Monilinia Blight update for April 19th, 2016

Tuesday, April 19, 2016

It is still relatively early in the growing season but due to the snow leaving early, soil moisture staying quite low and excellent drying conditions for late April, blueberry plants are starting to move along.

I was in several fields in central NS today and saw a few fruit buds at the F2 stage but many fruit buds are beginning to swell.

Just to remind everyone Fruit and Vegetative buds become susceptible to Monilinia infection when they reach the F2 or V2 stage.

Generally speaking, we aim our first treatment around the 40-50% F2 stage. However, in order for an infection to occur there needs to be an infection period, meaning the temperature and leaf wetness need to be of a significant duration for an infection to occur.  The warmer it is, the shorter the wet period has to be in order to cause an infection.

Look at this factsheet for wetness and temperature duration. Monilinia Factsheet  Generally speaking, a wet period lasting longer than 6 hours would mean there is infection risk, unless it is just above freezing.

If you are looking for controls for Monilinia look at the 2016 Wild Blueberry Pest Management Guide for  registered controls.  Propiconazole based products are still highly recommended for the first application and do allow for some back-action if applied a day or two after an infection period.

Remember, if you are at 40% F2 but the forecast does not call for rain, it is best to wait to put the first application on, if at all possible.  Only buds that are in the F2 and V2 stage are protected from infection. Buds that open up after an application are not protected by that application.

Reports for various regions:

Musquodoboit (several fields averaged) - 3 % F2 - no pins, or cups seen

South Western Nova Scotia - will be approaching 40% F2 this week.

I will be adding more sites on Friday, April 22nd.