Highbush Blueberry E-Bulletin 2011-6

Wednesday, May 18, 2011

A. Mummy berry forecast for May 18, 2011

Prerequisites for Spray Decision:

1. Past history of Monilinia Blight on the farm.
2. Flower buds become susceptible to infection at the F2 stage (bud scales separating).
3. Once fields reach 40-50% F2 and beyond, a fungicide is required within 72 hrs of the start of an infection period. This application will provide 7-10 days protection.

Observations at Tim Strong’s farm as of May 18th, 2011:

All blueberry varieties are at or beyond the 40-50% F2 stage and mature apothecia cups are still present. There have been two long wet periods over the last week with conditions suitable for infection.


Thursday May 19th (tomorrow) will be four weeks since apothecia cups were first observed at Tim’s Farm on Brooklyn Street. Individual cups are reported to release spores for two weeks at an average temperature of 10 °C. Taking into consideration a staggered emergence of cups, time to mature, and the cool wet spring, the season for mummy berry infection should be starting to wind down. Having said this, there have been two additional long infection periods over the past week and apothecia cups can still be found in the field. Moreover, the forecast is calling for more showers over the coming week so growers can decide for themselves whether they need to make another fungicide application. If they choose to do so, I would expect that no additional applications (for mummy berry control) would be required in 2011.

Once again, I remind grower’s that these recommendations apply to Tim’s farm in King’s Co. only and it is a guide only for other farms.

Refer to “Management of Mummy Berry in Highbush Blueberry” factsheet for pictures of F2 stage and temperature and wetness requirements for an infection period.

Refer to AgraPoint’s “Hishbush Blueberry Insect and Disease Management Schedule” for a list of registered products for mummy berry (Monilinia) control in highbush blueberry.

B. Anthracnose fruit rot management:

If anthracnose has been a problem in the past, consider a program of targeted Bravo sprays at green tip stage (now past), pink bud, and petal fall followed by Maestro/Captan (pre-harvest interval of 2 days) just before harvest as fruit ripens. Bravo should not be applied beyond petal fall or it can burn developing fruit. The Bravo treatment timings are also effective for Phomopsis canker control.
There are a number of other effective fungicides for anthracnose and Phomposis control and these can be reviewed in AgraPoint’s Insect and Disease Management Schedule highlighted above.

C. Botrytis blossom blight and fruit rot management:

Where Botrytis blight and fruit rot have been a problem, consider an early bloom fungicide application and again 7-10 days later. Registered fungicides for Botrytis blossom blight and fruit rot include Maestro/Captan, Elevate, Lance, Ferbam, Switch, Pristine, and Serenade. Consult the AgraPoint Highbush Blueberry Insect and Disease Management Schedule for more details on the specific formulations and rates. Read labels carefully for application requirements and warnings.

D. Fertility rates and timing:

The traditional recommendation for fertilizer applications was for a split application between bud break and 6 weeks after. However, new research suggests that there must be leaf emergence and growth before you have any significant uptake of nitrogen by the blueberry plant. As such, the correct timing for the first N-P-K application is now considered to be at bloom or early petal fall. A second application should be made 4-6 weeks later.

Most mature plantings require 50 – 70 pounds of actual nitrogen per acre annually but rates vary according to soil type, organic matter content and management. Also, remember that nitrogen should be in an ammonium form – either ammonium sulfate or urea. I highly recommend that grower’s tissue test to verify if your tissue nutrient levels are in the optimum range and make adjustments accordingly. The procedure and timing for tissue testing can be found on the AgraPoint website.

E. Callisto – a new herbicide for highbush blueberry.

Callisto 480SC is a newly registered herbicide on highbush blueberries that growers should be aware of. It has both “pre-emergent” and “post-emergent” activity on weeds and controls a number of broadleaf weed species including redroot pigweed and common ragweed. Only one application of 0.30 L/ha is permitted per year but the window for application is relatively long, extending up to the 8 leaf stage of weeds and “pre-bloom” for the crop. Application should be a ground application directed down the base of the row.