Northwest Michigan 2009 summary

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.


Like all other regions in the state, northwest growers endured an unseasonably cool summer. The overall degree day totals as of September 21 are as follows: 3,143 base 42 and 1,947 base 50. Both of these accumulations are behind our 19-year averages where we accumulated 3,471 base 42 and 2,266 base 50. In essence, we are 328 GDD behind for our accumulations base 42 and 320 GDD behind for our accumulations base 50. This summer may have seemed even cooler if we compare this year’s degree day averages to the warm years of 2005, 2006, or 2007 where we were between 500 and 700 GDD (base 42 and 50) warmer during those seasons.

The overall rainfall total was 17.3 inches. The spring was fairly wet, and we hit a short dry spell in the second week of June for 20 days. We had ample rainfall in July and August, but September has been dry as the first rain fell in the region on September 21.

Tree fruit

Despite the cool temperatures, all crops faired pretty well in the north, although a little on the late side. The sweet cherry crop was manageable this season; however, dark sweets suffered from July rains that caused cracking in many area orchards. Brine cherries also set well but unfortunately, the market for these fruits was down considerably. Many brine cherry orchards are anticipated to come out of the ground this fall. The tart cherry crop was the biggest since 2001, and the USDA underestimated the size of the crop. Northwest Michigan picked out at 184 million pounds, 34 million pounds over the USDA estimate. The large crop was similar in other tart cherry growing states, and the total production in the United States this season was 353.6 million pounds, which was 70 million pounds above the USDA average. Tart cherry prices are expected to be considerably lower than 2008. Peaches sized beautifully this year with all the rain, and growers that waited for the late season sun had nice color. Some growers had difficulty moving peaches this season due to a large crop. Apple harvest has really just begun in the last week. Gingergold harvest is underway and MacIntosh are just starting to come off the trees. Apples are large and have excellent color this season. However, growers are concerned about selling the fruit, particularly apples grown for the processing market.

Tree fruit pest summary

Fire blight was less of a challenge for apples this season with the dry and cool spring conditions. The weather provided a single two-day period during bloom (May 8 through May 29) when conditions pushed the epiphytic infection potential over 100. Apple scab was present in substantial levels region-wide as nine days in June provided conducive conditions for scab development; primary scab extended into late June and early July in many are orchards. Orchards with scab are currently being screened for fungicide sensitivity levels. Plum curculio damage was unusually low in apple blocks this year with little or no damage to managed blocks. Codling moth trap catches were also low this season, particularly at the beginning of codling moth emergence which made setting a biofix difficult; however, we received reports of sustained codling moth catch from around the region during the first and second weeks in June. Overall codling moth numbers at the NWMHRS were low and pressure increased only marginally later in the season. Low trap catch made it difficult to differentiate between generations, and we recorded one distinct peak in late June and continued to catch moths through last week (see trap catch summary table). Spotted tentiform leafminer emerged in late April early May, and we continued to catch them through last week with peak flight on August 11 with an average of 1,150 leafminers per trap. Obliquebanded leafroller were first caught on June 22 in the station apple blocks with variable trap catches throughout the season and a high trap catch of 32 moths on June 29. Growers reported difficulty in controlling obliquebanded leafrollers in apple and a high amount of variability in larval maturity within orchards, particularly early in the season. Apple maggot was detectable in many orchards this season but overall, this pest presented no serious threat to the crop.

Cool and damp conditions this spring resulted in the expression of the cherry yellows virus in northwest Michigan. Significant defoliation, particularly in older cherry blocks (20-plus years old) was intense and raised concerns about crop ripening. With significant leaf loss from virus early and many orchards with a heavy cropload, growers are concerned about winter hardiness. Cherry leaf spot infections were frequent this year with the NWMHRS weather station predicting cherry leaf spot infection periods for 37 days from June to August and untreated tart trees becoming completely defoliated by mid-August at the NWMHRS. Early season cherry leaf spot control was good, but infection levels increased quickly late in the season due to 160 hours of wetting during the last two weeks of August. However, most growers were successful at keeping leaves on trees into the early part of September.

Considering the increased amount of fruit cracking that occurred in dark sweet cherries this season, American brown rot was well managed in most blocks. Here at the NWMHRS, we recorded 50 percent infection in untreated Ulsters by late July. Low American brown rot incidence was a welcome change from last year when much of the region suffered from epidemic levels of this disease. Bacterial canker was present this season, although not particularly intense despite cool conditions in early spring.

American plum borer were first caught in mid-May, and continued to be caught well into September. Lesser peach tree borer has been emerging since early June with adult trap catches peaking in mid-late June and continuing through last week. Greater peach tree borer emergence began the first week of June, peaked in mid-late August and extended into September with a maximum trap catch of 29 on August 24. Plum curculio began emerging in May and fed for an extended period until conditions were right for egglaying. We observed ovipositioning scars into mid-July. Obliquebanded leafroller adult emergence began around June 22 with steady emergence all season-long, but two peak flights were recorded in late June and late July, perhaps indicative of first and second generations. We caught our first cherry fruit fly on July 7, and the population peaked during the last two weeks in August. Many area orchards recorded exceptionally high levels of cherry fruit fly, and growers are applying post-season insecticide applications to bring down the populations.

Small fruit

Grape growers are banking on this September sun and warmth to ripen the fruit. This season’s cool weather has impacted grape growers more than others, and many are hoping for this warm spell to continue in order to harvest grapes with adequate brix. Verasion is apparent in many vineyards, a good sign after many weeks of green fruit.

Surprisingly, downy mildew has been more prevalent than powdery mildew this year, but neither disease has caused significant issues in well-covered vineyards. Botrytis has been a sporadic issue particularly in vineyards affected by grape berry moth. Grape berry moth numbers were significant in some of our scouted vineyards, and overall potato leafhopper numbers were lower than anticipated with the many early season rains. Potato leafhoppers were managed in many region vineyards. Lecanium scale nymphs were spotted blowing into vineyards from surrounding windbreaks – likely a result of the extremely high populations in non-crop tree species. Rose chafer arrived in late June and some vineyards experienced intense pressure and warranted control. Japanese beetles arrived in low numbers in late July and all throughout August, but we heard no reports of control measures against the beetles. Phylloxera, snailcase bagworms, grape plume moth and fall webworm were also observed in low numbers this season.

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