Northern Michigan FruitNet 2003
Weekly Update
NW Michigan Horticultural Research Station

Jim Nugent                     Gary Thornton                       Bill Klein
        District Horticulturist           District Fruit IPM Agent         Farm Mgr, NWMHRS

      Duke Elsner                                                            Jim Bardenhagen
            Agricultural Agent                                              Leelanau Extension Director

June 10, 2003

GROWING DEGREE DAY ACCUMULATIONS as of June 9, 2003 at the NWMHRS
 
Year
2003
2002
2001
2000
1999
13 yr. Av. ('90-2002)
GDD42
729
610
822
904
1000
779
GDD50
347
317
422
455
557
411

WEATHER

Recent rains this past weekend delivered 0.25" to 0.72" of rain.  An additional 1.16" fell on Tuesday at the NWMHRS.

GROWTH STAGES at NWMHRS
Apple: Red Delicious – fruit set
Pear: Bartlett – no fruit
Sweet Cherry: Napoleon – 12 mm
Tart Cherry: Montmorency – 12mm
Apricot – no fruit
Plum: European type – 7mm
Grapes: Chardonnay – 4-8" shoots

INSECTS & DISEASES
By Gary Thornton 

Apple: The rains that started on Sunday resulted in a heavy infection period for apple scab in all areas except the Benzie county weather station. Tuesday's rains resulted in a heavy infection for apple scab in most areas. Spores are still being caught in some areas in southern Michigan, so primary has not ended yet for scab. Fireblight was not a threat during recent rains, however, the warmer temperatures forecasted for later this week indicate that growers with open bloom in their orchards will need to spray if a rain is imminent from Friday through the weekend. Codling moth trap catches have been higher than usual this year. Trap catches averaged 7.3 moths per trap this past week in Leelanau County. Most growers have biofixed by this time. Rosy apple aphids are curled up tightly now and are difficult to control. Oblique banded leafrollers remain active in some orchards; control is difficult when they are rolled up in leaves. Spotted tentiform leafminer trap catches were down to 88 per trap in Leelanau County.

Cherry: Cherry growers experienced a heavy infection period for cherry leaf spot from Sunday's rain, and a moderate infection from Monday's. European brown rot was found in one tart cherry block in Northport. Indar and Benlate/Captan are the two main control options. Green fruitworms are up to ¾ inch long. Plum curculio stings have been found in tart and sweet cherry. Sweet cherries need to be protected from now until harvest. In tart cherries with low populations of plum curculio, treatments will not be needed until 375 DD base 50 after full bloom. Currently the NWMHRS is 209DD base 50 past its full bloom date of May 17. 

Salt injury to trees along the highways desiccated the buds and fine wood, but did not kill the structural wood. Adventitious buds are breaking or will break, even on tart cherry. Most of these trees will recover. 

Rose chafer was found in SW Michigan, so be on the watch for it in NW Michigan. This is the week it typically shows up here.

Strawberries have shown some crown injury where there was no snow and straw covering. This injury doesn't appear to be severe and should heal.

Peaches are just coming out of the shuck. This is a critical time for tarnished plant bug injury. Growers should be sure to have an insecticide on, particularly prior to mowing.

GIBBERELLIC ACID ON CHERRIES 
By James E. Nugent
District Horticulturist, MSUE

Gibberellic acid (GA) is used in young tart and sweet cherries to reduce flowering and fruiting which maximizes growth and minimizes pollen transmitted virus infection. GA is used in mature tart cherries to increase the fruiting capacity by stimulating the development of lateral shoots and spurs.

Tips for use:

1. The proper application timing for GA on tart cherries is typically 3-4 weeks after full bloom, or when trees have 5 to 7 leaves (3 to 5 leaves fully expanded) on terminal growth.    2. Apply when high temperatures are expected to be above 70 ° F for a couple of days, if possible. Applications made when high temps are expected to be below 60 ° F have given poor results. Leaves expanding under low temperatures are less efficient at uptake than leaves growing under normal to above normal temperatures. 

3.  For mature tart cherries – to increase long-term fruit production.

a) Use 10-20 ppm of gibberellic acid. Lower rates are typically used on more vigorous orchards or where GA was used successfully last year; higher rates are used on low vigor orchards. Rates of about 15 ppm are most common.

b) Rates of ProGibb 4% on mature trees are as follows:

10 ppm response = 6 fl oz/acre
15 ppm response = 9 fl oz/acre
20 ppm response = 12 fl oz/acre

c) Research with surfactants has given results varying from no effect to over-response with phytotoxicity. The phytotoxicity occurred with silicon based surfactants. Therefore, we suggest not using a surfactant with GA unless a grower has enough experience with a particular surfactant to have confidence in the response. Never use a silicon-based surfactant.

