June 16, AppleTalk Call Summary

AppleTalk Conference Call Summary
Tuesday, June 16, 2015, 8:00 – 9:00 AM
Guest speaker: Larry Gut, Michigan State University, Tree Fruit Entomology
Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America; questions or comments, pwerts@ipminstitute.org

June 16th Call download: Click Here


Sun scald
Damage could be a result of UV intensity and interaction with a surfactant.  Conventional growers can apply captan to prevent fruit rot.


Fruit injured by sunscald, collected on June 10 in the Upper Mississippi River Valley

Frogeye leafspot
Symptoms are defined by their purple to red margins around the leaf surface with a brown middle.  Lesions appear several weeks after petal fall and will grow to 3-6 mm in diameter.  Frogeye leaf spot can be confused with phytotoxicity from pesticide application, use the purple margins as defining characteristics of this disease.  Once present on the leaf surface, this disease will not release spores or cause additional infections.


Summer disease
Currently 185 LWH have accumulated.  First summer disease fungicide is typically applied at 250 LWH.

From July 1, 2014 AppleTalk: It is suggested to track rainfall from the date of the petal fall fungicide application or last systemic fungicides application, until two inches (cumulative) of rain has fallen.  At that point begin calculating leaf wetness hours (LWH).  If two inches of rain has not fallen, begin calculating LWH after 21 days.  Mark date of either scenario and track LWH to 185.  Apply/reapply summer disease fungicides before this date to protect against infection.  Sooty blotch and fly-speck can develop on stored apples if this criteria is not meet.  Leaf wetting hours from last fungicide application to harvest is included in this suggestion.

Scaffolds Fruit Journal. June 23, 2014, http://www.scaffolds.entomology.cornell.edu/2014/SCAFFOLDS%206-23-14.pdf

Rainfast characteristics of codling moth insecticides
Heavy rains over the past few days and a volatile five-day forecast presents challenging conditions for codling moth management.  When timing an application, or reapplication, it is important to compare the rainfast characteristics of insecticides with the forecast and storm totals.  Reapplying is necessary to maintain a toxic dose of pesticide on the fruit surface for ingestion by codling moth larvae.  No insecticide can be exposed to two inches of rain and effectively control codling moth.  A reapplication may be necessary if heavy rainfall was experienced with consistently high trap counts.  Applying insecticides at a higher rate may provide extended protection from rain and extend the reapplication interval.

This is John Wise’s updated article on insecticide rainfast characteristics: http://msue.anr.msu.edu/news/rainfast_characteristics_of_insecticides_on_fruit

Apple curculio
Apple curculio is a weevil, similar in appearance to plum curculio (PC) and is becoming an increasingly common pest in our orchards.  Injury resulting from apple curculio (AC) is rounder and deeper than that of PC.  Localized, yet significant pressure in orchards has been observed in recent years.  AC may become a difficult pest to control since damage is not easily distinguishable and materials applied at this time in the season do not provide adequate control.

Apple curculio migrates into orchards later in the season than PC and has the ability to reproduce in apples.  AC damage results in distinct scaring around the hole and looks similar to tarnished plant bug and PC feeding.  While scouting look for fruit with holes all over the fruit.  If damage is observed cut radially across the fruit to see how deep the larvae traveled, reproduction may have been successful if tunneling goes to the center of the fruit. Note: Tarnished plant bug feeding typically does not produce a visible scar.

Obliquebanded leafroller
Obliquebanded leafroller (OBLR) are beginning to hatch in the southern half of the state.  Larvae are small green worms with caramel to black head capsules.  Scout fruit, if cultivars have set terminals.  Damage will be on the surface of the apple and at harvest will be difficult to distinguish from other lepidoptera.  Large flights now is a result of the overwintering generation not being controlled; may result in high population for second generation.  These worms are offspring from the first flight of OBLR this season.  Worms at petal fall and first cover are overwintering larvae from last year’s second generation flight.  In addition to feeding on foliage, larvae will also feed on fruit and are capable of causing economic damage in some years.  Products, i.e., Altacor (chlorantraniliprole) or Delegate (spinetoram), applied for codling moth, except granulosis virus and mating disruption, should provide adequate control of OBLR.  Beneficial insects should also aide in suppression of this pest.  Second generation larvae can be more problematic and more difficult to control then first generation OBLR.  High populations may cause damage to fruit and significant damage to terminals on young and non-bearing trees.

Scouting for fruit and foliar feeding should begin seven to ten days after moths are caught in pheromone traps.  There are no established action thresholds and trap counts do not correlate well to the potential for feeding injury to fruit or growing terminals.  OBLR is resistant to many of the organophosphates and most of the neonicotinoids are not very effective on OBLR.

 Flower thrips
Observe terminals and shoots for leaf curl, resulting from feeding.  The damage is most prevalent on the midrib of the leaf.  Brown, feeding scars will be present on the underside of leaves.  Thrips will continue to feed until terminals have set may be of concern on young or non-bearing trees; usually not a concern on mature trees.



