Hello.
I'm Diane Alston, extension entomologist with Utah State
University, and we're at the Kaysville Research Farm today.
And we're talking about woolly apple aphids.
So the first section we talked about its biology, its life
cycle, how it overwinters on the tree,
and now we're going to talk a little bit
about its management.
So there is some natural biological control.
And one of the most effective biocontrol agents
is a parasitic wasp that is specific to woolly apple
aphid called Aphelinus mali.
The challenge with this parasitoid wasp
is that it doesn't tend to build up in population size
until later in the summer.
And that's too late to provide good suppression
of woolly apple aphid in terms of economic reduction
to protect fruit crop yield.
So there are a handful of generalist predators
that are also very effective.
So these include a number of species of lady beetles.
Here at the Kaysville Farm, we've
seen the convergent lady beetle, as well as
the Asian multicolored spotted lady beetle.
Also, syrphid fly larvae are good predators, as well as
green lacewing larvae, and several species
of predatory true bugs.
Also even European earwigs, which
can be a pest on fruit crops as well,
but they are also a predator.
So they're omnivorous in their feeding habits,
and they will also feed on woolly apple aphid.
And they're not deterred by the waxy, woolly white covering.
They'll chew into that and get in to feed on the aphids.
Another common way, or probably the most common way
that commercial producers manage woolly apple aphids
is with insecticides.
So back in the '80s and early '90s
when organophosphate insecticides were commonly
used for codling moth control and other key
pests, such as leafrollers, we didn't
have as many woolly apple aphid issues.
And as we transitioned away from an organophosphate-based
insecticide program, we've noticed that woolly apple aphid
populations have increased.
So there's two key timings for managing woolly apple aphid.
The first is if you had a problem in an orchard
the previous year, or if at pruning the orchard
that late winter early spring you
notice overwintering populations in the tree,
you can use a delayed dormant spray.
So it's best to do this with a dormant oil,
and then add a very strong product like Diazinon
into the mix.
And that is fairly effective on suppressing early populations
of woolly apple aphid.
The next opportunity is going to be after bloom.
And these are going to be materials
that you're going to be targeting to apply on the tree
while the aphids are active.
So the main product here in Utah that we've
had good success with is Ultor.
And this is the common name spirotetramat.
It's in a group of insecticides called
tetronic and tetramic acids, or it's Insecticide Resistance
Group number 23.
And the unique feature about this particular insecticide
is it has what's called two-way systemic movement.
So that means when you apply it as a spray on the tree,
it's taken up by the foliage and by the stems, by the twigs,
by the new growth, and it moves upward, so moving
into other shoots.
But it also moves downwards, and it moves down
into the roots of the tree.
In a study that we did a number of years ago,
we actually were taking out trees
that had had woolly apple aphid that were or were not
treated with Ultor insecticide.
And we found that the aphids on the overwintering root galls
were also very suppressed or non-existent where
we had used Ultor But where we had not used Ultor
there were a lot of aphids on the tree root galls.
So that's a unique mode of action.
Another group of insecticides that has also
shown some good efficacy on woolly apple aphids
is the product called Closer, which is the chemical name
sulfoxaflor.
And this is in the neonicotinoid group.
It's a sulfoximine in the group 4C.
And this product does not have the two-way systemic movement,
but it does have local systemic uptake, where
it's taken up locally in the area
where it's applied on the tree.
And it's good on suppressing insects
that feed in the phloem tissue, such as woolly apple aphid.
In this particular trial or study
that we're standing in here today,
we did an assessment of comparing Ultor,
the insecticide that I mentioned was very effective,
against some new chemistries.
Unfortunately, we didn't see that the new chemistries worked
that well.
They work well on other species of aphids,
but not on woolly apple aphid, which
is one of our more tough aphids to manage.
And so in this particular trial, we've
seen very good results with almost completely clean trees
where we applied Ultor just after petal fall and then again
two weeks later, as compared to these other novel
insecticides that we were looking at to see if they would
also have efficacy.
But unfortunately, we didn't see that.