Posts tagged infested

Centipedes, millipedes and more Japanese beetles

 

 

Master Gardener Intern, Sue Levasseur, answers two questions frequently asked of the Hortline:

 

            Q.  How can I get rid of those metallic-green bugs that are eating my plants?

The Japanese beetle has become a significant pest in Iowa during the past decade.  The head and thorax are shiny metallic-green, and the wing covers are coppery red. A row of five tufts of white hairs grow on each side of the abdomen.

            Japanese beetles are a double threat insect in the home garden.  In the larvae stage they are white C-shaped grubs that are approximately 1¼” long when fully mature.  They inhabit the soil from August until June where they feed on turf grass roots and organic matter.  Adult beetles emerge in June and eat the foliage and flowers of over 300 plants.  Foliage is consumed by eating the tissue between the veins, a type of feeding called skeletonizing.

            Control of adult beetles is difficult because they emerge every day for a period of several weeks.  Handpicking or screening of high-value plants may be of benefit in isolated situations with limited numbers of beetles.  Spot spraying infested foliage of high value plants with carbaryl (Sevin), permethrin (Eight) or cyfluthrin (Tempo) may reduce damage for several days but multiple applications are required to maintain control.  Spraying the adult stage is not an effective strategy for prevention of white grubs.  Use of floral lure and sex attractant traps is not recommended; research suggests that they are not effective in controlling moderate to heavy infestations and they may attract more beetles into a yard than would occur otherwise.  However, the traps may reduce damage and beetle populations where landscapes are isolated from other Japanese beetle breeding areas or when mass trapping (everyone in the neighborhood) is used.  

            Q.  What is the difference between centipedes and millipedes and how can I get rid of them in my house?

            House centipedes are approximately 1½” long with 15 pairs of long, threadlike legs extending from their body segments (one pair per segment). In contrast, millipedes are about 1¼” long and have 30 pairs of short legs extending from their body segments (two pair of legs per segment). 

            House centipedes are found both indoors and outdoors, but prefer living in damp portions of basements, bathrooms, and unexcavated areas under the house.  They feed on small insects, insect larvae and spiders.  Thus they are beneficial and considered harmless to people but most homeowners consider them a nuisance.

            To deter centipedes from your home dry up and clean the areas that serve as habitat and food source for centipedes as much as you can.  Residual insecticides can be applied to usual hiding places such as crawl spaces, dark corners in basements, baseboard cracks, openings in concrete slabs, under shelves and around stored boxes.

            Millipedes are usually found outdoors where they feed on decaying vegetable matter.  They are one of nature’s harmless “recyclers”.  Millipedes are accidental invaders in the house.  Capture and discard the offending invader.

Gardening Questions?  Call the Linn County Master Gardener Horticulture Line @ 319-447-0647.

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Not so sweet pest

Entomologist Donald Lewis, of Iowa State University Extension, offers the following information about the bane of sweet corn:

One of the pure pleasures of summertime in Iowa is eating sweet corn fresh from the garden or farmers market. To the dismay of gardeners, growers and sweet corn aficionados, however, there is the matter of an occasional pest to consider. The most important and best known insect pest of sweet corn in Iowa is the pudgy, hairless “worm” found at the tip of an infested ear, the corn earworm.

Corn earworms come in a variety of colors, ranging from light green, to tan, brown, pink or nearly black. The caterpillar’s body is marked with light and dark stripes running lengthwise and the skin texture is coarse due to microscopic spines that cover the surface.  Earworms are only in the ear for three to four weeks but during that short time they grow to nearly 1 .5 inches in length.  Infestations may be present throughout the summer but are generally worse in late summer.

Unlike hardy residents of the state the corn earworm does not survive Iowa winters.  Instead moths that lived and grew in southern states on either corn or cotton last year are blown here during May and June each year to reinfest the state.

These recent-arrival-moths fly after sunset and reproduce by depositing their eggs on the fresh, green silks of the sweet corn ear. These eggs hatch in two to six days and within an hour the tiny, young larvae crawl into the silk channel and move to the tip of the developing ear. The larvae feed on the silk and developing kernels and foul the ear with excrement.  About three weeks after silking the sweet corn is ready to harvest and eat, and there, waiting for you at the end of the ear is the much-grown earworm caterpillar.

The amount of corn earworms in the sweet corn crop varies from place to place, from year to year and with the time of the year.  Mostly the damage is determined by the number of moths in the vicinity which depends on the weather and other factors. Some varieties of sweet corn are more or less susceptible to earworm attack, and genetically modified varieties are available that produce their own defense against caterpillar attack.

Growers and gardeners who want “clean” sweet corn must work to prevent the earworms from getting into the silks. If the caterpillars are already crawling toward the ear tip it is too late to stop them. A typical preventive management strategy is to spray insecticide on the corn ears throughout the entire period when green silks are present. 

Insecticides for the home gardener include azadirachtin (Neem), Bacillus thuringiensis, carbaryl (Sevin), or permethrin. Spray at the first sign of silk emergence (one or two days after tassels appear) and again two days later after silks have elongated. For complete protection, especially in later plantings, spray a third time three days after the second spray.  After the silks turn brown there is no benefit to spraying.  

Admittedly, this is an extensive amount of insecticide but it is currently the most practical method for assuring worm-free sweet corn.  The alternative is to not treat at all.  Instead, cut off the damaged tip of infested ears and enjoy the remainder of the ear.

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