This week, we've received a few more reports and samples of cranberry wilt. Cranberry wilt, often followed by tissue browning, is caused by water stress and since new growth is much more prone to desiccation, it is commonly observed during spring. We think water stress may be more pronounced this year because of recent weather conditions; high air and vine level temperatures, little or no rain, low dew points, and windy conditions. Even growers who were irrigating during this period have reported minor damage in dry spots with poor sprinkler coverage. It is possible that the record number of frost nights and saturated soils this spring may have impacted the root function. Perhaps for the same reason, we continue to see variability in growth stage within beds where no late water was held.
With bloom approaching up to 20% or more, it is time begin bloom and out of bloom counts for timing fertilizer and fruitworm applications. This also means that if you haven't started your fungicide applications against fruit rot, now is the time! Ideally, your first fungicide application should not be delayed past 50% in bloom.
Callisto has a 45-day PHI. Only two applications total are permitted and applications must be separated by at least 14 days. Spot-treating counts as an application, so if you chemigate twice you cannot also spot-treat. If you need or want to spray during bloom, you should not expect any issues with Callisto. It is recommended that Callisto be used with an adjuvant. Avoid applying on very hot days, and be cautious about the potential of adjuvants, especially crop oil, to injure cranberry flowers. Injury from crop oil is more likely on a hot humid day. If the spray is not pressing and you are worried about injury, wait until bloom is mostly passed.
Tomorrow afternoon, the Cranberry Station will host a gathering organized by CCCGA, from 3:00 to 5:00pm, to go over nutrient management and other topics of the day. Extension plant pathologist, Erika Saalau Rojas, will be available before and after the workshop to answer any questions or discuss your fungicide choices for fruit rot management in 2016.
Stay tuned for more updates by liking our page on Facebook @UMassCranberryStation and/or following @esaalau on Twitter.