Northwest Michigan fruit regional report – July 29, 2014
Tart cherry harvest is underway and growers are harvesting through the night
The weather conditions over the weekend were pleasant, but the region cooled off on Monday, July 28. Daytime highs were in the mid-60s. Cool temperatures were accompanied by rain. The Northwest Michigan Horticultural Research Center (NWMHRC) received just under 0.5 inches of rain on the weekend. Conditions were dry across the region and the rain was needed. However, some growers are still harvesting sweet cherries and rain around harvest is not always welcomed. Michigan State University Extension specialists received reports of hail in the region, but little hail damage to fruit. The forecast is predicting cool weather with a potential of rain for each day for the remainder of the week.
Sweet cherry and tart cherry harvest is overlapping this season, and both crops are coming off as quickly as possible. Sweet cherry quality still looks good despite the rain. We have observed cracking in some blocks, particularly on trees with a light crop. Tart cherry quality is also good. We had high winds last week, which resulted in some wind-whipped fruit. Despite the 35 mph winds, most fruit is still looking surprisingly good.
In the last week, tart cherry harvest ramped up, sweet cherry harvest is ongoing, and for the most part, conditions have been good for harvest. On Saturday, July 26, we received rain showers throughout much of the region that could have caused fruit cracking in some orchards; American brown rot can develop quickly on cracked fruit and could be a concern if cracking is present in orchards with brown rot. Saturday’s rain event also resulted in cherry leaf spot infection periods. The cherry leaf spot model on MSU Enviro-weather recorded potential moderate to high infection periods for East Leland, Eastport, Elk Rapids, Kewadin, Northport, and Old Mission, Michigan that began on July 26. A low cherry leaf spot infection period was recorded on July 27 in Bear Lake, Michigan. There is a chance for rain and thunderstorms every day this week; if possible, tissue should be protected from leaf spot infection and fruit should be protected from American brown rot. Powdery mildew took a foothold and is evident particularly on interior leaves of trees in some orchards.
A total of three spotted wing Drosophila (SWD) were trapped at the research station this week in Montmorency tart cherries. We have not checked the regional trap line at this time and will report SWD catches later this week. Cherry fruit fly catches remain low, a total of two cherry fruit flies at the station. In the last week, cherry fruit fly catches have been variable in the region with most reports of low cherry fruit flies (less than three per trap) and up to 18 cherry fruit flies on a trap. So far this season, both SWD and cherry fruit flies have been detected on Old Mission and in Antrim, Benzie, and Leelanau counties. Growers need to be diligent about controlling both SWD and cherry fruit flies through harvest to prevent infested fruit at harvest.
We have received a few isolated reports of plum curculio larvae in fruit. The larvae are large and are likely late instars. Mature plum curculio larvae will exit fruit to pupate and overwinter in the soil. Unfortunately, when larvae are in fruit, it is likely too late to treat for plum curculio. Obliquebanded leafroller catches at the station have been low this season and we have not reached the threshold of 20 moths per trap to set biofix. This week we found an average of one obliquebanded leafroller moth per trap and have not found a substantial population of summer generation larvae in cherry trees at the station. Although obliquebanded leafroller populations have been low in most scouted orchards, in orchards where high obliquebanded leafroller populations of 20-plus moths per trap have been found, growers should consider a pre-harvest application targeting obliquebanded leafroller larvae to prevent shaking larvae into tanks at harvest.
Cool and wet conditions that are predicted in the coming week should slow the development of two-spotted spider mite and European red mite populations. We will continue to monitor mite populations in the coming weeks. Peachtree borer and American plum borer activity is ongoing at the station with an average of 11 greater peachtree borers, 8.3 lesser peachtree borers, and 16 American plum borers per trap.
In apples, second generation spotted tentiform leafminer moths at the station are on the decline with an average of 63.5 moths per trap. We have not found signs of substantial populations of codling moth and obliquebanded leafroller or larvae damage/entries in fruit at this time. We found an average of one codling moth per trap and two obliquebanded leafroller moths per trap.
The first catch of apple maggot was last week and we found a total of one apple maggot fly this week. In some orchards, aphid and leafhopper feeding has distorted leaves on terminals. A few isolated incidences of low apple scab infection have been observed. The last apple scab infection periods recorded by the MSU Enviro-weather scab model occurred over the weekend on Saturday, July 26 in East Leland, Eastport, Elk Rapids, Kewadin, Old Mission, and Northport, Michigan.