May 28th Apple Talk Call Summary


Apple Talk Conference Call Summary

Tuesday May 28th, 8:00 – 9:00

Presenters: John Aue, Threshold IPM; Patty Mc Manus, University of Wisconsin.

Moderator: Peter Werts, IPM Institute of North America; questions or comments,

May 28th Call download;1MTYyOTk3OTI=1

We are frozen in place and are observing very distinct differences between far south and far north.  In far south we have some varieties with 20mm fruit and others in bloom, with most in the middle.


What are the current levels of concerns re stress?  Most growers through area have received lots of moisture.  Trees have used lots of energy to push out blossoms and weather will impact what trees hold onto re fruit set.  Warm sunny days and cool nights is best for the metabolism for the tree.  Cloudy and cool will cause less stress than cloudy and warm.  Keep in mind there is no point in applying thinners on a cloudy cool day.

If you have blossoms the concerns for fireblight is present, but not the same as last week when we had hot weather. If we are still in bloom, need to watch the temperatures.  As long as temps stay cool, risk should be low. 

If we have blossoms that are still opening or newly planted trees that may bloom late could also be at risk for blossom blight.

We are very close to the end of primary scab season and can help determine how intensely we need to manage diseases the rest of the season.  If we have some primary scab now, need to really focus hard on that management now.

The warm weather a last week brought ascospore maturity nearing 100% based on the degree day model of McIntosh green tip with a base temperature of 32°F.  During warm rains, most spores would have been shot out at the beginning of the rain event.  Protection would have only been needed at the beginning and the longer the rain goes on, fewer spores will be released, because they are not maturing as fast.  If we don’t have any more ascospores to mature, then there are no more being released.

John always emphasizes that it is the scab we find during thinning which surprise most, and would often be an early infection period around green tip. If you already have scab lesions appearing, e.g., underside of fruit clusters.  Look at leaf number on the leaf with scab, e.g., second or third leaf or fourth, want to then be looking at those leaves for additional scouting.  If we have found scab now there will be secondary conidia developing on leaves. These conidia will be re-infect during rain events. The infected leaf corresponds to when in the season the infection occurred.

Codling moth

Many folks have flights last Monday or Tuesday may 21 or 22.  John does not believe they lasted more than three nights.  Theoretically, if all CM flew last week, e.g., 20 in a trap over two nights, we are over threshold and have a biofix.  Females mate and immediately begin laying eggs.  If they cannot lay eggs after they mate, they begin loosing viability.  Eggs become non-viable in five or six days after mating.  We could consider throwing away those numbers and not using as a biofix.  This is only applying to those that caught the moths already.  CM only fly at night and conditions that prevent flights include temps below 62 degrees, winds over 3 mph and rain.  If we have any of these three conditions, CM will not fly.

It is not too late to get up mating disruption.  If you hang mating disruption it is important to increase number of traps.

Remember trap height and placement. We improve our codling moth trap captures when we hang the trap in the top 1/3 of the tree canopy.

Plum curculio
Warm hot bloom provided ideal temps for PC movement in the south east and several orchards have found PC damage.  Is there utility in perimeter sprays?  Can we apply alternate middle sprays?  This weather is creating a window of opportunity to assess PC.  It is hard to assess PC with a beating tray when the weather is cold.

PC have strong preferences for early-sizing fruit.  Anything beyond 10mm will be attractive to PC.  When the weather was warm, PC was show strong preferences.  Even if it is too cold, we can detect PC by looking for oviposition scars.  If we are beyond petal fall, should be looking for oviposition.  Growers not as far along could be sampling with a beating tray.

PC oviposition may overlap with CM.  Most materials will give some codling moth control.

Using neonicotinoids for PC control will impact ability to use it against apple maggot this summer.  For example, if we use a neonicotinoid for PC during a CM flight, it will have an impact on the first generation of CM, depending on our degree day model for CM.  If we apply neonicotinoid for AM, we will need to apply a different material for CM, since CM may have been exposed to a neonicotinoid during its 1st generation, if used for PC.  The bottom line is that we can’t spray the same material against two generations of CM, even if it is not our target, e.g., a neonicotinoid applied for PC or rosy apple aphid, and then need to spray for apple maggot during second generation CM.

Organic growers should remember that a heavy application of surround for plum curculio is like having a cloudy day and is somewhat like stressing the tree and the tree will eventually produce more chloroplast.  This could have some thinning effects.  Pyganic should be applied at dusk on the warmest night, PC do the most of their oviposition at night.

Several native stink bugs are beginning to show up and can be confused as BMSB

John is now seeing the small parasitic hymenoptera (wasps) falling on beating trays.  Avaunt and Imidan do seem to have impacts on these wasps.  The ability to isolate pc pressure could allow spot treatments.

Lots of RAA colonies being managed by beneficials. Some parasites, these do provide some control of bark borers.

The longer we can hold off on our PF spray, gives more time for the beneficials to work on secondary pests.