Northern Michigan FruitNet 2009
NW Michigan Horticultural Research Station
District Fruit IPM/IFP Agent
Farm Mgr, NWMHRS
Agricultural & Regional Viticulture Agent
June 9, 2009
GROWING DEGREE DAY ACCUMULATIONS AS OF June 8th AT THE NWMHRS
Growth Stages at NWMHRS (6/8/09- 4:30 p.m.)
Apple: McIntosh – 10 mm fruit
Yellow Delicious – 11 mm fruit
Gala – 8 mm fruit
Red Delicious – 11 mm fruit
Pear: Bartlett: 11 mm fruit
Sweet Cherry: Hedelfingen: 13 mm fruit
Napoleon: 13 mm fruit
Gold: 13 mm fruit
Tart Cherry: 12 mm fruit
Balaton: 13 mm fruit
Apricot: 26 mm fruit
Plum: 8 mm fruit
Grapes: 4-8” shoots
The weather continues to be cool in the north, much like other regions of the state. We have accumulated 662 GDD base 42, and our 19-year average is 777.5 GDD. Base 50, we have accumulated 301 GDD, which is ~100 GDD less than our 19-year average. We received significant rainfall so far this month: 0.57 inches on 7 June, 0.36 inches on 8 June, and 0.61 inches on 9 June. Overall rainfall totals for June are 1.84 inches.
Crops are moving along slowly with the cool temperatures. Pears at the NWMHRS are 11-13mm in diameter while apricots are at a whopping 26mm. Galas are at 8mm, Macs at 10mm, and Red and Golden Delicious are at 11mm. Cherry are at similar sizes: 12mm in Montmorency, 11mm in Balaton, and 13mm in sweet cherry. Grapes seem to be hanging on at 4-8” shoots, where they have been for over a week. Apple growers have been trying to find a window to thin, which has been difficult with the cool temperatures, but also with the rain. Growers are also thinking about gibberellic acid applications in cherry, but most likely they will wait until next week when we have the recommended 3-5 fully expanded leaves. Strawberry harvest is predicted to start around 19 June.
In apples, spotted tentiform leafminer numbers are down for the second week in a row with an average of 12 adults per trap. We caught our first codling moth two weeks ago, none last week, and 2 per trap as of this week. We have had no reports of sustained catch in the region. Oriental fruit moth catch has an average of 2 moths per trap. The area has received heavy rains that triggered a light scab infection on Monday, despite the cool temperatures. The severity of the infection forecast has increased as the current wetting event continues with most of the area under a moderate to heavy infection as of Tuesday morning. As of today, the model estimates 100 percent ascospore maturity and 80 percent dispersal. The fire blight model will not accumulate an EIP over 100 in the coming week based on the forecast that temperatures will remain cool.
In cherries, American plum borer numbers have rebounded slightly this week with an average of 15 moths per trap, compared to 6 moths per trap last week, and 37 two weeks ago. We also caught our first lesser peach tree borers. As fruit develops, growers should be aware of potential damage from plum curculio, particularly as temperatures warm at the end of the week. Based on a biofix (full bloom date) of May 15, we have accumulated 150 DD50 according to the tart cherry plum curculio model. This model has been commonly used when applying organophosphates. Despite the cool temperatures (averaging 45-50°F), cherry leaf spot infection will occur around the region as the wetting period exceeds 24 hours.
We caught a couple more grape berry moths this week both on Old Mission and Leelanau Peninsula. Our first grape berry moths (two to be precise) were caught in a Leelanau vineyard last week. So far only one lone potato leafhopper has been caught on Old Mission. As rain arrives from the south, we could observe potato leafhopper arriving in more significant numbers.
For an updated version of the pest report during the week, call (231) 947-3063.
APPLE SCAB FUNGICIDE SENSITIVITY SCREENING 2009
Erin Lizotte, District IFP/IPM Educator
The NWMHRS, in collaboration with the Michigan State University Tree Fruit Pathology lab, will be screening apple scab samples from northwest Michigan for sterol inhibitor and strobilurin sensitivity. We are looking to screen 30-50 sites and need to collect 50 leaves with active, brown scab lesions. If you have a site with symptoms, we can collect the sample or you can bring the sample to the Research Station or the next IPM Update in your area. To collect a sample yourself, collect 50 leaves from as many trees as possible and store in a paper bag in the refrigerator until you can deliver them. They may be stored together in one bag. A brief history of the use of sterol inhibitors and strobilurins for the orchard along with your contact information is greatly appreciated. For more information, please contact Erin Lizotte at (231) 946-1510.
USING GIBBERELLIC ACID TO ADJUST CROPPING IN CHERRIES
N.L. Rothwell, District Horticulturist, NWMHRS
Jim Nugent, Retired District Horticulturist, NWMHRS
Gibberellic acid (GA) is a plant hormone that promotes growth and elongation of cells. In tart and sweet cherries, GA has been used successfully to reduce flowering during the early years of an orchard's life. The reduced flowering and subsequent reduced fruiting helps young trees increase vegetative growth. In addition, minimizing flowering in early years slows the transmission of pollen-borne viruses in young trees. We have also shown that GA used in mature tart cherry orchards can increase fruiting capacity by stimulating the formation of lateral shoots and spurs. This technique can be particularly advantageous on Balaton blocks where trees have a tendency to produce blind wood (branches without leaves or blossoms).
