MSU Extension

Weather

Last week brought temperatures in the low to mid-80s. Evapotranspiration rates increased last week. A few areas benefitted from rains on Monday, July 15, but in general there was very little rainfall last week and soils are drying out. We continue to be a week behind the five-year average in growing degree days (GDD). Check your local weather station and conditions at Enviro-weather.

Southwest Michigan GDD summary from March 1 to July 14

Tree fruit

Recent heat stress has caused weak trees to develop yellow leaves. Adult Japanese beetle trap catch numbers have increased somewhat over the past week. Spotted wing Drosophila (SWD) adult male and female flies are increasing as small and tree fruits ripen. No reports of brown marmorated stink bugs.

Trevor Nichols Research Center trap catch of San Jose scale males has begun again, which should be the start of the second generation. According to the Michigan State University PETE model, emergence of the second generation is 825 GDD base 51 after the start of the first generation (May 20), which calculates to July 13 using the Fennville Enviro-Weather station data. New crawlers are expected 500 GDD51 from the start of the second generation flight, two to three weeks from now.

Peach harvest of Early Star, PF5D and Harrow Diamond is underway in Berrien County. Leaf drop due to bacterial spot infections are continuing. Brown rot control programs and possibly insect control of SWD will need to be ramped up as we approach harvest. Oriental fruit moth trap catches are continuing to rise for the second generation flight.

Sweet cherry harvest is nearly done with late varieties such as Sweetheart still being picked. Brown rot and fruit cracking was the big problem this year with some varieties having over 25 percent cracked fruit. . Post-harvest sprays for cherry leaf spot, cherry fruit fly and spotted wing Drosophila will help to hold down these problems.

Tart cherry harvest is continuing, but winding down. Fruit quality has still been generally good to very good, but the current heat will increase soft fruit problems. Cherry leaf spot symptoms have increased noticeably recently. Growers should protect against fruit flies, including spotted wing Drosophila, and the diseases cherry leaf spot and brown rot.

The first plum variety of the season, Jewel (Oushi Washi) is being harvested now, along with some early spot-picking of Methley, with Early Magic to start soon. Japanese plum leaves are riddled with leaf spots and shot holes caused by bacterial spot, but Michigan State University Extension says control measures for this disease now are too late. Fungicide sprays for brown rot should increase as fruit begin to color. Fruit with insect and bacterial spot damage are more prone to brown rot infections.

Apple fruit at the Southwest Michigan Research and Extension Center (SWMREC) are 2 inches in diameter for ‘Golden Delicious’ and ‘Gala’, 2.5 inches” for Red Delicious and 3 inches for ‘Zestar’. No reports of sooty blotch and fly speck symptoms on apples and pears. Trap catches for oriental fruit moth and codling moth vary considerably from orchard to orchard, but are generally increasing for the area as a whole. According to the Washington State University model for codling moth that uses Jan. 1 as the starting point for growing degree day accumulation, start of the second generation moth flight is expected at 1,125 GDD50 which is July 7 for the Watervliet/Bainbridge Enviro-weather station, and the beginning of the second generation egg hatch is 1,425 GDD50, which is predicted for Thursday, July 18, for the same location.

Fire blight spread by wind is showing up in young apple blocks east of older blocks showing symptoms earlier. No reports of apple maggot fly catch, but the close cousin blueberry maggot has been caught in blueberry fields. MSU’s predicted apple harvest dates for 2013 based on the SWMREC location are:

• McIntosh – Sept. 11
• Jonathans – Sept. 27
• Red Delicious – Oct 3

These are four to six days behind the long-term normal date, and 28 to 34 days behind 2012.

Red mites, green aphids and wooly apple aphids have built to noticeable levels in a few orchards.

Pears fruit (Harrow Sweet) are approximately 1.5 inches in diameter. Growers should monitor for pear scab symptoms, fire blight and pear psylla activity. Pear psylla numbers are generally low. Small, green immature pear fruit are generally not real attractive to codling, but will occasionally be damaged by this pest.

Small fruit

In grapes, juice and most wine grape varieties now have bunches closed. The Concord grape berry weight model predicts that grapes will be at half of their final weight at 1,200 GDD base 50 past April 1. It appears that we will reach 1,200 today (July 16) for South Haven and Fennville. Other location in southwest Michigan reached 1,200 GDD July 6-10.

Trap catches for grape berry moth continue to be fairly low. Second generation grape berry moth egglaying is underway, and growers should be checking bunches for feeding by larvae, in addition to checking traps for flight of adult male moths. The Enviro-weather grape berry moth model predicts the start of second, third and fourth generation egglaying (810, 1620 and 2430 GDD base 47 F from the biofix of wild grape bloom respectively). We set biofix for grape berry moth in some parts of Berrien County on May 25, and May 26-28 in other parts of Berrien and Van Buren counties. For Benton Harbor, using a biofix date of May 27, 810 GDD occurred on Friday, July 5.

Excellent coverage of clusters before bunches close is needed to achieve optimum control of grape berry moth. Insecticides that are active on eggs and young larvae such as Intrepid, Alticor and Belt should be applied as soon as possible if they aren’t already on. The optimum time for the application of broad spectrum products such as Imidan is 910 GDD and was predicted to occur Tuesday, July 9, for Benton Harbor.

Growers of hybrid and vinifera grapes should watch for Japanese beetle activity. Adult activity is increasing.

Symptoms of black rot are showing up on fruit. Certain vinifera cultivars remain susceptible to black rot through veraison. The frequent early morning ground fog and dew create a favorable environment for the development of downy mildew. Similarly, high humidity is favorable for the development of powdery mildew. Both are appearing with increasing frequency and severity in unsprayed sentinel plots we monitor.

In blueberries, mechanical harvest of early varieties is underway and hand-harvesting of Bluecrop has begun. Fruit size is excellent due to the rainy June. Growers report problems getting adequate labor. Growers with ripening fruit need to scout for blueberry maggots and spotted winged drosophila (SWD). SWD have been trapped in Berrien and Allegan counties and is probably flying in Van Buren County as well. Not all SWD traps are catching flies, but growers who are not monitoring for this pest should be applying controls. Growers should also be applying sprays to suppress anthracnose and Alternaria fruit rots.

In strawberries, renovation of fields is generally done and irrigation is needed to regenerate the plants. Everbearing strawberries have begun to re-bloom and should be producing more berries in a couple of weeks.

Bramble harvest of summer red raspberries is underway. Growers should be monitoring their raspberry plantings now for SWD. Although we have not collected SWD from several traps we monitor, numbers have increased for others. No larvae have been recovered from fruit in the high tunnels yet. Our highest single trap catch last week was six females and two males from a trap in south Berrien County. One of the signs of infestation in raspberries is a red stain present on the receptacle when the raspberry is picked. Insecticides to control SWD in brambles and other insect problems should not be applied while bees are actively foraging.

Upcoming meetings

The annual Viticulture Field Day will be held at SWMREC July 31. For more information, contact Diane Dings at dingsd@anr.msu.edu.

A hop production workshop is scheduled for Aug. 7 at SWMREC from 8:30 a.m. until 3:30 p.m.

The next in-season grape IPM meeting will be at Lemon Creek Winery on Aug. 27 from 6 to 8 p.m. Contact the Berrien County MSU Extension office at 269-944-4126 to register or for more information about the program. Registration is $15 and includes supper.

A Peach and Plum Variety Showcase will be held at SWMREC Aug. 27 from 4 to 7 p.m.