That is a fungicide, not a pesticide. Won't do anything for the sawfly larva.

Nitpicking mode on:

Pesticide is an umbrella term.

Thus,
A fungicide is a pesticide;
An insecticide is a pesticide;
The Cornell formula is a fungicide, which is a pesticde.

Mode off.

Hi all,

Actually, I think this is a very good question. The two organic means to control sawfly larvae that I've seen are insecticidal soap and Hort oil (I guess they are both considered organic?). Cornell mixture has Hort oil in it.

We wanted to spray with Cornell, AND we had (have) sawfly larvae, so we thought we'd see if it helped. I think (from memory - please don't go by me for these amounts) the Cornell mixture says 2 Tablespoons Hort Oil per gallon. The Hort oil says 2.5 - 5 Tablespoons per gallon for insect control (and it lists sawfly larvae). My husband sprayed with the typical Cornell amount - 2 Tablespoons. He drenched Heritage, which is being eaten alive by them, including the undersides, and they survived. Hmmm. So - it might have worked, but he didn't use enough I guess.

The next week I sprayed with Insecticidal Soap (Concern), drenched them. No sign of them on Heritage anymore (what's left of its leaves), but I did see some still on other roses I treated. Rather frustrating.

So - is there any harm in just upping the amount of the Hort Oil in the Cornell mixture to kill two birds (or rather, one bug and one fungus) with one stone (or spray)?? Can I spray Cornell again or just Hort Oil within 2 weeks of the first Cornell application?

Any thoughts on that?

Judy G. in MD

Judy G, just guessing, but I think if you increase the hort oil, it might be better to spray only oil and water. Both oil and baking soda are somewhat phytotoxic, so the foliage might better stand 3 or 4 TB of oil if there is no baking soda or soap. Besides, you only need spray the affected areas to control the rose slugs.

Spraying and coating any insect pest with an oil will certainly give it a sick feeling, if not kill it outright. So, to answer your quastion, yes, the Cornell formula will help with sawfly larva. It will also smother any remaining eggs.

My regular formula is
4 tsp baking soda
2 tbsp. canola oil
1 tbsp. dish soap

However, in earlier spring, when I was particularly concerned about rose slug,s I added about 5 tbsp. canola oil and 2or 3 tbsp. dish soap to one batch that I sprayed. I did have a small amount of burnt foliage, so now I've gone back to the usual 2 tbsp canola oil.

Things are a little better this spring than last in the rose slug department.

I might try the same with hort. oil in the future.

Elvie--is that recipe mixed with water or used straight? I'm assuming it's diluted in some way, so would appreciate the ratio. I get slugs on my Thomas Lipton shrub roses and was planning on just digging them up this year, but I'd like to have a go at saving them if I can.

Sharon_P, I assume you've figured it out by now. But I tried the recipe in 24 oz. of water and it burnt my rose a little. I would recommend diluting it in at least 2 quarts of water.