Larry Gut joined us on the line to answer a wide variety of questions about internal fruit worms, with a focus on codling moth. Download the recording and read the transcript below.
Recording
Download the recording of the June 26 call here.
Call Topics
Updates
Updates on diseases and insects
   Apple scab
   Plum curculio
   Mites
   Apple maggot
   On Japanese beetle
   Lesser apple worm and Oriental fruit moth: When can we expect them?
   Lesser apple worm and Oriental fruit moth: thresholds and OFM mating disruption
   How can we interpret the CM spikes we saw this season?
   Predicting next season’s CM
   On the photoperiod signal for first generation CM
   On first generation going into diapause?
   On moths’ fruit-finding ability
   On degree day generation time for CM
   On rainfastness of CM insecticides
   On the effectiveness of OPs on OP-sensitive populations, and detecting resistance
   On the situation with Guthion, Michigan, and the EPA
   On what to do for second-generation CM
Call Transcript
Updates on diseases and insects
Apple scab
John: Clearly, if you are stretching sprays
out and avoiding putting materials on at this point because of low codling moth
or low fruit, and if you have scab in the orchard, keep an eye out for new
lesions on the most recent growth at the ends of shoots. Presumably, all of the
lesions should be quiet even if they look dark. Conidia should not be viable
with the high temperatures that we’ve had. However, if you start seeing any
new, small lesions on new growth (if terminals have set, look at the
very tip of the shoots), that’s you would need to consider putting a little bit
of Captan on the scab-susceptible varieties.
Plum curculio
John: I just want to warn you that I’ve been
in a couple of orchards over the past few days that have PC adults continuing
to lay eggs. Even though the PC migration into the orchard has ceased, if you
haven’t controlled those PC, you need to stay on top of it to make sure you won’t
be surprised by a bunch of new damage. If you haven’t put any PC control on –
or if you did more than 4 weeks ago – then you want to keep scouting: the PC
are still ovipositing.
Mites
John: Even if you’ve had low mite pressure so
far (whether that’s because you’ve had no history with mites, because your
early oil sprays worked well, or because of predator activity), stay on top of
mite scouting, especially on the mite-susceptible cultivars. The heat that we’ve
had in the last couple weeks has allowed the European red mites to out-distance
the predator mite populations on the susceptible cultivars. If you only have a
little fruit, you’re going to want to be cautious about spending money on
miticide. However, the mite populations can increase so quickly that you will
probably see bronzing within a week or two. Even if your trees have no fruit,
you don’t want to send them into the fall all bronzed up. Doing that would weaken
the new fruit buds as they prepare to overwinter.
Most important message: keep checking for mites in your
scouting, and keep track of the populations.
Apple maggot
John: I just want to remind everyone that if
you’re using the yellow boards, you need to seed it with attractant if
they don’t come already seeded: they need ammonium acetate or ammonium
carbonate. If you have the traps that come pre-loaded with attractant, you need
to be changing them every week. If the cards are just yellow, with no
attractants, you can’t rely on them for monitoring purposes. They will pick up
a lot of picture-wing flies, but they won’t be very effective at picking up
apple maggots.
On Japanese beetle
John: I almost forgot to talk about Japanese
beetle. They’ve been hitting some orchards hot and heavy. In other orchards, it
hasn’t really started yet. So, stay on top of the JB. We don’t have time to
talk about trap crops right now. But if you see a high population of JB pop up
all of a sudden in your Honeycrisp or whatever variety, using a neonicatinoid
at a high rate is not the best way to go. You need to use something that will
kill the beetles quickly, rather than something like a neonicatinoid that is
mainly an antifeedant.
Once the population is already there, you need to clean them
off with something before you start using the antifeedant material.
Hopefully, the population will be somewhat lower than last
year, but it hasn’t started out looking very promising.
Visit from Larry Gut
Lesser apple worm and Oriental fruit moth: When can
we expect them?
