Northwest Michigan fruit regional report – June 23, 2015
Fruit is sizing across the region. Warmer, drier weather is welcomed after long, ongoing wetting events.
The storm that was predicted for last night, June 22, skirted by the region, and thus far we have not heard of any reports of hail nor tornados, thankfully. We did receive some rainfall, less than 0.1 inches, Monday afternoon, and we had no more rain overnight. The wind picked up into the night and early morning, but a sunny and clear day is predicted for today, June 23. We have also heard most of the fruit growing regions around the western part of the state were not negatively impacted by yesterday’s storms.
We have accumulated 1,087 growing degree days (GDD) base 42 and 611 GDD base 50. These numbers remain comparable, but are falling slightly behind our 25-year averages: 1,126 GDD base 42 and 643 GDD base 50. There is rain in the forecast for Thursday, June 25, but the weekend is predicted to be sunny and warm.
Many vinifera grape vineyards are looking better after a week of good shoot growth. Bloom has started on some varieties of vinifera and hybrids. The small, delayed shoots arising from injured canes higher in the canopy are still growing, but these will likely wither if we get into a warm or dry period, or when their demand for vine resources increases after fruit set. It should be very obvious now which sites are going to make a good recovery and which ones will suffer long-term consequences.
Injury from rose chafer adults has been very minor thus far as the population of this insect appears to be low this year. Rose chafer adult activity should peak soon and be essentially over in about two weeks. Feeding injury of green fruitworm first generation is over. The second generation of these insects are rarely important in vineyards. Potato leafhopper populations have remained low in Michigan’s Grand Traverse region.
No symptoms of powdery mildew or downy mildew have been reported.
If you have a vineyard site that has suffered severely from the winter cold, you may be able to take advantage of some of the provisions of the Tree Assistance Program (TAP), administered by the USDA Farm Service Agency (FSA). TAP provides financial assistance to qualifying orchardists and nursery tree growers to replant or rehabilitate eligible trees, bushes and vines damaged by natural disasters. Read more on the TAP program. Growers considering assistance should contact Kathy Kozlowski, FSA County Executive Director in Antrim, Leelanau and Grand Traverse counties, at 231-941-0951 ext. 2.
Some saskatoon fruits are beginning to color; a close look may reveal that many of these berries have some sort of injury from internal feeding insects. Healthy berries are still quite green on the shaded side. Rose chafer adults are still feeding on leaves. Green fruitworm larvae and pyramidal green fruitworm larvae are done with feeding now.
Michigan’s annual Fruit Crop Guesstimate will take place June 24 in Grand Rapids, Michigan, where we will have the official estimates for all fruit crops for the 2015 season. In general, the tart cherry crop in northwest Michigan is estimated to be 75-85 million pounds. West central Michigan is estimating their crop to be in the 32 million pound range, and the southwest Michigan crop seems to be growing and is now estimated to be 31 million pounds. The sweet cherry crop continues to ripen, and most fruit are losing the green color. We are also in the midst of June drop in sweet cherries, and we hope cherries that were not pollinated continue to drop as we approach harvest.
The apple crop is sizing, and we are observing more frost scars in developing fruit.
Conditions finally dried up throughout the region with the exception of a little rain last Wednesday, June 17, a light sprinkle Saturday, June 20, that was so minimal it was not recorded on the Michigan State University Enviro-weather station, and rain yesterday afternoon, June 22. As a result of drier conditions, we have had few reported infection periods, which has been a welcomed break from seemingly ongoing wetting events this season.
We have observed cherry leaf spot conidia on the undersides of infected leaves, and most orchards have cherry leaf spot infection at this time. We have received reports of moderate to high levels of cherry leaf spot infection in a few orchards as a result of recent wet weather that has been challenging for growers to keep tissue covered. Preventing the spread of cherry leaf spot conidia to adjacent tissue is critical for preventing high levels of cherry leaf spot and pre-mature defoliation. There is a chance for rain possibly overnight Wednesday into Thursday and again over the weekend. Most growers will need to recover tissue before the coming rain. Growers should use caution if they are planning to use copper this week as phytotoxicity could be a concern if temperatures are high this weekend; some forecasts showed a high of 80 degrees. Powdery mildew is apparent in untreated cherries at the Northwest Michigan Horticulture Research Center (NWMHRC) at this time.
Apple scab spore catches at our monitoring site have remained low (less than one per spore rod) following wetting periods in the last two weeks. At this time, the Enviro-weather apple scab model is reporting 96 percent of spores have been discharged since the NWMHRC biofix of April 19. Primary apple scab ended in southeast Michigan two weeks ago and last week in west central Michigan; it is likely that most orchards in the northwest are also at the end of primary apple scab at this time. However, Michigan State University Extension cautions more northerly growers that primary may not be over in those areas as spore discharge, according the Northport Enviro-weather station, is lagging behind the NWMHRC at 91 percent discharge with biofix of April 23. We have observed symptoms of low levels of apple scab infections on leaves and fruit, and growers with orchards that were infected with apple scab during primary will need to continue managing this disease to prevent the spread of secondary infections.
Overall, there has been little insect activity in the trap line at the NWMHRC since last Tuesday. Borer activity continues to be relatively low; we found 0.3 American plum borers per trap, four lesser peachtree borers per trap and we still have not caught greater peachtree borers at the NWMHRC. The next possible borer management timing should be targeted for later season lesser peachtree borers when greater peachtree borers become active.
Obliquebanded leafrollers began emerging this week and we found one moth in a pheromone-baited delta trap Monday, June 22. Rose chafer activity is ongoing and some growers have sprayed for these beetles in the last few weeks. Although we previously caught codling moth for two consecutive weeks and set biofix for June 9, we did not catch any this week.
Cherry fruit fly traps should be up in cherry orchards, and as a reminder, traps should be placed in the upper third of the tree canopy, along orchard edges and in visible locations (i.e., in areas with high sunlight reflection, southern exposure, etc.). We have not detected cherry fruit flies at the NWMHRC at this time, but expect this pest will become active soon.
Spotted wing Drosophila (SWD) were not detected in any of the 71 traps currently out in northwest Michigan last week. The first SWD detected in the state was found in Benzie County June 11 and this SWD was a female fly captured in a Trece lure baited trap. Sweet cherries, and in some areas tart cherries, are ripening and are at the straw-colored stage. Previous research at the NWMHRC has shown straw-colored cherries are susceptible to SWD egglaying. Growers, consultants and scouts should put SWD traps up in orchards at this time if they are planning to monitor for SWD this season. Furthermore, most of the first detections of SWD in the statewide monitoring network have been female flies, thus positive identification of males and females is critical for early detection of flies. We welcome those who are monitoring for SWD to bring suspected SWD specimens to the NWMHRC for identification and confirmation of the species. Our address is 6686 S. Center Highway, Traverse City, MI 49684.