[NAFEX] ants on apples?

list at ginda.us list at ginda.us
Thu May 5 21:14:17 EDT 2005


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 at 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
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