July 11, 2000

GROWING DEGREE DAY ACCUMULATIONS through July 10th at the NWMHRS

Year         2000       1999       1998        1997
GDD42    1668       1821       1836       1346
GDD50      971       1135        1128        798

GROWTH STAGES:
Pear: Bartlett -- 32mm
Apple: Red Delicious -- 47mm
Sweet Cherry: Napoleon -- 23mm, coloring
Tart Cherry: Montmorency -- 20mm, coloring
Grapes: Chardonnay -- buckshot berries

WEATHER

Rainfall this past week amounted to 0.19", while evaporation totaled 1.43". Evaporation exceeds rainfall by 1.24" for the week and by 10.18" for the growing season.
 

Date	Weekly Rainfall	Weekly Evaporation	Rainfall vs Evaporation +/1	Rainfall vs 75% Evaporation +/-
5/9	0.63	1.85	-1.22	-0.76
5/16	1.24	1.08	+0.16	+0.43
5/23	0.98	1.06	-0.08	+0.19
5/30	0.10	1.14	-1.04	-0.76
6/6	0.56	1.09	-0.53	-0.26
6/13	0.66	1.59	-0.93	-0.53
6/20	0.54	1.41	-0.87	-0.52
6/27	1.00	1.39	-0.39	-0.04
7/4	0.21	1.61	-1.40	-0.38
7/11	0.19	1.43	-1.24	-0.88
Total	6.11	13.65	-7.54	-3.51
for
Period

PESTS AND DISEASES
By Gary Thornton, District Fruit IPM Agent

Apple growers, in some cases, are seeing high trap catches for codling moth. We should be approaching the end of the first generation by now, but I have given up trying to predict this pest! Growers should treat trap catches accumulating in greater than 5 moths per trap as a biofix. Sprays should be applied 250 DD base 50 after the biofix. Pears are not susceptible at this time. Apple maggot was first caught on June 29^th in NW Michigan. Growers who are not trapping should be controlling for it at this time. Growers who will be trapping for it should hang their red sticky spheres out now. Aphids continue to build in untreated blocks. Spotted tentiform leafminer trap catches have been quite high, but, no mines have shown up yet from this generation. White apple leafhopper adults can be found but not in high numbers in most cases.

Cherry fruit fly adults are now commonly showing up in commercial cherry blocks. Cherry growers should continue to control for brown rot, leafspot and alternaria. The high humidity is ideal for fruit to fruit spread of brown rot. Ten day schedules for brown rot are appropriate for this time of year. Leafspot pressure is slowing as the terminal buds continue to set. Despite numerous wetting periods, the actual leafspot infections have been very low so far this year. Two spotted spider mites are just starting to build as the ground cover dries up.

Plums are starting to see an increase in mite pressure as well. Pyramite is now labeled for use in plums, with a 7 day PHI. It is excellent on European red mites and good for controlling two spotted spider mites. 

MISCELLANEOUS

Possible Crop Disaster Programs
by Jim Bardenhagen, Leelanau MSU Extension Director

While it's way too soon to tell, there is a chance that Congress may make some crop disaster assistance programs (some familiar, some revised, some new) available this year through the Farm Service Agency (FSA). This is due to light crop yields and other crop disasters in the US. In order to ensure eligibility for maximum benefits, it's important that growers certify their 2000 crops with FSA and provide past actual production history (APH) to FSA for your crops by July 17^th. Crops covered under the crop insurance program may not need certification or past production information - ask FSA to be sure.

We know that everyone's busy with harvest, but you may want to call FSA at 941-0951 to be sure that you have met the filing requirements before it's too late.

The Northwest Michigan counties, via FSA, have already filed reports requesting crop disaster assistance programs for 2000 fruit, maple syrup and hay crops.

Apple Leafminer
By Gary Thornton

Apple leafminer is a pest that is becoming more common in NW Michigan. It first showed up in Benzie county apples and has now been reported in cherry. The following information is taken from Scaffolds No. 16, 7/3/00, written by Art Agnello, Dept. of Entomology, Cornell University.

Apple Leafminer, Lyonetia prunifoliella 
This lepidopteran pest was formerly known as L. speculella, and it has been most evident in the upper Hudson Valley in recent years, particularly around the Capital District. Larval food plants recorded for this species are apple, plum, cherry (including pin cherry), birch and grape. Female moths oviposit in tender new foliage by piercing the undersides of leaves and depositing single eggs inside the leaf tissue. The hatched larvae form serpentine mines, which are visible as wavy brown lines on the tops of leaves. As the larvae grow, they enlarge their mines into brown blotches, within which they consume all of the leaf tissue between the upper and lower epidermis. Larvae eject their black feces through slits in the bottom of the blotches. When they become full-grown (third instar), they leave their mines to pupate, usually by descending to lower leaves on a silken thread. Just before pupating, the larvae spin silken cocoons, which are suspended by threads and resemble a hammock. There are probably 4-6 generations per year in this area, but only the late summer larvae are noticeable (or problematic); moths are generally never even caught before the end of July. 

Larval feeding is confined to the youngest foliage, particularly terminal leaves of vigorously growing shoots. Root initials or water sprouts that are partially shaded are the preferred sites for feeding and pupation. Severely mined leaves turn brown and die; most such leaves drop off prematurely, thereby decreasing the number of some of the most photosynthetically active leaves. The potential for damage is greater in young orchards than in mature ones, and vigorous trees (i.e., those on dwarfing rootstocks) usually suffer more injury than do less vigorous ones. 

Populations of apple leafminer normally do not attain high abundance and cause noticeable damage until the beginning of the harvest period. Insecticidal control of larvae or adults may not be a reasonable tactic because of the pre-harvest intervals of most candidate materials (i.e., carbamates that are used against STLM). Broad-spectrum insecticides used in cover sprays are unlikely to control larvae or adults because leafminer numbers have increased in orchards that have been sprayed regularly with these chemicals. A 1990 field trial in West Va. compared the effectiveness of different insecticides applied 2 times (7-day interval) in August against different life stages of this insect. All the materials tested - Asana, Thiodan, Lannate, Vydate, Cygon, and (to a lesser extent) Carzol - effectively reduced population levels of larvae and pupae, and Asana also had some effectiveness against egg numbers. 

Two cultural practices may affect the amount of larval damage obtained. The preferred food of the miners is the new growth of vegetative shoots. The removal of root and water sprouts may greatly reduce the amount of available food for larvae, and thereby control the growth of moth populations. Another practice that may influence leafminer abundance is fertilization. Application of fertilizer in excess amounts or late in the season would enhance vegetative growth, particularly late in the growing season. Abundant larval food at this time would permit additional generations of the insect. These leafminers cause very little injury to unfertilized apple trees with poor or moderate shoot growth. For the present, a good pruning program and restraint in fertilizer use may be the best available means to control populations of this leafminer. 

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

Last Revised:7-11-00