MSU Extension

Crop and weather report

In addition to the hot and dry weather across northwest Michigan, the humidity has also been on the higher side. Daytime temperatures have consistently been in the mid- to high 80s and into the low 90s. Nighttime temperatures have also been higher than we typically see in northwest Michigan: high 60s into the low 70s degree Fahrenheit. We have accumulated 2, 100 growing degree-days (GDD) base 42 and 1,348 GDD base 50. These accumulations are slightly higher than our 20-plus-year average.

We received rainfall across the region last Thursday, July 21, and our Northwest Michigan Horticulture Research Center Enviro-weather station reported 0.41 inch. We also had a hint of rainfall here at the station July 24: 0.02 inch. The region is quite dry, and there is little rainfall in the near-term forecast.

Tart cherry harvest is in full swing, yet some growers are still harvesting sweet cherries. The season has been incredibly compressed with the warm conditions. There is a lot of fruit out in the orchard, and harvest has been quite slow going. With the large crop, processing facilities have been pressed to take on all the large amount of fruit, so they are moving at a slower pace as well. Removing this season’s entire crop in a timely manner will be a challenge for the region. The heat is also hastening ripening, and these high temperatures are causing hail-damaged fruit to show more bruising. Recent high winds also likely impacted overall fruit quality.

Pest report

Last week, we detected a few spotted wing Drosophila (SWD) larvae in large intensive samples for research projects in sweet and tart cherries. We have also had reports of SWD larval infestations of sweet cherries in blocks that were harvested two weeks ago. Larvae have been detected in young tart cherry blocks that were not intended for harvest and were managed minimially for SWD. Finally, we have been finding SWD larvae in several alternate hosts including honeysuckle and brambles in the last few weeks.

Michigan State University Extension encourages growers to continue SWD management with tight intervals of effective materials and reapply materials as necessary. This is not the time to stretch intervals between applications or from the last application until fruit will be harvested. Growers will need to be diligent with spray programs to minimize the potential for larvae in fruit. Growers should be aware that SWD egglaying will continue until there are no suitable host fruit available.

Unlike some of our more familiar fruit pests, like cherry fruit flies, SWD has multiple generations per season on many different hosts throughout the landscape, and all lifestages (e.g., eggs, larvae, adults) of this pest can be present at the same time within an orchard. SWD has been particularly challenging for the industry this season as growers and processors are trying to balance harvest dates, quotas, spray coverage and managing unharvested fruit. The research center found that crushing or destroying cherry fruit on the ground results in fewer larvae compared with fruit that are left intact on the ground (see “How to manage unharvested or diverted cherries”). Growers will need to decide whether destroying unharvested, intact fruit is necessary for minimizing SWD populations in their orchard or adjacent orchards.

*May and June catches have been removed from table

Total catches per region:

• Centerville Township - 287
• South of Suttons Bay - 88
• Old Mission - 178
• M-72 W corridor - 31
• Elk Lake Rd. – 138
• N. of Suttons Bay – 11
• Eastport - 1
• Northport-Omena – 549
• Benzie – 824
• Yuba – 8
• Bingham – 3
• East Leland – 11
• East of Suttons Bay – 1
• Manistee – 191
• South of Elk Rapids – 21
• Northwest Michigan Horticulture Research Center – 48
• Bingham – 3
• Abandoned block in Centerville – 293
• Stoney Point – 49
• Williamsburg – 5
• Leland – 2
• North of Elk Rapids – 1
• South part of Grand Traverse County - 15

Cherry fruit fly activity is ongoing albeit at low numbers in the region. We have had reports that numbers are the lowest they have been in recent years. This pest was not detected at the research center this week.

Very small obliquebanded leafroller larvae were found in low densities in commercial sweet and tart cherry orchards last week. We observed these larvae under a microscope while sampling for SWD larvae in fruit. Adult obliquebanded leafroller numbers remain low in cherries with an average of seven moths per trap, but higher than they have been in the last three to four weeks. Obliquebanded leafroller counts in the research center’s apples continue to be low this week with a total of one moth per two traps.

American plum borer moths are approaching or at peak flight of the second generation with an average of 11 moths per trap. Lesser peachtree borer and greater peachtree borer numbers were slightly higher this week with 15 and eight moths per trap, respectively.

The first apple maggot adults took flight within the last week; we found an average of four per trap at the research center. The research center is currently using yellow baited sticky boards for pre-oviposition monitoring of apple maggots. However, previous research has shown that a red sticky sphere baited with fruit essence was more effective than the yellow baited sticky board for apple maggot monitoring, particularly as fruit turn color and apple maggots begin laying eggs.

Codling moth second generation adult flight is underway and trap numbers were higher this week compared with previous weeks. We found an average of 2.5 moths per trap, a total of five moths in two traps at the research center. Some growers set second generation biofix over the weekend.

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