IPM Conference Calls 2011: August 9, Summary and Download

Recording

Download the recording of the August , 2011 call here.

Announcements

-          This was the last call of 2011! Thank you all for listening, contributing, and being all-around great people to work with.

-          Also, a big Thank You to John for all his work throughout the season in leading the calls and fielding questions for callers every week, both on and off the air.

-          Keep an eye out for the feedback request I’ll be sending later on. We want to make the conference calls even more engaging, informative, and useful for next year, and we need your input in order to do that.

-          IF YOU HAVE IPM-RELATED QUESTIONS in August or September, please send them to either John (jgaue@mwt.net) or Alex (armccullough@wisc.edu). We will respond to them and might even post an update to the AppleTalk blog.

 

Call Transcript

-          TODAY’S THEME: An overview of all the insects and diseases you should be paying attention to as you scout in the following weeks.

 

Tree Phenology (2:20)

-          Most growers in southern Wisconsin and northern Illinois are seeing fruit development 1-2 weeks behind normal.

-          This means that there is a dramatic difference in the timing between this year and the last, as well as in terms of how long those apples will be sitting out there and how long you will have to pay attention to insect and disease pests.

  • Last season we were harvesting fruit about a week early. At this time last year, most people had put their final spray on.
  • This year, there is still a ways to go before harvest. Even the earliest Fall varieties (like Zestars) are still 2-3 weeks away from harvest.

Diseases

Disease prevention in storage (4:06)

-          Yesterday’s Cornell Scaffolds journal has a great article about storage problems written by Dave Rosenberger. See the article here: http://www.scaffolds.entomology.cornell.edu/2011/SCAFFOLDS%208-8-11.pdf

On conventional fungicide protection in late Summer and Fall (04:40)

-          On our call with him a few weeks back, Dr. Rosenberger suggested that growers use a material other than Captan as a protectant in the last fungicide application, for two reasons:

1)      Some of the other materials you might use would have longer-lasting protection against fruit rot, secondary Apple scab.

2)      You will avoid having Captan’s visible residue on the apples on harvest.

-          If we have scab in our orchard, what should be our approach to minimize pushing scab resistance if we don’t use Captan?

  • All of the alternative materials are single-site fungicides. That is, they are all likely to encourage resistance development if they are used improperly.
  • What is the proper way to use these fungicides late in the season?
    • Do NOT use them within 4-5 days after a rainfall. Even if scab is less likely to spread at this time of year than earlier in the season, it is more likely that it will spread after a rainfall than at any other time. So if you want to put a fungicide out other than Captan as a final fungicide, do not apply it right after an infection period (rainfall).
    • I’m not as concerned about dew-caused infection periods. That type of wetting is less likely to spread the fungus as much as rainfall. An infection period from dew is more likely to cause localized spread on a leaf or fruit, while rainfall can send the conidia far and wide.
    • You could consider combining one of these materials with a lower rate of Captan. This won’t prevent resistance development if you’re applying it 24 hours after an infection period, but you can get some benefit from the Captan without using so much that the residue becomes an issue.

Fruit rot (10:06)

-          Fruit rot has been an increasing problem for us over the last 5-6 years. Last year, when we had more overall degree day development, we ended up with more fruit rots (particularly bitter rot) than ever.

-          What fruit rots are we concerned about?

  • Bitter rot: This is of the most concern, because a Bitter rot lesion on an apple has the ability to spread to other nearby fruit. In a month’s time, a single infection can spread over most of the tree.
  • Black rot and White rot: These rots don’t tend to spread from fruit to fruit.

-          I have NOT seen any one of these rots in any significant amount this year.

  • I’ve found some initial infections around lenticels, especially where there is Blossom end rot or sun scald, but the amount I’ve found has been minimal so far.
  • However, considering that we’re a long way away from harvest on many of these varieties, you need to keep looking for these fruit rots.
  • If you have a question about what you’re seeing, contact John (jgaue@mwt.net) or Peter Werts so that we can help you differentiate between the lesions of those three diseases.

-          One last point: There is no way to eradicate these rots once they are established; we can only protect against further infections. We can remove Bitter rot innoculum by removing the infected fruit. Other than that, we’d depend on the traditional protectant materials to control spread.

Secondary scab (13:57)

-          When Dave Rosenberger talked about secondary scab spreading, he said that secondary scab would begin to spread in the Fall, when the leaves start to senesce and become more susceptible. He said that lesions lesions would appear more typically on the undersides of leaves.

-          However, the secondary scab may already be starting on some orchards. I’m already seeing new secondary scab lesions on the undersides of leaves.

  • How am I differentiating new lesions from old lesions? By comparing their shape, color, and size.
  • The lesions I’m seeing on the leaf undersides are dark-greyish-black, fairly small, and clumped around other lesions. They look very active, and don’t look shut down by the heat or dryness.

