Northern Michigan FRUITNET'99
JUNE 22, 1999
Evaporation this past week totaled 1.39". For irrigation scheduling purposes, this implies the need for approximately 1.04" of moisture. Precipitation this past week at the NWMHS totaled 0.03".
GDD 50: 657; GDD 42: 1139
Codling moth trap catches were down this past week, indicating that the adult flight is between generations. Apple growers may need to apply a second insecticide spray for the first generation, depending on their trap numbers. Potato leafhoppers are common in grapes, apples and plums. European red mites and two spotted spider mites can be found on the interior of apple and tart cherry trees, but numbers remain low so far. Apple maggots have not yet been trapped but are expected some time in the first week of July.
The first cherry fruit fly adult was caught in an abandoned orchard in Benzie County on Wednesday, June 16th, and at the NWMHRS on the 17th. Growers should put traps out immediately if they are planning to do their own trapping. Growers who will not be scouting for cherry fruit fly need to have their first spray on 7-10 days after the first catch, which would be by June 23rd. A cherry fruit fly adult was caught on Monday, 6/21, in a commercial orchard in Leelanau County.
Cherry leaf spot has had no infection periods this past week but continues to be a problem in some tart cherry blocks. An occasional sweet cherry block also has leaf spot. Growers should use a full cover of an appropriate sterol inhibitor and Captan to slow its spread, if the disease already has a start in the orchard. Brown rot pressure will be high this week as temperatures rise and humidity increases. Appropriate fungicides should be used on a protectant basis, particularly on sweet cherries. Powdery mildew symptoms are common on tart cherries.
With more hot weather predicted, tarnished plant bug will remain a concern on peaches.
Plums are very susceptible to potato leaf hopper injury; all plums should be scouted for it. Guthion or Imidan can easily control this pest.
Grapes (By Duke Elsner): Some
vineyards now have foliar symptoms of powdery mildew, downy
mildew and black rot. This is an important time to protect
clusters from infection by these diseases. Potato leafhopper adults
and nymphs are widespread, starting to cause cupping and yellowing of
leaves and shortened internodes. Forester moth larvae are now nearing
maturity, over one inch in length. Larvae of the larger sphinx moths
should be active now -- check young vines for their defoliation. Phylloxera
and other leaf galling insects are active on wild vines.
Ethephon and Heat
It is always tough to decide what to do about ethephon application in hot weather. My suggestion is this:
1) If temperatures are expected to be in the lower to mid 80's for the next two to three days, then decrease the ethephon rate by about 25%. This should achieve comparable response to normal rates when highs are expected in the 70's.
2) If temperatures are expected to be in the upper 80's and/or 90's, then delay application until temperatures decrease.
Wanted: Volunteers for Orchard Study
This summer the NWMHRS will be studying pH and nutrient levels in orchard soils to ascertain the potential value of precision applications of fertilizers. The study will be run in cherry and apple orchards of at least 5 acres in size and 15-30 years of age in the 5 county area of NW Michigan. We want one or two blocks per grower. Blocks will be mapped and sampled in sub-units based on soils and tree growth to assess nutrient variability. Participants will be provided with the results. Growers interested in volunteering may do so by calling 231/946-1510.
Phytotoxicity on Tarts
I have observed a problem with phytotoxicity on tarts that early assessment indicates may have been caused by a combination of Syllit and a calcium chloride product applied during a period of high temperatures. The temperature at the actual time of application was only approximately 70ºF, but the high later in the day reached the mid to upper 80's. The injury is a brown speckling on fruit, with more of a bronzing on the underside of the leaves. Because other products were also in the spray mix, I can not be absolutely sure of the cause, but strongly suggest that this combination be avoided until more is understood about the problem.
NW Michigan Horticultural Research
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