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Healthy Fruit 2008 Vol. 16:14

Jul 1, 2008

Current degree day accumulations

  • Belchertown, UMass CSO observed (01/01/08 – 06/30/08): Base 43, 1300; Base 50, 814
  • Belchertown, UMass CSO SkyBit (01/01/08 – 06/30/08): Base 43, 1381; Base 50, NA

Note: this will be the last degree day report for 2008

Observations from Belchertown

The turbulent weather has continued all week. Still, most orchards have managed to escape any major damage form hail or wind. As one grower put it "the way things are going, we'll be lucky to get anything in the box!" Let's hope it calms down for the remainder of the season. The cherry harvest is in full swing for those that have cherries. Last year was a great cherry season, however, this year is turning out to be just the opposite. Birds have been more problematic than ever, and cracking and brown rot has been much worse than usual. Cherries are a very minor crop for us here in Massachusetts, but it's safe to say the harvested yield will be well below 50% of what we are capable of.

Last week we applied Lorsban 4E (Dow AgroSciences) to trunks of peach trees for peachtree borer. It might be a bit on the early side, as peak adult emegergence is early- to mid-July. Still Lorsban has staying power, but if you have not done it yet, now would be a good time. Interestingly, adult peach tree borers start laying eggs within 24 hours of hatching out, and each female deposits 200 to 600 eggs in the week she is alive. See my YouTube video on applying Lorsban for control of peachtree borer(s).

I still have not seen potato leafhopper (PLH) in apples yet, but they are around -- last week I observed a significant infestation in raspberries in the Connecticut River Valley. Be on the lookout, and young trees always rate treating for PLH. Best control bets include Provado (Bayer CropScience), Actara (Syngenta), Assai (Cerexagri-Nisso)l, Calypso (Bayer CropScience), and Clutch (Valent USA). Also watch for Japanese beetle as they usually make an appearance on or about the 4th. Sevin, Assail, or Provado are good choices for controlling Japanese beetles as soon as they show up.

J. Clements

Healthy Fruit Disease Elements, July 1, 2008

Recently, the weather reports have been pretty repetitive – "humid with a chance of showers or thunderstorms in the afternoon, showers or thunderstorms in the evening." This is heaven for many tree fruit pathogens. On stone fruit, both bacterial spot and brown rot pressure will be high this year. On apples, scab infections will continue to cycle in those orchards that had primary infections. In addition, sooty blotch and flyspeck will do well in these moist conditions.

Bacterial spot, caused by Xanthomonas arboricola pv. pruni, has been increasingly problematic in New England. It's moving into the region, and while it may not have been a problem in the past, keep an eye out for it this year. In orchards with a history of bacterial spot, if it is left uncontrolled, the disease will first cause leaf spots, and later fruit spots and, if severe, cracking. In bad years further south, the disease can defoliate trees. Other symptoms include shoot symptoms that show up in summer or spring. (See 'IPM Scouting in Stone Fruits - Bacterial Spot' from Michigan State University.)

The first line of defense is to choose cultivars of peaches and nectarines that are not susceptible to the disease.

For this season, much of the epidemic has already happened. Infections develop from the beginning of the season, and continue from there. The standard program to manage bacterial spot in the Southeast as outlined by Dave Ritchie of North Carolina State is a preventative strategy using 3-5 applications of copper from budbreak through petal-fall with rates reduced as tree growth progresses. This is followed, usually starting at shucksplit, with oxytetracycline (Mycoshield or Flameout), or low rates of copper, or an alternation of these.

In a typical year in North Carolina, a standard program looked like this:

  • Cuprofix Ultra 40DF 5.0 lb @ bud-break to 1% pink
  • Cuprofix Ultra 40DF 2.5 lb 5-10% bloom;
  • Cuprofix Ultra 40DF 0.625 lb 50-75% petal-fall;
  • Cuprofix Ultra 40DF 0.313 lb + FlameOut 17W 0.75 lb shuck-split to shucks-off;
  • FlameOut 17W 0.75 lb 1/2-inch diameter fruit;
  • Cuprofix Ultra 40DF 0.235 lb 1-inch diameter fruit;
  • FlameOut 17W 0.75 lb pits not hard 10 May;
  • FlameOut 17W 0.75 lb 0.156 lb pits hard;
  • FlameOut 17W 0.75 lb, 13 Jun

That's nine applications. At this point of the season, the final two Flameout applications are all that would be left in most of New England. In other words, it's late in the season to be spraying the first bacterial spot sprays.

Brown rot – fruit rot. Peaches and nectarines are in a relatively non-susceptible stage of development right now. Infections that may have started in blossoms or during shuck split and the two weeks following are now latent, that is, there but not growing. However as fruit get to within 3 weeks of harvest, then they will be very susceptible to brown rot infections.

