Answer: The University of Idaho has a publication on fruit tree sprays and timing which you can download. Here's the web address: http://www.ag.uidaho.edu/mg/publications/CIS0603.pdf
In brief, you start with dormant oil and later in the season use lime/sulfur.
Dormant oil is a special weight oil that suffocates eggs and scale insects. Apply during late winter or early spring (February-April) when trees are dormant. This spray controls aphids, mites, pear psylla, and scales. It is necessary every year on badly infested trees. Do not apply dormant oil when temperatures are below 45?F or when freezing temperatures are expected within 24 hours.
Prepink spray consists of an appropriate insecticide (not dormant oil) applied just before the buds reach the pink stage before bursting. This spray is useful for controlling aphids, scales, and some caterpillar pests. It is usually applied from mid to late April, unless dormant oil has been applied. If pest problems continue, use a prepink spray. CAUTION: To prevent killing bees and other pollinators, DO NOT use pesticides during the bloom period.
Apply petal fall spray just after blossoms have fallen from the trees.
Postbloom or summer
Postbloom or summer sprays are usually applied about 21 days after full bloom, generally in late May for the first spray. Use insecticides appropriate for the pest. When multiple pest problems occur, appropriate insecticides may be mixed and applied as one spray or purchased as mixed sprays. These are necessary for controlling codling moth and summer populations of aphids and pear psylla.
Codling moth control requires repeat sprays every 10 to 14 days through the season.
The last sheet of the publication suggests products for use against pests and diseases so if you download it you can keep it for future reference.
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