WEATHER:

July continues to be rainy. The NWMHRS during the week of 7/14 to 7/20 had measurable precipitation 5 of the 7 days, totaling 1.69". Rainfall from 7/1 to 7/20 totals 6.89". Evaporation for the past week totaled 1.73".

GDD 50: 1370; GDD 42: 2144

INSECTS:

Apple Maggot - Trap catches were very high this week at our abandoned site, 59/trap being the high. If growers are not trapping for AM, they should have a spray on to control this pest.

Codling Moth - Trap catches remained low at the Station and our abandoned site. The degree days are appropriate for the second generation to start, but moth flight is down so far at the Station. The warm weather and early season should be ideal for a large second generation adult flight, so I would expect a strong second generation flight.

Cherry Fruit Fly adults have been caught in very high numbers recently. Growers with more than 5 days to harvest should have their crop protected with an insecticide unless they have traps out and are closely monitoring those remaining orchards. Traps should be less than 2 weeks old to be considered usable; fresh traps should be hung if their effectiveness is in doubt.

Green Apple Aphids are building in some apple orchards.

European Red Mites and Two Spotted Spider Mites - In the last two weeks, populations have increased. Some apple and plum blocks are now over the threshold of 10/mites/leaf. Tart cherries, apples and plums harbor the highest populations. The threshold for tart cherries after harvest in a season with abundant mid-summer moisture is at least 30 mites/leaf (lower in years of drought).

DISEASES:

Cherry Leaf Spot - Old burned out lesions combined with new infections have recently led to a wave of yellow leaves showing up in the top of trees. This wave in some cases can be partially due to the Ethrel 

being applied to the trees. Leaves that have a very low level of leaf spot infection, that might otherwise not have enough lesions to cause leaf drop, can be induced by Ethrel to turn yellow and drop. This occurs because cherry leaf spot infection causes ethylene to be produced within the leaf, which ultimately leads to leaf yellowing and drop. An Ethrel threatment can add to the cherry leaf spot induced ethylene to cause greater total leaf drop. High rates of Ethrel will increase this problem.

Brown Rot - Where appropriate fungicides have been used, this fungi has been controlled. Hot, humid weather in the next few days will be ideal for its development.

Alternaria Fruit Rot - This fungi is not controlled by sterol inhibitors and has been very common this year. It generally colonizes injured areas, such as cracks in sweets or wind whipped areas in tarts. Rovral and Captan will provide some control of alternaria

MISCELLANEOUS:
Summer Pruning By Gary Thornton and Jim Nugent

We have had good success with post-harvest pruning of tart cherries in past years. However, we suggest delaying summer pruning on tart cherries this season until after August 1^st. There is concern that pruning done prior to that time will result in regrowth this current season. This concern is the result of both the early season and lots of currently available soil moisture.
 

NW Michigan Horticultural Research Station
Insect Trap Count Averages - 1999 
 

DATE	Codling Moth	Spotted Tentiform Leaf Miner	Lesser Peach Tree Borer	Greater Peach Tree Borer	American Plum Borer	Oblique Banded Leafroller	Grape Berry Moth
5/18	0	660	8		30
5/24	0	88	1.3		14.3	0
6/1	.6	85	17		4.6	0	9
6/8	2	15	17.3		2.7	0	7.7
6/14	1	342	11	6	.3	7	4.3
6/21	.33	511	10	5	0	2.3	1
6/28	.75	455	6.3	1.6	.75	2.3	16.3
7/5	0	357	7.3	1.6	2.6	0.3	2.3
7/19	1.6	188	2.3	6	7.3	2	3.6

 
 

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

Last Revised:7-23-99