IPM Conference Calls 2011: July 26, Summary and Download

Recording

Download the recording of the July 26, 2011 call here.

Summary

Insects

00:11 – On Japanese beetle

-          Question for growers: Is there anybody on the line now who wants to report anything about issues with Japanese beetle and what you’ve done about them?

• Peter Werts: I was in four orchards down in the Milwaukee area. The JB pressure down there seems to be incredibly variable. One orchard had high pressure, another had moderate pressure, and two other orchards had only a few beetle and a tiny bit of feeding damage.

 

-          Japanese beetle pressure seems to be variable all over the place.

-          JB pressure has been light the last couple of year, but this year it has increased. According to Phil Pelliterri, UW Diagnostic Lab entomologist, last year’s moisture helped the JB reproduce extremely well.

-          3:00 – JB biology review:

• JB only has a single generation.
• All the larval and pupal stages take place in the soil.
• The larvae feed mostly on grass roots, not tree roots. At the larval stage, they are therefore mainly a pest of turf grass.

-          Because the larval stage did really well last year, we are seeing an intense emergence this year.

-          In general, the places that are getting hammered by JB this year are the same places that have had bad JB problems in the past four years.

-          On emergence timeline:

• Phil said that the JB can emerge over a fairly long period of time – in some cases all the way into September.
• In our experience over the last few years, the numbers have dropped by mid-August.
• My hope is that the high heat we had last week pushed the whole envelope forward and will cause the emergence period to be shorter (yet more intense).

-          On management of adults:

• Do not use the traps, because they will attract JB from a large radius.
• Rather, use a combination of toxic material that will kill them quickly with some repellent material that will keep them off for a longer period of time.
  • The materials usually have to be used in that order.
  • Repellant materials: Neem oil or neonicatinoids.
• In our experience, the repellant materials won’t remove the JB once they are around in large numbers.
  • If you have only a small problem with the JB, the repellant materials should work fine on their own.
  • However, when the JB are calling in 10 times their numbers, for example, then the repellant materials won’t be nearly as effective.
• On managing JB when they are causing fruit damage:
  • I just talked with a grower who is getting a tremendous amount of JB fruit damage. The JB can turn fruit into something that resembles a wiffle ball.
  • The grower was concerned that because the JB were feeding more on the fruit than on the leaves, the non-repellant, short-acting, mortality-causing pesticides (Pyganic, Evergreen, Carbaryl, Imidan) might not reach the JB.
• On scouting:
  • If you have a JB problem, be sure to take notes on the time of day that you see them.
  • Phil Pelliterri said that the middle of afternoon was their peak time of movement into the trees.
  • Therefore, if you are visiting the orchard in the morning or toward dusk, you might not get as good a reading on the populations.
• Once the JB show up, it takes them 2 or 3 years to build up enough numbers to cause real problems.

-          43:15 – One grower suggested to me that it might be effective to target-spray with a wand or backpack sprayer, especially if Japanese beetle are inside of fruit. If you used a wand, you could apply something highly toxic directly to the JB that you wouldn’t want to airblast spray on the whole orchard.

• If you took this approach, you should do it in the middle of the afternoon in order to catch JB at their peak activity.

10: 11 – On stinkbugs

-          We won’t talk too much about them. It is an ongoing menace that we will have to deal with.

-          Whether you are a certified organic grower or not, using Surround is very effective against stinkbugs even though it is only a repellant.

• I can’t stress enough how important using Surround is, especially if you have some other reasons to use it (like Apple maggots or sun scald on small trees).

-          August is normally the month when we get stinkbug adults moving back into orchards.

-          I suspect that we will have a banner year for stinkbugs starting in August. I say this because we saw a lot of egg masses in the last couple months.

-          On control:

• We don’t have a lot of materials to control them (whether they are Green stink bugs, or Brown, or Dusky, or Brown marmorated).
• The best method to control them is to keep them out with repellants: Surround, Neem oil, neonicatinoids. It’s easier to keep them off than it is to kill them, whether you are conventional or certified organic.

13:14 – Codling moth

-          Quite a few people sent me their degree-day numbers. Most of the people were fairly close together in their totals.

-          Most people have second generation CM already, at least from La Crosse area to Kenosha and down into northern Illinois.

-          The second biofix should be relatively easily calculated. For the areas in SW Wisconsin, I set it at July 22 or 23. If you run out the estimated degree days for the next week or so, we’ll reach 250 degree-days for egg hatch some time in early next week (Monday, Tuesday, or Wednesday).

