May 26, AppleTalk Call Summary

AppleTalk Conference Call Summary
Tuesday, May 26, 2015, 8:00 – 9:00 AM
Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America; questions or comments,

May 26th Call download: Click Here

1. Discuss apple scab pressure and effects of Memorial weekend infection period (15 Minutes)
2. Current status of plum curculio, apple curculio and codling moth
a. Basic to advanced IPM approaches
b. Effects of cooler, weather on PC, CM bio-fix, and CM flight and egg viability
c. Need for a more inclusive pesticide selection strategy
d. Layout possible management scenarios (Organic and IPM production)
3. Thinning discussion
a. Three growers detail their thinning actions to date
b. Round-table Q & A

Apple scab 0:00
Primary-scab season is likely complete for the majority of the region.  This season’s short wetting events caused spore releases that did not result in many infections.  The gradual release of spores helped to reduce the severity of infection periods, when spores reached 100% maturity, i.e., the May 14-15 infection event did not likely result in a large spore release.

Continue to scout for scab lesions by scanning the undersides of leaves of scab susceptible varieties or in blocks with a history of scab, for light gray lesions.  If lesions are found, look for trends on terminal shoots and fruit clusters to help determine when an infection took place.  Active lesions will continue to infect new-leaf tissue through conidial infections (secondary infections).  Focus control measures on problem blocks for the next six weeks or until the leaf tissue has matured.  New leaf and fruit tissue is extremely susceptible to infection.

Systemic fungicides, e.g., DMIs, strobilurins, SDHIs, can still be applied through first cover, if the fungicide class was not used more than twice during primary scab season.  These fungicides will offer additional protection for powdery mildew and rust diseases.  Note: it is not recommended to apply a systemic fungicide after an infection event or past first cover.

Plum curculio 10:40
Current crop phenology and weather conditions suggest plum curculio (PC) are active in orchards.  Plum curculio movement into the perimeter of orchards begins when temperatures are above 60°F, at this temperature feeding and oviposition (egg laying) injury can be observed.  This is a gradual process, as PC are primarily nocturnal and the entire population does not migrate into the orchard at the same time.  When evening temperatures exceed 70°F, PC feeding and egg-laying accelerates and can quickly result in significant damage.

Growers who applied a petal fall insecticide for PC should expect about two weeks of efficacy from insecticides, pending no significant rain fall.  Growers should begin scouting the orchard border and interior, towards the end of the effective life of the insecticide.  A perimeter application may be applied seven to ten days following a petal fall insecticide, if injury is found or to prevent the further migration of PC into the orchard.  This year, because of low temperatures, PC activity may be extended for a longer amount of time and may overlap with codling moth management.

We can use a degree day model from 95% McIntosh petal fall to predict the end of PC migration from overwintering sites.  After the accumulation of 308 degree days, base 50°F, PC will no longer be moving into orchards from overwintering sites.  If no additional injury is found at this time, insecticide applications targeting PC may cease.

If you have not applied a petal fall application, using a perimeter application may be a useful tool even if you are planning to apply a cover a later time.

Organic orchards have the option of applying Surround (kaolin clay) to the orchard.  Another strategy is to leave trap rows of early varieties, without Surround, that would be targeted with an insecticide, e.g., PyGanic.  An insecticide should be applied during warm nights when PC are active.

Apple curculio 18:00
Apple curculio (AC) is becoming an increasingly common pest.  Apple curculio emerge from the same overwintering sites as PC, but migrate into the orchard at a later time in the season.  Apple curculio injury looks like a hollowed out bowl (distinct scaring will form around this injury).  Apple curculio has the ability to reproduce in apples.  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.

Codling moth 19:20
Fluctuating temperatures over the last two weeks have resulted in sporadic codling moth (CM) flights.  If trap captures have been below threshold, i.e., less than five CM per trap per week, continue to check traps every several days to determine an accurate biofix.  Biofix is our first sustained flight, where we capture moths multiple days in a row.  Begin keeping track of degree days accumulated from biofix.  Codling moth fly between 6-11 pm and will not fly when wind is in excess of 3 mph, temperatures are below 60°F or if it is raining.  Assign the biofix date for the warmest, calmest night.  Note: When checking traps, fluttering CM had likely flown within the last 48 hours.

The biofix date may be delayed if cool evening temperatures (below 60°F) and low trap captures followed the initial biofix date.  By delaying the biofix until temperatures warm and flights become more consistent, compensates for the reduction in fecundity (egg-laying potential) of the female moths.  Fecundity is reduced approximately 25 percent for every 24 hours a codling moth female is delayed from mating after she has emerged from her cocoon, but is not mated.  Females that emerge during a period of cool weather will likely produce very few offspring.  If trap captures are over threshold, i.e., five moths per trap, it is not recommended to delay the biofix date.

