During my last post I mentioned this agricultural strategy in passing, and I’m actually fairly surprised that the topic hasn’t come up anywhere on the blog before. After all, IPM is an increasingly effective and interdisciplinary way to curb economic losses in crops around the world, and one that often attempts to reduce reliance on environmentally unfriendly chemicals like pesticides.
Completely eliminating an agricultural pest is not the ultimate goal of IPM. In fact, due to ecological intricacies and the risks of removing certain species from an ecosystem, merely lowering the number of pests to numbers that do not cause significant economic damage is more advisable. Achieving this reduction in pest populations “requires an understanding of the ecology of the cropping system, including that of the pests, their natural enemies, and the surrounding environment,” according to Professor Anthony Shelton of the Entomology Department at Cornell University. For example, knowing that a certain pest caterpillar species has certain predator species, a farmer might introduce some of the natural predators into his crop to prey on the harmful caterpillars. If the farmer also physically removes the caterpillars by hand and the pest population dwindles to zero, the natural predators might turn to a beneficial insect, like a pollinator, or even attack the crop itself. This is a very vague and hypothetical example but one that reflects the need to understand causes and effects in an ecosystem if one is planning to employ IPM effectively.
The Environmental Protection Agency defines IPM in technical terms as “the coordinated use of pest and environmental information with available pest control methods to prevent unacceptable levels of pest damage by the most economical means and with the least possible hazard to people, property, and the environment.” Professor Shelton further explains the process by describing the tactics employed in IPM, which include “pest resistant or tolerant plants, and cultural, physical, mechanical, biological, and chemical control.” He adds that “applying multiple control tactics minimizes the chance that insects will adapt to any one tactic.”
So what are the IPM strategies that can apply to cranberry growing? Let’s go through some of Professor Shelton’s list of controls, starting with cultural ones. The sanding, flooding, and draining that I mentioned in my last post are cultural controls that disrupt pests’ natural life cycles, not to be confused with mechanical controls of physically removing pests, such as weeding or pulling caterpillars off plants. There are also several means of biological control in the bog. Insecticidal nematodes, which are tiny roundworms, enter the pest insects through natural orifices and then release bacteria that can kill the host insect within a couple days. There is also a bacteria called Bacillus thuringiensis (Bt), which affects several insect species’ larvae (caterpillars in particular) by immobilizing their gut and causing blood poisoning — the uses and effects of Bt are actually quite fascinating and can be read about here (note the disclaimer at the top of the page, however). Another effective biological control on cranberry bogs are synthetic chemicals that insects react to as if they were sexual pheromones, interfering with the pest insects’ mating cycles.
Chemical controls are those that we are most familiar with: fungicides, herbicides, and insecticides. Ideally, these are kept at minimal use, but they tend to be highly effective given their cost, so in general their success can lead to unwise levels of application. Hopefully the combined strategies of IPM help cranberry growers — and thousands of other farmers working other crops — reduce their chemical usage. IPM is one of the few ways organic production of food can be sustained, since chemicals are excluded from the list of tools farmers have to combat pests.