We weren’t able to get Larry Gut on this week (hopefully next week!), so we did another round of updates on a wide range of topics for growers to think about at this time of the season, with a focus on Codling moth and Apple maggot monitoring and control.
Recording
Download the recording of the June 19 call here.
Resources and Materials
- NEW: Spotted wing drosophila pest alert/fact sheet(thanks, Peter Werts)
- This week’s Cornell Scaffolds journal with important articles on Codling moth and Apple maggot: here
- John Wise’s recent addendum to his research on the rainfastness of insecticides: here
Call Topics
- Organizer’s Note
- ***Re-announcement of upcoming scouting workshop series!***
- Logistics Update
- Update on stone fruit
- On drought stress and bitter pit
- Update on Japanese beetle
- Update on Stink bugs
- Update on White flies
- Update on plant hoppers
- Updates on Codling moth
- Grower question on A-hump, B-hump, and resistance management
- Things to think about as you approach the end of first-generation CM
- Grower question: What about tank-mixing two materials that are rated fair on another insect like Apple maggot?
- On organic methods of control of CM:Â virus
- On Potato leaf hopper and White apple leaf hopper
- On rainfastness of pesticides
- On Apple maggot trapping
- Apple maggot trapping: Putting unbaited traps in rows adjacent to problem varieties
- On Oriental fruit moth and Lesser apple worm
- On borers
Call Transcript
Organizer’s Note
We apologize to everyone who had trouble getting into the conference call this morning. The call service was experiencing some technical problems.
***Re-announcement of upcoming scouting workshop series!***
For those of you that may have missed it before, please read our post on the upcoming scouting workshops hosted by IPM Institute, CIAS, and Threshold IPM. They’re coming up quickly (the first one is on June 26), so sign up ASAP. See the post here.
Logistics Update
Larry Gut wasn’t able to join us this week. We are going to try to get him on the line next Tuesday. If Larry can’t be on next Tuesday, we will do a webinar on internal fruit feeders.
We will not be having a call on Tuesday, July 3 in observance of the 4th of July week.
Update on stone fruit
John: There were some peach varieties that fruited heavily this year. Those were the peach varieties that flowered early. The later-flowering varieties tended not to set fruit.
Those early-flowing peach varieties are now showing lots of damage and stress. Some of it looks like bacterial leaf spot and bacterial canker. How much of that is due to the crop load and water stress that the trees are under right now, or due to the cold, wet conditions we had in April, I don’t know.
John: I’ve seen fruit flies in large numbers over the last couple of weeks. I’ve seen more than usual around stone fruit, in particular. I haven’t been around any strawberries. Whether any of those are Spotted wing drosophila or not, I don’t know.
If you have any stone fruit or strawberries left, you might want to be sampling for Spotted wing drosophila. You can use a low-tech trap that we tested last year: it’s basically a 32-ounce clear deli container baited either with a liquid yeast solution or with apple cider vinegar.
If you have questions about your stone fruit, give me a call.
On drought stress and bitter pit
John: I don’t need to remind anybody what those trees – especially the young trees – are going through in this heat that we’ve been having. I did want to remind everyone, however, that this weather is custom-made for bitter pit: hot, dry weather. This is especially a concern with varieties like Honeycrisp and Cortland – you probably know best which varieties in your orchard tend to get bitter pit. As Phil Schwallier said a couple weeks ago, it’s going to be extremely difficult this year to get enough calcium into that fruit to prevent widespread bitter pit.
So, unless you’re irrigating, which would help your trees pull more calcium up from the soil, it’s probably going to be a big issue on these lightly-fruited cultivars that are already susceptible to bitter pit.
What can you do? All you can do is put as much calcium on those susceptible varieties, as often as you can.
Update on Japanese beetle
John: Many people in SE Wisconsin and Northern Illinois have already seen Japanese beetle. One of my growers down near Beloit started to find JB in the middle of last week. I would imagine that they’re emerging now in quite a few places.
Bill Stone: In 6 traps, I’ve caught multiple JB in 5 of them. They started over the weekend.
John: Have you taken your traps down, then?
Bill: Yes, I have.
John: Good. I would advise anybody in the SE Wisconsin or northern Illinois to take down your JB traps if you have them up. Unless you’re paying close attention to it, it will soon turn into a JB magnet.