For more information visit Weather can be your ally in managing codling moth, Larry Gut, David Epstein and John Wise, Michigan State University Extension

Managing insecticide resistance
Codling moth have two generations per year and enhance the likelihood of developing resistance to insecticides over time, when the same insecticide mode-of-action is applied to more than one generation of the target pest, per year.  To prevent resistance, it is important to accurately time applications with appropriate materials and monitor weather conditions between applications.  Monitoring pheromone traps and establishing biofix is critical for effective control.  Traditionally, 250 DD, base 50°F, from biofix is the earliest a larvicide is applied; when the population is at 3% hatch.  If high trap counts (10-15 moths in first week) are experienced at biofix, it is suggested to apply a material at this time.  If captures are low and higher numbers are experienced later in the flight, waiting to apply a material later may be wise.  Applying a larvicide at 350 DD, when the total population is at 15% egg hatch, allows a greater number of larvae to come in contact with the insecticide.

Resistance results from a combination of the genetics of an insect and how this interacts with prolonged use of insecticides with the same mode-of-action.  When we fail to rotate or insecticide mode of action between generations of a pest or expose pests to sub-lethal doses of an insecticide, we are setting ourselves up for management failures which can take many or only several years to develop.  For codling moth, resistance can begin to appear as later flights of codling moth.  Note: It is better to miss early in the hatch, when larvae are not exposed, than later in the hatch when, material is present, and larvae are exposed to a sublethal dose.

Mating disruption
If mating disruption is used, hang at least one CM combo lure (CMDA) per block and at least two oriental fruit moth (OFM) traps per orchard.  The CMDA lure will attract female and male CM moths.  Damage caused by OFM is very similar to CM damage.  OFM lures will also attract lesser appleworm (LAW); OFM has three flights per season, first flight can begin as early as pink.  LAW flights correspond with CM. Materials registered for codling moth, are also effective for LAW and OFM management.  Note: Orchards without mating disruption should also monitor these species to determine population trends.

Thinning discussion: Three growers detail their thinning actions this spring 45:00
Mark Vignieri, Sunrise Orchards

  • Sunrise Orchards typically applies NAA and carbaryl at petal fall and 6-8 mm and has continued to receive undesirable thinning results on Gala and Honeycrisp with this technique.  In an attempt to achieve more uniform thinning Mark implemented a lime sulfur and oil thinning protocol developed by Matt Stasiak at the UW Peninsular Agricultural Research Station.

Lime sulfur and oil thinning trial

  • Varieties: Gala and Honeycrisp
  • Full bloom: lime sulfur (2.5 gallon) + oil (2%)
  • Petal fall: lime sulfur (2.5 gallon) + oil (2%) + carbaryl (1.5 quart)
  • 6-8 mm: NAA + carbaryl
  • Thinners applied with 100 gallons water per acre

Initial observations show a lower concentration of fruit on the outer portion of the canopy and more fruit on the interior of the tree.  Low amounts of leaf curl are seen on Honeycrisp; more leaf curl is present on Gala.

Note: Lime sulfur and oil is approved for organic production.  Product can harm fruit finish, cause phytotoxicity and leaf damage.  Results less predictable than alternatives.  Lime sulfur is caustic and responsible for farm worker eye and other injuries.

Richard Polansky, Hafs Road Orchard

  • Bloom was compressed this season, with many varieties reaching petal fall by May 15.
  • Petal fall: MaxCel applied at 100 ppm on Gala and Empire (heavy bloom)
  • Additional thinning may not be need on Gala.  Applied carbaryl to Empire a few days ago for additional thinning.
  • Honeycrisp and all other varieties in the orchard received 10 ppm NAA.
  • Some varieties are over thinned, may not need to re-thin Honeycrisp.  Believes that warm temperatures following petal fall thinning allowed thinners to work effectively.
  • Over-thinned varieties: Golden Delicious, Surprise.
  • Varieties needing additional thinning with carbaryl: Cortland, Ginger Gold, McIntosh.
  • Varieties with target fruit set: Honeycrisp, Ida Red

Richard recommends following the ‘Nibble Thinning’ guidelines.  For more information visit PGR’s and Thinning Strategies GLEXPO 2013, Philip Schwallier

Steve Louis, Oakwood Fruit Farm

  • Chemical thinners were applied on May 20-21; ideally would have applied sooner on Gala and Honeycrisp.
  • McIntosh: MaxCel (80 fl. oz.) + carbaryl (1 pint)
  • Gala: NAA (10 ppm), decided to not apply carbaryl because fruitset was uneven
  • Honeycrisp: NAA (15 ppm) + carbaryl.  Plans to reassess need for additional chemical thinning due to large fruit size and heavy set.  NAA is used with Regulaid for more consistent results
  • All thinners are applied with 100 gallons water per acre.

Oakwood uses the Predicting Fruitset Model to monitor fruit size while thinning.  For more information visit Predicting Fruitset Model

Additional resources
IRAC mode of action classification table
Agrian Label Lookup