GROWING DEGREE DAY ACCUMULATIONS through Aug. 7th at the NWMHRS

Year       2000      1999       1998       1997
GDD42   2402      2648       2668       2134
GDD50   1481      1738       1736       1361

WEATHER
By Jim Nugent

We received some much needed rainfall at the NWMHRS during the last 4 days of July, with a storm total of 1.44". However, the total rainfall since July 1 has only been 2.15 inches.

Evaporation and rainfall rates at the NWMHRS are as follows (for irrigation scheduling purposes we have included the 75% of evaporation vs. rainfall calculation):
 

	Evaporation	Rainfall	Evaporation less Rainfall	75% of Evaporation	75% Evaporation less Rainfall
Past 2 weeks	2.6	1.59	1.01	1.95	0.76
Past 4 weeks	5.89	1.75	4.14	4.42	3.11
Since May 1	23.52	9.3	14.22	17.64	10.67

PESTS AND DISEASES
By Gary Thornton, District Fruit IPM Agent

The main concern for cherry growers at this time is cherry leafspot. Many growers have a post harvest spray on now, while others with clean orchards have chosen not to apply one. Populations of two spotted spider mites remain low in most orchards; a few blocks, however, are near or above threshold. If it remains dry they will likely continue to increase in number. Plum nursery mites are causing browning in some tart cherry orchards. When mite damage is combined with drought stress, firing can occur. Pyramite seems to work fairly well on plum nursery mites when used with lots of water (2x) and a surfactant. Growers should continue to keep an eye their mite numbers for another 10 days. Many yellow leaves have been dropping from sweet cherries, due generally to a combination of ethephon and drought.

Apple growers who have not been trapping for apple maggot should keep their fruit protected by an insecticide. Apple maggot have emerged in very high numbers since the rains came about 12 days ago. 

Plums are also susceptible to apple maggot. Codling moth is between generations, with moth trap catches down to 1 per trap. The second generation should begin emerging anytime. Spotted tentiform leafminer adult flight remains high at 523 per trap at the NWMHRS. Although most apple orchards are below threshold, some have more than 5 mines per leaf. Provado, Lannate and Vydate will control the sap feeding stage, but not the tissue feeding stage. Potato leafhoppers remain active in orchards not treated with Spintor.

Peaches become very susceptible to brown rot in the pre-harvest period. Pre-harvest fungicide sprays not only protect the fruit prior to harvest, but also extend the post harvest shelf life.

Grapes now have ample symptoms of powdery mildew, black rot and downy mildew in unsprayed vineyards. Additional sprays of a sterol inhibitor will only increase the chances for resistance. Stylet oil is labeled in Michigan and works well to suppress established populations of powdery mildew. This has been used successfully in New York. The recent hot, muggy weather and frequent rains has been ideal for downy mildew development. Potato leafhoppers are active in some vineyards. Two spotted spider mites are above threshold in some areas.

NWMHRS Insect Trap Catches, Aug. 7th

Pest	Insects per Trap
Apple Maggot (abandoned)	22
Codling Moth	1
Oriental Fruit Moth	6
Spotted Tentiform Leafminer	523
Greater Peach Tree Borer	2.6
Lesser Peach Tree Borer	5.6
American Plum Borer	2.3

If you are interested in the weekly CIAB raw product report, you can access it at CIAB's website: www.cherryboard.org

Please send any comments or suggestions regarding this site to: 
Bill Klein, kleinw@pilot.msu.edu

Last Revised:8-08-00