John: There is a confusion in my mind about
the flights of these two species. I usually think of OFM having three flights
early, middle, and then late in the summer. I think of them as following the
Codling moth flights pretty closely. But yesterday’s Scaffolds indicated that
the peak of OFM (that is, the second OFM flight) is coming up on us, as well as
the second flight of LAW. Most of us are at least a week or two away from the
second flight of Codling moth, which means that Scaffolds is saying that OFM
and LAW will be flying earlier than usual. What do you think of that scenario,
Larry?
Larry: Was Scaffolds showing actual catches?
John: They were not showing catches of LAW,
but they were showing picking up low numbers of OFM, which doesn’t surprise me.
They predicted that LAW second flight would start by later on this week.
Larry: Well, I think they’re mistaken. I have
no idea how it would be starting that early, unless its development is somehow
different this season. I’ve always seen the LAW and OFM flights timed like you
said: with the CM flights. It should start right at about CM. Our
second-generation OFM is just getting going. I don’t expect LAW to start until
a couple weeks from now, when OFM peaks.
John: Okay, good enough.
Lesser apple worm and Oriental fruit moth: thresholds
and OFM mating disruption
John: There are no established thresholds for
LAW and OFM based on trap counts, right?
Larry: No, there are not, as far as I know. I
don’t think there are any for LAW. But they could have thresholds in New York
that I don’t know about. Here, we hardly trap for it.
OFM has no established thresholds. The reason it doesn’t is
because high counts don’t mean anything.
John: Oh really?
Larry: They don’t mean nothing, but high
counts with OFM could mean either that you have a problem, or mean that you don’t.
The moth flies so much that you can catch big numbers and not have an OFM
problem. That’s why nobody uses a threshold.
However, I believe that low numbers always tell you
something. If you’re catching less than 10 in a trap in a week, I think
that’s a pretty low number. Those low numbers with OFM are pretty informative.
Regarding LAW thresholds: I don’t know much about LAW
thresholds. I would guess that they would be something like with CM, where low
numbers indicate a problem, because it attacks the fruit.
John: Most people who aren’t using mating
disruption put something on most of the orchard for codling moth, meaning that
in those orchards we normally don’t have to worry about Lesser apple worm.
Larry: No one in your area has OFM mating
disruption out?
John: No. I’m not even sure whether OFM mating
disruption is registered in Wisconsin and Minnesota. There was a question about
that at one point, but nobody has had enough OFM, yet, to have to worry about
it to that extent. The only time we’ve had OFM populations was when we brought
in organophosphate-resistant codling moth. Then we ended up after a few years
with orchards with runaway codling moth problems. In those years, when I put
out OFM traps, I would catch 100-200 OFM in a flight.
But within a year or two of hammering on the codling moth,
the OFM numbers dropped to nearly nothing.
Larry: I just asked about mating disruption
because even though it’s not the label, the OFM mating disruption knocks the socks
off of LAW. It just eliminates it.
John: That’s a really good point. Guys, keep
that in mind: if you’ve put on a larvacide on for LAW because you caught 75 LAW
in a trap this summer, then you may want to look at OFM mating disruption to go
along with your CM mating disruption next year.
John: We have had catches of 50-75 LAW this
year, larger than normal; I presume this is a reflection of actual pressure.
You said that with LAW, we should be worried about low numbers. So, should we
be even more concerned about these high numbers?
Larry: Yeah, those are pretty high.
John: They’re scary.
Larry: Yes, they are.
John: Okay, that’s all I need to know. So, for
all of you: watch the LAW. We mostly put up OFM traps, because that’s the one I
usually want to make sure we don’t ignore. So those numbers of LAW are actually
being caught with an OFM lure.
Larry: Do you have fruit on the trees? Do you
have fruit for them to attack?
John: Yes.
Larry: Okay. We have none.
John: Let’s put it this way: it’s spotty. Most
growers who are on the phone have somewhere around a 20% crop. The number of
people who have a 50-70% crop are few and far between.
