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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