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Tight Cluster to Open Cluster
Apple scab. For effective scab control, apply at least two halfsprays or one complete spray before the first infection period.
Caution, oil-fungicide injury. The tight cluster to open cluster spray should not follow oil for at least 5 to 7 days and until two new leaves unfold when captan or sulfur is used. Both conditions should be met.
Rosy apple aphid. In orchards where rosy apple aphids have caused problems, an aphicide such as Lorsban 75WG or Vydate may be needed.
Spotted tentiform leafminer. Synthetic pyrethroids (Asana XL, Baythroid, Danitol, Decis, Proaxis, Warrior, and permethrin) or Vydate provide excellent early season control. Endosulfan and Carzol are effective in controlling adults during the prebloom period. Exercise caution when using the synthetic pyrethroid insecticides. These products are known to exacerbate mite problems even several weeks after their application. Even the tight cluster to open cluster application can affect postbloom mite populations.
Powdery mildew. The period of most rapid spread is during the active terminal growth period. Where needed, add an effective fungicide to all sprays until terminal shoots stop growing. Standard types of wettable sulfur are not suggested after first cover spray. Bayleton, Nova, Rubigan, Sorvan, and Flint are effective in controlling apple powdery mildew. They should be applied at pink, bloom, and petal fall. If mildew is very severe, additional fungicides should be applied at the tight cluster bud stage and at first cover.
Pesticide Recommendations for Apples, Tight Cluster to Open Cluster
Table 5-1: Recommended rates of Nova for well-pruned orchards.
Refer to Table 5-2 and Part II, Diseases, Pests, and Natural Enemies, for management recommendations.