If this weather continues, then sprays of Elite, Indar, Orbit, or Pristine should be applied in blocks with any history of brown rot. These fungicides are excellent against fruit rot and need to be applied every 7 to 10 days, or 2 to 3 applications per season. Pay attention to limits on the number of applications per season – they vary with each product.

  • Elite – no more than 3 lb./acre per season (6 full rate applications)
  • Indar – no more than 8 applications per season
  • Orbit – no more than 2 applications per season for fruit rot
  • Pristine no more than 5 applications per season

Sooty blotch and flyspeck. Normally, there is a grace period from the last primary-season scab fungicide spray at about first cover, until enough wet weather has happened to trigger a need for sooty blotch and flyspeck fungicides. This is usually 220 hrs. of accumulated leaf wetness. We are well beyond that already. At that point, it's time to maintain fungicide protection, as listed in one of last years Healthy Fruit. Given the conditions, either a Topsin plus captan spray, or Flint, Sovran or Pristine should be used at some point soon. Thereafter, regular sprays with less expensive captan should be adequate as long as they are applied at recommended intervals.

We have shown that calcium applied with captan enhances captan activity against SBFS, and allows rates of the captan to be reduced significantly, down to ½ lb captan 50W per 100 gal., with no drop in efficacy.

Organic growers, in particular, may be interested in the fact that Serenade plus Biotune performed well in the same trial.

D. Cooley

Jmcextman blog posts

TUESDAY, JULY 1, 2008 Lorsban trunk spray for peachtree borer

Enhancing Return Bloom on Apple with Plant Growth Regulators

By Win Cowgill, Rutgers Cooperative Extension, and Wes Autio, UMass Amherst reprinted from Rutgers Plant & Pest Advisory, Fruit Edition, June 17, 2008

Apple flower buds are formed in June and July for most varieties. Roughly 25-30 days after full bloom is the rule of thumb for the end of the thinning window, and the beginning of the flower bud development stage. Though this is a rough guideline, actual physiological responses are a result of degree day accumulations (and daylength).

In addition to utilizing the hormonal type chemical thinners (NAA, NAD, 6-BA, ethephon) at the normal thinning windows both NAA and ethephon can be also be applied in supplemental applications to enhance flower bud formation for the following season.

Beginning 4-6 weeks after full bloom and after June 'drop,' growers can begin using ethephon (Ethrel brand Ethephon, Bayer CropScience; Ethephon 2, Arysta LifeScience) or NAA applications to stimulate return bloom. June Drop is the key time marker here, as the timing of this event varies from year to year. Ethephon Ethephon is a synthetic compound that is broken down in plant tissue to form ethylene. When applied during flower bud development on apples (June-Early July), Ethephon can be effective in influencing return bloom by promoting flower bud formation.

Based on our research work at the Rutgers Snyder Farm we have changed our recommendations for ethephon. We are suggesting 4 weekly applications of ethephon at 150 PPM which is 0.5pints/100 gallons beginning at 35 mm fruit size on varieties that tend toward biannual bearing. These would include Honeycrisp, Fuji, and Suncrisp. (Note Fuji is very hard to thin so 30 DAFB is not too soon to begin at the 150 PPM rate.)

PGR's are always better applied TRV dilute but 100 gallons per acre should be a minimum target. Ethephon can be combined in your cover sprays as well to save trips through the orchard.

Growers may wish to avoid use of ethephon on Macoun for bloom return as it has caused premature ripening in NY, or at least limit to two applications. NAA may be the better choice here.

No more than 1-2 applications should be made on early maturing cultivars like Gingergold, Paulared and other August maturing varieties.

Non-bearing trees Ethephon on non-bearing apples can be used at 2-8 pints per acre (300-450 ppm) beginning 2-4 weeks after full bloom. However these trees should have filled their space and be ready to bear the following year. Tree growth with ethephon will be reduced.

NAA NAA (Fruitone-N,-L) can also be used for return bloom. One approach is to consider use of NAA at 30 days after full bloom at 5ppm and make repeat applications at 5ppm at 7-10 day intervals for at least 4 applications. West coast growers have experimented with up to 5 applications. Our work suggests that NAA may not be as effective as Ethephon.

Cautions • Ethephon applications at high temperatures and high rates can de-fruit trees; make sure you are past June drop and observe the temperature for the day of application + 2 days. Temperatures over 85 Fcan cause severe fruit drop. • NAA can reduce fruit size; this may be a concern on small-fruited cultivars.

Benefits Enhanced bloom the following year; breaking of a biennial cycle.

Conclusion Growers considering the use of PGR's for return bloom need to be in tune with their orchard conditions before making any application. PGR's can be very beneficial to a growers operation, but their use requires a careful understanding of all parameters their application can influence. Begin slowly and follow all label rates, guidelines and precautions. The label is the law.

Note: The above information was developed from research and observations in the Mid-Atlantic fruit growing region and research at the Rutgers Snyder Farm and the UMASS Cold Spring Orchard.