Larry: So, the growers who are trying to
harvest 20% crops should consider the LAW threshold to be even lower than
normal. Those few moths are going to find the fruit. So LAW/OFM is even more of
a concern. I’d be very leery.
John: From what I know about the searching
behavior of CM females, it seems like they can find fruit pretty effectively.
Are you suggesting that LAW probably are the same?
Larry: Yes.
John: So, if you have a 10% crop and the LAW
are able to find those fruit, the same number of LAW is going to infest a far
greater percentage of your fruit, if you’re not putting anything on to control
it. If you had a full crop, you might lose 2-3%. With a 10% crop, you could end
up losing 50% to LAW infestation.
Larry: Why do you think you have so many LAW
this year, John?
John: Well, the places where we are catching
the most are the places where the growers have had mating disruption for a
number of years and haven’t applied any insecticide for CM, unless they catch
them with AM or PC sprays.
I would presume that the mild winter also contributed to the
LAW numbers. The temperatures might have led to a little less mortality.
On codling moth
How can we interpret the CM spikes we saw this
season?
John: Very early this spring I thought CM
populations might be larger than normal, because we had no temps low enough to
cause winter mortality. I conjectured also that CM numbers might be reduced by
the freezes at pink and bloom.
Most orchards in Wisconsin, Minnesota, and N. Illinois had a
very definite biofix. The CM came it all at once on May 3/4 or 12. After that
first biofix, in many orchards, very little happened. Then, there was another
spike on June 9/10. We had plenty of nights where flight conditions were
perfect, but saw no codling moth except on these peak days.
Is it plausible that the May spikes represented the part of
the population that began to develop (came out of diapause) before the freezes,
and the spike in June was the portion that developed (came out of diapause)
after the freezes, during bloom? Is that just too much hot air?
Larry: It sounds like it, but I don’t know. We
didn’t experience what you experienced. We had the early spike. The reason for
the early one is pretty obvious. We had moths that continued to develop while
overwintering, because the development threshold is 50 degrees. But because
their flight threshold is 60 degrees, they didn’t do anything; they just built
up in the orchard. Then, when we had our first nice weather, all the moths that
had come out early in the year were all out there to find traps for the first
time. Evening temperatures got warm for the first time, and we had all the
moths come out of their overwintering site in a cluster.
But, in Michigan, after that, we got a little bit of cold
weather, then it got warm and stayed warm. Since then, we’ve had continual
codling moth flight that is probably the highest I’ve seen since I’ve been
here. It overwhelmed all the mating disruption blocks. It’s been pretty
amazing, actually. Of course, it has tapered off now. But it was really high
everywhere, and I can’t explain why, except that the emergence got pushed
together so the peak was bigger and the tails were smaller. The whole flight
was packed together because of our winter and summer conditions and just
overwhelmed our defenses.
Grower: Larry, did growers respond to that, or
did they let it go because of the lack of crop?
Larry: I did some research on the best course
of action. What we did was try to get people to take advantage of the condensed
flight. Because the whole flight was packed together and because growers wanted
to avoid an expensive control program, my suggestion was to wait until 350 or
400 degree days to apply a larvacide so that one application would cover 70-80%
of the egg hatch. That’s what many growers did, and that’s what I did. The idea
was that we could get control of the entire codling moth generation with one
spray.
We had another issue that dominated our landscape, which was
crazy: that is, people had too much Guthion sitting around that they thought
they wouldn’t be able to use in the future.
Grower: With codling moth, 500 degree-days is
50% egg hatch, so at 350-400 degree-days they were at 30-40% egg hatch?
