Northwest Michigan fruit regional report – July 15, 2014

Cherry harvest nears in northwest Michigan as growers apply loosener and concentrate on keeping the cherries clean for harvest.

Weather report

The past week has been seasonable with daytime highs in the mid-70s and nighttime temperatures in the 50s and 60s. On Tuesday, July 15, a cold front moved down from Canada, and daytime temperatures are expected to be in the mid-50s. As we approach the middle of July, we have accumulated 1,579 growing degree days (GDD) base 42 and 972 GDD base 50. We are still behind our 24-year averages of 1,722 GDD base 42 and 1,061 GDD base 50. The Northwest Michigan Horticulture Research Center (NWMHRC) recorded very little actual rainfall on two dates, but the forecast for today, July 15, is predicted rain and isolated thunderstorms.

Crop report

Stem-on sweet cherry harvest for the brine market has begun in northwest Michigan. Fruit size is relatively small, but the quality for briners remains good. Growers are hoping that the rain will help size the large crop of cherries destined for the canner market. Growers have been diligent about keeping the crop disease-free, particularly as cherries size and getting spray into tight clustering varieties becomes more challenging. Ethephon is going on now in sweet cherry orchards.

Tart cherries are also ripening, and in blocks that have a light crop, fruit is ripening quickly. Some growers believe that they may harvest a light block of tart cherries before they harvest a heavy crop of canners. Ethephon is also going on in tart cherries.

Apples are sizing and the crop is looking good at this time.

Strawberry harvest is over for most northern Michigan farms, and the season seemed shorter than in past years.

Pest report

As mentioned previously, orchards continue to look clean and mostly free of diseases; we have not received reports of orchards that have been devastated by diseases or insects this season. Although the weather has been favorable for disease development throughout this season, growers have done an excellent job keeping tissue protected to prevent infection.

American brown rot is evident in trials here at the NWMHRC, and we are able to find a few orchards with this disease in the fruit. Currently, temperatures are cool and wet conditions are in the forecast for today; temperatures are predicted to warm up later this week, which will once again be concerning for diseases. Growers should continue to keep tissue protected from American brown rot and cherry leaf spot infection through harvest and, if possible, after harvest. Michigan State University Extension would like to remind growers that using a SDHI fungicide as the last spray before harvest will provide the longest effective American brown rot and cherry leaf spot control post-harvest. In some areas, dark sweet cherry and tart cherry harvest might overlap and as harvest ramps up, protecting fruit and leaf tissue may be challenging.

Spotted wing Drosophila (SWD) are active at the research station and in the region. We found a single female in a Montmorency tart cherry block at the station this week. So far this season, we have detected SWD in Grand Traverse, Leelanau and Antrim counties in a vineyard, tart cherry orchard and in a strawberry patch, respectively. At this time, cherries are susceptible to SWD egglaying and growers should be protecting fruit from SWD, especially where this pest has been detected (Yuba area in Grand Traverse County, Ellsworth and southern Leelanau County, near the NWMRHC, and East Leland, Leelanau County).

The number of SWD that we have found in traps recently has been low, which could be a result of mortality due to cold temperatures over the winter and current cool conditions. However, we cannot be certain that the cold temperatures had a drastic impact on SWD populations, and SWD can develop rapidly as soon as temperatures warm. Therefore, protecting fruit from SWD egglaying is critical for keeping SWD populations low as well as preventing infested fruit at harvest. At this time, small fruits such as raspberries and blackberries that begin ripening will be susceptible to SWD.

It has been several weeks since we first observed cherry fruit flies on a leaf at the research station, and we finally caught the first cherry fruit fly on a trap at the station this week. Last week, cherry fruit flies were detected in Leelanau County and on Old Mission, and were found on a trap on Old Mission again this week. Growers need to be diligent about controlling both SWD and cherry fruit flies through harvest to prevent infested fruit at harvest. Please refer to the “2014 Michigan Fruit Management Guide” for more information on registered insecticides that provide SWD and cherry fruit fly control. We would like to remind growers to check pre-harvest intervals (PHI) and processor restrictions to avoid having issues with detectable residues that exceed maximum residue limits.

Obliquebanded leafroller activity is ongoing and trap numbers remain low at seven moths per trap. Growers should consider a pre-harvest application targeting larvae in orchards where high (20-plus moths per trap) obliquebanded leafroller numbers have been detected to prevent shaking larvae in trees into tanks at harvest.

Disease development and insect activity has been quiet in apples at the research station and we have not received reports of any major pest issues in the region. In our traps we found a total of one codling moth and three obliquebanded leafroller moths. The second generation of spotted tentiform leafminer is underway with 40 moths per trap at the station this week. Green apple aphids and leafhoppers have been active and some growers have been incorporating materials for aphids in sprays over the last few weeks. Most apple orchards are scab-free; in orchards where primary infection occurred, growers may need to start their secondary scab program soon.

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

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