Potato leafhopper
Potato leafhoppers maybe appearing on terminals and shoots, particularly orchards in close proximity to hay and alfalfa fields.  These are also often only a problem on young and non-bearing trees.  Symptoms include upwards, cupping of leafs on terminal shoots.  Potato leaf hoppers do not overwinter in the upper Midwest and are brought to our region on heat thermals and in warm-summer storms with winds from the south.

San Jose scale
Monitoring for San Jose scale (SJS) crawlers should begin across the region.  Monitor known hotspots with black electrical tape applied to suspect scaffold branches.  With adhesive side towards tree, wipe a thin layer of petroleum jelly on the outside of the tape.  If populations are high, concentrate a few traps in areas with greatest pressure.  Increasing the number of monitoring sites may help eliminate false negatives.  Low trap captures do not reflect overall pressure, i.e., false negatives.  Low trap captures may indicate the beginning of the hatch.  First generation SJS hatches over a narrow period, while second generation hatches over a wide period.  Catches of 10-15 crawlers in a couple of days or 10 crawlers on one tape with zero on all other tapes, may warrant application.

Dogwood borer
Dogwood borer traps can still be set in orchards.  Trap counts will provide information on hatching larvae in a few weeks.

European red mite
Summer populations of European red mites should be visible in orchards.  Identify hot spots now.

Dr. Larry Gut, Guest Speaker, Michigan State University Tree Fruit Entomology, Q & A with John Aue, Threshold IPM Consulting


  • Across our region CM flights has been abnormally light, even where adjacent wild hosts typically yield sustained heavy flights, these have lasted only one-two weeks. Biofix dates vary from May 15 to May 31.
  • Use of mating disruption is growing slowly. Many isolated retail orchards use it for a year or two, but are unhappy with the ratio of labor cost vs. larvacide savings.  The aerosol-dispensing technology has generated significant interest.
  • Most (IPM) growers rotate between applications of a diamide or spinosyn, with a neonic added where management of plum curculio (1st generation codling moth) or for apple maggot (2nd generation codling moth).
  • Orchards are currently at 250-450 DD from biofix.

Please discuss use of mating disruption (MD) in MI orchards: % of growers, newer puffer technology, etc.?

  • MD use is very high in the Michigan “Fruit Ridge” area, which makes up 40-50% of the fruit production in the state. There is less MD used in the northern part of the state.  A majority of state is using aerosol emitters.  The Canadian company SemiosBio Technologies Inc. in conjunction with Wilbur-Ellis, offered an entire management system this year which includes camera traps, a weather station and MD.  Most growers who have been using MD for a long time continue to use the hand applied disruption.

 Do MD growers in Michigan still typically apply one or two larvacide applications per generation, whether for CM or OFM/LAW or OBLR?

  • If populations are low, growers make a spot treatment or in some instances do not apply a larvacide at all.

Has monitoring for OFM or LAW become standard in MD orchards? Have either OFM or LAW become more common in MD orchards?

  • Growers that have had OFM damage are beginning to apply a petal fall insecticide for this pest and OFM MD will have 100% control of LAW

If we still have no established action thresholds based on male flight of OFM/LAW, would you give us your best ballpark estimate for a threshold?

  • There is no action threshold, but Larry Gut uses the approach of whenever OFM is a problem you catch a lot, e.g., 600-700 per trap. When populations are low you may catch around 100.  100 moths per trap is threshold.  OFM is the biggest issue in locations where stone fruit is grown; regionally and locally.  Additionally, OFM does not overlap with CM, however, LAW and CM flights overlap

Our CM flight this year across MN, WI, and northern IL have been variable, even when favorable evening flight conditions would indicate; relative to the last 12-15 years we have so far caught historically low numbers. Is a more significant CM flight merely being postponed?

  • It is not likely a large flight will happen later and it is recommended to trust the traps. An alternative word for biofix is ‘cohort’.  A larvacide should target the brood from a cohort of moths that was large enough to result in damage.
  • Two moths per trap is insignificant.

Is this minimal flight reflective of what one grower termed “a Significant Biological Non-event”, i.e., is there some ostensible biological factor responsible for no numbers?

  • It is unlikely overwintering has been delayed.

Factors affecting CM flight – temp, precipitation, wind. On a population level, how rigid are these thresholds?

  • Temperature is akin to a light switch. When the temperature drops below 60°F, the flight shuts down.
  • Codling moth will not fly in the rain or winds over two or three MPH.

Any new research findings re CM biology (e.g. overwintering or fall/spring pre-pupal mortality factors?  Behavioral adaptation to MD or speculation on whether precipitation is a significant mortality factor for newly hatched larvae? Any evidence globally of metabolic resistance developing to neonicotinoids, diamides, and/or spinosyns, even where these MOAs are used against alternating generations?  Has Exirel been as effective as Altacor for control of CM?

  • Yes, Exirel is effective and may be used for apple maggot.
  • First instar larvae can be washed off during heavy rains.
  • There is no cross resistance to codling moth with these newer insecticides. Resistance is occurring in OBLR, where significant resistance to Delegate has been observed.
  • Most larvae overwinter in the soil and leaf litter of high density orchards on smoother bark rootstocks and in older plantings CM overwinter in bark scales