When GA is applied to cherry trees in late spring, a percentage of the flower buds forming for the following season will be converted to vegetative buds. Therefore, GA application in 2009 influences flowering in 2010. The effectiveness of GA is dependent on rate, timing and temperature. Figures 1 and 2 (below) demonstrates the importance of rate for GA applications. Surfactants have also been shown to influence GA applications. As a rule of thumb, high GA rates are required to keep a young tree from fruiting, whereas much lower rates are used to keep bearing trees in a good balance between vegetative and fruit production. GA applications should be made when daily high temperatures are expected to be above 70° F for two to three days, if possible. We have observed poor results when applications are made when daily high temperatures are below 60° F.
GA is typically applied to non-bearing cherries with a hand gun, so rates are applied on a dilute basis. The best results are generally achieved with two applications of 50 ppm (20 fl. oz. of 4% formulated product per 100 gallons of water). The first application should occur 3 to 3 ½ weeks after full bloom, followed by a second application 2 ½ to 3 weeks later. An alternative method, though slightly less effective, is to apply a single treatment of 100 ppm (40 fl. oz. per 100) at about 3 to 4 weeks after bloom. GA should not be applied to trees during the year of planting, due to possible phytotoxicity. Vigorously growing trees in their second leaf do not need GA, as these trees naturally produce little fruit the following year. GA application often starts in year three, but may be desirable in year two if trees start off poorly. These high rates should continue until the year prior to first harvest/year of production.
Early bearing trees
To bring young cherries into bearing following GA treatments with high rates, growers should phase down GA rates rather than discontinuing GA use all at once. A sudden drop of GA from high rates to nothing will result in oversetting of fruit and potential tree stunting. Trees that have been kept vegetative with GA use have a tremendous capacity to set (overset) fruit. The year prior to when growers first desire fruiting, they should apply GA at 30 to 40 ppm if spraying dilute (12-16 fl oz./100 gal.) or 20-24 fl. oz./acre if applied at a concentrated rate. This rate per acre for concentrate spraying already takes into account the average tree size of this age tree, therefore 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 concentrate. The following year, 10 ppm is optional but often not required. In orchards where growth is weak, growers should continue annual GA applications at 10-15 ppm as described for bearing trees.
Growers should apply GA 3 to 4 weeks after bloom or when trees have 5 to 7 leaves (3 to 5 fully expanded) on terminal growth. GA should be used at rates of 10 to 20 ppm or 4 to 8 oz/100 gallons of ProGibb 4% (or equivalent) when applied dilute. For concentrate application to full-sized tart cherries, use 6 oz/acre of product to achieve a 10 ppm response or 12 oz/a for a 20 ppm response. Lower rates are typically used on more vigorous orchards or those with previous successful use of GA. Adding surfactants has caused varied responses—everything from increased phytotoxicity to no GA-related effects. Therefore, adding a surfactant is not suggested unless a grower has enough experience with a product to have confidence in the response.
GA Use on Balaton
Balaton appears to have less need for GA during non-bearing years to maintain good tree growth, but as it matures, the variety produces a lot of blind wood. Therefore, using GA is strongly encouraged on bearing Balaton trees. Figure 1 shows the successful use of GA to increase lateral shoots and spurs in a Balaton orchard at the NWMHRS. However, we cannot conclude that GA applications improve Balaton yields based on 2007 and 2008 data (Figures 3 and 4), although GA does appear to help with yield. We will continue this trial this season.
Figure 1. Average number of shoots with terminal buds in a Balaton orchard (2007).
Figure 2. Average number of shoots with terminal buds in a Balaton orchard (2008).
Figure 3. Average yield of Balatons with different rates of GA (2007)
Figure 4. Average yield of Balatons with different rates of GA (2008)
WEEKLY APPLE THINNING CARBOHYDRATE MODEL
SPECIAL CONSIDERATIONS FOR PRIMARY PEST MANAGMENT IN TART CHERRY
Erin Lizotte, Nikki Rothwell, and John Wise
With all of the new insecticides on the market, growers have a lot to consider for pest control in tart cherry. In order to address the variety of insecticides available, the following table was developed to address our major pests of tart cherry throughout the season: oblique-banded leafroller and green fruit worm early in the season, followed by plum curculio during mid-season, and ending with cherry fruit fly and 2nd generation OBLR and other secondary lepidoptera around harvest. As we target each of these pests, there are multiple considerations depending on the insecticide of choice.
Here is a link to the Table (PDF)
Insect and disease predictive information is available at:
Information on cherries is available at the new cherry
Fruit CAT Alert Reports
This issue and past issues of the weekly FruitNet report are posted on our website at: http://www.maes.msu.edu/nwmihort/faxnet.htm
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Last Revised: 6-9-09