NEIGHBORHOOD GARDEN FOR JULY 25, 2009

NEIGHBORHOOD GARDEN FOR JULY 25, 2009

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DON ’T KILL YOUR BENEFICIAL INSECTS PART #2

BY GEORGE EDGAR

I have written before about Integrated Pest Management. IPM is the combination of appropriate pest control tactics into a single plan to reduce pests and their damage to an acceptable level. Relying only on pesticides can cause pests to develop resistance. There are a number of choices on how to control your garden insect pests. These include natural controls, host resistance, biological control, cultural control, mechanical control, and chemical control.

HOST RESISTANCE is selecting plants that are less prone to serious insect problems.

Biological control involves the introduction or conservation of natural enemies including predators, parasitoids, and pathogens to suppress insect pest infestations. This approach includes applying an insecticide only when it will be most effective, and as selectively as possible, so as to promote the natural activities of the beneficial insects.

Cultural control includes altering the environment, the condition of the host plant, or the behavior of the pest to prevent or suppress an infestation. It also includes practicing good sanitation in your garden as many insect pests overwinter in plant debris, and includes using proper watering, fertilizing, and good growing practices so you have healthy plants.

Mechanical control is a great option and includes physically preventing certain insects from attacking your plants. Nets (row covers) over plants during periods of high pest activity and physically removing the insects and eggs and destroying them. This can avoid chemical use.

Chemical control should be used only when needed and only as one component of your insect management plan. Remember, insecticides need to be used properly and always follow the instructions. When using insecticides, start with the least toxic, such as insecticidal soap, so you don’t kill the beneficial and other good bugs.

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 is highly toxic to the ladybugs that eat aphids? And Sevin is 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. Season long grub control put on too early, or too late, 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 our lawns come from masked chafer ( June ) beetles. They lay their eggs in July and these eggs start to hatch out around the first of August. Imadicloprid (Merit) or Mach 2 (Scotts Grub Control) should be applied from late June through mid-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.

If you did not get your season long control on and you have noticed grub damage, Dylox and other short residual insecticides will kill grubs but needs to be applied when the grubs are small and present. This is usually from mid-August at the earliest to about mid-September. 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 a harsh 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. Remember, not all insects are bad.

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.