May 12, AppleTalk Call Summary

AppleTalk Conference Call Summary
Tuesday, May 12, 2015, 8:00 – 9:00 AM
Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America; questions or comments,

May 12th Call download: Click Here

Big picture IPM: The arm-chair philosopher on managing the complexity of IPM 3:30
Its only mid-May and I have already traveled over 1,000 miles to scout orchards.  Driving down the road to the next orchard, I think about the evolving complexity, costs and challenges of our pest management.  At its simplest, Integrated Pest Management (IPM) is another data-driven process your business can rely on, but it is more than that.  From the first oil spray and until the beginning of harvest, we can use monitoring data, phenology models, thresholds and scouting observations to guide our pest management.  This is what IPM is all about, but the implementation can be a logistical nightmare.  To make it more manageable, I suggest growers establish goals for specific pests, horticultural practices or monitoring processes.  We get very busy this time of year, but it is important to think about the future, as we work in the present.  Taking a moment to evaluate past success and failures and define the plan of attack, prevents us from resting on our laurels.

IPM addresses the bottom-line costs of pest management and the most advanced practices can significantly minimize impacts on human and environmental health.  We accomplish this by focusing on the little things.  These all add up to support our IPM programs and bring success to our hard work.  During the weeks and months ahead, common threads in IPM we will discuss include:

  • Differentiating between pests and management strategies which impact tree health vs. crop quality or bearing vs. non-bearing trees.
  • Identifying novel approaches to pesticide applications which save money and preserve beneficial insects, e.g., alternate-row-middle and perimeter sprays.
  • Using reduced-risk pesticides or selective pesticides which conserve beneficial insects or mitigate resistance.
  • Opportunities to use non-chemical strategies including biological controls, mating disruption, orchard floor sanitation and summer pruning.
  • Using our knowledge of pest biology, behavior and phenology models, to improve timing of sprays.

When you have the strategy sketched out, use these calls to get your questions answered!  It is helpful if we can get questions 24 hours before the call.  Please feel welcome to contact any of us, John Aue, ; Thomas Bernard, ; or Peter Werts, .  If we can’t respond to the question on the call, we can address it in a blog post or with a direct message to you.

Apple scab 28:10
Primary scab season is nearing completion in many regions.  The cool, damp, weather this week is ideal for the spread of conidial infections, i.e., secondary-scab infections.  Continue to monitor apple scab infection events and maintain spray coverage accordingly for at least two more weeks.  Note: If good coverage has been maintained far and a full rate of fungicide was applied within the last five to seven days (rainfall ≤ 0.5 inches) reapplication may not be necessary until this weekend or early next week.  If 1.5 – 2.0 inches rain has accumulated since the last cover, reapply a fungicide before the next wetting event.

Begin scouting for scab lesions at petal fall to confidently plan future fungicide applications.  Scan the undersides of leaves of scab susceptible varieties or in blocks with a history of damage, 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 lesion will continue to infect new leaf tissue through conidial infections.  Focus control measures on problem blocks for the next six weeks or until the leaf tissue has matured.

Fire blight 34:00
Fire blight infections are temperature dependent and require temperatures above 65°F; temperatures below 65°F stall development.  Visit the May 5, 2015 AppleTalk Call Summary for step-by-step instructions for calculating the potential for a blossom-blight infection during a 24-hour period; reset the epiphytic infection potential (EIP) to zero if temperatures drop below 40°F.

Cultivars at petal fall are no longer vulnerable to infections transmitted through blossoms.  Damage resulting from high winds or hail, may result in infections later in the season.  Antibiotics can be applied within 24 hours of a serve weather event that results in damage.  To reduce transmission of bacteria after bloom, only conduct summer pruning if the forecast is dry for at least three day after pruning.

Newly planted trees, which may bloom later in the season, are susceptible to infection.  Fire blight bacteria may be present and the EIP will need to be reassessed when these trees enter bloom.

Powdery mildew 39:50
Powdery mildew (PM) needs new, expanding tissue to develop and spread.  Warmer temperatures expedite the spread of PM.  An application of Rally (myclobutanil), tank-mixed with captan or an EBDC, at petal fall will offer the best efficacy for controlling PM.  Rally has the best reach back for PM and will extract infections that occurred at pink.  Rally may not be very effective against apple scab in orchards which have experienced prolonged use of this fungicides.  Sulfur may also be used as a protectant for powdery mildew or tank-mixed with systemic fungicides for resistance management.

Black rot
Warm and humid temperatures, an abundance of winter injury and tree stress, promotes black rot infections. Early season removal of dead and dying limbs and trees will help reduce inoculum and the spread of spores. Remove all trees that have died or are extremely stunted in development, the chance of survival of these trees are low.

