Fungicide sprays during April and May are critical to preventing disease on susceptible varieties. With the warm spring this year, we may have to start sprays in March. The first spray should go down when leaves appear. A fungicide that is available to homeowners and very effective for control of apple scab and cedar apple rust is myclobutanil (Immunox). There are several formulations of Immunox but only one is labeled for fruit. Check the label. Sprays should be done on a 7- to 10-day schedule to keep the protective chemical cover on the rapidly developing leaves and fruit. These diseases are usually only a problem during April and May.
An insecticide will need to be added to this mixture after petal drop to prevent damage from codling moths that cause wormy apples. Methoxychlor or malathion have been used in the past but labels are changing and these products may no longer be labeled. A new homeowner product with the trade name Bonide Fruit Tree and Plant Guard is labeled and would be effective for all common insect pests on apples. It also contains two fungicides. The active ingredient for insects is lambda-cyhalothrin. The fungicides are Pyraclostrobin and Boscalid. The fungicides only suppress cedar-apple rust and so are not as effective on cedar-apple rust than Immunox. In order to protect bees, DO NOT use any insecticide during bloom.
An organic control with the trade name Cyd-X is also labeled but will control only codling moth.
Although gardeners may continue to use myclobutanil throughout the season, certain other fungicides are more effective on summer diseases such as sooty blotch and fly speck. Consider using Bonide Fruit Tree and Plant Guard after petal drop as it contains both an insecticide as well as two fungicides. However, you are limited to four applications per year.
A spreader-sticker can be added to the fungicide-insecticide chemical mixture to improve the distribution and retention of the pest control chemicals over the leaves and fruit. A hard, driving rain of about 1 inch or more will likely wash chemicals from the leaves and fruit. In such cases, another application should be made. You can find information on controlling insects and diseases on fruit trees in our publication titled "Fruit Pest Control for Home Gardens" at http://www.ksre.ksu.edu/bookstore/pubs/c592.pdf Below is the spray schedule I would recommend. Sprays are applied ever 10 days.
Leaves Appear: Immunox
Petal Drop: Add Bonide Fruit Tree and Plant Guard to the Immunox and so the mixture is Immunox + Bonide Fruit Tree and Plant Guard
June 1: Drop the Immunox so you are applying only Bonide Fruit Tree and Plant Guard