Northwest Michigan fruit update – August 7
Cherry harvest is winding down, and quality remains quite high despite the hot conditions. Apples are coloring and sizing.
Daytime temperatures were hot over the weekend, especially on Saturday, 4 August when some Enviroweather stations in the north reporting 90+ degree F. Things cooled off at the start of the week, but the forecast is predicting daytime highs in the mid-80s for the remainder of the week. The region continues to be dry, however, there were isolated rain showers early this morning; the NWMHRC recorded 0.39” of rain. Prior to this rain, the last rain events reported at the NWMHRC were 0.05” on 1 and 2 August, and on 26 and 27 July, we received just under ¼” of rain. Lastly, we received reports that hail hit the southern part of Old Mission Peninsula on 1 August and caused some damage to winegrapes and the vines.
Sweet cherry harvest is finished in the north. Size of the fruit was an issue this season, and we are collecting some information to determine if the weather played a significant role in sizing the fruit. Other than size, the quality of the sweet cherry crop was good. With the dry conditions, we had little disease pressure and American brown rot infections were minimal. Growers are still harvesting tart cherries in the region. The quality of this crop also continues to be quite good despite the hot conditions. The latest weekly raw product report that ended on 28 July stated that northwest Michigan processed 64.7 million pounds; the 2018 estimate was 150 million pounds. Some growers are indicating that they may pick out shorter than this estimate.
The apple crop is sizing but likely slower than anticipated with the dry conditions. Apples are also starting to color. Some growers are hand thinning at this time. Fruit quality is looking excellent at this time
Brown marmorated stink bug adults were detected in traps at the NWMHRC yesterday (6 August), and we observed activity at our residential trapping location in Leelanau County over the weekend and early this week. While this pest had been detected in residential areas in our region in previous years, we found the first BMSB in a trap adjacent to a commercial cherry block in Grand Traverse County (near Yuba) on 1 August. The BMSB found at the station this week were in traps placed along a woodlot adjacent to a high-density apple block. Thus far, we have found a total of nine BMSB adults since we began trapping for this pest two weeks ago. We have continued to observe nymphs in areas near traps at the residential trapping site.
We found a total of two apple maggot flies at the research station this week, and we have received reports of additional detections in commercial blocks near the station. Thus far, AM seems to be in low abundance in some parts of the region while it is high in others; the AM populations are low in the Hart area. However, more southerly regions of the state continue to report high populations. We will continue to monitor AM for the potential of higher flushes of emergence over the coming week.
Second generation codling moth adult activity has picked up, and based on degree day accumulations egg hatch is underway from moths that emerged a few weeks ago. We found a total of 19 moths in traps at the station this week.
We are likely at peak San Jose scale male flight at this time with some traps catching more than 1,000 males in four days. Scale incidence has increased in recent years, particularly populations in sweet cherries. This season, some sweet cherry growers have considered a post harvest application to target the second emergence of crawlers. Crawler activity has not been detected at this time.
Hot and dry weather has favored spider mite and European red mite populations in tree fruits this season. Bronzing in apples and some firing symptoms in cherries have been observed at the station. Commercial blocks also have substantial mite populations. European red mite numbers should start to subside in the coming weeks and adult red mites will begin laying eggs that will overwinter.
Spotted wing Drosophila (SWD) trap numbers in our region have remained relatively consistent over the last two weeks. This insect has been somewhat unpredictable this year. We hypothesize that the overall hot and dry weather decreased activity and thus there are fewer SWD in traps.
There is very little cherry leaf spot incidence at the research station and in the region. Growers who have finished harvesting have started post-harvest applications. In contrast, this season was conducive for powdery mildew and this disease is evident in many cherry blocks across the region.