-          Question: Could you explain the different ways of calculating degree-days (as mentioned by Larry Gut at his recent CM talk)?

• If you’re using Specware and the data logger that you read in the field, you can’t change the way it does its calculations. It calculates the degree-days using an integrated method.
• There are three different methods for calculating:
  • First method: High-low. Just averages the high and the low temps, disregarding the number of hours clocked at the high or low temp. It assumes that the temperature never stays completely constant. If all you have is a thermometer, this is the method you will be using.
  • Second method: Sine wave. This method assumes that the temperature follows a sine wave curve – that is, it is always changing at a variable rate. This method gives pretty similar results to the High-Low method.
  • Third method: Integrated. Loggers like the Spectrum products will read the temperature at short intervals throughout the day and calculate degree-days based on the number of hours spent at each temperature. For example, if, in a 24-hour period, it was 70 degrees for 20 hours and rose to 90 degrees in the four-hour period that the sun came out, it will give more weight to the 70-degree reading.
• Usually, by the end of the year, the totals will be pretty close, no matter which method you’ve used.

 

-          Side note on Oblique-banded leaf roller:

• I’d be curious to know if anyone has caught any OBLR, because managing the last OBLR hatch and CM go hand-in-hand. We try to deal with them both and with the same set of materials.
• Most of the OBLR I’m seeing right now are not in traps as adults, but are late instar from summer generation. I wouldn’t expect to see them flying in significant numbers for another week.
• However, this year has been a good year for OBLR, so you may have already started catching some where you are.

19:22 – Apple maggot

-          On apple maggot trapping:

• Some apple varieties have reached or are about to reach harvest.
• The closer you get to harvest on any apple, the less attractive an un-baited red sphere will be to Apple maggot. Therefore, you won’t be able to effectively monitor for AM in the varieties close to harvest by using the red sphere.
• What can you do?
  • Bait the red sphere with the apple volatile. This will risk bringing some AM adults in from the outside.
  • Or use fresh yellow sticky cards with ammonium bait. Make sure that the trap remains clean and fresh. Change the bait on a weekly basis. If the card comes already scented with the bait, change the card every week.
• We have to worry more about the early apple varieties than the later ones. By the time we get to Paula Red and Macintosh, we don’t have to worry nearly as much about AM emergence.

22:05 – White apple leaf hopper (second generation)

-          The Scaffolds newsletter mentioned yesterday that they have begun catching second-generation WALH nymphs at their research site in Geneva.

-          Geneva is fairly close to our tree phenology (although that doesn’t necessarily mean insect phenology).

-          In any case, if you had concerns about first-generation WALH, you should keep your eyes peeled for second-generation nymphs during  the next week.

-          You should look for them inside the canopy of the tree. Start looking around where you see damaged leaves. You won’t find them on the shoots (where you’d look for Potato leaf hopper nymphs).

23:10 – Wolly apple aphid

-          Keep an eye on the colonies and try to get a sense of whether the colonies are growing or shrinking. Check the size of the colonies, the number of Serphid predators, the number of parasitized mummies in the colonies.

-          Depending on what toxins we spray out in an orchard in August, the WAA can explode into an exponential growth curve in late August and early September.

24:35 – Question: Could we possibly see another generation of Potato leaf hopper, or are they gone?

-          You could definitely see some more PLH this season.

-          However, it is unlikely. Why?

• Once the shoots have stopped growing, the apple trees become less favorable hosts. Older leaves are less palatable to them.
• If you didn’t put anything on to control them and the nymphs reach adulthood and lay another batch of eggs.

-          Dry conditions can encourage growth of PLH numbers and higher PLH and plant bug damage.

• Deep-rooted apple trees can stay green and lush a lot longer than most forbs and grasses. So, when the insects lose a lot of their forb and grass hosts, they move to the apple trees.

-          PLH doesn’t come in discrete generations like you have with White apple leaf hopper. Most of the PLH you see now are late-instar nymphs on the terminals.

45:10 – Two-spotted spider mites

-          If your orchard has been really dry in the last couple weeks, don’t forget about Two-spotted spider mites, even if you haven’t had European red mites.

-          These mites don’t overwinter on the tree. They crawl up the trunk.

-          Scouting: Check for any leaf close to the main trunk of the tree, on the inside of the canopy. The colonies are not always easy to see, but if they’re there, you will recognize them by their fuzziness.

-          Art Ignello recently wrote something about Two-spotted spider mites in Scaffolds.

27:35 – On leaf analysis

-          Leaf analysis and soil analysis is generally a good idea. It is critical if you have any questions about plants in your orchard that don’t look healthy.