Larry: Probably not, and I’ll try to explain
why. This answer applies to Michigan, but it’s probably the same for you. Because
of all the programs we’ve had in the past, this whole codling moth flight has
had almost no tail. In the orchards that have been sprayed well for the last
several years, the beginning tail has disappeared. So, the 3% egg hatch that is
supposed to start at 250 degree-day s really isn’t starting until 300 or 350
degree-days. Most of those orchards get no egg hatch between 250-350
degree-days. So that early spray is a waste of time. There is very little
codling moth occurring in that window.
So, really, the 400 degree-days probably represented 10% or
20% egg hatch. Over about a 2-week period, we went from 10-20% to 80% egg
hatch. That sharp spike was what I was targeting.
Grower: I did something similar, but I waited
until 500 degree-days. I wonder if I waited too long, there.
Larry: I don’t think so. I think it’s great.
The amount of egg hatch that was occurring even up to your 50% was probably not
a lot because of the good control programs in the past, and because there just
is not a lot of activity. What did you spray?
Grower: Altacor.
Larry: Altacor is a tough one, because Altacor
actually affects CM adult flight: it stops them from flying, basically. So,
since you’re hitting adults and larvae, instead of just larvae, you probably
didn’t get all the benefit you could have gotten with the Altacor. Because by
then, you were probably well into emergence, huh?
Grower: Yeah. So Delegate would have been a
better choice, there, because they’re already flying so much?
Larry: I don’t think it mattered. You just
would have gotten a little more benefit if you had gone a little earlier. Both
Altacor and Delegate have really good residuals. So you probably covered
everything from that point on.
Grower: This is my first big mating disruption
year after your workshop at my place last year. But then I didn’t have any
apples to worry about, so I thought I’d just wait and apply Altacor.
Larry: A lot of the growers did that here,
too, because there was no fruit. That was the big question: should or shouldn’t
you put on mating disruption?
John: So a lot fewer growers used mating
disruption this year?
Larry: Oh, yeah. A lot fewer used it, and a
lot more who did use it put on fewer dispensers.
John: You said the mating disruption wasn’t
working, or that it was being overwhelmed. If the growers are not getting
area-wide saturation like they had been, and they’re also cutting back the
number of dispensers that you put out there…. Boy, if we get better winter
survival because we don’t get any lethally cold temperatures, and then you cut
down the number of disruptors…
Here we don’t have the contiguous orchard acres for it to be
a major problem for one orchard to stop using it one year. But, we have had
situations where the grower cut down on the number of disruptors. I’ve seen
that there is a break point. I don’t know whether it’s a linear relationship,
or what, but if you’re trying to eliminate your CM larvacide sprays, you have
to do everything you can to keep the numbers under threshold. If you get it
down to 70% of the flight but don’t keep it under threshold, you’re not going
to save yourself a larvacide spray.
Larry: No, but that’s what they did.
John: So the Altacor has some effect on
flight. Do you have any idea about the reason behind that?
Larry: Yeah, but I’m not supposed to talk a
lot about it, because it’s part of a graduate degree program of a colleague of
mine. Just know that it’s affecting adults and that’s a nice feature.
Predicting next season’s CM
Grower: Larry, with our weird weather and
weird management this year, what do you think is going to happen next year?
Larry: I was really encouraging growers not to
completely abandon their CM program, because I think what’s going to happen
next year will depend on what growers did for the first generation. So, if you
controlled CM first generation, I think you’re going to be in really good
shape. If you didn’t, then by the way the year is going right now, if you get
infestation in the second generation, you could have very high pressure later
on. In Michigan, it’s a good year for a third generation.
John: But if you have a third generation, it will
be a suicide generation, won’t it?
Larry: It could be.
On the photoperiod signal for first generation CM
John: That was one of my questions. Would you
review the first generation photoperiod requirements to for second generation
larvae to enter diapause?
Larry: As CM develops in the fruit and starts
getting big, they have to experience shortening day length. And those
shortening day lengths occur in mid-August. By mid-August, you have to have
large developing larvae in the fruit. If the larvae reach the large size later
than that, then they will go into diapause. So the ones that come out for the
next generation are the ones that have not experienced that shortening day
length.