Like usual with JB, their emergence comes at an awkward time. We’re at the period of the season when a lot of people are ending their first-generation Codling moth management options, and most people don’t have Apple maggot yet.  Ideally, we wouldn’t want to be spraying for anything right now.
When it comes to JB management, my perspective is that it’s better to do small spot sprays often than to wait until you start seeing a large population and extensive damage. Why? Because of the exponential growth in their population, and their aggregation pheromone that attracts huge numbers to the initial feeding sites.
So, as much as a pain as it is, it’s better to go out and spot spray on a frequent basis than wait until populations build up.
You can imagine that if you have a million JB on four rows of Honeycrisp: not only is it hard to kill a million of them, but they’re also attracting extra millions in addition. In that kind of situation, even if you spray something that works against the beetle, it might not appear that it’s working due to the increased immigration that covers over the mortality. This kind of scenario usually happens toward the middle period of their emergence pattern.
In any case, it’s better to prevent that buildup in the first place, if possible, whether you’re using a nerve toxin like Imidan or a repellant like one of the neonicatinoids or Neem products.
Update on Stink bugs
John: Boy, I’m seeing a lot of stink bugs, but I’m not seeing a lot of damage. Keep your eyes peeled, though. A bunch of people have found egg masses of stink bugs. If we do the webinar next week, I’ll show slides of those egg masses. Most of you have probably seen them in your orchards, when you’ve been doing hand thinning.
A lot of the stink bug egg masses have hatched out in the next few weeks. Most of the bugs I’m seeing are adults: green and brown stink bugs. Like I said, I haven’t seen the damage that we associate with them – at least I don’t think I have. Sometimes the evidence can be confusing.
If you have some fruit, stay alert and be aware that the stink bugs are out there. We’re hoping that they’re feeding on other hosts and not causing major fruit damage.
Update on White flies
John: This is an insect that we haven’t talked about, but one that I’ve seen for several years: white flies. If anybody grows anything in a greenhouse, you know about White flies. Worldwide, some of the White flies are major, major headaches. They have multiple generations, develop resistance very quickly, and transmit various plant diseases.
Anyway, here’s the news: I’ve seen White flies on the terminals of pretty much every cultivar that is still growing. If your shoots are still growing, when you’re out looking for something like an aphid or Red-banded leaf roller hatch, you may see little white things on the undersides of the growing point of the terminals. The little white things will start to fly when you try to touch them. They don’t fly fast; they’re not like hoppers.
I don’t have any information about what they might do to pome fruit, but I’ll try to get an answer by next week. I know that they can be a real nemesis to a lot of crops.
Update on plant hoppers
John: The other uncommon pests that you’re going to see frequently in orchards in weather like this are different types of plant hoppers: leaf hoppers, plant hoppers, frog hoppers. There are a bunch of different names for them. They are all basically long and narrow, similar in shape to Potato leaf hopper or White apple leaf hopper adults. When you try to touch them, they blast off: there one instant and gone the next, thanks to their jumping legs.
In a hot, dry year, you’re going to see a lot of insects coming off of plants that are drying up or that you have mowed, like forbs, grasses, and clovers. They might normally go back to something on the ground that is regrowing. But in a dry year when the ground cover is not regrowing, you’ll see the bugs up in the trees.
For the most part, I don’t think they’re going to be a major concern, but you should certainly stay on top of it, especially around young trees where they might be able to do some economic damage.
Updates on Codling moth
John: Most people should be at or approaching the end of first generation CM. The Scaffolds journal from Cornell from yesterday afternoon says that as of June 18, first generation adult emergence was at 98%. They don’t specify, however, which of the two sites (Geneva or Highland) they gathered that data from. Our area is more akin to Highland than to Geneva, in terms of tree phenology. Geneva is behind us, this year at least. For most people, if you’re up in the 600-700 degree-day range from your CM biofix, you should be approaching the tail end of the first generation flight.
That doesn’t mean you’re approaching the tail end of the egg hatch, however.
Last week, we talked about people catching Codling moth in what looked like the classic “B-hump†in the first generation flight. Some orchards caught them in significant numbers.
After look at traps for another week, I can say that it looks like it was a fairly short-lived “B-hump.†That is, they came in in a clump, sort of like the first flight in many orchards, where people had a very noticeable jump in flight that was identifiable as a good biofix, but then found very few just after that. In this case, a lot of these secondary flights seem to be short-lived.
