Rethinking Landscape IPM

First to be implemented was the concept of a "threshold." In other words, most of the pesticides were applied whether there were any bad bugs, weeds or diseases present. By using the concept of pest threshold, one had to look and determine if a pesticide was needed. In field crops we have "economic thresholds" where the dollar value of pest damage has to at least equal the cost of the pesticide to be used. In turf and ornamentals, we have to rely on "aesthetic thresholds" whereby the visual damage is determined to be too great to tolerate before a pesticide is used.

Second was increased reliance on non-chemical control tactics – cultural and biological. Cultural control includes making the environment less suitable for the pests to survive, using resistant plant material, physically destroying the pests (crushing of insects, pulling of weeds, etc.) and similar techniques. Biological control was to encourage predators, parasites and diseases to take their toll on the pest populations.

Finally, in order to determine thresholds and evaluate whether cultural and biological controls were working, monitoring techniques had to be improved. This has probably been the most important factor in IPM usage – look before you shoot! In landscapes, we now recommend targeting a spray only to the plant that needs it. Spot treating lawns where grubs are at damaging levels or small area applying of herbicides where weeds are actually present or likely to emerge are additional techniques. Records of past pest activity and looking at current activity is the recommended procedure to use before applying a pesticide.

Two new insecticides, imidacloprid (Merit) and halofenozide (MACH2) have appeared that may force modification of traditional IPM thinking. First, both insecticides work best when used as a preventative. While MACH2 can kill white grubs in later stages, it is most effective when applied at the time that the grub adults are laying eggs. Merit has to be used at egg laying in order to be effective. Second, both insecticides have greatly reduced toxicity and both appear to have little adverse effects on nontarget animals, including humans and pets. Third, both insecticides have relatively long residual activity periods, well over 100 days. Therefore, should we quit worrying about the pesticide ills of old products? Should we go ahead and use these products whether we have pests or not?

I vote that we keep all the good things we have learned about IPM! Don’t use these pesticides when they are not needed – not for safety issues, but for good stewardship reasons. History has shown us that when we use the same groups of insecticides time and time again, whether needed or not, the pests become resistant or the environment reacts in unpredictable ways. Look at this in another manner. Each new insecticide costs $80 to $100 million, minimum, to bring it to market! Each time we loose one of these because of our poor stewardship, another has to be developed and the next one is likely to be even more expensive.

I am also worried about applicator attitudes that halofenozide and imidacloprid are "miracle" pesticides. You merely apply them early in the season and don’t worry about grubs or borers for the rest of the season. Reports are coming in that Merit has had some "failures." In almost all cases, label instructions for watering in or returning clippings for the first mowing after application were not followed.

In summary, new pesticides offer much in the way of reduced environmental and health risks. Some are also tempting to overuse because they are extremely effective and have long residual activity. However, these compounds are difficult to discover and even more expensive to bring to market. We should use them wisely, which means use all the principles that were developed for IPM when pesticides were "less friendly."