John: So what you’re saying is that if second
flight starts 10-14 days from now, and we get egg hatch by the middle or last
part of July, the day length still may be too long to trigger diapause.
Larry: Right, they will not go into diapause.
They will come out for a third generation.
John: That makes sense. If we thought that the
third generation was going to be a suicide generation – in other words, that it
wouldn’t get far enough along to successfully overwinter – then we wouldn’t
have to worry about the first part of the second generation. I’m not
recommending that. But the latter part of the second generation’s egg laying
would be more likely to go into diapause than the early part. So it’s the
latter part of the second generation that would be more problematic in terms of
overwintering and causing a problem next year.
Larry: Correct.
Then, the whole diapause model gets modified a little bit by
temperature. Very, very hot temperatures will stretch out day length. If it’s
very hot – say in the mid-80s to 90s – then the larvae will continue on past
the normal photoperiod cutoff (mid-August) without going into diapause.
So what’s your situation in your part of the world? Do you
not normally have a full second generation?
John: We have a second generation. Let’s just
say that we rarely have a third flight.
On first generation going into diapause?
John: An old article written by Jay Brunner
mentioned that a portion of first-generation larvae could go into diapause. If
a significant portion of your first-generation CM went into diapause and didn’t
come out again until next year, and became the first generation next year, and
you’re one of the growers that uses the same CM material (same MOA) year after
year, then you would be putting heavy selection pressure on the few CM that
overwinter from first generation. Larry, do you think we should be at all
concerned about that first generation going into diapause?
Larry: No, I think that it’s not a big
concern.
On moths’ fruit-finding ability
Grower: You mentioned earlier how good the
moths are at finding apples. How do they do that? How are they so good at it
when they only have 5% of a crop?
Larry: The fruit gives off odors. There is one
odor in particular called beta farnasene that stimulates egg-laying. Varieties
that give off a lot of that compound are especially easy for the moths to find.
The moths get stimulated to lay eggs on or near that fruit. There are probably
several other volatiles, but that one is probably a major factor.
John: Which cultivars produce more of the beta
farnasene?
Larry: I actually did my Master’s on it, but I’m
really old, so those cultivars aren’t around anymore, I don’t think.
Grower: In my orchard, that 5% of remaining
fruit isn’t spread evenly over the orchard. There are a couple areas up high on
the hills that survived. So, should I concentrate more traps up in the areas
that have apples than in the areas that don’t?
Larry: Yes, for sure. The CM behavior is such
that the females will fly more when there is less fruit. Their search behavior
is such that they will look more for fruit when it’s harder to find. A typical
female in an orchard with a lot of fruit might lay all her eggs within a few
trees of where she lays her eggs and gets mated. But when there are fewer fruit
in the orchard, the female will tend to spread her eggs over many individual
fruit, over a larger distance. When she doesn’t find a lot of fruit, she
travels more.
So, they will find the fruit. It might take the females a
little bit longer to find them, but they will find them.
John: If you’re not using mating disruption in
those areas, then you do 1 trap per acre. That would be pretty dense trapping.
I’ve reiterated a bunch of times: If you get some
first-generation injury, then controlling second generation is nigh impossible,
especially with all this vegetative growth. It’s so hard to get enough
coverage, because they are so good at finding the weak spot in the coverage on
the fruit. Once we get a foot of growth on these shoots, how are you going to
get enough cover on to adequately control second generation?
On degree day generation time for CM
John: We normally have 1000 DDs between
generations of CM, but it looks like some growers will have a different length
of time. Example: two orchards approximately one mile apart. Orchard 1 is well
maintained with historically low CM pressure. Orchard 2 has been poorly
maintained for several years and was unsprayed in 2011. Orchard 1 biofix is
about 3 weeks later than orchard 2. Orchard 1 adult flight is declining.
