May 24, 2017
Here at the Research Station apples are at early bloom. Cherries are at full bloom.
The cool and wet weather has resulted in very little degree-day accumulation over the past week; we continue to be behind average for this time of year.
|Degree day comparison 2013-2017|
|Date 5/23||2013||2014||2015||2016||2017||20 yr avg|
INSECT & DISEASE CONTROL
Disease Pressure – The latest apple scab infections began Tuesday (5/22) or Wednesday (5/23), depending on location, and are currently ongoing as of Wednesday afternoon. Scab spores are around 80% mature in overwintering inoculum on the orchard floor. Precipitation forecast now and through the weekend will again result in infection events and a significant release of mature spores.
Continue applications of captan or one of the EBDC fungicides (Dithane, Penncozeb, etc.) to protect leaves through the end of primary scab season. With mildew- susceptible varieties, the addition of Luna Tranqulity, Inspire Super, or Merivon during the tight cluster through petal-fall time period will keep this disease under control. Other effective powdery mildew fungicides include the SI fungicides Rally and Indar or the stroblurin materials Sovran and Flint.
Fire blight during bloom may not be much of an issue this season if temperatures remain on the cool side. Daytime highs in the 70’s or higher are needed for bacteria to develop. If we do experience these higher temperatures during bloom. then protectant applications of a bactericide like Agri-Mycin or other streptomycin products should be made every 4-5 days during that time.
Insect Pressure – Green fruit worm and oblique-banded leafroller larva have been seen at low to moderate levels feeding on blossom clusters in the orchards that we scout. European red mite pressure has been light so far in most scouted orchards. Growers should scout blossom cluster at this time to determine if petal fall miticide applications will be necessary.
Disease Pressure -The first cherry leaf spot infection periods of the season were recorded on 5/17 and 5/22 or 5/23 depending on location on the peninsula. Unfolding leaves will need to be protected with fungicide applications to avoid infection where there is advanced leaf development. Products containing chlorothalonil (Bravo, Echo, Equus, etc.) are the fungicides of choice through shuck split for cherry leafspot control. Remember that there is a minimum 10-day application interval on these products.
Insect Pressure – Scout for presence of Green fruit worm larva as well as overwintering oblique-banded leafroller larva through petal fall. Spotted Wing Drosophila (SWD) have yet to be caught in traps that are in place throughout the county. Last year first catch was recorded in the second week of June.
Links to individual Enviro-Weather stations: