West Michigan tree fruit regional report – July 22, 2014

Apples are sizing nicely with heavy rainfalls.

Posted on July 22, 2014 by Amy Irish-Brown, and Phil Schwallier, Michigan State University Extension

Crop update

Apples in west Michigan continue to size quickly due to continued rain. Average fruit size ranges from 2 to 2.5 inches. Fruit is clean and generally blemish-free.

Tree fruit diseases

With the heavy rainfall and extended wet and humid conditions of late, sooty blotch and flyspeck protective fungicides are really important to have on developing apples. There is a great model on the Michigan State University Enviro-weather website to predict the need for summer disease fungicides.

Although most blocks are free of fire blight this year, there are hot spots. Storms with hail and high winds have exacerbated fire blight in some blocks. Terminal bud set is now occurring and this seems to be slowing down the spread of fire blight considerably.

Tree fruit insects

Codling moth adult flight is still low; second generation flight has not begun. First generation egg hatch is at 95 percent. A regional biofix was set for May 26 at 265 growing degree days (GDD) base 50; GDD since biofix is 947. End of first generation is expected in just a day or two according to the biofix. Trap numbers of adults have remained low. Lures should be changed to capture the beginning of second generation, which should begin any time.

A few apple maggots in the Grand Rapids, Michigan area have been reported on yellow boards, none on red traps. Traps need to be up.

Heavy rain has reduced European red mite adults as expected, but eggs remained and are now hatching. Predator mites are present and Stethorus punctum are also found. Continue to assess mites per leaf as they are beginning to build again in some blocks. Threshold is five mites per leaf for July. Monitor for beneficials – one per leaf indicates to wait a week and count again.

We are still continuing to find high numbers of two-spotted spider mites in some apple blocks, particularly those on sandier soils. Michigan State University Extension advises growers to continue monitoring.

Obliquebanded leafroller first generation egg hatch should be complete; all larvae that will be present should be able to be found over the next week. Adults of the summer generation should begin flight in the next week. A regional biofix was set for June 15 at 1,004 DD42. GDD since biofix is 922. In general, obliquebanded leafroller larvae continue to be difficult to find. Monitor for larvae feeding in terminals and spray if more than one per tree.

San Jose scale adult male flight of the second generation should begin in the next week or two. Renew traps and monitor for scale on stems and fruits.

Some initial spotted wing Drosophila flight has been reported in various Michigan locations. This pest is not an issue for apples, but monitoring should be done in soft fruits including cherries, peaches, plums and berries.

No reports of brown marmorated stinkbug egg hatch or nymphs in the Grand Rapids, Michigan area. Continue to monitor.

Green apple aphids are becoming more prevalent in apples, but still very low overall. In some blocks where terminal buds have set, they have moved on to other host plants. Woolly apple aphids were first found on July 2 – just the beginning of small colonies. Continue to monitor for all aphid species and the beneficials that often attack them.

There are very low overall numbers of white apple leafhoppers and potato leafhoppers. There seem to be more potato leafhoppers than white apple leafhoppers this year. Continue to monitor.

Oriental fruit moth second generation adult flight is well underway with some very high numbers being reported in stone and pome fruits. A regional biofix was set for May 19 at 295 GDD45. GDD since biofix is 1,346. Cover sprays in stone fruits are very important for oriental fruit moth where trap numbers are over 40 moths per week. Peak egg hatch will likely be the last week of July and cover sprays need to be maintained. There have been some high trap numbers reported in apples; weekly traps over 60 oriental fruit moth should consider a cover spray to prevent apple fruit injury.

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).