May 5, AppleTalk Call Summary

AppleTalk Conference Call Summary
Tuesday, May 5, 2015, 8:00 – 9:00 AM
Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America; questions or comments,

May 5th Call download: Click Here

Crop phenology 0:00
Across the region, orchards between tight cluster and full bloom on early varieties.  The short-term forecast is predicting warm day and nighttime temperatures, which will bring many orchards to full bloom by this weekend.  Cultivars currently at full bloom may enter petal fall by the end of this week.

Tree health 2:25
Symptoms of tree stress, e.g., leaves with a light-green color, small-spindly leaves, were widespread early last year.  Applying a foliar fertilizer, e.g., urea, 20-20-20, to reduce tree stress was recommended if symptoms were present before or during bloom.  If these symptoms are present this season, consider applying a foliar fertilizer at this time.

Fire blight 6:50
Blossom-blight infections occur when the fire blight bacteria (Erwinia amylovora) enter blossoms and cause a systemic infection.  Fire blight infections are temperature dependent and require temperatures above 65°F.  The potential for a blossom-blight infection, during a 24-hour period, can be assessed by following these step-by-step instructions:




12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11
55 54 53 53 53 53 54 58 60 65 68 72 75 77 80 80 80 77 74 68 65 62 58 57

Temperature (°F)


Step 1. Check if temperatures are forecasted to be above 65°F.

  • Temperatures greater than 65°F are forecasted for this 24 hour period, proceed to Step 2.

Step 2. Calculate how many hours were above 65°F.

  • The temperature was greater than 65°F between 9 AM and 9 PM = 12 hours

Step 3. Find the average temperature during the hours that were warmer than 65°F.

  • Average temperature between 9 AM and 9 PM = 73.4°F

Step 4. Subtract 65°F from the average temperature of Step 3.

  • 73.4°F – 65°F = 8.4

Step 5. Multiply the number calculated in Step 4 by the number of hours that were above 65°F.  This was calculated in Step 2.  This will determine the EIP (epiphytic infection potential).

  • 8.4 x 12 hours = 100.8
  • 100.8 is the EIP (epiphytic infection potential). When the EIP reaches 110 the bacteria have had enough heat to double their colony size and create serious infection during a wetting event, e.g., heavy dew or rain.  Only a quarter of a millimeter of water is required for an infection to occur.

If the EIP reaches 110 it is recommended to apply streptomycin, e.g., Agri-Mycin, Firewall, 24 hours before or after a wetting event.  Orchards that had infections the previous season, or have neighboring orchards that experienced fire blight the previous season, are recommended to apply streptomycin orchard wide, when the EIP reaches 110.  Tank-mixing streptomycin with an adjuvant that improves foliar penetration, e.g., Regulaid, can reduce the recommended rate of streptomycin by half.

For more information visit: Scaffolds Fruit Journal May 4, 2015

Fire-blight treatments and options 21:40

  • streptomycin, e.g., Agri-Mycin or Firewall, need to be applied 24 hours before or after a wetting event. One application restricts bacterial growth for 72 hours.  Reapplication is dependent on blossom development.
  • oxytetracycline, e.g., FireLine or Mycoshield, is not as effective as streptomycin. It does not get absorbed into the plant tissue and is not locally systemic.  Only apply prior to a wetting event.
  • kasugamycin, i.e. Kasumin, was developed for regions with streptomycin resistance. More effective than oxytetracycline.  Only apply prior to a wetting event.

Biological bactericides
Biological bactericides are not systemic and need to be applied more frequently than antibiotics, e.g., make four applications from 10% bloom to full bloom.  This will allow the biological ingredient to inoculate and colonize the flower surface and eliminate the fire-blight bacteria.  Examples of biological bactericides:

  • Serenade (Bacillus subtilis)
  • Bloomtime Biological (Pantoea agglomerans)
  • Double Nickel (Bacillus amyloliquefaciens)

Biological competitors
Blossom Protect (Aureobasidium pullulans) apply at late pink before blossoms open. Biological ingredient need to colonize the flower surface to outcompete fire blight bacteria.  It is critical to apply before EIP reaches 110.

Surface sterilant
Oxidate (hydrogen dioxide) will sterilize plant tissue surfaces if fire blight bacterial colonies are small. There is no residual with this product, continue to reapply if EIP is greater than 110.

Copper products

  • Cueva (copper octanoate)
  • copper hydroxide, e.g., Champ WG, Kocide. Extremely low rates of these products can be applied prior to wetting event.  Copper hydroxide products can be used to reduce the spread of fire blight to cultivars that are beginning to bloom.

Apple Scab 35:00
Scab ascospore maturity is high across the region.  The forecasted long wetting period over the next few days will result in heavy infections.  If infections occur during this time, lesions will not become visible for at least 10 days.  To reduce resistance concerns, it is not recommended apply a single-site fungicide with reach back active post infection.

Note: An application of Rally (myclobutanil), tank-mixed with captan or an EBDC, at petal fall will offer the best efficacy for controlling powdery mildew.  Rally has the best reach back for powdery mildew and will extract infections that occurred at pink.  Rally is not very effective against apple scab.

Insects during bloom
Pheromone traps
Codling moth, lesser appleworm, obliquebanded leafroller, oriental fruit moth, redbanded leafroller spotted tentiform leafminer, American plum and lesser peachtree borer traps should be up.  Plum curculio (PC) traps can also go out this week.  PC damage is not a concern at this time, yet the upcoming warm temperatures will initiate the start of PC migration into orchards.

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 lures (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.

Early season lepidoptera
Begin scouting for the following early season lepidoptera during bloom.

Green fruitworm (GFW) overwinter as an adult and are not affected by cold.  Begin monitoring GFW larvae at bloom.  Green fruitworm feeding is becoming visible on foliage.

Obliquebanded leafroller (OBLR) overwinter as a second or third instar larva on the tree and can be impacted by extremely cold temperatures.  OBLR are beginning emerge and will first appear as quarter inch long larva feeding on blossoms and shoots.  Note: Esteem (pyriproxyfen) is also registered for OBLR.  Early signs of leaf feeding, with no larvae present, may suggest efficacy of an application.

Redbanded leafroller (RBLR) and spotted tentiform leafminer (STLM) have not typically required insecticide treatments in recent years.  Monitor populations with pheromone traps to schedule visual scouting.  Traps for RBLR and STLM should be up at this time.

European red mite
European red mite (ERM) eggs and nymphs can be found around the base of leaf buds, fruiting spurs and leaf clusters.  Begin scouting historic hotspots for ERM at this time.  ERM populations may indicate applications of dormant oil, e.g., BioCover or Damoil (mineral oil), were ineffective.

Rosy apple aphid
Begin scouting for rosy apple aphid (RAA) in historic hotspots.  Look for curled leaves around flower clusters.  If a pre-bloom application of Esteem was applied for San Jose scale, RAA may have also been impacted.

Additional resources
Scaffolds Fruit Journal May 4, 2015