4.  In non-bearing tart and sweet cherries -- used to greatly reduce flowering and fruiting to achieve faster growth and delay pollen-transmitted virus infection.

a) With a handgun, apply either 100 ppm (40 fl. oz. of Pro-Gibb 4% per 100 gallons of water) in a single application 3-4 weeks after full bloom (slightly later if temperatures are exceptionally cool); or 

 b) 50 ppm (20 fl. oz./100 gal) about 3 weeks after full bloom plus a second application at 50 ppm 2½ - 3 weeks later. This two-application system at 50 ppm nearly always is more effective than a single application at 100 ppm.   c) Do not apply to trees the year of planting.   5. To bring young trees into bearing following treatment with high rates during non-bearing years, it is very important to not discontinue GA all at once. This results in oversetting of fruit and stunting of trees. In the past, we have suggested decreasing the rate to 15 ppm, however, this is not enough GA! There are probably two reasons why trees still tend to overset. First, trees that have been kept vegetative have tremendous capacity to set fruit. Second, often at this time growers are switching from handgun application to airblast and may be underestimating the amount of GA needed on these young trees. Based on recent experience (but unfortunately not based on research), I now suggest weaning trees off GA over two or three years. The year prior to desired first fruiting, I suggest 30 to 40 ppm be applied if spraying dilute (12-16 fl oz ProGibb/100 gal), or about 20-24 fl. oz./acre if applied concentrate. This rate per acre for concentrate spraying already takes into account the average tree size of this age tree; i.e., do not reduce the rate further based on tree row volume. The next year, decrease this rate to 15 to 20 ppm applied dilute (6-8 fl oz./100 gal) or 10-12 fl oz./acre applied concentrate. The following year, 10 ppm is optional but often not required. In orchards where growth is weaker, it may be desirable to simply continue annual GA applications at 10-15 ppm as described above rather than discontinue at this time. GA may also be applied later in the season on sweet cherries to increase fruit firmness and delay harvest. Results in Michigan have not been very consistent and may lead to increased cracking. This use is not discussed in this article.

PESTICIDE UPDATE 
By Gary Thornton, District Fruit IPM Agent

Lorsban 50W – Gowan company, the manufacturer of Lorsban 50W has made the decision to stop manufacturing this product. Growers can continue to use existing stocks and purchase any that may still be available at distributors.

IMPACT OF COOL WEATHER ON CODLING MOTH MONITORING AND MANAGEMENT
John Wise and Larry Gut, MSU Dept. of Entomology

The cool temperatures over the last three weeks have prolonged the calendar time normally necessary for codling moth to go from first sustained flight (biofix) to egg hatch. Most counties in the central and southern regions of the state biofixed for codling moth on the May 17-18 weekend, but have only accumulated 150 GDD base 50 since that time. The research that the codling moth degree-day model is built on shows early egg hatch to be at 250 GDD after biofix. Therefore the eggs that were laid by those initial codling moth adults three weeks ago still require an additional 100 GDD base 50 to hatch. This illustrates the benefits of monitoring GDDs, which correlate to insect development, instead of making management decisions solely on a calendar date basis.

It should be noted that not all insecticides should be timed for the 250 GDD egg hatch timing. For example, if you plan to use the insect growth regulator, Intrepid, then biofix + 150 GDD spray timing is optimal. The following chart, modified from the Michigan Fruit Management Guide (E-154) should help distinguish optimal timing and use of some insecticide options. 
 
Common name
(Trade name)		 GDD timing post-biofix Rate/acre PHI REI
Azinphosmethyl
(Guthion 50WP)
* 14 day REI for activities like hand thinning (see label)		 250 2 lb 14 d 48 hr*
Phosmet
(Imidan 50WP)		 250 2.25-3.0 lb 7 d 24 hr
Esfenvalerate
(Asana XL 0.66EC)		 250 9.6-14.5 oz 21-28 d 12 hr
Fenpropathrin
(Danitol 2.4EC)		 250 10.6-21.3 oz 14 d 24 hr
Spinosad
(SpinTor 2SC)		 250 7.5-10.0 oz 7 d 4 hr
Acetamiprid
(Assail 70WP)		 200-250 3.4 oz 7 d 12 hr
Methoxyfenozide
(Intrepid 2F)		 150 16 oz 14 d 4 hr
Pyriproxyfen
(Esteem 35WP)		 100 5 oz 45 d 12 hr

MICHIGAN STATE UNIVERSITY ORGANIC APPLE PROJECT THIRD ANNUAL FIELD DAY WEDNESDAY, JUNE 18, 1:00 TO 4:00.  CLARKSVILLE HORTICULTURE EXPERIMENT STATION.

MSU and the Organic Apple Team invite you to visit and experience the five-acre certified organic (OCIA) site and over 2500 trees now in the 4th growing season.  First time participants will get an introduction to key organic orchard concepts related to soil quality and fertility, pest and disease monitoring and management, and ground floor management techniques. Returning participants will get an update on research progress and evolving management strategies.

To help us prepare adequate transportation and handouts, please RSVP to Sandy Allen by Monday, June 16.  Let us know if you are a first time or returning participant. 

Voice: 517-355-8362; email: allens@msu.edu.  The station is located at Exit 59 off I-96 at 9302 Portland Road, Clarksville, MI.  For additional information call CHES at 616-693-2193 or email the station at huntjan@msu.edu.

ACTUAL AND PREDICTED DEGREE-DAY
ACCUMULATIONS SINCE MARCH 1, 2003

Please send any comments or suggestions regarding this site to: 

Bill Klein, kleinw@pilot.msu.edu
Last Revised: 6-11-03