-          It’s important to pay attention to this secondary scab on leaves. It is a harbinger of late fruit scab spread.

-          Again, if you have scab in your orchards and you have scab-susceptible varieties, do not assume that you’re done spraying for the year. If you get a lot more rain or more nights with heavy dew, you could end up with a lot more pin scab. If you sell your apples direct, this might not be a great concern; but if your apples are going into storage, pin scab can be a nightmare.

Root rots (17:41)

-          Some people are still seeing limbs go down with Black rot or White rot. You can’t do much about it except flag those trees and remove them during the winter.

Silverleaf (18:10)

-          We’ve seen a lot of SIlverleaf this year, more that we’ve seen over the last few years.

-          Dave Rosenberger talked about this on his call on July 19 (see it here: http://www.ecofruit.wisc.edu/appletalk/?p=587)

-          He said that the symptoms can disappear and reappear from one season to the next, a behavior that is typical to most xylem-limited diseases.

  • But it’s not benign: I’ve seen it progress to the point that it nearly kills the tree, or at least makes it susceptible to something else that ends up killing it.

-          What can you do?

  • Flag those affected branches or affected trees, not so you can prune them out, but so that you can follow their progress and determine if the symptoms disappear by next year. We need to understand its behavior better, and we can only do that by keeping an eye on the affected trees.

Insects

Codling moth (20:40)

-          If you are going to have to protect the fruit from diseases longer than you had to last year, the same is true for Codling moth.

-          Most people are somewhere in the range of 350-500 degree days from the second biofix (or around 1300-1500 degree days from first biofix). So, they are right in the sweet spot for second-generation egg-laying, and are starting to get to the time for maximum egg hatch.

-          If last year your final Captan or CM spray went on August 1, this year it may have to extend into the 3rd week of August. However, that is totally dependent on your CM trap catches, on rainfall, and on whether you are or are not using mating disruption.

-          You can determine how diligent you need to be about your scouting and trap catches by using the Codling moth phenology. I wouldn’t be slacking off before I hit 650-750 degree days from second biofix. Up until that point, you should be going about your scouting just like usual.

-          If you keep on top of things and don’t let off too early, you should be pretty well covered.

 

Stinkbugs (24:08)

-          August is always a big month for Stinkbug damage in fruit, and this year is no exception.

-          We don’t have a lot of different materials we want to use against Stinkbugs, so effective control is a question of monitoring and the judicious use of the few materials we do have.

-          I have a seen a lot more Stinkbug nymphs in the last week than I have seen adults.

  • By my memory, by the middle of August we are usually seeing Green or Brown adult Stinkbugs doing damage in fruit.
  • This year, however, we’re mostly seeing fairly small nymphs (at second, third, and some fourth instars). That means that we still have some weeks to go with Stinkbug.
  • These nymphs don’t have wings and don’t fly; the last instar has visible wing pads.

-          I’ve seen a good deal of nymph damage on apples.

  • A lot of the damage I’ve seen has been on clusters of apples clumped together. It makes sense that they would crawl into the center of the cluster for protection and then feed from the inside.
  • If you’re scouting for Stinkbug, pull some of those clusters apart and look inside for the circular, dime-sized, depressed bruise, sometimes with a very noticeable feeding scar.

-          Keep an eye out for Stinkbugs for the damage, not for the bugs.

-          Krista from DATCP sent us some traps for Brown marmorated stinkbug monitoring. I’ve had those traps out in an orchard all summer, and I haven’t caught a single Stinkbug of any type. The traps might not be working very well.

  • That means that the best way to monitor is to look for damage, not for the insect.

-          What are the best materials to use in controlling Stinkbugs?

  • None of them are great, but the neonicatinoids are the best things we have.

San Jose scale (29:10)

-          It’s important to stay on top of this insect. There are crawlers out there right now.

-          If you’ve had problems with SJS in the past, it’s important to monitor for second-generation crawlers in suspected hotspots, whether or not you saw any first-generation crawlers this year.

  • To monitor, tape branches with double-sided carpet tape. Check and change those tapes once a week.
  • Doing this monitoring is a small price to pay to prevent being surprised in September.

-          The damage between first-generation and second-generation crawlers can get exponentially worse. If we’re getting second-generation crawlers now, the damage may not stop increasing until the middle of September.

-          Some orchards that have had problems with SJS in the past are not seeing them at all right now. Hopefully that’s an indication that they did a good job controlling the first generation.

 

Wooly apple aphid (31:22)

-          We’ve had fewer problems with WAA this year. However, it’s possible to get WAA population explosions well into September. It has surprised me in the past, where I thought it was done before getting a caller from a grower on, say, September 10 with a WAA emergency.

