Northwest Michigan fruit regional report – August 25, 2015

It’s starting to feel like fall in northwest Michigan, but the cool, wet weather will help apples size and color up before harvest.

Weather report

Summer has turned to fall in the last few days in northwest Michigan. Daytime highs were in the 80s on Saturday, Aug. 22, and these summertime temperatures continue to fall; the high for today, Aug. 25, is expected to only be in the low 60s. Cool temperatures moving over the warm waters of Lake Michigan have brought some rainfall to the region, which is much needed. We received greater than 0.31 inches on Sunday, Aug. 23, and just under 0.1 inches on Monday, Aug. 24. We also are receiving some rain today.

Crop report

Our recent rainy conditions may lead to outbreaks of botrytis rot on storm-injured grape clusters. Powdery mildew is showing up on leaves and fruit clusters in many vineyards.

Whether it was from the cold injuries of winter and spring or the storm damage of August, there are a lot of vineyards in northwest Michigan that have a much smaller canopy than usual for this time of year. These vines are going to need everything they can get from the leaves that are there to mature canes and buds for overwinter survival. It is very important to protect what’s left of the foliage from powdery mildew this fall. In sites where the crop is so short that a harvest is not anticipated, sulfur can be used as a cheap powdery mildew material right through the end of the season.

Peach harvest is underway in the north. The peach crop is on the light side with the two recent hard winters. We are detecting some split pit in some varieties. Apples are sizing, and size will continue to improve with the rain. We are starting to see color develop on apples, and early varieties are expected to ripen within the week to two weeks. Growers that suffered hail damage to their fruit have been removing those fruit from the trees in an effort to improve tree health as we head into winter.

Pest report

Spotted wing Drosophila (SWD) eggs, larvae, pupae and adults can be easily spotted in fruit and wild or unmanaged hosts at this time. Interestingly, we have observed SWD flies lingering around garden tomatoes that cracked following recent rain. Identifying female flies is difficult without a trained eye, but males have a black spot on each of their wings that can be used to distinguish SWD from other drosophila species. Although SWD generations are overlapping at this time (i.e., all life stages can be found simultaneously), more mature or later instar larvae are relatively easy to see with the naked eye. Hence, salt tests should be effective for determining if berries, other fruit or non-crop hosts are indeed infested.

We suspect that as long fruit/hosts are available for SWD infestation, this pest will continue to be present until we receive a hard frost this fall. Cherry growers who are waiting to make fall foliar fertilizer applications may want to consider removing wild hosts, in particular mulberry, honeysuckle and unmanaged or wild caneberries from areas adjacent to cherry orchards in the meantime; the Northwest Michigan Horticulture Research Center (NWMHRC) found that these wilds hosts have harbored SWD larvae this season.

Insect activity in apples remains relatively quiet in recent cooler temperatures with a few apple maggots and codling moths still flying at the research station. Wet conditions could be a concern for growers who had difficulty keeping apple scab in check during primary scab in the spring. The second flight of San Jose scale males is underway and this flight was at its peak in the last week in both apples and sweet cherries. Scale crawlers typically appear about two weeks following male flight, and we expect we will begin seeing crawlers within the coming week. This generation of crawlers will find new sites on the tree or fruit where they will settle, insert their mouthparts, begin feeding and producing a white, waxy cap that will keep them protected through winter.

Brown marmorated stink bug (BMSB), an invasive insect pest originally from Asia, was detected in the northwest in a lure-baited trap located in a residential neighborhood of Grand Traverse County on Aug. 19, 2015. This BMSB was a juvenile fifth instar nymph; there are five instars or juvenile stages before BMSB becomes an adult stink bug. BMSB were also found at this location inside of the home in the 2014-15 winter and early spring. Thus far, we have not found BMSB in commercial orchards in northwest Michigan.

Michigan State University Extension recommends orchard growers and consultants monitor for BMSB as well as look for suspected BMSB feeding damage on fruit at this time. BMSB feeding on apples during this time in the season results in pithy, sunken in areas on the fruit where BMSB inserted its mouthparts and sucked juices from the fruit. Placing traps along orchard edges and using beat nets or sweep netting are strategies to sample for BMSB. Insects will fall from limbs that are jarred over a light colored canvas where they can be counted and identified. Using a sweep net to sweep vegetation along wood edges and adjacent to orchards will intercept any insects in the surrounding area; sweep netting will help to capture and detect BMSB before they enter the orchard as this pest typically moves into orchards from the surrounding landscape.

We encourage all growers and consultants to bring any suspected BMSB specimens or BMSB damaged fruit to the research station for further examination and ID. The Northwest Michigan Horticultural Research Center is located at 6686 S. Center Hwy, Traverse City, MI 49684.

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