Disease forecast for Thurs. May 19th 2011

MUMMY BERRY FORECAST
Northern Hancock and Washington counties

Mummy berry cups were found at Deblois, Montegail pond (north of Columbia Falls) and at Jonesport along the coast on Monday May 16^th and Tuesday May 17^th this week. Cups are NO longer present in Deblois and Montegail pond. Active cups were still producing spores in Jonesport on Thursday May 19th. Later fields are likely to still have active cups for the next few days.

This means most fields in this area were likely to have had infection periods on Monday May 16^th (reported in the last forecast) and Tuesday May 17^th but only later fields would continue to have a chance of mummy berry infection after Wednesday May 18^th.

There was an infection period throughout this area from Tuesday May 17^th 8pm through Wednesday May 18^th 9 to 10am. If you applied fungicide on or after Wed. May 11^th your plants would have been protected through this infection period. If they were not protected you would have until Friday evening to apply fungicide to kill off any infection, but considering no future infections will occur this is probably not necessary.

There was an infection period in many later fields overnight from Wed. May 18^th at 8pm or later through to Thursday May 19^th at 11am to noon. If you applied fungicide on or after Thursday. May 12^th your plants would have been protected through this infection period.

If your plants were not protected and you have a later field, then you have until Friday May 17^th evening to apply fungicide and kill off any infection that has occurred in this latest infection period starting on Tuesday May 17^th. This application would also protect your plants which are likely to be exposed to more infection periods starting tonight and continuing possibly into the middle of next week.

MUMMYBERRY SYMPTOMS

You will start to see symptoms of mummy berry blighted leaves and flowers at this time. I would like to remind you that these were caused by infections that occurred eight to nine days ago and there is no point to applying fungicides after the mummy berry cups are done since the spores produced on the dead leaves and flowers can NOT infect and kill leaf and flower buds. The spores on the infected flower and leaf buds will be carried to some of the healthy flowers and produce mummified fruit at harvest. Applications of fungicide have not been proven to be effective in lowbush blueberries to control this second type of infection of healthy flowers.

BOTRYTIS BLOSSOM BLIGHT

If your field usually gets Botrytis blossom blight, now is the time to start looking for early symptoms. Symptoms of dead flowers or leaves with thin black hairs sticking out of them may be found on flowers of early blooming blueberry plants and the dead leaves of red sorrel, also called Sheep’s sorrel (Scientific name: Rumex acetosella). The small dark hairs (use a magnifying glass or reading glasses to see them) are always found if you have Botrytis blossom blight. IF you have dead blossoms and they do NOT have black hairs then your flowers were likely killed by mummy berry blight. I have not recorded any frost in the past weeks, so frost is unlikely to be a cause of dead flowers