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[list@ginda.us]

A few weeks ago I speculated whether it might be ants that were preventing my apples from flowering.  Several of you said they didn't think so.  I have done some more research, and I think I now have the correct answer to my riddle.  How to get the plants to flower is a second question, but at least I think I know why they are not:

Winter Moth caterpillars

http://massnrc.org/pests/pestFAQsheets/winter%20moth.html

The caterpillars are now large enough to see (still tiny, maybe a millimeter or two) but they are clearly damaging the buds.  They are an imported pest that is now at epidemic levels in Massachusetts.  Apples and crabapples are among their favorite hosts, and they are known to selectively eat the inside of the fruiting buds.  (Although sterile blueberries from these pests are more common than sterile apples.)  When the population is high enough, the older phase can totally denude trees, although I don't have that level (yet).  As some of you suggested, I now think the ants were an indicator of a different problem - in fact, I suspect they were eating the caterpillars.

The grafts on the crabapple are the most vulnerable, because the domestic buds open a little more slowly than the crab buds, and so are most highly targeted.  The crab can host a large population of pests, and support gadzillions of eggs, and the resulting tiny worms all seek out the swelling buds.  Also, I suspect the higher levels of tannins (which are a form of toxin, created by plants in part to discourage things from eating them) in the crab part also encourages the worms to keep looking until they find the grafts.

It seems to be a hard pest to control.  During its most destructive phase, it is safely ensconced in the heart of the buds.  Later, as an inchworm, it is vulnerable to all bug-killers, but that's too late to save the flowers, and moths from other trees can easily move in and lay eggs for the following year.  My best bet is probably dormant oil applied during a January thaw.  (Apparently I need a couple of above-freezing days between early December when the moth lays its eggs and March when they start to hatch out.)  Because I have young trees with smooth bark and no lichen, this might work fairly well.

Ginda Fisher

On Apr 21, 2005, at 6:29 PM, list@ginda.us wrote:

> I've asked before about my grafts that don't flower.  Today, I may have found the reason.  Could it be that ants are eating all the flowering buds?
>
> I have a crab apple on which I've grafted 5 domestic apples.  Most of the crab is still there, and appears to be healthy.  It breaks dormancy a week or two before the grafts in the spring, and it goes dormant a few weeks before the grafts in the fall.  Mostly, the grafts look healthy.  They are 4-5 years old, and some of them are now quite large, with branches wider than my thumb.  But they never bloom.
>
> Today, I was examining the tree.  The crab is covered with tight pink clusters of flowerbuds emerging form the ring of baby leaves.  The grafts have about 1/4 to 1/2 inch of green tip showing.  As I often see, there's some damage to the grafted buds, tissue is brown and misshapen.  In the past I had assumed it was due to some fungus.  Maybe it is, but today, I noticed little brown ants INSIDE the damaged area on one bud.  It looked like it might have had flower-bud tissue that was being destroyed, although it's hard to tell.  There were ants all over the grafted parts of the tree - maybe one every linear foot, with a higher concentration in the buds.  AND, this might be a clincher, the ants and the damage were selectively in the "fat" buds, not the flat buds on the side of the branches that are obviously vegetative only.
>
> Has anyone seen anything like this before?  Any suggestions?  Do you think it's ants?
>
> Thanks,
> Ginda Fisher
> eastern Mass. zone 6