Grand Rapids, Mich., area tree fruit regional report – July 9, 2013
Summer has arrived and apple pests don’t take a vacation.
Fruit tree insects
Codling moth traps have been reported as declining for the past two weeks with some disrupted blocks with traps at zero. First generation codling moth flight should be ended now and any catches in the next few weeks will most likely be the start of second generation flight. This is a great time to change out your lures so as to set an accurate second generation biofix. Even though first generation flight has ended, there are still eggs to hatch and cover sprays are still necessary in blocks that were trapping moths within the past two weeks that were above thresholds. From the early biofix date of May 18, 2013, there have been 815 GDD50 accumulated which should be about 85 to 90 percent egg hatch. For later biofixed blocks (May 28, 2013), there have been 706 GDD50 accumulated with an estimated 75 to 80 percent egg hatch. Don’t let the tail end of first generation codling moth go if you have trap numbers that indicate high pressure.
Obliquebanded leafroller adult flight of the summer generation has leveled out and should be declining in our area soon if not already. Very small larvae can be found in light numbers. A regional biofix was set for June 16, 2013, and there have been 604 GDD42 accumulated since. This indicates peak egg hatch. Michigan State University Extension suggests this is the time to scout closely for obliquebanded leafroller larvae. They will be difficult to find, but become easier as they grow in the next 10 days.
Some initial reports of apple maggot adults on baited yellow boards have come in just this week in the Grand Rapids, Mich., area. Traps should be up for all maggot flies in all tree fruits at this time and checked at least weekly to determine first flight. Upon emergence, there is an eight to 10 day period before female flies begin to lay eggs and fruit needs to be protected.
All stages of European red mites are present. Beneficials are present. Continue to monitor for European red mites and their predators. Petal fall miticides are beginning to break and summer miticides might be needed where European red mite numbers are growing and beneficials are not present.
Green apple aphids can be found on terminal ends and continue to increase where not managed. There seems to be more beneficial insects in aphid populations each week.
Spotted tentiform leafminer second generation flight is well underway and adult numbers should be on the decline. New sap feeders should be found at any time. Continue to monitor. This insect is not a major pest, but one to be monitored for unusual population spikes.
San Jose scale crawlers have settled in to their permanent spots and are now difficult to manage.
Dogwood borers adult flight is declining, but will continue for several weeks. We are most likely at peak egg laying/hatch now. Trunk sprays should be applied to blocks with susceptible rootstocks and evidence of dogwood borer activity.
As far as invasive species, spotted wing Drosophila (SWD) has only been trapped in southwest Michigan so far, but that should change soon. Check traps twice a week for first trap catch in sweet and tart cherries, blueberries and summer red and black raspberries. No brown marmorated stink bugs in black light traps yet.
Japanese beetles and rose chafers are active now. Rose chafers should be declining and Japanese beetles will continue to increase. Continue to monitor and apply cover sprays for Japanese beetle as needed.
Oriental fruit moth second generation flight is well underway. A regional biofix was set for May 15, 2013, with 1,098 GDD45 accumulated since biofix, which indicates about 10 percent egg hatch for second generation oriental fruit moth. Cover sprays for generation will need to be applied again in the next few days to prevent fruit and shoot injury to stone fruits. This generation is not an issue in apples.
For tree fruit diseases
Continue to monitor for apple scab. All primary lesions should be present now if they are there. Apple scab was tough to stay ahead of this spring and there is quite a fair amount present that needs regular fungicide applications to protect susceptible fruits.
Powdery mildew has also been a bit higher than most would like to see, but not as widespread as 2012. In blocks with active mildew, fungicides need to be continued at least until terminal bud set, which could be a ways off with all the rain we’ve had lately.
Fire blight should still be on your radar screen if we get any storms that rip or tear foliage, especially in blocks with active blight infections, but all blocks could be at risk for trauma blight as long as apples are actively growing. We usually say that after the 4th of July, trauma blight is not a big risk, but with so much active growth and tender tissue still present, this date is not a good rule of thumb for 2013.
Summer diseases in apples need to have fungicides applied if not already.