A week of rain will challenge apple fungicide programs.
Posted on April 29, 2014 by Amy Irish-Brown, and Phil Schwallier, Michigan State University Extension
Daily temperatures have remained below normal or near normal averages and tree growth is very slow because of it. The early developing varieties were barely in the 0.25-inch green stage Monday, April 28, but a noticeable jump in growth could occur today with warmer temperatures and rainfall.
Stone fruits are slowly developing. Sweet cherry flower buds are expanding and the first green tissue is starting to show, but very sparsely as of April 28. Peach buds are breaking slowly as well.
Tree planting started on the Ridge and in Belding, Michigan, last week. Soil moisture conditions were perfect for planting ahead of this rainy week. Some are finishing up pruning and moving brush as well.
Tree fruit diseases
Apple growers were greatly encouraged to have a full fungicide cover on ahead of the rains predicted for the first five days of this week; it will most likely be our first apple scab infection of the season. Spore numbers have been higher than anticipated for the first few rain events so far. Spore numbers should be increasing quickly in the next two weeks with the typically highest numbers released between tight cluster and petal fall in apples. Cover sprays are very important to maintain now for apple scab.
Copper applications on sweet cherries and other stone fruits can be applied at any time. Michigan State University Extension advises growers to make sure there is no green tissue showing if you are using full rates to help with bacterial canker. Reduce copper rates as bud break nears.
Insects
Insect activity continues to be very much delayed with the cooler weather this spring. Oriental fruit moth traps should be up and lures can be added at any time to be ready for first flight. Growers are putting up mating disruption dispensers for codling moth in apples as time allows; it needs to be done by bloom in apples.
This article was published by Michigan State University Extension. For more information, visit http://www.cnchemicals.com/. To contact an expert in your area, visit http://www.cnchemicals.com/, or call 888-MSUE4MI (888-678-3464).