Quick update on apple scab and other IPM issues for this week

By Terence Bradshaw

April 25, 2017

Expected showers beginning this afternoon through Wednesday may trigger an apple scab infection period in Vermont orchards. There has been relatively little buds development or and not enough rain in the last week or so to wash off protective residue, so any orchards that received a full-dose protectant fungicide in the past seven days should be protected through this event. However, any rain that does come will add up to sufficiently wash off residue, and warm temperatures Thursday through Saturday should advance bud development substantially. For orchards that are3 at tight cluster now, this may be your last window to apply oil (1% solution, full soaking coverage) before buds advance too far. If you couldn’t get an oil application on and mites are an issue in your orchard, there is a number of different miticides options available now that may be used pre- or post-bloom. Those can be found in the spray tables at netreefruit.org.

Insect pressure is usually pretty low at this time, but we have seen an uptick in tarnished plant bug on buds. If you are trapping with white sticky traps, the threshold before requiring an insecticide application is three or five per trap (wholesale and retail orchards, respectively) at tight cluster and five or eight per trap at pink bud stage. Fruit grown for cideries do not need to be treated for pre-bloom insect pests since their damage is largely cosmetic.

If applying a prebloom insecticide, consider a synthetic pyrethroid material if possible. The jury is still out on the potential for neonicotinoid residue to carry over into pollen and nectar and adversely affect both managed and wild pollinators. And although news was recently made that EPA would not cancel uses of chlorpyrifos (Lorsban and some generics), we would be best to move away from that product as a canopy spray and save it for its use as a trunk spray to manage borers. There is only one use allowed per year, and if a canopy spray is made pre-bloom (the only time allowed for a canopy spray), then its use later on trunks when borers are more active will not be allowed.

Now is a good time to get your first soil-applied nitrogen fertilizer down. In many cases. Split applications are more useful than a single application, timed at tight cluster to pink and a second application at petal fall. Without a foliar analysis (which is always the gold standard for developing fertilizer recommendations), growers should err on applying a total of 30-40 pounds of actual nitrogen per acre whether in one or two applications. This is also a good time to apply the foliar tonic of urea (3#/100 gallons), boron (1# solubor or 0.1-0.2 lb actual B/100 gal) and zinc (many materials, use label rates). I wouldn’t mix this tonic with oil, do one and then the other in this next spray or two if needed.

It’s great weather for planting trees. If you have them in the cooler, get them in the ground.

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