-          It’s still not too late to take leaf samples, but it’s approaching the cutoff point. They should be taken in July. This year, even in early August it should be fine, because the phenology is a little bit delayed.

-          Method:

• Take one leaf per tree, 25 leaves in a sample. Take fully mature leaves from the mid-shoot region.  Put them in a paper sack and let them air dry. As long as it is air drying, it is not critical that you get it into the lab immediately.
• The leaves don’t have to be from single varieties; it’s fine if there is a mix.
• If you have a tree, a variety, or an area that has had problem leaves, take those as a separate sample. Make sure that you get a “normal” sample from elsewhere in the orchard to balance out the problem areas.

-          However, once the trees start looking aged – once they begin to senesce as the fruit starts to size – it is not a good time to take leaf samples.

Diseases – Reviewing Dave Rosenberger’s visit

30:44 – Apple scab

-          On the viability of conidia:

• The situation as we know it:
  • We know that Scab is supposed to be quiet when it’s hot and dry.
  • We also know that when have Scab in our orchard, the lesions never look quiet. Susceptible varieties, especially, have lesions that always look active.
• Our question was: How quiet/quiescent are those lesions in mid-July when it’s 95 degrees out and all the books say we don’t have to worry about Scab?
• Dr. Rosenberger’s response:
  • Yes, you’ll see the fuzzy grey ring of active growth around old lesions. But during this time of the year, those conidia are not very viable. Even though conidia are being produced, the heat restricts their viability.
• So, if the lesions we see out in the orchard in July and August are not viable, we should, in practice, be able to stretch out our fungicide protection program.

-          33:23 – On using strobilurins for late-season control

• Dr. Rosenberger discussed the strategy of using strobilurins to control Scab in the late season in order to avoid putting Captan residue on the fruits shortly before harvest.
• He also said that it would provide better protection from fruit infection/fruit rot organisms.

-          33:53 – You can take that information and play with it. If you have a variety or area of your orchard that is getting a lot of fruit rot (especially Bitter rot), then consider using something like a Flint or a Sovereign on a trial basis, even if you have some scab.

• Two cautions with those materials:
  • If you have Scab in your orchard and you apply this material after 3 or 4 days without a wetting period of any length, then there should be very little risk of resistance development.
  • Senescent leaves are more susceptible to Scab. As the trees age, the leaves start to senesce. Some people use August 15 as a rough date for the beginning of senescence. You should probably avoid using these materials after senescence has begun.

37:11 – On phosphoric acid fungicides:

-          (For example, Agri-Fos, Aliette, etc)

-          We talked about Silverleaf and Black rot in relation to these materials.

-          Dr. Rosenberger said not to get too excited about Silverleaf even though we seem to be seeing more of it this year than we’ve seen in a long time. He said that Silverleaf comes and goes. It may cost a scaffold branch here or a small tree there, but in general it progresses very slowly and can disappear altogether.

• He described Silverleaf fungus as a xylem-limited basidiomycete (just like Black rot and White rot fungi)
• Just Black rot and White rot fungi, Silverleaf can sit quiescent in the tree for years without causing problems. As long as the tree is not stressed, it will contain the fungus.
• John’s message: If you’re seeing more Silverleaf than you’ve seen before and you’re not sure what to do about it, the most important thing is to reduce stress on the tree.
  • I would also get some surveyors tape and tape as many Silverleaf-affected branches as you can see in the next month.
  • Then, don’t cut them out in the Spring. Instead, keep an eye on them and see what they look like next year. We could all learn something from that kind of monitoring.

41:00 – Fruit rots

-          I am seeing some fruit rot lesions. They are very small, just dark specks on the surface of the apple.  They can be easily confused with a lot of other things.

• If you see one or two dark circles or specks on an apple, it’s not a problem.
• If the dark specks are speckling half the fruit, however, then the situation is more critical. You should keep a close eye on things.

-          How do you control it?

• There is nothing you can do about current infections.
• The only thing you can do is protect from future infection. If I were seeing it on the trees, I’d spray for something.
  • For conventional growers, that would mean a strobilurin or Captan.
  • If you used OMRI materials, I would imagine that Neem and Serenade would have some effect.

46:30 – Cherry leaf spot

-          Cherry leaf spot still needs to be controlled for if you have sweet cherries or tart cherries, even if you have already finished harvesting.

-          If you were using a sterile inhibitor or other class of fungicides before harvest, those materials need to be reapplied one or two times post-harvest.