One grower had a good question related to those two separate, secondary flights. This grower had applied an insecticide at 250 degree-days from the first biofix. He didn’t catch anything between that time and that “B-hump.†His question: Could he treat that “B-hump†as a second biofix (vis-a-vis insecticide application)?
Yes, you certainly could. If you want to control that second set of eggs with a larvacide, for example, it makes far more sense to wait until the degree-days are approaching egg hatch for that “B-flight.†I don’t see any problem with setting a second biofix if there was very little flight in the interim period between first flight and the “B-hump.â€
Grower question on A-hump, B-hump, and resistance management
Question: Can we consider each “hump†– “A-hump,†“B-hump,†and the second generation – as separate generations? My concern is resistance management for that first-generation materials. You should use one material (or set of materials) on one generation, and a different set on the following generation, right?
John: Really good question. First, there is nothing that compels us to use the same material two, three, or four times. There are guys who are looking at their third spray of a particular larvacide in bad situations. In those cases, when you’re spraying multiple times within the generation, you certainly do not have to use the same material.
However, you do need to avoid using anything that you used in the first generation on the second generation.
So, the more things you use on the first generation, the more things you eliminate from your toolbox for the second generation.
Regarding the question about whether you should consider the A-hump and B-hump as separate generations: Biologically, you can’t. When we use the term “generations,†we’re talking about offspring from one generation producing the following generation, and so forth – genetic continuity from one time period to the next. What we have with the A-hump and the B-hump is not a parent-child relationship; it’s more similar to an elder sibling and a younger sibling. So, they represent two cohorts of adults, but they were produced by the same generation the previous fall.
It’s true that in many orchards the time lag between the A-hump and the B-hump, and then the B-hump and the second generation, will not be much different. They often follow similar time intervals. But from a genetic standpoint, the thing that we need to focus on is genetic continuity for the purposes of reducing resistance.
Things to think about as you approach the end of first-generation CM
John: If you’re approaching the end of first-generation CM, there are a number of concerns.
First, don’t let a small fruit crop, and perhaps a moderate-to-light-but-over-threshold CM flight trick you into thinking you don’t need to control the end of this first generation. Too often, we see that people put out expensive sprays or mating disruption early in the season, but aren’t very anxious to go out and spend more money controlling a small number of CM late in the first-generation. That has been a perennial problem. Why? If you went over threshold a week or ten days ago and you’re now approaching 250 degree-days from that second biofix, even if the flight was only 10 or 15, if you let it go, those moths will reproduce and get into fruit. If that happens, those eggs will emerge at the end of second-generation CM, just like the parents emerged at the end of first-generation CM. That means middle to end of August.
Why does this matter? You don’t want to be at the end of that second generation and be finding a bunch of CM flying in. They will no doubt come in larger numbers than what you caught in the first generation, if the eggs are successful.
So, it’s important that you don’t let go completely of this tail end to first-generation CM.
The question becomes: Are there affordable alternatives to the more expensive larvacides that we can use in this situation? My answer is Yes. If you have Apple maggot, Tarnished plant bug, Stink bug, aphid, or Oblique-banded leaf roller concerns – or any number of other secondary pest concerns – then you can look at using a material that is appropriate for one or several of those other insects. You can do this even if it’s only rated as Fair to Good for CM. Toward the end of first generation, the numbers of CM shouldn’t be very high, so using something that is rated less than Excellent will usually provide a reasonably good control. We haven’t seen failures in that sort of scenario.
If you caught 100 CM all at once in a block and used that material at the appropriate time (presuming its a larvacide, rated Fair to Good, used at 250 degree-days), you probably wouldn’t get 100% control. But if you’re at, say, 1/10th of that pressure, the control will usually be good enough to make it near impossible to find anything that gets through.
So, you can save some money if you’re careful with your insecticide choices at this time of the season and willing to use a material that is rated less than Excellent against CM.
Grower question: What about tank-mixing two materials that are rated fair on another insect like Apple maggot?
John: As we know, we don’t have a lot of options for Apple maggot management in conventional orchards. We have more than organic orchards, but not by very much. Basically, we’re relegated to organophosphates or neonicatinoids with the possibility of using something like Avaunt as a third mode of action. A lot of people use OPs. That means that you’re sort of limited to using the neonicatinoids, which have their own set of downsides.
