Rob:

Leafrollers are not caterpillars, but aphids. Dormant oil sprays can help to control overwintering eggs and greatly reduce, although not eliminate, aphid outbreaks on apples.

Bt has almost no practical applications on apple trees. Surround is said to be modestly effective on some insects such as plum curculio and codling moth, but not on aphids. As you are apparently aware, Bt has a very short effective life on its principal target, which is caterpillars. But caterpillars are not normally an issue on apple trees.

Good luck with your organic project. You have the advantage of living in a climate where the major apple pests have a shorter active season. Needless to say, in my climate I am not organic, but am always looking for ways to reduce chemical use, such as bagging apples. I am doing pretty well. Spraying is a lot of work.

Don Yellman, Great Falls, VA

Don,
I appreciate your quick response but you have me a bit confused. I believe we have both Oblique banded leafrollers and redbanded leafrollers, as well as oriental fruit moth to a lesser extent. I believe all three of these are lepidoptra and therefore susceptible to Bt. If I have a misunderstanding I would appreciate having it clarified...

We do also get small outbreaks of green aphids...and they will curl the damaged leaves but they are rarely a significant issue.
The leafrollers for us are a problem that starts around tightcluster and runs nearly all summer. I have squashed an awful lot of them the past few years (green worm with markings, that folds a leaf around itself) and they do a fair bit of damage if I don't walk the trees routinely.

I wish I had geared up for spraying over the winter and done dormant oil....it seems it would have helped with a number of issues this spring but I did not have my act together and am making the best of it now. Live learn and improve (hopefully)

I also wonder about Bt on apples. I guess i've never read where it was necessary. I sprayed one time last spring with Immunox (for CAR) and bagged. My apples were perfect, and the squirrels agree! We should have similar growing climate. This year i'm skipping even Immunox and hitting with Surround (as soon as the wind/rain go away) and bagging. I also hate spraying, not to mention that stuff isn't cheap.

Rob: just a thought, Bt must be ingested to work, if the target pest doesn't eat it because it is mixed with the dried Surround it wouldn't work. On the other hand, maybe leafrollers will eat a Surround + Bt coated leaflet, beats me. Spraying is work, no doubt about that.

An alternative to Bt MAY be Spinosad. My little bitty Fertilome brand bottle has it listed for Leafrollers and leafminers on apple. Just hosed down the 3rd leaf trees with it this evening as the darned rollers are starting to show up. Ask me how it worked in a few days.

BT should work on leaf rollers. But they are pretty protected once they roll up the surrounding leaves. I would echo michael's comments and wonder if Surround won't reduce feeding on the BT. I've used Spinosad on leaf rollers but can't really comment on how effective it was other than to say nothing seemed to get into their liar.

It would be a good idea to call the manufacturer (the toll free number will be on the label) of your Surround to find out about this tank mix. Obviously, they can't put every single appropriate use on their package label (nor every problematic mix), so they'll be happy to steer you in the right direction when you call.

Bt, though effective against leaf rollers, needs to be applied when the caterpillars are very young. So you need to find out when to expect them to hatch in your location. Spraying beforehand, and/or spraying when they are mature is a waste of time and money...and puts more bio product into the environment needlessly.

This is yet one more reason to do dormant oil spraying. Oils can go a long ways in smothering the eggs of leaf rollers.

I've never heard of aphids being called leaf rollers. It's a term used to describe a wide range of caterpillars. Aphids, however, ARE guilty of causing leaf curling and disfigurement.

My guess is that Don doesn't have leaf rollers where he is and is referring to the tendency of leaves curling up when being fed on by aphids, something you see a lot of with aphids on cherries.

I have never heard of oil smothering caterpillars, not saying it doesn't, my ears aren't everywhere. I know that it doesn't smother our tent caterpillar eggs, at least not enough for control. Every reference to oil I see in commercial recommendations is for aphids, psyla and scale.

I do want to give Surround a better endorsement than Don's as it not only has worked pretty well on sites we've employed it here but MSU sings it's praises with a full-throated voice. They are working hard to develop organic methods of fruit production.

My problem with the product is it takes forever to apply- especially that all-important first coat when the pressure to protect is really on. If I relied on the stuff I could only protect a fraction of the fruit I can with Imidan.

And then if you want to defend your fruit from fungus, good luck going organic in humid regions. It's disrupt the environment with endless lime-sulfur aps or relying on wishful thinking. That and the possibility of planting nothing but the likes of Liberty and Williams Pride.

I would not be worried at all about BT compatibility. If the surround stops the worms from feeding on it the battle is done anyway. I do agree that you shouldn't use the BT if your pest isn't susceptible and that contacting the manufacturer is a good idea. Also check the life cycle of your pests.

http://attra.ncat.org/attra-pub/PDF/omapple.pdf

For you wannabe organic fruit growers who live where it actually rains during the growing season, this might be interesting.

thanks for the thoughts folks. I had considered the issue of the leafrollers consuming the Bt once the Surround was on. I assumed that since Surround is not touted as effective against them, that they probobly are just eating the leaves clay and all.
Fruitnuts comments about the rolled leaf affording protection had also crossed my mind. But I believe(certainly don't know) that the worm is hiding in the leaf during the day and foraging outside at night. I usually only find one worm per leaf cluster, and often the damage that catches my eye is not the rolled leaf itself but those surrounding it. Perhaps they feed on the one rolled leaf and then move on. Certainly by the time they reach 5/16" a single leaf is not going to feed them for long.
My biggest concern in mixing the two was pH as I have read that Bt is fairly sensitive to the pH of the spray...I guess I will just have to test that on my own.
Rhizo, I have also read that the timing for Bt can be crucial both due to it's short lived effectiveness and the greater effect on early developing worms....I think idealy I should have hit things at pink...live and learn. I am paying much closer attention to the my pests this year in hopes of improving my understanding of local timing...although this year is such an oddball it may not be good to draw too many conclusions.
Harvestman,thanks for the link i will check it out later.Sso far fungal disease hasn't really been an issue. We are lucky in that there are not any red cedar for many miles. Scab hasn't really turned up much yet either, which is suprising given the vast number of wild apple trees all around us. I suspect we will start seeing it soon. Our cool mountain weather may well moderate the pressure for us.
On a seperate note I wonder if my concern over the leafrollers has more to do with the size of our trees, as young stuff obviously takes a larger proportional hit from a hungry bug. I do not notice the damage as particularly severe on many of the wild roadside trees in the area. Perhaps as our trees grow up the the worms to tree/leaves ratio drops off.
A last note. Don's comments had me go back and check my pest Id's. And i realized that what I had thought was redbanded leafroller is actually the larva of the pug moth...that doesn't really effect this discusion but I was glad to discover the error.

Rob, go for it. I tank mix Surround with about anything. The only thing not to mix it with is a non-drying oil since that will cause the Surround to not flake off on the bugs.

Scott

Scott, is there any non-drying oil that you'd spray on a leafed out tree? That is besides fish oil for thinning purposes?

Stylet oil and Saf-T-Side are both drying mineral oils and they are the main two oils I use. Non-drying oils include cottonseed, canola, etc.

Scott