April 2017 - Page 11

Spring Apple Tree Sprays

Q: Spring is upon us and it is time to be thinking about your apple trees!

A: Two common diseases on apple trees are cedar

apple rust and apple scab. Though some apple

varieties are resistant to these diseases — including

Liberty, Jonafree, Redfree, Freedom, Williams Pride

and Enterprise — most varieties are susceptible.

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 are not as effective on cedar-apple rust as 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.

Below is the spray schedule I would recommend. Sprays are applied every 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