The Cougar Blight model over at NEWA is predicting a high risk of fire blight for this coming week, due to the coming hot weather and high humidity along with a chance of showers.

Currently May 5-9 looks like a high risk period for infection. Growers should apply antibiotic to any apple or pear blocks with open blossoms prior to any risk of infection. Streptomycin and oxytetracycline formulations are generally thought to provide 1-2 days protection and possible 24 hours back action. A predication of high risk over a 4 day period may require 2 applications 2 days apart, especially if there is rainfall, and/or the orchard is not yet at full bloom. Follow the label rates. 24 ozs. of strep/acre should suffice. Check your local conditions using NEWA and check back daily as the prediction may change.

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Peach

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 desiccates (sometime between petal fall and shuck split).

Petal Fall Insect Complex: An OFM biofix was set in southern counties on 4/20. Treatments for the first flight will be due at 170-200 degree days after the first trap captures or “biofix.” This timing usually coincides with late petal fall to shuck split. Be sure all petals are off before applying insecticides. Imidan, Lannate, and synthetic pyrethroids (Asana, Ambush/Pounce, Danitol, Mustang/ Mustang Maxx, Warrior, Baythroid) are rated for control of petal fall insect pests. Diamide and diamide mixes are also labeled, and include Altacor, Belt, Voliam Flexi and Voliam Express, Belt and Tourismo, and the new diamide, Exirel. When used alone the diamides are only effective against Leps. such as OFM. Exirel is a second generation diamide and will also control PC, but must be used at the higher rate to do so. This makes it expensive to use. The spinosyn, Delegate is effective for OFM and other Leps, and thrips if they are present in nectarines. Experience has shown that the pyrethroids may be weak at lower rates against plum curculio (PC), especially in hot weather. If using any of the pyrethroids, use a high rate in order to control both OFM and PC. Rotate pyrethroids (IRAC group 3) and O.P.’s (IRAC group 1B) with different chemistries for resistance management. The key arthropod targets at petal fall are OFM, PC and various catfacing insects, primarily tarnished plant bug and native stinkbugs.
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