Cleveland Pear Eaten by Inch Worms

Just noticed that our 25' foot Cleveland Pear that had been covered with blossoms a week ago is now covered with inch worms. The blossoms are gone, and the leaves are on their way to being decimated. I read on this site that Bacillus Thurigensis (sp) or Bt is the recommended remedy but I don't know how to apply it to a tree. I've only seen directions for plants. Has anybody used this or has anybody solved this problem another way?

I think fruit trees have to be sprayed before the blossoms open up to prevent worms. It is likely too late now- but I am no expert. Hopefully someone can give you some good news!

Thank you. If this is true, what then is the prognosis? A bad season or fatal? I'll try to research but what I've read on the internet so far hasn't helped.
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Editing my own post: Half an hour later and I've learned a few things:
-using BT after the larvae stage is pretty much useless
-perhaps Neem Oil might be an alternative for now
--one blog post was in defense of the little buggers, saying they are fairly harmless. Tell my poor Cleaveland Pear this. However it claims the tree will return next season as long as it is not an older tree or in a weakened condition.
Anything anybody can add to this-- elucidate, elaborate or illustrate with experience would be welcome.

This message was edited Apr 21, 2013 9:06 AM

Spray ASAP.

A Cleveland Pear (Pyrus calleryana 'Cleveland'), I am assuming, is grown as an ornamental, not for fruit.

Caterpillars will eat a leaf or flower that has been sprayed and take the Bt into their system where it kills them. The larger the caterpillar the more Bt it has to eat, so the more leaves they have to eat before they have a lethal dose. This means they will keep eating the leaves for several days or longer. If the caterpillars are pretty much ready to pupate, then they stop eating, so spraying Bt is useless. Other sprays may kill them, then you are stopping the next generation. The ones you kill will not mature into breeding adults.

The defoliation will not kill the tree, though it can weaken it. The tree will recover. It may even grow more leaves, once the caterpillars are no longer eating them.

Diana, you are right- Clevelend is a flowering pear- so no sweat there. I would still want to get rid of the worms .

If the caterpillars are still very young (small) then spray with Bt.
If they are a bit larger then you will have to spray with something else. I think Sevin is one possibility, but read the label to be sure it kills caterpillars, and that Pyrus calleryana is listed as a safe plant to spray. There are probably other products that will kill caterpillars, too.

So just for clarification, it's not necessary to get rid of the worms but a matter of preference? Am I understanding you correctly?

Well, not so much a preference, but what is practical, and possible.

1) Baby caterpillars are going to eat just a bit while they are small, so are easy to poison (Bt). But they will eat a lot as they grow, so killing them while they are young is best.

2) When they are ready to pupate then control is pretty much worthless.
a) They have quit eating, so Bt won't work.
b) They have quit eating, so THESE inchworms won't be doing any more damage.
c) They will emerge as adults that may fly away, or may lay eggs in these trees, and this is not good. So killing the mature inchworms might still be good- you are preventing THESE from becoming adults.
d) The inchworms that are surviving and pupating at your neighbors' houses will become adults, so even if you kill yours, there will still be adults to lay eggs and continue the problem.
e) As difficult as it is to kill large caterpillars (takes a large volume of fairly strong pesticide) you are also killing a lot of beneficial bugs, and this might cause an increase in population of some other pest that the beneficial bugs were keeping under control.
Compare to BT, which targets caterpillars, and is safe to use around most non-caterpillars, meaning it does not kill beneficial insects.

3) Somewhere in between baby caterpillars and ready to pupate:
If you spray Bt, you will still kill them, because they are still eating.
But they will have to eat more to get enough Bt to kill them.
This is still safer than using stronger pesticide, just not as fast.

Here is what I would do:
This year:
Spray Bt. if the inchworms are still young or at least still eating.
Monitor the ages of the caterpillars and spray again if there is a second hatching.
Do not spray the older, 'ready to pupate' caterpillars.
See if there are any ways I can encourage the natural predators (think : Birds)

Next year:
Monitor the population, and spray Bt at the first sign of them.
Be ready to spray Bt several times if there are more hatchings.
Get them while they are still so young they are not doing much damage.