SW Michigan Fruit Update

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July 12, 2005

Mark Longstroth
Bill Shane
Al Gaus

Weather

Last two weeks were warm with highs in the 80s and 90s and lows about 60. Strong thunderstorms moved across the area July 4 with some general rain following. This was the only significant precipitation. Areas close to the lake received one or two tenths of an inch while inland areas received a half or more. Drought stress symptoms are wide spread and winter injured plants are collapsing. Soil temperatures are about 75. This week’s forecast is for continued warm weather with highs in the 90s and lows about 70.

Southwest Michigan Growing Degree Day Totals March 1 through July 10, 2005				Grapes April 1
Location	GDD 42	GDD 45	GDD 50	GDD 50
SWMREC:	2005	1729	1312	1290
Bainbridge:	2058	1777	1353	1330
Hartford:	1881	1611	1205	1182
Grand Junction:	2073	1793	1369	1345
Fennville:	1855	1589	1187	1167

Tree fruit

We are catching picture wing fruit flies such as apple maggot, blueberry maggot and cherry fruit flies. Japanese Beetles are increasing. These pests emerge from the soil and we expect their numbers to increase following any significant rain. Potato leafhoppers have been found. The second generation of Oriental fruit moth is flying. Redbanded Leafroller trap catches increased sharply. Codling moth and Obliquebanded leafroller trap catches are declining. Aphid and mite numbers are building in many crops.

Apricot harvest is underway with Goldcot being harvested in Berrien County. Fruit are relatively clear of bacterial spot due to dry conditions.

Early Peach harvest has begun. PF1s are being harvested in Berrien County. With current dry conditions sugar content of peaches is high and flavor very good.  We are past peak egg laying for the second generation of Oriental fruit moth the end of egg hatch should be about 2100 to 2200 GDD base 45. We are picking up about 35 GGD per day, so egg hatch should last another 10 to 14 days. Trunk sprays for Peach Tree Borer are applied in July. Two spotted spider mites are building and green peach aphids numbers are increasing.

Cherry harvest is ending. A few late season sweet cherry varieties such as Sweetheart and some Balaton tart cherries remain to be picked.  There were no reports of brown rot. Cherry fruit flies are being trapped in abandoned cherry plantings. Very few symptoms of cherry leaf spot have been found. Cherry growers should watching the weather and protecting against cherry leaf spot if rain seems likely.

In Plums, White apple leafhopper injury can be found. Second generation eggs will begin to hatch soon so growers should be scouting for nymphs. Brown rot has shown up on fruit damaged by insects.

Apple fruit are about 2 inches in diameter. We are catching apple maggot adults. See the article on apple maggot monitoring and control in the June 28 Fruit CAT Alert. Fire blight has appeared in some new locations but generally is confined to older orchards with a history of the disease. Green apple aphids are becoming common and can spread the infection to healthy trees. Codling moth trap catches are low. The first generation of Codling moth should end at about 1000 GDD after biofix. We biofixed for codling moth on May 20 at 334 GDD base 50. We are now at 1312 GDDs, almost 1000 GDD after biofix. The second generation of Codling moth begins to emerge 1200-1250 GDD after Biofix. We are picking up about 30 GDD a day so we can expect an increase in adult trap catch next week. Obliquebanded leafroller Biofix was June 6 at 935 GDD base 42.  We are at 2000 GDD base 42 and the end of egg hatch is 1000 GDD after biofix, so egg hatch should end this week. See the article on summer leafroller control in the June 21, 2005 Fruit CAT Alert. We are finding leaf roller larvae in abandoned orchards. The second generation of Oriental fruit moth is laying eggs. European red mite numbers are increasing and this hot weather may make them explode. The treatment threshold for European red mite from mid July to mid August is 7.5 mites per leaf. The mines of the second generation of Spotted Tentiform Leafminer are showing up. White apple leafhopper eggs will begin to hatch soon so growers should be scouting for nymphs. Examine 50 leaves from 10 different trees and treat if the average is more than one nymph per leaf.

In Pears, European red mites are turning pear leaves black. Pear psylla numbers are building even though growers have recently treated for this pest.

Small fruit

Blueberry harvest is underway and the first pickings of Bluecrop have begun. Blueberry maggot adults are being caught. Japanese beetles are becoming easier to find. Rufus Isaacs has an article on blueberry insecticides in the June 28 Fruit CAT Alert. Harvest fungicides should target Alternaria fruit rots. See the article in June 14 Fruit CAT Alert. More and more reports of cane collapse due to Phomopsis are coming in but the dimensions of the disease are still less severe than reported in more northern growing regions. Growers who can irrigate should maintain their irrigation so that they can size the smaller berries for later pickings. Under the hot conditions, blueberry fields use as much as a quarter inch of water per day.

Grapes are at berry touch. We are past the 1200 GDD base 50, and grape berries are about half of their final weight. In sandy soils, dry conditions are slowing growth and vines are wilting. Berry size has not increased very much in the last few weeks. Grape berry moth feeding continues. Phomopsis, black rot and downy mildew symptoms can be found. These hot humid conditions are prefect for powdery mildew, but we have been getting temperatures high enough to inhibit fungal growth and spore germination. Growers should be protecting the fruit clusters from diseases.

Strawberry renovation is completed or underway.

Summer Raspberry harvest is underway. Fruit size is small and crumbly berries are common due to drought.

Miscellaneous

Younger fruit trees, both stone and pome fruit trees are collapsing due to the combination of winter trunk injury and lack of water.