NEIGHBORHOOD GARDEN FOR JULY 22

NEIGHBORHOOD GARDEN FOR JULY 22, 2006

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ONLY 3% OF INSECTS ARE DESTRUCTIVE PART #2

BY GEORGE EDGAR

Did you know that there are over 1,000,000 insect species that have been described by entomologists? Do you know how many of these are actually garden pests? According to a University of Wisconsin Extension Horticulture Educator, less than 100 are actually garden pests. As reported last week, only 3% of all insects are destructive and not all of the bad insects are found in the garden. The other 97% of the insects can probably be classified as follows:

· Beneficials

· Nuisance insects

· Neutral or incidentals

If you use a general purpose insecticide like Sevin, Eight, malathion or bifenthrin every time you see a bug, you may be doing more harm than good. Make sure there are insects present that are actually hurting a plant before spraying, and then Use the right insecticide, at the right rate, at the right time, on the right insect.

What is the right insecticide? Do you know that Sevin does not work very well on aphids, but is highly toxic to the ladybugs that eat aphids? Sevin is also highly toxic to bees that pollinate your flowers, cucumber, squash, and many other plants. Also, grubs can be very destructive to a lawn but some chemicals are better than others, and the wrong chemical, at the wrong time will not cure the problem or prevent damage to the lawn. Grub control put on too early, or not watered in, becomes ineffective and is not available in the top 2 to 3 inches of the soil when needed. In Eastern and Central Nebraska the grubs in your lawn come from masked chafer (June) beetles. They lay their eggs in July and these eggs start to hatch out around the first of August. Merit (Bayer Advance) or Mach 2 (Scotts Grub Control) should be applied from late June through early July and should be thoroughly watered in with at least ½ inch to ¾ inch of water. These products when properly used will protect your lawn for the rest of the summer. Dylox and other short residual insecticides will kill grubs but need to be applied in early August when the small grubs are present. Again, adequate irrigation after treatment is essential for acceptable control. Remember, the bag may say the product inside will kill grubs, but not specify how well and usually does not say when to apply IN NEBRASKA. Some chemicals get tied up in the thatch and never reach the grubs which are feeding below the soil surface. Milky spore is advertised as an organic control of grubs, but it does not work in Nebraska and the Midwest where our primary species is the masked chafer grub.

When controlling aphids I use insecticidal soap first as this product does not injure the beneficial predators (lady beetles). Insecticidal soap is also good for spider mites and many other destructive insects. It can be used in the vegetable garden up to the day of harvest. Use the right insecticide, at the right rate, at the right time, on the right insect.

People have asked me, “When is the right time to spray?” Pollinators, and many beneficial insects, are most active in the morning. They go back to the hive or nest about noon and avoid the heat of the day. The best time to apply an insecticide, therefore, is in the evening after most beneficial insects have gone to bed. If you have fruit trees, or nut trees that need insects for pollination, do not apply fruit tree spray when the trees are in bloom or you will destroy all the pollinators. The flowers attract the pollinators and spraying during this time period is very destructive.

If you have applied too high a rate of insecticide, or applied an insecticide when not needed, you have probably killed many of the beneficial insects that are helping keep your insect pests under control. Not all inhabitants of your landscape are hurting your plants, or your lawn. Many people want to kill the night crawlers in their lawn. They don’t want to be bothered with those worms on their driveway or sidewalk after a heavy rain, or don’t like the bumps in their yard from the night crawlers. But these worms are nature’s aerators. We pay people to core aerate our lawn, but then apply chemicals to kill off nature’s workers. Sometimes our behavior just does not make any sense.

Use the right insecticide, at the right rate, at the right time, on the right insect. I have had people ask how to attract Butterflies. I tell them to plant flowers that attract butterflies, but also make sure you have plants that the butterflies will lay their eggs on. These plants are ones that the larvae (caterpillars) then eat before they turn into butterflies. In Nebraska there are only certain plants that butterflies lay their eggs on. Two of the most common include milkweed that Monarch butterfly larvae (caterpillars) feed on and dill that the Swallowtail butterfly larvae eat. Insects are clever and lay their eggs on plants that the young can feed on as soon as they hatch out. Sometimes the same people that want butterflies say they don’t like those nasty caterpillars eating their plants. What they don’t realize is that those caterpillars will become butterflies if left alone. And this means sacrificing some plants to the caterpillars. Remember, not all insects are bad.

Integrated Pest Management or IPM is an approach in which you first identify the insect on your plant, and then apply the least invasive treatment possible at the correct time, but only if the insect is actually damaging your plant. If you think you have a problem, go to the local County Extension Office, a full service garden center, or other expert for an accurate diagnosis and informed recommendation.

References:

“The Gardener’s Guide to Common-Sense Pest Control” by William Olkowski, Sheila Daar, and Helga Olkowski. Published in 1995 by Taunton Press: Newtown, CT. Chapter #4 is on “Meet the Beneficials”.

“Insects and Gardens” by Eric Grissell, published in 2001 by Timber Press: Portland, Oregon.

“Growing Plants to Attract Beneficial Insects” by Fred Birdsall, Colorado Master Gardener, and Carl Wilson, horticulturist, Colorado State University Cooperative Extension. Copyright by CSU/Denver Cooperative Extension Master Gardener 1999-2006. For a copy go on the internet to http://www.colostate.edu/Deps/CoopExt/4DMG/phc/benefici.htm

I want to thank Dr. Frederick P. Baxendale, Ph.D. for his excellent review and editing. Fred is a Professor and Interim Head of the Department of Entomology at the University of Nebraska-Lincoln, and a regular panel member of Backyard Farmer on Nebraska Public Television.