants.

Plastic Lined Trenches

Another exclusion strategy is the use of plastic-lined trenches as a barrier to CPBs entering a potato field.  Beetles can walk on clean plastic mulch at an angle, but once the plastic is coated with fine soil particles, this becomes impossible. Trenches with walls sloping at greater than 46° will retain an average of 84% of all adults caught under field conditions. A potato field surrounded by plastic-lined trenches might see its population of overwintered adult beetles reduced by nearly half. Small numbers of beetles escape from the trenches during periods of rain, but once the plastic dries, footing again becomes impossible for the insects.

Straw

According to another study, mulching with wheat or rye straw may reduce the CPB’s ability to locate potato fields, and the mulch creates a microenvironment that favors CPB predators. In the first half of the season, soil predators-mostly ground beetles-climb potato plants to feed on second- and third-instar larvae of the CPB. In the second half of the season, ladybird beetles and green lacewings are the predominant predators, feeding on eggs and on first and second instars. Mulched plots supported greater numbers of predators compared to non-mulched plots, resulting in significantly less defoliation by CPB. Tuber yields were increased by a third.

Biological Control

CPB has several natural enemies, but they are rarely seen in commercial potato fields because of heavy pesticide use and lack of habitat to support them. Even under organic growing conditions, where natural enemies are more abundant, they will probably not completely control the CPB. The generalist predators—ladybird beetles, lacewings, predatory stink bugs, spiders, etc.—provide some control. There are also a number of CPB parasites. Doryphorophaga doryphorae and D. coberrans are two species of fly that parasitize CPB larvae; a wasp, Edovum puttleri, parasitizes eggs.

Increasing habitat for natural enemies by providing pollen and nectar sources along field borders or by planting insectary strips in the field can increase the effectiveness of these biological controls.

Varietal Resistance

Several genetically-engineered potato varieties are available to commercial growers, but these are not permitted in certified organic production. A few traditional potato varieties (e.g., ‘Russet Burbank’) seem to be more tolerant of CPB than others, but none of them can be considered “resistant”.

The April 1989 issue of National Gardening highlighted research on planting early-maturing varieties that develop potato tubers before CPB populations explode. It lists seven varieties that mature in 75 to 88 days-Caribe, Norland, and Yukon Gold-and illustrates the growth stage of the potatoes versus CPB emergence and larval development. This practice may prove especially beneficial to growers in northern regions, where cooler temperatures slow insect development.

Sulfur

Sulfur is available in most lawn and garden centers or farm supply stores, including organic brands such as Espoma 5 Lb. Garden Sulfur Natural Acidifier. A single 5 lb. bag of sulfur is enough to treat 5 lbs. of potatoes that will be planted.

Curing potatoes in sulfur will retain their moisture and the sulfur helps to prevent rotting. Sulfur works as a fungicide as well as a insecticide, keeping away insects such as potato bugs.

FYI, for next season. Dust potatoes with half a bag of sulfur and let set three days before planting to allow the potato to cure. Dust the top of the ground after planting with the remainder of the sulfur.

Bioinsecticide

Spraying Bt – the bacterium Bacillus thuringiensis – is a common method for controlling a variety of insect pests and is one of the main approaches to chemical-free pest control in agriculture. Bt is found naturally in soils and on plants and exists as many different varieties that each have a preference for infecting different organisms. Bt strains that are specific to certain insects rely on being able to infect those insects ability to reproduce.

For more information:

http://en.wikipedia.org/wiki/Colorado_potato_beetle

www.organicgardenpests.com/colorado-potato-beetle/

http://organicgardening.about.com/od/pestcontrol/p/coloradopotatobeetle.htm

This entry was posted on Monday, June 28th, 2010 at 5:32 pm and is filed under Dirty Little Secrets, What's Happening?.