Apple pest report by Vf6Vc1wa


									Apple Pest and Maturity Report: Thursday, August 19, 2010

Current fruit maturity
      Flyspeck and Sooty Blotch

                                                 MONMOUTH: Date Flyspeck               SANFORD: Date Flyspeck
                                                infection could become visible      infection could become visible
                         Final Application          (worst case scenario* in            (worst case scenario* in
    Fungicide(s)                date                     parentheses)                        parentheses)
                             August 1                Sept. 24 (Sept. 13)                Sept. 18 (Sept. 11)
      Pristine              August 10              past harvest (Sept. 29)               Oct. 21 (Sept. 25)
                            August 20              past harvest (Oct. 14)              past harvest (Oct. 11)
       Flint, or             August 1                Sept. 24 (Sept. 13)                Sept. 18 (Sept. 11)
     Sovran, or             August 10                Oct. 22 (Sept. 24)                  Oct. 21 (Sept. 25)
Topsin M + captan, or
 phosphite + captan          August 20              past harvest (Oct. 2)               past harvest (Oct. 2)
                             August 1                Sept. 7 (Sept. 4)                   Sept. 11 (Sept. 6)
    captan alone             August 10               Oct. 2 (Sept. 17)                   Sept. 27 (Sept. 15)
                             August 20               Oct. 22 (Sept. 24)                  Oct. 21 (Sept. 25)
         *Worst case scenario assumes weather beyond forecast range is in the top 20% for both climatic
         average temperature and leaf wetness hours.

      Storage Scald
           The following excerpts are from an article in the August 9 Cornell Scaffolds by Dr. David
      Rosenberger. The full article is at

            “…apple storage operators have used postharvest drenches containing diphenylamine (DPA)
      and a fungicide to prevent storage disorders and postharvest decays in apples that were to be
      stored more than three months after harvest.

            “In the mid 1990’s, the DPA-benzimidazole combination began to fail because P. expansum
      [ed. = blue mold fruit decay] populations in many packinghouses had finally become resistant to
      the DPA-benzimidazole combination.”

            “Increased attention to bin sanitation helped to stem the rising losses, but the real solution
      came with the registration of two very effective new fungicides: Scholar (fludioxonil) and Penbotec

           “The recycling drenches traditionally used to apply DPA and fungicides are increasingly
      viewed as posing unacceptable food safety risks.”

             “One way to bypass postharvest drenches is to apply DPA as a fog after storage rooms are
      filled. Most storage operators in New York have found that no fungicide is needed if apples are
      kept dry after harvest, so an increasing number of apple storage rooms are being fogged with DPA
      each year.”

          “Several packinghouse operators in New York devised a different approach for bypassing
      DPA drenches. They mixed up the same concentration of DPA that would be used for postharvest
drenching and then sprayed 2.5 qt of the DPA solution over the top of each filled bin of apples as
the bins were being moved into storage. This low volume application resulted in little if any runoff
from the bottom of the bins, but it reportedly controlled storage scald and CO2 injury.”

     Tests conducted by the NY Apple Research and Development Program of this nonrecycling
drench method (NRD) found that -
       “DPA applied as a nonrecycling drench was just as effective as when it was applied using the
traditional recycling drenching method.”
But with the following caveat -
      “Nevertheless, small storage operators who fill rooms slowly may have less success with the
2.5-qt NRD method because the ratio of treated fruit surface area to total air volume of the storage
may be too low to get effective action from DPA vapors.”

     A major incentive to switch to a non-recycling drench is to prevent inoculating fruit with
spores of fruit decay fungi.
      “Is a fungicide needed if DPA is applied via the 2.5-qt NRD method? Our results are
inconclusive because the answer will largely depend on how much inoculum is present on fruit and
bins that are being stored.”

      “By switching to the NRD treatment system (i.e., applying water without recycling it), we
reduced decay incidence by nearly 65% without using any fungicide.
      Keys to keeping inoculum levels low include using clean bins and sanitizing storage rooms at
the end of each packing season. The latter is important because huge spore-loads can persist on
floors in nonsanitized rooms and these spores will become airborne again, due to forklift traffic and
blower fans, during room filling.
      Finally, storage operators should use caution when adopting any new practices that might
impact the quality of fruit coming out of storage. The experiments reported here provide an
overview of what might be feasible, but at least one more year of research is needed before we
can recommend broad-scale adoption of DPA application via the 2.5-qt NRD method.”

Insects and Mites
      Until August 31, the recommended treatment threshold for European red mite and
Twospotted spider mites is an average of 7.5 mites per leaf, or mites present on 86% of middle-
aged leaves. Acramite, Envidor and Kelthane all have a 7 day preharvest interval on apple.
Kanemite and Zeal have a 14 day preharvest interval.

