MSU Extension

Weather and crop report

Temperatures have remained cool across northwest Michigan. Tree development has moved gradually with the recent cool temperatures, but growers have disease control in mind with new green tissue continuing to show up, albeit slowly. Daytime temperatures over the weekend barely reached 60 degrees Fahrenheit, and overall average temperatures have been in the mid-40s for the past week. Weather predictions for the coming week are variable and range from a high of 68 F to a low of 54 F for the daytime highs. If warmer conditions prevail, tree development will move quickly and growers should continue to protect against spring diseases. Thus far, we have accumulated 223 growing degree-days (GDD) base 42 and 85 GDD base 50.

Rain has been predicted at low levels over the weekend and into this week. We received some spotty rainfall throughout the region May 1, but at the Northwest Michigan Horticulture Research Center, the Michigan State University Enviro-weather station did not record any rainfall. Soil moisture conditions are drying out, as we have had no appreciable rainfall since April 24-25.

Tree planting continues across the region. Growers are also removing brush from the orchard and wrapping up pruning for 2016. With bloom time for cherries in the near future, growers are preparing to move bees into the orchards. So far we have received reports that the strength of honey bee hives is strong.

There has hardly been any change in the condition of wine grape buds. The only variety to show any signs of bud swell at the research center is Frontenac. Things should start to move along later this week if the predicted temperatures come to pass.

The next “First Friday” meeting, co-hosted by Parallel 45 Vines and Wines, will be May 6 from 3-5 p.m. at 2 Lads Winery on Old Mission Peninsula. Mark Ledebuhr of Application Insight will be presenting information on sprayer rate controllers, drift management and visualizing deposition patterns.

Earlier saskatoon sites are getting into the white tip stage. I have not seen any insect activity yet. We are not certain of the prime infection periods for Entomosporium leafspot or saskatoon-juniper rust, but these fungal diseases may now be releasing spores if rainy weather occurs. The 2016 pesticide recommendations for saskatoons are now available.

2016 growth stages as of May 2, 2016

• Bartlett Pear – Green cluster
• Potomac Pear – Early white bud
• McIntosh – Tight cluster
• Gala – Tight cluster
• Red Delicious – Tight cluster
• HoneyCrisp – Early tight cluster
• Montmorency – Late green tip
• Balaton – Bud burst
• Hedlfingen – Late bud burst
• Gold – Bud burst
• Napolean – Early bud burst
• Riesling – Scale crack

Vineyard volunteers needed at the Northwest Michigan Horticultural Research Center

We still have a lot of pruning and tying left to do at the research vineyard. We are looking for volunteers to help finish the job next Wednesday and Thursday, May 11 and 12. Weather permitting, we’ll start at 8 a.m. and work until 5 p.m. With a big enough crew, it might be possible to wrap it up in one day.

Please contact Duke Elsner at 231-357-8353 or elsner@msu.edu if you can help out or would like more details. Please bring your own pruning shears and loppers. If the weather is questionable, call me before heading over to the research center.

Pest report

Some areas across the region received a small amount of rain over the weekend, but because the wetting period was short and temperatures were cool, there were no apple scab infection periods reported on MSU Enviro-weather for the northwest region. Although rain was not reported on the Traverse City (NWMHRS) Enviro-weather station, conditions were wet Sunday, May 1, and we checked for spore discharge; no spores were found.

It is still early in the primary apple scab phase and MSU Extension encourages growers to be ready to protect green tissue when the forecast calls for rain, which is currently predicted tonight into tomorrow morning, May 3-4. The research center set biofix on April 17 and according to the apple scab model, 17 percent of ascospores are mature and 3 percent have discharged at this time.

Inoculum levels for American brown rot have been relatively low in most orchards due to low infection levels in the last two seasons; however, some orchards may have a higher level of inoculum. As we approach bloom time in sweet cherries, American brown rot could be a concern if overwintering mummies are present, temperatures are warm during bloom, and if we have rain followed by high relative humidity of about 90 percent. No rain and a low relative humidity (60 percent or lower) significantly reduces the likelihood of blossom infection from this disease. Several sterol inhibitors are available for American brown rot management; however, Rovral 4 F at 2.0 pints per acre is still the optimal option for excellent efficacy and for resistance management.

As we approach bloom in tart cherries, European brown rot could be a concern if the weather continues to be cool and wet, particularly in orchards that have slow drying conditions. Growers with European brown rot-susceptible orchards that are in the popcorn stage, particularly Balatons, should consider protecting these trees from possible infection as the forecast is currently predicting temperatures in the 40s and rain for Wednesday, May 4. Although the variety Balaton is more susceptible than Montmorency, we have observed European brown rot in Montmorency when weather conditions favor this disease. So far, conditions this spring have been conducive for European brown rot. Two applications of an efficacious material, one application at popcorn and one application at bloom, is the recommended strategy for European brown rot management. Please refer to “New-old options for European brown rot control in tart cherries” for current information on fungicide efficacy.

Cherry leaf spot is a concern in cherries that have unfolded bract leaves and true leaves. Due to challenging conditions last spring, many orchards became infected with leaf spot early that resulted in high infections and earlier than normal defoliation. Preventing early leaf spot infections will help to minimize the degree of infection later this season; this is particularly important for trees that could have been stressed by early leaf loss last season. We would like to remind growers of the 10-D retreatment interval for chlorothalonil when applied using alternate row middle applications and full cover applications.

American plum borers and oriental fruit moths have not been detected. We found an average of seven green fruitworm moths in traps at the station this week.

Dr. Rothwell’s work is funded in part by MSU’s AgBioResearch.