I recently wrote an article about Integrated Pest Management (IPM) Principles for the Home, Yard, and Garden Pest Newsletter (link is at the end of this post). I wanted to add a few things to the article.
First of all, IPM sounds intimidating. You see a bug and you just want to squish it; you don’t want to think about something that sounds like it belongs on an official agenda somewhere. That’s completely understandable, but IPM is actually very simple and straight-forward. There are several principles (see the article) and a decision tree, but what it all comes down to is this: does this pest need to be controlled, and if yes, how do I do that in an effective, safe, and economical way?
I specifically wanted to talk about IPM today because of a few phone calls we’ve received at the Plant Clinic in the last week. One was from a nursery producer. He had 20 red maple trees, all with the same problem which he identified as tar spot, a common fungal leaf disease. He called us because the disease is spreading, despite the fact that he destroyed the original 20 infected trees. Unfortunately for him, this pathogen spreads via the wind and the weather this year has been very favorable for this disease, so destroying a source of inoculum may not be enough to stop new infections (as he found out). More unfortunately, tar spot is considered a “cosmetic” disease; it affects the appearance, but not the well-being of an otherwise healthy tree. And since maples are deciduous, the infected leaves would have fallen in autumn and, when the new leaves formed in spring, there’s a very good chance that they would have been healthy and infection-free provided he removed the infected leaves and that next year is not a particularly favorable year for the disease. The end result is that he destroyed 20 trees and got little to no benefit.
(Photo of classic tar spot symptoms on maple)
Another call was from a pesticide applicator. He was asking about controlling armored scale insects on trees. Armored scale adults produce a waxy coating that makes them impervious to topical pesticides; for good control, the chemical must be applied when the insects are juveniles, before they have produced the covering. This part of their life cycle is usually in spring, though some may go through multiple generations a year. The applicator knew all this information, but he was calling to see if there was anything he could apply now. When I said no, he replied “well, I guess I’ll just apply the pesticide anyways since my clients want to do something about it now.” He is failing his clients by failing to educate them, wasting their money, and adding to the pesticide load in the environment for no benefit.
(Photo of various armored scale insects)
So how could IPM have helped in the above two situations? With the maple trees, the caller had done the first step in IPM: identifying the pest. Unfortunately, he didn’t go to step two, which is deciding if it needs to be controlled; instead he jumped directly to controlling the pest (and he did it poorly). With the armored scale, the caller had also identified the pest, and decided that it needed to be controlled; however, he skipped using knowledge of the pest's life cycle to optimize control. Instead, he decided on control while overlooking the fact that he will get very little to no control of the problem by applying a pesticide at this time.
I hope these examples make IPM a little easier to understand. For a longer explanation of the principles and an example of the decision-making process, please see my article in the Home, Yard, and Garden Pest Newsletter here.