-          The beneficial that we rely on to control WAA are not super-abundant this year.

  • The wasp parasites and the fly predators (Syrphid and Gall midge maggots) have not been very common this year.

-          Despite the lack of predators, we haven’t seen large, rapidly-expanding colonies of WAA.

-          However, I’ve seen some orchards where WAA populations are on the increase.

-          How should you monitor?

  • If you’re just looking at the fruit as part of your monitoring for harvest, you probably won’t see the colonies that are covered up with the year’s new leaf tissue.
  • When they’re moderately-sized, you need to look carefully, and look beyond the fruit, in order to noticed them.

-          Keep an eye out for the WAA predators. Knowing where they are will give you a better idea of whether the WAA population is likely to explode late in the season. :

1)      Last week I mentioned that there were a lot of adult Syrphid flies in the orchards. In the past seven days, I’ve seen a few Syrphid maggots in WAA colonies, which marks an increase in Syrphid predation.

2)      However, I’ve seen a sudden increase in wasp parasitization of WAA in the last week. When an aphid is parasitized, it turns black and becomes a “mummy.” I’ve seen a number of the parasitic wasps themselves.

-          On insecticides and WAA:

  • I’m worried that WAA has developed resistance to neonicatinoids.
  • One material that we’ve used successfully over the past few years is Imidacloprid/Provado. We’ve applied that on WAA in late August and early September with really good results.
  • However, now that the generic Imidacloprid (Provado, Alias) is available, it is being used more often and against a wide range of insects like Apple maggot, Stinkbugs, Japanese beetle, or first generation San Jose scale.
  • I’ve seen a lot of cases recently of the WAA populations not decreasing the way they used to in response to Imidacloprid applications. This may indicate that WAA is developing resistance.

Apple maggot (39:42)

-          It’s a given that people need to pay attention to Apple maggot traps at least until the end of August, and probably into early September.

  • Again, the attention you have to pay to AM will depend on your orchard’s history with it.

-          The timing of AM flight has fluctuated pretty dramatically from one year to the next. In some years, we see them flying in the middle of June, and in other years they’ve flown after Labor Day.

  • (When I say “flying,” I mean flying in enough numbers to be of real concern).

-          AN IMPORTANT NOTE: Be sure to keep your AM traps clean and sticky. You want to be confident that your AM traps are working effectively and that you can monitor them with confidence. The next week to 10 days is good timing to clean the dirty traps off because it’s likely you won’t be applying insecticides over the next two or three weeks.

-          Of course, spot-spraying for AM late in the season is a tried and true method, but it is all dependent on having traps that work.

Japanese beetle (43:20)

-          I’m hopeful that the emerging populations are in the process of dropping off. Depending on where you go, there is some evidence of that. But I’ll repeat that they could continue to emerge in numbers for another three weeks.

-          JB will go to just about every fruit crop that there is. The only thing they don’t seem to attack is pears. They certainly have their preferences, but if they don’t have what they prefer, they will go to less tasty plants.

Other insects

-          Second-generation White apple leaf hoppers (45:15)

  • I’ve seen the nymphs around. If the first generation was an issue in your orchard, now is the time to be checking for them, and for the next two weeks.
    • If you don’t see them in the next two weeks, it’s unlikely you’ll have a problem with them.

 

-          Mites (45:53)

  • Some growers that don’t usually have a problem with mites are having one this year. This seems to be the case mainly in areas where the weather has been really hot and dry.
  • Under hot and dry conditions, the European red mite and Two-spotted mites can outgrow their predators, even in orchards with decent predator populations.
  • We don’t usually see Two-spotteds, so I don’t know a whole lot about them. I don’t know how much to be concerned about them. I know they can bronze trees rather rapidly, and bronze trees will not finish fruit very well.
    • This can be a big issue on varieties that are sensitive to stress like Macintosh.
  • The action thresholds that we have increased from June to July to August. Nonetheless, I don’t think we can ignore mites at any point in the season, because they are able to do a whole lot of damage within just a couple weeks’ time.
  • The important part is preventing bronzing of trees. Don’t wait until the trees are bronze before you start scouting mites or applying a miticide.
    • If your trees are already bronze enough to see from the road, then it’s too late and there’s usually no reason to put on a miticide, because the population is about to starve to death and crash on its own.
  • Some advice for people who have not yet had to control mites:
    • Every year is different.
    • You can play around with mite control if you have predators. You can wait and see for a week or two to see what that population does. But you should never totally ignore it; you should always be keeping an eye on it.

 

-          Apple rust mite (51:05)

  • Apple rust mite is a different story than Two-spotteds. They are much less threatening.  At this point, rust mites are not worth trying to control with any kind of spray.
    • The populations tend to crash after the terminals have set
  • You can get severe rust mite damage on shoots, but it won’t spread past the shoots.