Integrated Pest Management: Less Is More
By: James Gill, Gill Landscape Nursery
Integrated Pest Management, aka IPM, is a systematic method of pest control that emphasizes safety, efficiency, and cost. Basically, it is using the least toxic means that will solve our problem. This requires not a more fully stocked armory of heavy pesticides but instead a better understanding of pests and our environment.
For example, if you find aphids feeding on new growth in your garden or landscape, you should first scout for any predators that may be able to control the aphids. Tiny Aphelinus wasps will lay eggs on aphids, and the larvae that hatch from the egg will devour the aphid from within, and then morph into an adult which will seek out and destroy hundreds more aphids.
You will know if the wasps are present by the appearance of aphid “mummies”, looking like a puffed up brown paper bag.
Other beneficial insects that might be present are ladybug adults or larvae, and lacewing adults or larvae. Learn to recognize these garden friends, and if you see them, DO NOT SPRAY pesticides. They and their offspring will continue to seek out and eliminate pests.
You can also knock healthy aphids off plant leaves with a sharp stream of water or spray with insecticidal soap or horticultural oil, which will not harm beneficial insects that may come by to pick off the few remaining aphids the next day.
Some pest problems will be here today and gone tomorrow, so if its tomorrow, you no longer need to control. For example, if you see a big fat tomato hornworm eating your tomato plant today, you pick him off and look for more. If you see branches being denuded on your oak tree, you look for caterpillars on your tree and for frass (poop) on the ground underneath, and if you find them present you spray with Bt Worm Killer or Thuricide on the leaves, and as the caterpillars eat it, they will get sick and die. Both are specific to caterpillars and will not hurt humans, birds, cats, or dogs. If you see a chewed edge on a leaf and the chewed edge is already brown, and you do not see any caterpillars or frass, then that pest is long gone and there is no need to spray anything.
Another concept of IPM is “threshold of damage”. If you find a grubworm as you are digging in your garden, don’t panic. But keep digging to see if you find more. Texas A&M considers a grub or two as no problem, they cannot eat roots as fast as the plant can grow new roots. But if you find 5 or more grubs within one square foot of area, then it can be a problem worthy of your attention. You can apply beneficial nematodes for a long-term control, but that is likely to be slow acting. Beneficial nematodes are microscopic “worms” that attack and kill grubs and flea larvae. If you want faster kill of a damaging population of grubs, you can apply conventional grub pesticides, but following IPM principles, you would scout and determine where those concentrations of grubs are, and limit treatment to those spots, leaving the rest of the yard safe for beneficial insects.
The most basic IPM principle may be pest avoidance by choosing, planting, and maintaining healthy plants less susceptible to pests. To choose, rely on local garden centers for knowledge of best adapted plant varieties and possible pests. To plant, assure proper drainage, planting technique, and soil conditions for healthy growth. To maintain, do not over- or under- apply fertilizers, prune properly, and rely on fungicides and pesticides as a last resort, not as your first choice.