So, suppose you’re at the end of first-generation CM, you’re over threshold, and you want to put something on. You want to use one of the larvacides like Altacor or Delegate that is rated Fair for Apple maggot control. The question is: if you were to tank mix another material that was rated Fair for AM control, would those two Fair-rated materials be additive in their effectiveness against AM?
My answer is: I don’t know, but I suspect not. I suspect that if you use two materials that are rated Fair for an insect like AM, you probably won’t see an additive effect. On the other hand, if you use two Fair-rated materials on an insect that actually eats the insecticide (like CM larvae or leaf roller larvae) and as it goes into a leaf or an apple, and ingests enough material to induce mortality, I think you would see an additive effect. I wouldn’t go to the bank with it, but that’s my hunch.
To summarize: I don’t think using two Fair-rated materials together will give you much benefit for Apple maggot management.
Having said that, if it’s rated Fair, and your AM pressure is very light, then you might be in a similar situation to the one I just laid out for CM: if the AM pressure is light, the Fair-rated material might be enough on its own.
On organic methods of control of CM: Â virus
John: The one organic-approved material for CM management that both conventional and organic people have used, and that is extremely appropriate at the end of first generation or at the end of second generation, is the virus. Using the virus at the end of the first generation makes an awful lot of sense. I think it makes more sense to use it at the end of first than at the end of second, because the virus will hang around and perhaps be effective on some of the second generation as well. What I mean is that you spray it on there, kill 1000 CM worms, and that increases the number of virus particles that persist in the orchard into the second generation.
It’s a little harder to use than some of the conventional insecticides, yet it works just as well (but not for as long) as most of the conventional larvacides that we’re used to using.
On Potato leaf hopper and White apple leaf hopper
Question from Peter Werts: What about White apple leaf hopper and Potato leaf hopper? I was in an orchard last week where the things came in and did quite a bit of damage, but all that I could find was the exuvium from them. There weren’t many nymphs, and I saw just a couple adults here and there on the tree. Will those produce another generation, or have they likely moved on to another place?
John: It sounds to me like what you saw was Potato leaf hoppers. Is that what you thought?
Peter: Don’t Potato leaf hoppers cause a little more leaf curling? This definitely was the classic “speckled hopper burn.â€
John: Well, those are two different things. Speckling is the loss of chlorophyll. It looks like white specs on the leaves. That isn’t hopper burn. There is a difference between those two leaf hoppers in terms of the toxicity of their saliva and so forth.
With Potato leaf hopper, you will see leaf cupping, and at the advanced stages, you will get necrotic, hopper burn, browning on the leaf edges. It’s sort of a strange year, because there are adult Potato leaf hoppers everywhere.
Peter: Would what I was seeing maybe have been White apple leaf hopper, then?
John: Yes, what you were seeing was White apple leaf hopper. If you saw white speckles on the leaves, then it was definitely White apple leaf hopper.
I just am mentioning that Potato leaf hopper is ubiquitous right now. What is strange, though, is that they have been around for many weeks, but I’ve yet to see many nymphs. It is the nymphs that cause most of the problem, in terms of hopper burn. As we’ve said in previous weeks, Potato leaf hopper and hopper burn is really only a concern on young trees that you’re trying to get shoot elongation out of. So, it’s important to be watching those terminals, on the undersides of the growing points. for the tiny nymphs. That’s where you need to be paying attention to Potato leaf hopper concerns.
With White apple leaf hopper, on the other hand, if you saw white speckling on the leaves and you don’t see any of the leaf hoppers, then you’re probably at the end of first-generation WALH. So, you don’t want to spray anything for it right now.
In my experience, if you see significant speckling from WALH by the end of first generation, you will have a problem by the end of August with second generation. I don’t have a degree-day model to model the second generation emergence. But the eggs that are laid by the adults right now will hatch probably 4-6 weeks from now, and when they come out and start feeding, you will see an exponential growth in populations and damage.
WALH is fairly easy to control for conventional growers, with all the different modes of action that we have available to us. But you will definitely have to be careful to put the material on at the appropriate time to prevent significant chlorophyll lost.