       Potato leafhoppers (PLH) have been found in Maine causing marginal leaf burn and cupping
on apple leaves. While apple leafhoppers (WLH) are also present. Even if present, neither may be
at a level that requires treatment (1 per leaf for PLH on young trees, don’t bother on older trees
unless; 2 WLH per leaf, with lower threshold if history of WLH interfering with pickers at harvest).
        Reduced rate application of either Provado or Sevin gave good leafhopper control in NY
trials. Assail was not included in those tests, and cutting the rate with a newer material like Assail
is not advised. Assail is also rated for “Good” efficacy apple maggot, and has a 7 day preharvest
interval (PHI). Sevin has a “Fair” rating against apple maggot, and a 3 day PHI. Provado has a
“Poor” rating against apple maggot, and a 7 day PHI. Pyrethroids are also effective against both
leafhopper and apple maggot, but their use at this time would have maximum negative impact on
predator and parasitoid species. The PHI for pyrethroid insecticides on apples ranges from 7 to 21
      Late season or postharvest are effective timing for controlling persistent weeds (bindweed,
brambles, dandelion, goldenrod, vetch etc.) with a carefully targetted glyphosate (Roundup)
application. But there is also increased risk of systemic tree damage from misdirected spray and
on trees with root suckers with late-season application, requiring extra caution for application
method and wind. Remove root suckers at least one week prior to application. Trunks protected
with white paint may be less susceptible to glyphosate damage. The preharvest interval for most
glyphosate formulations is 1 day on apple and pear, and 17 days on stone fruit.

      Glyphosate is the most commonly used herbicide in New England orchards. But no
discussion about use of glyphosate around fruit trees is complete without a reminder about the
need for drift control. There are Maine apple trees that have been killed by off-target glyphosate

      Moreover, an article in the August 2 Scaffolds newsletter
( by Dave Rosenberger, Mario
Miranda Sazo, Craig Kahlke, Hannah Mathers, and Chris Watkins outlines a disturbing set of
possible negative effects from use of glyphosate around apple trees. The full article is well worth
your time.
      Among the concerns described in the article are
      - Potential for decreased winter hardiness.
      - Preliminary evidence of internal browning during CA storage of Empire apples (the only
cultivar tested).
      - Possible weakened tree defense against fungi that cause trunk cankers.
      - Inactivation by calcium and magnesium ions in hard water, and interaction with iron (so
not to be used with steel spray tanks, but stainless steel is OK), that interferes with weed control.
      - Reduced soil availability of calcium, magnesium, manganese, copper, iron, nickel, and zinc.

      Among their conclusions (paraphrased from the article cited above) are:
      1. Never apply glyphosate to Macoun apples.
      2. Avoid using glyphosate for sucker control on apples because doing so will probably reduce
winter hardiness and may increase the probability of internal browning (at least on Empire). Nor
should glyphosate be applied immediately after suckers are cut because glyphosate is readily
absorbed by freshly cut stems.
      3. We suspect that early summer applications of glyphosate are less likely to create
problems than are late summer applications. However, even glyphosate exposure in spring can
result in elevated levels of shikimic acid for at least a full year following the exposure.
      4. Drift control is of utmost importance when using glyphosate. Use a drift inhibitor in the
tankmix, low pressure (e.g. 20-30 psi), a hooded boom sprayer if possible, and never use a
controlled droplet applicator to apply glyphosate (because they produce fine droplets)
      5. Only add a surfactant (spreader) if that is suggested on the label. High concentrations of
surfactants may increase uptake through tree bark, so cheaper generic products that do not
contain as much surfactant may actually be safer around trees.
      6. Until more information is available on the interaction between phosphite fungicides (e.g.
Agri-Fos, Fosphite, Fungi-Phite, Phostrol, ProPhyt, Topaz) and glyphosate, phosphite fungicides
should not be used more than once or twice per year in orchards where glyphosate is used.

     Having highlighted various potential negatives associated with glyphosate, it seems
important to provide some balance implied by the authors’ concluding paragraph:
      “In summary, glyphosate can be a valuable tool for managing weed problems in orchards. It
is especially useful for eliminating noxious weeds such as Canadian thistle, poison ivy, and other
woody perennials. However, glyphosate can also cause extensive damage to trees, so it should be
used only when necessary and then with special precautions aimed at minimizing glyphosate
contact with tree foliage, root suckers, and trunk tissue.”

Upcoming Event
      Agricultural Council of Maine (AgCOM) public meeting with Maine gubernatorial candidates
Libby Mitchell, Shawn Moody, Paul Lepage, and Eliot Cutler on Tuesday, August 31 from 9am–
12pm, at the Sportsman's Alliance of Maine facility at 205 Church Hill Road (Just off Route 3) in

Closing Words
   “It is not always granted to the sower to live to see the harvest. All work that is worth anything is
done in faith.”
- Albert Schweitzer

- Glen
Glen W. Koehler
Associate Scientist IPM
Voice: 207-581-3882 (within Maine: 800-287-0279)
Pest Management Office, 491 College Avenue
Orono, ME 04473-1295
Putting Knowledge to Work with the People of Maine

A member of the University of Maine System
Nondiscrimination statement, disability resources, nondisclosure statement

To top