Orchard 2 is at 900 degree days with strong flight continuing. The demarcation
between first and second flights is not difficult in the first orchard,
but the CM flight is likely to be continuous in the second orchard. How do
you separate the two generations in the second case? We want to know in
order to know when to switch modes of action.
Larry: Oh, so that’s why you wanted to know
whether there would be another generation. I don’t think it’s all that
critical, normally, because you’re just targeting the peaks in the flight, then
add 250 or 300 degree days from when you have a flight you want to respond to,
and then spray.
John: The guy is catching between 5-15/day per
trap on average. He has maintained cover from 250 degree days. He didn’t have
the luxury of going to 350 or 400 because he caught 30 or 40 int he first
couple of days.
Larry: And how many sprays does he have on,
then?
John: He just put his third larvacide on. But
he switched from Delegate to Guthion. As you were saying, he had some Guthion
he wanted to use up. The spray is a few days old, and the numbers in the traps
have dropped. He should be OP-sensitive, but we went sure. Anyway, the spray
may make it easier for him to determine when the second generation begins. But
when he sprayed Delegate, he didn’t see a drop-off.
So, my question is: if you don’t get a drop-off and the
pressure is constant, how do you know when to switch materials from first
generation to the second?
Larry: I don’t know the answer. But I guess if
you’re just doing it by mode of action, and that’s your critical criteria, then
I think you should just stick with the 1000 degree days. Then, the sprays you
put on after that should be rotated.
The other part of your question is, Why is this happening? Everything
that happens in the first generation is directly related to the overwintering
of the second generation in the previous year, I think. So, that grower must
have had a pretty good population escaping right at harvest. He must have had a
big population late in that second generation in the year before. Those moths
will emerge very late in the following year’s first generation. So, that’s why
he has this big tail-end flight.
I would just switch after that 1000 degree days if I had to
make a decision.
On rainfastness of CM insecticides
John: A question related to John Wise’s work
on rain fastness:
This is really not a concern this year, because the degree
days have been so high that we’ve been romping through the generation times,
here. So, insecticide life hasn’t been our major issue this year. In most of
the years, though, it’s a question.
Insecticides’ effective lives are typically described in
calendar days, while insect development in degree days. Excluding washoff, the
effective life of an insecticide for CM is concerned with leaf and fruit
expansion. But in cooler weather if CM generation time is longer, the non-rain
weathering concerns would also be slowed.(ie insecticide should last longer
than calendar days might suggest). What do you think? Has John attempted
to integrate elapsed degree days into his residue studies?
Larry: Yeah, I don’t know about that. I don’t
know if John has done that or not, because I haven’t talked to him.
But in addition to leaf and fruit expansion, you have the
simple breakdown of the material by UV degradation, as well as absorption,
overall chemical decomposition – those all play a big role, too.
John: I guess it was more of a “Golly gee I
wish†type of question.
Larry: Yeah, I don’t think it’s a matter of “I
wish.†I think you’re in trouble.
Fortunately, some of the materials we’ve started to use,
like Delegate and Rynaxypyr, have a little longer residual and more leeway than
we used to have. They’re actually pretty good. So, you might be able to span
them out a little bit. But that’s up to you, because I can’t make a
recommendation.
On the effectiveness of OPs on OP-sensitive
populations, and detecting resistance
John: When OP-sensitive populations were
exposed to Imidan or Guthion, and we had adult mortality, for how long would
something like a 2-pound application of Azinphos kill adults?
Larry: It’s all a gradual change. If you put
on that spray when they were really sensitive to it, you would have traps
completely shut down for at least a couple weeks. And then, as resistance would
build up – and this is based only on the experience that I and others have had
working in orchards – you might see catch in the second week up to 50% of what
it was instead of near 0%. Then, when you got to the point of field failure,
you would see in the second week that catch wasn’t down very much.
So if you had a low catch one week, and now your catch is
back up the next week, then I’d say that you probably don’t have a really
sensitive population.
