Hello, I'm Diane Alston.
I'm an extension entomologist with Utah State University.
Um, in this time of social distancing due to COVID-19 virus,
we are, um, making a field day via video this year.
So, I won't wear the mask for the whole time
but uh, just to give you an idea of, of what it's like to,
to do field research with covid-19, um, impacts.
It's not nearly as much fun.
So my topic today is, uh, woolly apple aphid.
Woolly apple aphid is one of the more tenacious aphids in terms of its management.
And it has a little different, uh, biology and life cycle than some of the more,
the other common aphids in apple and other fruit trees.
So woolly apple aphid, um, a big key factor of why it's so challenging
is it has a lot of woolly, waxy material that covers it,
and that makes it, um, more impenetrable, to um, insecticides, to weather,
[Diane Alson off-screen]: to predators, to things that are going to uh, come and,
and want to, uh, eat or take advantage of it.
Underneath that white, waxy, woolly covering,
um, the aphids themselves tend to be a reddish brown in color in the adult stage
and in the immature stage their more of a salmon color.
So this- eh uh- this aphid is actually native to North America.
Many of our past aphids, um, are not native to North America.
But this particular one is.
And it actually, um,
its primary host in the eastern United States is the American elm.
And so the American elm is its primary host,
and then where it would overwinter, and lay eggs.
And then during the spring and summer it would move, it moves on to apple,
where it would develop colonies like this.
Here in the western United States we don't have, um, American elm.
And so, here, w-woolly apple aphid has adapted
or evolved to stay on apple trees year round.
And so here in the west, they primarily overwinter on the roots of the tree.
And on the roots they can form these galls,
um, from their feeding damage as- as they, as they feed there,
and it's a, good nutrient source for them throughout the- the winter time.
And then in the summer time they move up into the canopy of the tree
and spread and start to, um, develop new colonies.
However, we have noticed here in, in northern Utah,
that as our winters have become more mild,
we start to see more and more aphids that will overwinter
actually on the above ground part of the tree.
And so we'll show some close-ups of that in a little bit.
But they can overwinter on the pruning scars, so the old scars,
especially where they're right on, right near on the main trunk.
They can also overwinter on these twig or limb galls
that the aphids form during the summer,
and a few of them reside there throughout the winter and survive to the next year...
One of the key factors in managing woolly apple aphids besides insecticides,
which we'll talk about in just a moment, is root stock selection.
So the Malling-Merton rootstock series,
which is an older one, the MM series, um, was developed with uh,
trying to develop some resistance for w-woolly apple aphid.
Also there's a newer Geneva rootstock series
that is also resistance to woolly apple aphid.
And it's based on um, the, apple, um, species malus robusta to-
that provides that resistance to, to the tree, to the aphids.
So what kind of injury do woolly apple aphids cause?
So, as they're feeding on the above limbs, shoots, new growth,
you can see some um, here, um, right here on the, um, the new limbs.
They um,
they cause, um, uh, reduction in the.. vigor and the vitality of the tree.
They can yield to fruit reduction, uh, yield reduction.
They can russet fruit.
They'll form um, honeydew, which is the sticky material
that they, uh, that's from the sap, the excess sap that they feed on
out of the phloem tissues of the tree.
And that will drip down onto the apples, especially in the stem bowls,
you get this black sooty mold that will grow there,
and that can be difficult to wash off.
So the timing of activity of the aphid is again following mild winters,
you'll see a lot of them overwintering up on the above ground parts,
following more severe winters they tend to show up later,
so more not until June and July,
when they have to move up, um, from the, the roots of the tree.