Plum curculio monitoring and management 41:40
Temperatures during bloom were warm enough to prompt plum curculio (PC) migration into the edges of orchards.  Cool temperatures this week may reduce PC activity; oviposition (egg laying) activity will increase as evening temperatures warm above 60°F.

Scouting is the primary tool for monitoring and determining a management threshold for PC.  At petal fall, scout for crescent-shaped oviposition scars and adult weevils on outside rows of early season varieties.  Beating trays can aide in scouting.  To monitor PC effectively conduct scouting multiple times a week.

If damage is noticed on the perimeter of a block scout interior rows to determine how far PC has traveled into the orchard.  If a petal fall insecticide has already been applied continued to scout for activity.  In blocks with high pressure a perimeter and spot spray for PC may prove beneficial.  Note: To effectively monitor PC scout for multiple times a week.

The threshold for PC is one oviposition scar or one adult weevil.  Once this threshold is reached an insecticide can be applied.  Note: Insecticides targeting PC should be applied on a warm night, when PC is most active.  Apply insecticides during evening, night and early morning hours when target varieties are at petal fall or beyond to reduce exposure to pollinators.  Insecticides targeting PC can cease at 308 DD (base 50°F) from 90% McIntosh petal fall.

Early season lepidoptera 43:30
Insecticides applied for early season lepidoptera, e.g., green fruitworm, obliquebanded leafroller, need to be consumed by active larvae.  Cool temperatures this week may reduce feeding activity.  Consider waiting to apply an insecticide for these pests until temperatures warm.

Green fruitworm
Feeding damage to fruitlets and foliage, i.e., large smooth holes and chewing along leaf margins of terminal shoots, is typical of green fruitworm (GFW).  Because GFW develop quickly and have one generation, populations are usually not large enough to justify control.  As GFW increase in size, nearing pupation, they will consume less leaf tissue.  For greatest efficacy apply an insecticide while GFW is small and actively growing.

Spring cankerworm
Spring cankerworm are common and are a small, dark grey to brown larvae, whose movements resemble an inchworm.  Damage can be seen as foliar feeding to all sections of the leaf excluding the midrib and fruitlets.  In two to three weeks the larvae will be pupating.  Old feeding can be determined by observing the amount of new growth beyond the damaged tissue.

Forest tent caterpillar
Forest tent caterpillar look similar to the eastern tent caterpillar but do not form tents.  Forest tent caterpillar is not typically an economic pest. 

Obliquebanded and redbanded leafrollers
The larvae of obliquebanded (OBLR) and redbanded (RBLR) leafrollers can be distinguished by inspecting their head and thoracic shield; OBLR is tan to brown or blackish and RBLR is yellow or green.  Now is the time to set OBLR traps.  Scouting for foliar feeding now may help predict future management decisions later in the season: feeding damage on less than 5% of terminals or 3% of fruit clusters indicates acceptable populations.

Codling moth
Codling moth (CM) overwinter as a full grown larva on trees; temperatures below -15⁰F will provide some mortality.  The first CM capture has traditionally been around petal fall and pheromone traps should be hung as soon as possible.  The long-life lures (CM L2) are active for eight weeks: if traps are deployed May 1 replace lures by July 1.  If the standard-lure (1x) is used, wait until McIntosh bloom to hang traps; replace lures after three to four weeks.  Hang CM pheromone traps in the upper third of canopy.

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.

Thinning discussion 45:45
Precision thinning and crop-load management from Phil Schwallier, MSU:

Terence Robinson’s, Cornell, thinning presentation offers specific rates of chemical thinners that may be applied during the four different “windows” for chemical thinning.  These recommendations include rates for NAA or Fruitone, MaxCel and carbaryl.

Cornell NEWA station carbohydrate models
Stations available for: Lake City, La Crescent, White Bear Lake, Elgin and other Minnesota locations.  Gays Mills is the only Wisconsin location.  Locate a weather station:

Using the carbohydrate model
Cornell carbohydrate model explained:

Carbohydrate supplies are influenced by solar radiation, i.e., sunlight, and temperature.  When there is a surplus of carbohydrates, there is less of a response to chemical thinners and when carbohydrate deficits exist, there will be a stronger response to chemical thinners and more of a natural drop.  Warm and sunny days create the high supply of carbohydrates and during this time, there is minimal tree stress.  The other extreme are warm and cloudy days, which create peak carbohydrate deficits and lots of tree stress.  During this time is when trees will respond best to chemical thinners.  It is important to consider the weather during the next three days after the application of a thinner, in addition to the weather during the day of thinning.

Additional resources
NEWA weather stations