SW Michigan Fruit Update

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May 17, 2005

Mark Longstroth
Bill Shane
Al Gaus;

Weather

Last week was cool with highs in the low 60s and 50s and lows in the mid 40s. This cool weather really slowed down insect activity. Rain fell on May 11, 13 and 14. The rain event on May 13^th and 14^th was an infection event for most diseases. Precipitation totals for last week were about an inch or more in most locations. Topsoils are moist. Soil temperatures are about 55. This week is forecast for warming from Thursday through the weekend with little chance of rain.

Southwest Michigan Growing Degree Day Totals March 1 through May 15, 2005				Grapes April 1
Location	GDD 42	GDD 45	GDD 50	GDD 50
SWMREC:	572	443	300	278
Bainbridge:	597	465	316	293
Lawton:	567	480	306	285
Hartford:	537	418	277	257
Grand Junction:	622	486	328	303
Fennville:	509	382	254	234

Tree fruit

Insect activity was scarce. There were no fresh signs of plum curculio, which likes warm conditions for egg laying. We expect to see egg laying when we get warmer weather perhaps this weekend. See the notes on plum curculio monitoring in last week’s Fruit CAT Alert. Plums, pears and tart cherries, fruit crops that were blooming between the April 23 snow and the May 4 frost have light fruit set.

Apricot fruits are 18 mm in diameter. Fruit set is good.

Peach fruit are 8mm in diameter. Oriental fruit moths in Southern and Central Berrien County are laying eggs. Biofix for the first flight was April 15 at 175 GDD base 45, we are now at 443 GDD, 268 GDD past Biofix. Oriental fruit moth egg hatch has begun in Berrien County. For the rest of the region, Oriental fruit moth Biofix was May 6 at 320 GDD base 45 and we are 123 GDD past Biofix. We can expect a heavy flight and egg laying when warm weather returns. Growers treating bearing orchards for Tarnished plant bug and plum curculio should check the insecticide efficacy table on page 56 of the Fruit Management Guide, E-154.

Cherries: Sweet Cherries are at pit hardening and about 12 mm in diameter. Tart Cherries are 8 to 10 mm in diameter. Fruit set looks light. It appears that the earliest blooms, which opened before the snow have set. Those after the snow have not set. This was probably due to cool conditions slowing down pollen tube growth and the ovules were not fertilized. There are still fruit in the shuck from the final bloom after the May 4 frost. Many of these look good. Shoots are 3 to 5 inches long with 5 to 7 leaves are out. Rain on the 13^th and 14^th was a cherry leaf spot infection. Growers should be monitoring for plum curculio when the weather warms into the 70s. Black cherry aphids were found in sweet cherries.

Plums are out of the shuck. These fruit will be a target for plum curculio. Fruit set generally looks light.

Apple bloom has ended. Fruit set generally looks good. There is still some rat-tail bloom so the danger of fire blight is not past. Warm rain with only a few open blooms could still cause a fire blight blossom infection. The risk of fire blight remains high when the average temperatures is above 65 F. Friday’s rain was an apple scab infection period in most areas. Apple leaf scab was found in an abandoned apple orchard in central Van Buren County. European red mites are scarce. Redbanded Leafroller trap catches are declining. Spotted Tentiform Leafminer eggs should be hatching and growers should scout for sap feeders. Later this week, Thursday and Friday may be our best apple-thinning window. Temperatures are forecast to rise into the 70s through the weekend. Last week, we biofixed codling moth on May 8 at 256 GDD base 50. Cooler temperatures have shut down flight and many sites did not catch codling moth. We have only accumulated 50 GDD since then. We are going to throw out the earlier biofix and wait for a good sustained flight. This will probably be this weekend. Traditional materials are applied at about 250 GDD after biofix, but some new materials need to be applied as early as 100 GDD past Biofix. This means these early treatments should go on later this week. Check the article on using new insecticide materials in last year’s Fruit CAT Alert, which includes information on timing.

Pear bloom is over. Fruit set is generally light or nonexistent.

Small Fruit

Blueberries are blooming and early varieties and sites are at petal fall. Growers should apply fungicides to control mummyberry if we get rain or leaf wetness for more than four hours. Redbanded Leafroller trap catches are declining signaling the end of the first flight. There are reports of leafroller larvae feeding, but this is probably due to overwintering obliquebanded leafroller. Cherry Fruitworm and Cranberry fruitworm adults are now being caught. During bloom grower should only apply insecticides with low toxicity to bees and when bees are not foraging. This will protect the bees. Egg hatch has not begun so insecticide sprays can wait until after bloom. In some plantings, shoots are collapsing due to phomopsis infections that have girdled the shoot. These dried up shoots with purple or blue leaves are very noticeable.

In Grapes, Concord shoots are 8 to 10 inches long, have three leaves out and the flower clusters are elongating. In Chardonnay, primary shoots are about four inches long and have three leaves out and the flower clusters are emerging. The secondary buds in chardonnay are swelling and bursting.  Grape berry moth adults are being trapped, but egg laying has not begun, so insecticide sprays are not needed now. Fridays rain was a black rot infection. Growers should be protecting the shoot and flower cluster from phomopsis and other diseases.

Strawberries are blooming and early varieties have small green fruit. Many growers irrigating and protected against frost so there was little damage Wednesday. Growers should apply fungicides during bloom to control fruit rots.

Summer Raspberries are blooming. Fall raspberries have emerged from the ground.

Cranberry buds are swelling and some varieties have begun to green up.

Miscellaneous

The next Monday Update meeting will be, Monday May 23, at the Fruit Acres Farm in Berrien County at 5 PM. Apple thinning will be a main topic of this meeting. There will be one MDA restricted use pesticide recertification credit available at this meeting.