West Michigan tree fruit regional report – April 26, 2016
The up and down weather rollercoaster continues in west Michigan.
Weather and growth stages
The crazy Michigan weather continues with much above-normal temperatures pushing us to about 10 days ahead of average. Thunderstorms moved through the area late on April 25 and brought hail to some areas. Damage appears minimal at this time. Growing degree-day (GDD) totals for the Michigan State University Sparta Enviro-weather station are 807 GDD base 32, 346 GDD base 42, 260 GDD base 45 and 153 GDD base 50.
Apples are right between the tight cluster and pink stages. Peaches are in full bloom, European plums are nearly full bloom, sweet cherries are beginning to bloom and pears are in the white bud stage.
With the much warmer weather, it is likely that full bloom for apples will be slightly ahead of normal dates – most likely in the first full week of May rather than the second week. MSU Extension suggests growers make contact with their bee company to be prepared.
Between tight cluster and 20 millimeters, apple fruits are especially sensitive to fruit finish issues. When you add in variables such as temperature, moisture and tank-mixes, it is important to use caution with any spray applications during this sensitive fruit stage.
Regarding apple scab, there have been rain events that have led to infections for some areas and not others. Spore numbers have increased significantly with the rain event last week. You can follow the development of apple scab infections and symptoms on MSU Enviro-weather.
Thunderstorms moved through west Michigan during the night on April 25, bringing hail to some areas. Being prior to bloom, the risk for fire blight trauma is much lower; however, if you have blocks with a recent history of blight, cover sprays are recommended. Using prohexadione-calcium (Apogee, Kudos) is highly recommended to prevent potential future spread of blight from this event.
Once bloom is present in sweet cherries and peaches, the need for fungicides to prevent brown rot are important until shuck split.
Warmer weather has driven some early developing pests forward, but overall insect development is slightly behind crop stages.
The first black stem borer adults were caught 10 days ago with warm temperatures. Monitor blocks for burrowing damage and apply trunk sprays in blocks of concern.
Green fruitworm adults are flying. We should be at peak flight. First small larvae could be found this week.
Redbanded leafroller flight started about a week ago and continues in low numbers. Expect peak flight in the next five to 10 days. Pink sprays take out small larvae.
Obliquebanded leafroller activity has not been reported in commercial apples. Overwintering larvae should be found soon in terminals. Continue monitoring for feeding damage in terminals.
First apple grain aphids are being reported in very low numbers. Apple grain aphids should be seen more readily on terminals. Rosy apple aphids usually appear around pink and really increase during bloom.
Overwintering San Jose scale are present. Pink is the next timing for San Jose scale management.
Spotted tentiform leafminer adult flight of first generation began two weeks ago and is tapering off. Monitor for it if you’ve had high numbers.
Sustained oriental fruit moth flight just began over the weekend in southern Michigan. There has been some early flight in Grand Rapids, Michigan, but no biofix. Flight will be delayed in cooler weather. Oriental fruit moth mating disruption pheromone can be put up at any time in stone fruits if pruning is done. First adult flight typically happens around pink stage in apples; average first flight is 330 GDD 45. As soon as warmer weather moves back in, traps will jump.
Codling moth adult flight has been not been reported in the Grand Rapids, Michigan, area. Codling moth mating disruption pheromone can be put up at any time, but before bloom is best. Traps should be placed for codling moth before petal fall.
European red mites are in the egg stage. No activity has been reported. Monitor for overwinter mortality; if eggs look pale or clear instead of bright red, they are not viable.
Plum curculio activity has not been reported anywhere in Michigan. No controls are needed in apples until petal fall.
Tarnished plant bug has not been reported in this area, but growers should continue monitoring.