Chemical control is simply using chemicals, both natural or synthetic, to reduce pest populations. Most people consider chemical control to be limited to pesticides or those chemicals which cause immediate death of pests. Chemical controls also include repellents, attractants or pheromones, and hormone-like chemicals called growth regulators. Unfortunately, there are few of these other chemical controls registered for use to control turfgrass insects and mites.
Turf Qualities Which Influence Chemical Controls
Pesticides used on turfgrasses have generally been treated the same as when used in field crops. Unfortunately, the comparisons do not hold up well. Turf is grown as a perennial crop which covers the soil. Field crops are usually grown and harvested in a single season and the fields may be left bare before the next crop is planted. Therefore, estimations of potential surface water and ground water contamination cannot be directly transferred from field crop systems to turf. Likewise, turfgrass is a non-food item so that ingestion residues are not comparable. On the other hand, people often play, walk or sit on turf and residues that may rub off after an application are of concern. Many of the current labels contain instructions which will aid in reducing the chance of contamination or contact with residues.
The presence of considerable organic material in turf, often as thatch, also presents problems. Many pesticides may stick to this organic matter and are either inactivated or do not come into contact with the target pest. Therefore, an integrated approach which reduces thatch buildup will improve most pesticides¹ performance.
Pest Resistance
Pests placed under severe pressure by pesticides usually develop methods to counteract this pressure. Often this results in resistance. Certain white grubs, billbugs and chinch bugs have been identified to have resistance to the older chlorinated hydrocarbons. We know that pesticides with long residuals, used continuously, tend to cause development of resistance. Therefore, short lasting pesticides, used sparingly (only when needed), may reduce the chances of developing resistance in a pest. There is no known resistance to currently registered insecticides by turfgrass insect or mite pests found in Ohio.
Preventive vs Reactive Pesticide Applications
Another concern about pesticides is the use of preventive versus reactive treatments. Preventive treatments are made to prohibit an outbreak or establishment of a pest. Reactive treatments are made after pests are developing, but hopefully before any significant damage is done. Obviously, preventive treatments are preferred by some turf managers because no thinking or sampling is required. Reactive treatments require careful monitoring and decision making. Generally, preventive treatments, as a tactic, runs counter to the IPM principle that mere presence, or in this case the expectation of presence, is no justification for control action. Preventive applications are often made when no pest damage would have occurred! This results in the unnecessary application of a pesticide.
On the other hand, certain annual weeds, diseases and nematodes are best controlled by using preventive pesticides. Using a preemergent crabgrass herbicide is more preferable to the use of pest emergent products. Many diseases must be kept from invading turf plants because control is almost impossible once infection has occurred. Most insects, however, can be adequately controlled after they are discovered but before they cause significant damage.
Newly developed chloronicotinyl and diacylhydrazine insecticides work most effectively when applied as preventives. These insecticides are most appropriately used where turf has a history of insect attack or the turf has attributes that put it at high risk of having insect damage (e.g., thatchy, sunny turf).