Northwest Michigan fruit regional report – July 19, 2016

Growers have been challenged with an overlap of sweet and tart cherry harvest this season.

Weather and crop report

The summer weather continues throughout the region. Mid-week last week was hot, and daytime temperatures soared into the 90s. Thankfully, those temperatures only lasted two days, and the remainder of the week and into the weekend was seasonable; temperature averages were in mid-60s and low 70s. Temperatures are predicted to rise again this week, and we will likely see daytime highs in the 90s on Thursday and Friday, July 21-22. Hopefully, the temperatures will cool again as we are in the midst of cherry harvest.

Most of the region received some rainfall Sunday, July 17. The region is dry and we could use the rain, but rain is not welcome until we have the sweet cherries off the trees, as there is concern with cracking. The Northwest Michigan Horticulture Research Center received 0.34 inch of rain Sunday.

We are in the throes of cherry harvest across the region. Sweet and tart cherry harvest is overlapping, and many growers are bouncing between sweet and tart cherry harvest. Growers have commented that sweet cherries are not coming off the trees easily. In these cases, growers have moved onto tart cherry harvest and will come back to sweet cherries at a later timing.

Despite the rain that moved through the region over the weekend, we have seen little cracking in sweet cherries. Rain will help size the tart cherry crop as tart cherries are quite small with a big crop and little rainfall this season. Fruit quality in most blocks is good, even in areas that received hail on July 8. However, we have seen some internal bruising in sweet cherries as a result of the hail and wind whip marks on tart cherries. Additionally, some tart cherry blocks will not be harvested due to the hail damage.

Wine grape vineyards in the Grand Traverse County region continue looking very good, except for sites that were heavily damaged by the hail event on July 8. Based on reports and observations, the hardest hit vineyards are in Leland Township of Leelanau County. Hybrid varieties received the greatest injury to fruit clusters due to the high cordon training systems commonly used for these varieties. Fruit clusters of vinifera varieties were more sheltered from direct hits by hail because the fruit is positioned lower in the trellis and under the canopy of shoots.

Japanese beetle adults have appeared during the last week. We have also seen a few potato leafhoppers in some vineyards.

Saskatoon harvest is essentially done in the Grand Traverse area.

Pest report

Spotted wing drosophila (SWD) numbers are on the rise throughout the region. Last week, some traps were catching flies in the triple digits in Michigan’s Northport-Omena area and Centerville Township. Most growers are in the midst of cherry harvest and managing harvest while trying to also maintain SWD coverage in blocks that have yet to be harvested will be challenging. In particular, growers should determine a spray strategy that begins seven to 10 days before harvest in order to keep fruit protected and also meet pre-harvest intervals. This strategy can be complex, particularly when deciding whether or not a three-day material is needed and which three-day material should be used. Exirel, Danitol and Pounce are materials with a three-day pre-harvest interval with differing levels of SWD efficacy. Some growers have used Exirel at a 13.5 fluid ounce per acre rate for SWD this season rather than at the 16 fluid ounce per acre rate that is suggested in the “2016 Michigan Fruit Management Guide” by Michigan State University Extension.

We have found excellent efficacy for SWD using Exirel at 16 fluid ounces per acre in trials at the Northwest Michigan Horticultural Research Center and Trevor Nichols Research Center. However, we have also found that 13.5 fluid ounces is adequate if growers are sure to harvest after the three-day pre-harvest interval is met. We caution growers that if they have to stretch this interval due to unforeseen circumstances, we recommend the 16 fluid ounce rate, as Exeril at the lower rate broke down much faster than the higher rates.

Danitol has also shown excellent results for SWD in efficacy trials. Additionally, Northwest Michigan Horticultural Research Center research has shown that the miticide component of Danitol is effective for minimizing twospotted spider mite outbreaks after harvest. Pounce and other pyrethroid products containing the active ingredient permethrin have provided variable results for SWD in research trials. Permethrin insecticides likely breakdown quicker in the orchard and therefore lose effectiveness for SWD faster than some of the other pyrethoid options. Furthermore, permethrin could contribute to pest mite flaring. Some growers have managed for SWD post-harvest or are planning to do so to maintain low populations and low pest pressure for neighboring blocks that have yet to be harvested.

Cherry fruit flies are active at the research center at this time; we found a total of two cherry fruit flies on traps this week. Cherry fruit fly activity began a few weeks ago in the region, and most growers have used materials for SWD that would have also been effective for cherry fruit flies.

Obliquebanded leafroller trap numbers continue to be low in the research center’s cherries with an average of three moths per trap. We have not observed larvae at the research center, but there has been at least one report of very small obliquebanded leafroller larvae in a cherry block. Most of the obliquebanded leafroller larvae that have been reported have been in apple orchards; we found a total of two obliquebanded leafroller moths in a trap in an apple block at the research center.

Borer activity is ongoing. We found an average of eight American plum borer moths per trap; this is the second American plum borer flight of the season. Lesser peachtree borer numbers are on the downswing with 12 moths per trap. There was an average of three greater peachtree borers per trap.

For growers that have yet to harvest, American brown rot and cherry leaf spot are the target diseases at this time, but most growers are focused on harvest. Fortunately, we have received very few reports of American brown rot development in damaged cherries and also few reports of cracking following recent rain.

If orchards that were impacted by severe storms a week and a half ago experienced trauma blight, symptoms should be apparent at this time; trauma blight symptoms could have appeared as early as late last week. 

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