We’ve said it many times: In general spray pesticides do not make up a solid or well-supporting segment of an IPM program. They usually do more harm than good, even when the product is supposedly compatible or biorational. Not to say the claim’s a lie, it’s not, but the subject just runs deeper than expected and using sprays can impact a successful program in ways we don’t think of. There are, however, times when spraying something just makes sense. Here are some examples:
Bt for Caterpillars
We usually recommend Trichogramma spp. to parasitize certain moth and butterfly eggs, but if the timing isn’t right, and the typically narrow window of opportunity has closed, the mini-wasps aren’t going to do a thing to help at that time — which is why it’s so important to know your pest’s life cycle. If the eggs have hatched and the pests are now in larval or caterpillar stage, our first recommendation at that point in most cases is going to be to spray Bacillus thuringiensis or Bt. It seems to make the most sense. It is a low-impact product, environmentally speaking, and whether it is compatible or not makes little difference in the scenario described. Do, however, be sure to read our disclaimer at the end of this entry.
Soap Spray
We used to offer all sorts of supposedly safe sprays, we used to even encourage growers to try an incorporate them into their programs. Thanks to a better understanding of the issues that would arise as a result of this, we stopped doing this for the most part. But we still offer insecticidal soap. Soap is hardly safe to use with biocontrols, though. It suffocates and kills non-selectively. It’s not even very good for plants if used too often as it suffocates the plants as well. But we don’t recommend using it broadly. Quite the contrary. It should be used selectively to target groups of specific pests. The nice thing about soap is once you’ve used it against some pests, it’s rendered ineffective to others insects and mites quite quickly. As soon as it dries to the touch, in fact. If you have a hot spot of aphids for example, showering them with a little soap might be a good thing, just be sure not to soak them if they were likely parasitized by Aphidius spp. (still on sale until 3/13/09).
Horticultural Oil
This is very much like the soap above. It differs in only a couple of ways. Hort oil suffocates, but stays wet longer. It also more effectively suffocates, both critters and plants. It also differs in the fact it can be used on fruit trees and what not during the dormant season when other critters aren’t out and about. Oil is helpful against scales, mites, and others. This is not to say you can’t do some harm if there are good bugs over wintering in and among your pests — but if there is you might not need the oil to being with. The point is, it can be used wisely and selectively.
Disclaimer
We do say soap and oil are biorational, but that’s because of the way we suggest they be used. Even though these products are some of the best candidates as far as it concerns IPM integration when used according to our advice, they are dangerous if used improperly, too broadly, too often, or without concern for other critters in the area. One still has to exercise extreme care. And as far as we’re concerned, these products should be a last resort.
These products, the Bt, the soap, the oil, are just some examples. There are certainly other products that can be used at times or in ways that make them very selective and effective, especially if the number one concern is spot eradication of pests. When selecting a spray, choose wisely, know what you’re using, and don’t fall for exaggerated or even false claims about some “organic” sprays that naturally-derived. This doesn’t at all mean they’re safe, even if the pitch almost convinces you of this (without actually saying it). Avoid systemics for sure, and barring repellents, anything time-released or that lasts longer than the drying time of the product needs to be avoided.
Please understand that we didn’t suddenly have a change of heart and are pro-pesticide. We’re not, but we are trying to give you the most accurate and balanced reporting possible. Since we started in 1992 we’ve always held onto the notion that if you’re successful then we will be, too. Cheers to our success — all of us.
