West Michigan tree fruit regional report – June 17, 2014
Primary apple scab is over in West Michigan.
There is a slight window still open to do some final apple thinning, but fruits are gaining size quickly. Use normal rates of thinners at this time. June drop is beginning.
Tree fruit diseases
Primary apple scab is over for the general Grand Rapids, Michigan, area. For Hart and Ludington, Michigan, areas farther north, Michigan State University Extension advises you should protect for the current rain and then primary should be over for those areas as well.
Continue to be on the lookout for fire blight trauma blight symptoms. If there are any hail or high winds associated with storms this week, be ready to cover for trauma blight in highly susceptible appel varieties. Don’t confuse nectria shoot blight with fire blight, particularly in Romes and Gala. Nectria is a fungal disease that infects the purse area of varieties, and the characteristic and the flagging of shoots can look exactly like fire blight at first glance.
Tree fruit insects
No new reports of plum curculio egglaying in the Grand Rapids, Michigan, area. Areas north could still have activity in stone fruits. Continue to monitor for egglaying scars.
Some blocks are reporting building or static numbers of European red mite. Heavy rain will reduce adults. Continue to assess mites per leaf; they are beginning to build again in some blocks. Threshold is 2.5 mites per leaf for June. Monitor for beneficials; one per leaf indicates to wait a week and count again.
Codling moth adult flight continues, but seems to be declining. Egg hatch is at 20 percent. A regional biofix was set for May 26, 2014 or 265 growing degree days (GDD) base 50; GDD since biofix is 360. Continue coverage for blocks that are over threshold: five moths per trap accumulated or one to two moths per trap in disrupted blocks. Be sure to reapply as needed with rainfall. Peak egg hatch is expected around the end of next week, June 29, 2014.
Some initial flight of obliquebanded leafroller occurred last week. A regional biofix was set for June 15, 2014 or 1,004 GDD42; GDD since biofix is 64. Monitor traps to set your own biofix. The start of egg hatch is estimated for June 30 or so. San Jose scale overwintering scale are present. Adult male flight is occurring in the Grand Rapids, Michigan, area, and o crawlers have been reported yet. A few are starting in other southern areas of Michigan. Continue to monitor known hot spots for activity. Crawlers typically appear in mid-June. Use of black electrical tape, sticky side out, on limbs with scale will trap crawlers. Targeting crawlers is the next control window for San Jose scale.
Flight of second generation of spotted tentiform leafminers is beginning. Continue to monitor. Green apple aphids are beginning to be found in apples. Continue to monitor for all aphid species and the beneficials that often attack them. White apple aphids should begin to show up soon.
Numbers continue to be low for white apple leafhoppers; they should be past peak egg hatch. There seem to be more potato leafhoppers than white apple leafhoppers. Continue to monitor, especially potato leafhoppers. All stages can be found of white apple leafhoppers and potato leafhoppers.
Some suspect plant bug damage in small apples, but not exactly typical plant bug damage. Continue to monitor. Borers in stone fruits are at peak flight and egg hatch; trunk sprays should be started. Some initial dogwood borer flight. Dogwood borer trunk sprays are best timed for peak egg hatch, typically around the fourth of July.
First generation oriental fruit moth adult flight and egg hatch should be ending. A little flagging has been reported. A regional biofix was set for May 19, 2014 or 295 GDD45; GDD since biofix is 590. Cover sprays in stone fruits are less important for a few weeks until second generation begins. This is a good time to change out lures if needed.
Hedging demonstration: Tuesday, June 24, 2014 from 3 to 5 p.m. at the farm of Harold, Steve and Mitch Thome, 2137 7 Mile Rd., Comstock Park, MI 49321. Please drive in by the large white building to the east of the house and follow the lane back to the orchard site.