West Michigan tree fruit regional report – June 10, 2014

Codling moth egg hatch is underway in West Michigan.

Crop update

Daily temperatures have been average to above average with less than normal rainfall amounts. Irrigation systems should be running now to compensate for the lack of adequate rainfall amounts in the last several weeks; we are running into a deficit situation very quickly.

Tree fruit diseases

Primary apple scab spores are declining. All West Michigan apple production areas should be at 100 percent spore maturity and one or two good daytime rains will discharge all remaining spores. Rains were very light on Sunday, June 8, with no spores caught. Michigan State University Extension advises it would be best to maintain primary scab fungicide rates through the end of this week for the next rain predicted for today, June 10, and tomorrow.

Be on the lookout for fire blight trauma blight symptoms this week from the windy conditions we had June 2 and 3. This was a marginal trauma risk event and if it got by you, flagging of shoots could be noticed any day. Don’t confuse nectria shoot blight with fire blight, particularly in Rome and Gala. Nectria is a fungal disease that infects the purse area of varieties with the characteristic and the flagging of shoots can look exactly like fire blight at first glance.

Tree fruit insects

There have been continued reports of plum curculio egglaying. Maintain cover sprays until apples are 20 millimeters. Continue to monitor for egglaying scars. European red mite numbers appear reduced in blocks with petal fall miticides, but there are some reports of increasing numbers again. Continue to assess mites per leaf as they are beginning to build again in some blocks. Monitor for beneficials.

Codling moth adult flight continues. Adult numbers are still high in some blocks. Egg hatch is just beginning. A regional biofix was set for May 26 (265 GDD50); GDD50 since biofix = 249. Sprays targeting egg hatch are needed in the Grand Rapids, Michigan area right now for blocks over threshold: five moths per trap accumulated or one to two moths per trap in disrupted blocks.

Obliquebanded leafroller larvae are getting large and difficult to control. Pupation is reported. Traps should be up. Expect first flight at any time, approximately 1,000 to 1,100 GDD42 from Jan. 1. San Jose scale overwintering scale is present; adult male flight is occurring in Grand Rapids, Michigan area. 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.

A few spotted tentiform leafminers can be found with some pupation. Second generation flight could begin at any time. Continue to monitor, but this is a very minor pest and seems to be low in numbers this spring. Various species of aphids are found in all tree fruits, but overall numbers appear to be much lower than expected. Continue to monitor for all aphid species and the beneficials that often attack them. Wooly apple aphids should begin to show up soon

White apple leafhoppers overwinter as eggs and a few newly hatched nymphs are found in low numbers. They should be nearing peak hatch, but numbers are still quite low. Peak egg hatch typically occurs around first cover. The earliest nymphs are often found on the underside of older leaves. A few plant bug adults can be found in terminals and on broadleaf weeds. Mullein bug (Campylomma) feeding has been reported in Southeast Michigan, but not Grand Rapids, Michigan. Continue to monitor. If you see them now, they are predators and do not warrant management.

Apple rust mite should be present now. They overwinter as an adult female. Monitoring should begin as soon as possible in blocks with a history of apple rust mites. Red Delicious is a favorite variety for rust mites. American plum borer flight is increasing. Peach tree borers should begin to fly at any time. No dogwood borer flight yet – no pupation reported. Monitor with traps for activity. Dogwood borer frass can be found – a few pupal cases are being found.

Oriental fruit moth first generation adults are at or just past peak flight. Egg hatch should be at peak. No reported flagging yet. A regional biofix was set for May 19 (295 GDD45); GDD45 since biofix = 445. Cover sprays in stone fruits are very important in stone fruits through the end of next week when first generation egg hatch will be over.

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