John: The one caveat there is that if he has a
trap on the edge of the orchard near abandoned trees or unsprayed trees, then
that trap will continue to catch new migrants that haven’t gotten the full
exposure to the material. So if the rest of his traps are low or at zero, but
he has one trap on the edge that’s high, then that would make sense. You wouldn’t
expect all of them to experience immediate mortality as soon as they fly into
the orchard.
Larry: Correct.
On the situation with Guthion, Michigan, and the
EPA
John: Did your guys end up spraying a
larvacide where the mating disruption didn’t work, then?
Larry: Yeah, I’m pretty sure. The problem is
that so many of our growers put on Guthion – I can’t stop them – and in at
least 80% of our orchards in Michigan, it’s ineffective. It won’t do anything;
it was a complete waste of money.
John: Still? Even though it’s been a few years
since they started using other materials? The populations haven’t reverted at
all, yet?
Larry: They might have reverted a little bit,
but they’ll come right back. So, you’re right, they might have gotten some
effect. I hope so.
We actually have a battle going with the EPA and we might be
able to save Guthion. It’s pretty close right now. The head of the EPA Registrations
just visited Michigan for three days. We’ll see what they do.
John: Well, that would be pretty big news,
that’s for sure. When do they anticipate a decision?
Larry: I don’t know the answer. That’s all
political with all of our grower groups. I was just a resource. They’ll be
sued, of course, so we’ll see.
Grower: It might end up affecting Michigan,
specifically, mightn’t it?
Larry: You know, I don’t know the answer to
that. It wasn’t the argument that we presented. It would have included the
whole Eastern and Midwest region, at least. But it could just be for cherries,
too, because that’s the real fight. So, I don’t know, and I don’t want to say
things that I don’t know. But it isn’t a completely done decision, yet.
John: Thanks for spending the hour with us,
Larry.
Follow-up questions
On what to do for second-generation CM
Grower: So, if you want to do the best job on
second-generation codling moth, what are you thinking of doing? You talked
about the difficulty of getting good coverage with all the leaf growth. You
might be able to slow down and use more water. But what are you thinking about
timing?
John: Well, it’s problematic if you have
mating disruption up. Going over the portion of the orchard in which you saw
hatch that overwhelmed the mating disruption – which could have happened
because the females flew in from across the road already mated. In any case,
where you have fruit that is infested this generation, you will obviously have
more issues in those parts of the orchard than where you don’t have
infestation.
But your L2 traps should reflect that difference, as well.
There is a possibility that you won’t get much
second-generation flight from the abandoned orchard, because they left because
there was no fruit. So, if you don’t get a second flight from there, your
mating disruption might actually work better for the second flight than it did
for the first, because you won’t have to be dealing with that second source of
adults.
On the other hand, when you get L2 traps out in a mating
disruption orchard, and you catch 3-5 in a trap when we know that 1 is supposed
to be the threshold: Larry has said in previous years that if you get 1 or 2 in
a couple weeks in an L2 trap with mating disruption, don’t get bent out of
shape about it. If you were to get considerably more than that – say, 5, 6, 8,
even 10 in an L2 trap with mating disruption – that’s clearly problematic.
In any case, you’re still looking at a minimum of 250 degree
days from that flight before you put out your larvacide. Then, it’s just a
matter of hoping for the best.
In terms of coverage, you can put on more water. If you’re
only using 40 gallons and you have a lot of vegetative growth, you will clearly
benefit from jumping it up to 60 or 75 gallons. You will have a better chance
of covering those few fruit that are inside that canopy. But there is a limit
to how much coverage you can achieve. Really good growers with really good
equipment will probably not be able to get 100% control of second generation if
they have a lot of that growth. But you do the best you can.
Grower: I’m hoping the mating disruption kicks
in and becomes more effective after this other orchard has cleared out. Then,
of course, the Japanese beetles are starting to fly, too, so we’ll have to be
dealing with that.
