Room to Grow : Plan ahead for Japanese beetles
Posted on Sunday, May 11, 2008
URL: http://www.nwanews.com/bcdr/Agriculture/61687/
If history repeats itself, then in a few weeks we can expect to see the plague-like onslaught of Japanese beetles in the home landscape. The anticipation of these pests presents the home gardener with an excellent opportunity to implement an Integrated Pest Management strategy. IPM combines cultural, mechanical, biological and chemical-control methods to reduce pest populations to tolerable levels.
Unfortunately, Japanese beetles are here to stay, and since no silver bullet for their control has been discovered yet, some level of toleration is inevitable.
Too often gardeners break out the spray boom at first sight of a detrimental insect. The presence of that insect is not the problem.
The problem is when there are great numbers of insects, which are not kept in check by their natural predators. IPM entails management rather than eradication. Elimination of the pest is not the goal of IPM, but rather preventing significant damage to plants while avoiding adverse effects on the environment.
Your IPM plan for Japanese beetles should include a variety of control methods utilizing cultural, mechanical, biological, and when necessary, chemical controls. Cultural control methods include planting resistant, or nonpreferred, plants species. Although Japanese beetles don’t seem to discriminate against plant species, some plants noted for their resistance to adult beetle feeding include redbud, dogwood, burning bush, magnolia, red maple and boxwood. More susceptible plants include rose, crape myrtle, grape, apple and althea.
The most common of the mechanical control methods are the pheromone traps. Although the traps kill huge numbers of beetles they also attract beetles, so be sure to locate to traps at least 100 feet from your garden or landscape plants that you’re trying to protect.
There are various biological controls available commercially, and generally are used only to control the grubs which over winter in the soil and feed on the roots of lawn grasses. Milky spore is from the bacterium Bacillus popillae and upon ingestion reproduces inside the grub’s gut to eventually kill the grub. Nematodes (Heterorhabditis bacteriophora ), which feed on grubs, are another biological control for Japanese beetles. The nematodes inject bacteria into the grub, which eventually kills it. Take note that biological controls may take more time to establish in your soil and there are environmental factors which may reduce their effectiveness. Additionally, biological methods are more effective if they are implemented on a community-wide basis.
Chemical controls for Japanese beetles are available and have the potential to reduce populations significantly. The most commonly used chemical for population knock down is Carbaryl. Fortunately for the environment, but unfortunately from a control standpoint, the residual effects of Carbaryl are short lived. Pyrethroid products may also be used and generally provide longer lasting protection of approximately two weeks. A botanical insecticide which has been used with some success is Neem oil but like Carbaryl has short residual effects. You can also treat for the grubs in the spring with Imidacloprid. These are the more commonly used chemicals labeled for Japanese beetle control, but remember the goal is not total elimination but rather population reduction to tolerable levels. Chemical pesticides are an integral part of a complete IPM plan. However they should be used sparingly and wisely to avoid detrimental affects to humans, wildlife, and natural resources.
• • • Mark Bray is a county extension agent with the University of Arkansas ’ Cooperative Extension Services. His column appears on Sundays. Call him at (479 ) 271-1060 or e-mail mbray @ uaex. edu.