The PHI for Imidan and Guthion on apples is 7 days. Applying early may mean that you don t have the maximum residue of insecticide present at egg hatch, but it will insure that you have met the legal requirements of the PHI and not have excessive residues on the fruit at harvest. Even though it has been dry, you never know when the rains may come so, wet weather during the apple harvest period can lead to the development of pinpoint scab and other fruit infecting diseases such as sooty blotch and fly speck. Pinpoint scab can infect fruit up to and during the harvest period if wet weather persists at this time, however, the symptoms of pinpoint scab may not show up until the fruit have been stored for several months. Late season apple scab can also build up on leaves after harvest, resulting in large quantities of primary scab spores the following season, even though a good spray program was followed early this year.
Late summer is a good time to inspect trees for above-ground symptoms of collar rot.
Keep in mind that such symptoms are general stress symptoms that may be caused by a number of factors, e.g. wet feet, mouse injury, trunk decay, root rot, etc. However, trees that show the above-described symptoms and also have a canker at or just below ground level are likely infected with collar rot. If collar rot is suspected we advise the use of Ridomil 2E in the fall after harvest. Apply Ridomil as soon as possible after harvest so it will be in place before the fall rainy periods begin and possible new infections occur. Also be sure to concentrate your Ridomil treatment on surrounding healthy appearing trees, not just trees already showing severe symptoms of collar rot.