Monday, December 22, 2008

March of the Millipedes!

Due to the cold weather, we might notice another animal crawling indoors, a millipede. The adult millipedes overwinter in protected areas, so we may see them inside structures, such as greenhouses or homes. Millipedes in Texas are typically brownish in color, but can vary from red to yellow to orange. Their bodies are rounded in shape and they have four legs per body segment. Most species are less than ½ inches in length, but the species in west Texas can be up to 4 inches in length. Another characteristic of millipedes is they curl into a spiral to protect themselves when disturbed.

In the spring, the millipedes become active and the females of some species will lay eggs in the soil, while other species will give birth to living young. The immature millipedes are smaller in size with fewer legs compared to the adults. Additional segments are produced after each molt, so the millipede grows in size. Millipedes usually develop into adulthood within 21 to 25 weeks.

Millipedes feed primarily on decaying organic matter so they are generally not regarded as a pest. However if there are large numbers of millipedes, they may attack roots and leaves of seedling plants. Millipedes, such as the garden millipede, can become a pest in the greenhouse and damage crops with their chewing mouthparts. If a structure becomes infested, then control measures are usually necessary.

In addition, millipedes can excrete an irritating fluid that can irritate eyes, blister the skin or cause allergic reactions to sensitive people so control measures may be needed.

Some Control Options:

Non- Chemical Controls:

Remove areas that provide harborage such as trash piles, rocks, boards, leaf piles, compost piles. If flower beds are mulched against structures, occasionally turn the mulch to allow it to dry out. Check around doors, windows and pipe penetrations for any points of access and then seal any accessible areas that may allow millipedes to crawl indoors.

Chemical Controls:

Perimeter sprays around the foundation of a structure may prevent millipedes from moving indoors. Some products such as those containing deltamethrin, permethrin, bifenthrin or cypermethrin as active ingredients can be used. If treatment inside structures is necessary, all cracks and crevices should be treated. Products such as those containing lambda-cyhalothrin, cypermethrin, permethrin, bifenthrin, or d-limonene can be used.

Photo of a millipede, (Diplopoda). Photo by Bart Drees, Professor and Extension Entomologist, Texas A&M University.

Wednesday, December 3, 2008

Inviting Thrips Indoors

As the cooler weather approaches, we will begin to move our potted plants indoors. One insect that may go undetected are western flower thrips. These insects are very tiny (almost microscopic) but can be a nuisance since their mouthparts are able to penetrate into human skin, causing a prickly sensation.

Female thrips lay eggs inside plant leaf tissue, using a serrated ovipositor to cut through the plant tissue. This allows the eggs and larvae to be well protected from insecticides and natural enemies. The immature thrips will feed on the plant tissue until it falls to the ground to pupate. Thrips undergo a prepupal and pupal stage before becoming an adult.
Thrips have rasping-sucking mouthparts that allow them to cut open epidermal cells to release the cell contents that are then ingested. This causes the cells to collapse due to absence of its contents. Their feeding also causes discoloration and deformities of leaves and petals.
As thrips feed, they inject salvia into the plant tissue which allows viruses to be transmitted, such as Tomato Spot Wilt Virus and Impatiens Necrotic Spot Virus.

Some Control Options:

Cultural Control Tactics:

1) Dispose of weeds, trash or debris to reduce the thrips population, since these areas may serve as overwintering sites for thrips.
2) Avoid planting thrips susceptible plants in areas close to wheat or rye fields. Wheat and rye are both good overwintering sites for some thrips species that can move over to feed on landscape plants.
3) Discard infested plant materials to avoid infesting other plants.

Biological Control Tactics:

Some natural enemies of thrips include the adult minute pirate bug (Orius sp.), which attacks both immature and adult thrips; Neoseiulus spp. predatory mites, which attacks the first instar thrips and the soil-dwelling predacious mite, Hypoaspsis spp., which attacks the prepupal and pupal stages of thrips in the soil. Also Beauveria bassiana, a fungus, is sold in biopesticide products and is effective at controlling thrips.

Some Chemical Control Tactics:

Some chemical control options include products containing abamectin,, chlorfenapyr, chlorpyrifos, dimethoate, fenoxycarb, methiocarb, novaluron, pyridalyl, and spinosad applied as foliar sprays or systemic products containing such chemicals as imidacloprid or acephate.