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Myth busters III
Taking on insects on your golf course isn’t easy. Knowing what’s right and wrong about insecticides gives you a leg up.
Editor’s note: For the past two years, the January issue of GCM has featured “Myth Busters,” articles authored by a development manager for Bayer Environmental Science. The first article tackled myths concerning fungicides, the next covered herbicides. Both articles were so well received that we’re including here the third installment, this time focusing on insecticides.
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Myth No. 1:
All insecticides kill all insects!
No, in fact they don’t. The need for better and lower-dose products has prompted basic manufacturers to develop insecticides that are more specific in their activity. Twenty or 30 years ago, products were applied at rates of 10 or even 20 pounds of active ingredient per acre. These products killed most, if not all, insects on a golf course — both pests and beneficial insects. Now we have products that are applied at 0.01-0.4 pound per acre and are active on only one or two pests. The toxicity to beneficial insects often is nonexistent.
Currently, turf managers rely on a variety of products, all of which have toxicological advantages over what they were using 30 years ago. Each of these newer materials is active against a narrow spectrum of pests and is much less detrimental to nontarget pests. Fipronil is a great example. It’s used in turfgrass at the low rates of 0.0125-0.025 pound of active ingredient/acre. The level of control at these low rates far exceeds anything that older chemistries can provide. (Always read and follow label instructions.)
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Myth No. 2:
Preventive grub control is not IPM.
Integrated Pest Management is defined as using a variety of methods to effectively manage pests from the standpoint of environmental friendliness, cost and safety to nontarget or beneficial insects. Using an intelligently designed combination of chemical, biological and cultural management tools traditionally results in lower pesticide use without economic loss or injury to the crop. Use of an effective IPM strategy usually means that turfgrass managers only apply pesticides when necessary.
In certain instances, a preventive treatment is a sensible component of IPM. It’s difficult to scout for certain pests; subsurface feeders like grubs are a classic example. Methods of predicting the incidence and severity of a grub infestation are inexact. Turf managers who apply a product only when they run into damaging populations also run the risk of encountering an out-of-control infestation that threatens to cause severe economic loss. To fix the problem of a severe infestation, they actually apply more pesticide than if they had used a low dose of an active ingredient like imidacloprid in the first place.
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Myth No. 3:
Insecticide resistance is inevitable.
Resistance depends on the type of insecticide and the biology of the insect. Dose-transfer of the insecticide to receptor sites inside the pest, the sensitivity of the target site within the insect and the ability of insects to metabolize the toxin differ among insects. As a result, resistance develops more slowly in response to some insecticides than others. Many pests have been treated with the same class of chemistry for decades, and resistance never developed.
The frequency of application also is important. Typically, resistance develops in environments where there is a rapid turnover of generations in a single season. A classic example is a greenhouse, where you have a new generation of whiteflies, spider mites or mealybugs developing every few weeks. Because these pests often attack numerous varieties, managers often make multiple consecutive insecticide applications to control them. These repeat applications often result in the development of resistance.
In the case of turf insect pests, materials are generally applied only once or twice a season. As a result, superintendents do not select for genes that confer insecticide resistance. Furthermore, there usually is “immigration” in a golf course setting — or numerous individuals moving into the managed turf area that haven’t been exposed to insecticides. Immigration allows susceptible genes to mix with any resistant genes that may have been selected for by the insecticide application. Whatever resistant genes survive the pesticide application will be quickly overwhelmed by the influx of susceptible individuals.
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Myth No. 4:
If an insecticide application doesn’t work, it must be because of resistance.
The reasons for insecticide application failure are numerous. The formulation of the insecticide may be unsuitable for the environment, the application timing may be wrong or the application method may be faulty.
As insecticides become more and more sophisticated, they require more precision to obtain maximum efficacy. For example, if superintendents apply a product after the pest has become established, performance can be compromised. Preventive treatments are always better than curative treatments from the standpoint of maximum efficacy with minimum amount of applied product. It’s important to remember that modern products can be extremely specific in the insects they control. Read the label before you use the product to ensure that the pest in question is susceptible and that you select the proper dosage.
Formulation affects performance. Different active ingredients are formulated in different ways, depending on the use site and other environmental conditions. Placement of the insecticide also is important. If you apply Merit (imidacloprid) to a tree at the wrong location, the tree will not take it up and control will be poor. If mulch is on the soil surface, the insecticide will get bound up in the mulch and the roots will be unable to absorb the product. If the ground is bone dry and the tree isn’t transpiring, efficacy will be compromised.
Seldom, if ever, is resistance the reason for an insecticide failure, particularly in turf and ornamentals.
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Myth No. 5:
Pesticides kill insects and that’s all they do.
Not true. There’s a growing body of evidence showing that certain biochemical mechanisms in plants are positively affected by pesticide chemistries. These beneficial noninsecticidal effects include stress mediation and promotion of growth.
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Myth No. 6:
Application of combination products is not cost-effective.
An application of a combination product provides broad-spectrum control of a variety of different pests that attack turf at roughly the same time. Combination products are an easy, flexible option, as opposed to putting one product out for pest X and coming back two weeks later to spray for pest Y. Instead, you control both at the same time.
With combination products, the amount of product applied has been optimized for control of the targeted pests. So a single application of a well-designed combination product will provide effective control of all pests. Fewer applications are being made and overdosing is less likely, which saves time and labor and uses less chemical. And there are no worries about tank-mix compatibility, either.