Brown Rot: Blossom infections from the brown rot fungus can occur whenever pistils are exposed and a favorable climate exists. Infections can occur during any wetting period when temperatures are between 41 and 86 °F. However, optimum conditions for infection occur with wetting and temperatures in the mid 70’s. During long wetting periods (several days or more) blossoms can be infected regardless of temperature. Generally infections that occur when conditions are sub optimal are less severe. Blossoms and fruitlets will remain susceptible until the pistil dessicates (sometime between petal fall and shuck split).
Oriental Fruit Moth: A biofix point for OFM was set at the Rutgers Agricultural Research and Education Center in Bridgeton on April 5. The first insecticides for first generation Oriental Fruit Moth control should be applied at 170-200 degree days after biofix. This timing generally coincides with petal fall in peaches. As of April 17 we have accumulated 169 degree days at the Rutgers Research Farm in Bridgeton. Insecticides for OFM can be applied between 4/17 and 4/20 in southern counties. Do not apply insecticides until all petals have fallen to protect native bees and honeybees. In Northern counties a biofix was set on April 12th. The current prediction for timing the first insecticides will be between 4/27 and 4/29.
Green Peach Aphid: GPA colonies begin forming sometime during bloom. Examine trees for the presence of colonies from pink to shuck split. Count the number of colonies on ten trees and use a treatment threshold of 2 colonies/tree at petal fall for peach, and 1 colony/tree for nectarine. The best way to scout for aphids during bloom is with a beating tray. Blossoms may also be collected, opened, and examined for the presence of aphids using a hand lens. Last week aphids were found at low levels in nectarine blossoms in several southern county orchards. See the 2016-2017 NJ Commercial Tree Fruit Production Guide for recommended materials and rates.
Tarnished Plant Bugs and Other Catfacing Insects: This is the other key insect complex at this time of year. Tarnished plant bugs will become more of an issue as temperatures warm and mowing and other ground cover activities become more common. General spray timing at this time of year should still be targeted for Oriental Fruit Moth and/or Plum Curculio (PC).
Bacterial Spot: Copper formulations should be used starting now to suppress bacterial spot. Generally we recommend starting at 0.5 ozs metallic copper and gradually lowering the rate as the season progresses. The rate applied will depend on the formulation. Dr. Lalancette published a chart listing common copper formulations and rates for peach and nectarine applications. Avoid combining copper with captan especially if it has been overcast for several days, or if applying rates higher than .5 ozs. metallic copper. Also avoid acidic spray solutions when applying copper.
Peach Scab: In addition to Rusty Spot and Bacterial Spot, peach scab requires protective applications at this time. Topsin, Topsin/Captan combinations, Gem, Inspire Super, and especially Quadris Top are the best materials for blocks that had scab last year. Both Gem and Topsin should be used at the high rate to deactivate overwintering lesions on the wood. Quadris Top contains azoxystrobin (Abound), which is phytotoxic to many apple varieties. Phytotoxic residues can remain in the tank for long periods after an application is made, even if a tank cleaner is used. Do not use Quadris Top or Abound in the same sprayer used for apples.
Rusty Spot: An effective material should be included at petal fall, and continue through 2nd cover on rusty spot sensitive varieties. Rally at 2.5 – 5 oz./acre is the longtime standard. Other effective materials include Gem, Inspire Super, and Quadris Top. Both Gem and Quadris top will control all diseases at petal fall.
European Apple Sawfly (EAS): This insect is active and will be active through bloom and into petal fall and first cover. Adult females lay eggs just under the skin of freshly set fruit, and the young larvae mine just under the skin. Where this insect is active, it is a primary target at petal fall. In orchards of mixed variety plantings, the petal fall spray for the entire planting is prolonged. This enables EAS to start damaging the first varieties where petals fell earlier before a petal fall spray could be applied to the entire block.
Diseases: Apple Scab, Powdery Mildew, Cedar Apple Rust, are diseases of concern at this time. The NEWA scab models are estimating about 70% ascospore maturity during this period in southern NJ. Northern counties will have less ascospore maturity. Primary apple scab spores are released during any substantial wetting and infection period. Cedar apple rust infections can occur anytime between pink and 3rd cover.
Fire Blight: The first blossoms opened in southern counties last week. For shoot blight suppression start applications of low rates of apogee during bloom. In southern counties the window for the first applications of apogee is rapidly closing. From a calendar perspective, blossom sprays using Streptomycin should be applied anytime temperatures are 65°F or above and the relative humidity is 60% or above and blossoms are open or there is trauma from extreme weather. Mycoshield now has a supplemental label allowing use on apples and pears. Rotations of Streptomycin and Oxytetracyclene will help manage resistance. These antibiotics are not recommended after bloom.