Chlorophyll loss is a concern whether you have a crop or not. It’s like Spotted tentiform leaf miner. When they get so severe that they’ve damaged a significant portion of the leaf surface, you end up with trees that have a hard time getting through the winter, whether they have fruit buds or are young trees. That kind of damage turns into a big drain on the tree’s resources.
There is no good way to sample for second-generation WALH except by looking underneath shoots for the new nymphs. With WALH, they’re not going to be at the terminals; they’re going to be all over the place. Wherever you are seeing damage from first generation will be a good place to start looking for new hatches in second generation.
On rainfastness of pesticides
John: John Wise, the entomology professor from MSU that has worked on the rainfastness of insecticides, just published an addendum to his research in the FruitCat newsletter (click the link to see the article). If you’re interested in rainfastness of these materials, you can access his article there. The information has not changed significantly from the last year, as far as I can see, but it’s still darned good information.
On Apple maggot trapping
John: I wanted to reiterate my opinion about AM trapping. A lot of people have put AM traps out in the last week. Some people bait, and some people don’t.
My opinion is this: If you have you not seen AM in your orchard and you’re primarily sampling the perimeter for migrants coming into your orchard, then using unbaited red sphere traps seems to work quite well. The important thing to recognize is that, when unbaited, they are visual traps. You can’t hide them under the canopy. They need to be visible on the tree from 10-30ft away.
If you’re worried about those unbaited traps not being effective enough because they don’t have a volatile attached to them, your alternative is to just put more of the unbaited traps up along the perimeter. Statistically speaking, that will help eliminate the concern about false negatives.
Last week, we also talked about putting those unbaited traps inside the orchard, in the varieties that are likely to have an AM population underneath them already – those varieties would include any early summer apples, as well as things like Williams Pride and Redfree. If you have cultivars like those, it is perfectly legitimate and effective to place an unbaited red sphere in the block – up until the point at which the fruit begin releasing volatiles themselves. As those early apples start to emit volatiles 2 to 3 weeks before they are ripe, your unbaited red sphere will lose effectiveness relative to the increased attractiveness of the apples on the trees.
I would not want to put a baited red sphere in a Redfree tree in the middle of somebody’s orchard and then find out that I was pulling AM in from a wild host a ½ mile away. On the other hand, if you know that you have AM in that particular variety – if you had them in that variety last year, for instance – then there is no concern at all about pulling in AM from the outside. So, if you know that you already have AM, you should bait the red sphere. You want the flies to come to the trap, and not to the apples. You know you have the AM in the soil; your main concern is keeping them from your apples.
Apple maggot trapping: Putting unbaited traps in rows adjacent to problem varieties
John: A more complicated scenaro: Say you have other varieties that have been clean over the last few years in close proximity to the cultivars you know are problematic. In that case, you should put some unbaited traps in the adjoining cultivars, especially if they are right next door. For example, if you have Redfree row that you know has AM in it right next to a row of Galas, then you NEED to put an unbaited trap in the Galas next door. This rule applies whether the Redfree traps are baited or unbaited.
Why? Because when it comes time to apply a management tool, you don’t want to spray the whole orchard for AM if you don’t have to. So, whatever you’re using – whether it’s Surround, Pyganic, or Imidan – it’s a lot nicer to be able to spot spray.
On Oriental fruit moth and Lesser apple worm
John: The Scaffolds issue from yesterday mentioned that the second flight Lesser apple worm and second flight of Oriental fruit moth are both approaching. Here in Southern Wisconsin and Northern Illinois, we should already be in the second flight of Oriental fruit moth – it has already started. The LAW should start within the next couple of weeks.
Again, the more we change our protocol and stop spraying broad-spectrum materials on a regular basis, the more important it is to have traps up for some of these internal worms. As I said last week, I’m seeing more and more Lesser apple worm adults in peoples’ orchards, and I certainly don’t want to see the worms. We need to stay on top of that adult flight.
On borers
John: This is for anybody that has had problems with borers: the sort of weather that we’ve been having this year is going to exacerbate whatever borer issues you already have. They will cause more problems, because of the stress the trees are under.
I know that most of you will not be putting things like Lorsban on the trunk if you really dont’ need to.
But if you have stone fruit, you need to look closely at that bark and determine its condition. The amount of oozing I’ve seen coming off some of the bark and branches has me concerned about the longevity of some of those trees. Of course, you can’t put anything on stone fruit until after harvest, anyway.
