2015 Fruit Pest Update

April 20, 2015

At the station: APPLE are at silver tip to green tip, CHERRY are at side green to early green tip and GRAPE are starting to show some bud swell.

Check at bottom of page for detailed Apple, Cherry & Grape disease and insect updates.

A QUICK ASSESSMENT OF EARLY SEASON APPLE SCAB DEVELOPMENT According to the table below, in part copied from the Sturgeon Bay Enviroweather site page, we could be progressing toward the first apple scab infection of the season. The rain that started at 10 p.m. on Sunday night has so far resulted in a wetting period duration of 18 hrs (as of 4 pm Monday). This means that, as of the writing of this update, we are 67% of the way to having a scab infection period. We will need just another 8 hrs of leaf wetness, or a total of 26 hrs from the start of the wetting period, for this to be the case. The bottom line is that if you have apples with green tissue showing, infection could occur if a fungicide application has not been made prior to the start of the event.

Station Start of wetting period End of wetting period Duration (Hrs.) Avg temp (F) Rainfall (in.) Apple Scab (leaf) Wet hrs @ avg temp for 1st infection Progress toward infection
Sturgeon Bay 4/19 10-11PM Ongoing. Last hour with moisture: 4/20 3-4PM Wet: 18 Span: 18 41 0.36 None 26 67%

One factor to consider with this early disease event is the maturity of overwintering inoculum in the form of developing ascospores on last years leaves, now on the orchard floor. Mature ascospores, that are necessary to cause an infection, may not be developed enough to be released, as sufficient development temperature accumulation has not yet occurred. Model data on the Enviroweather site shows that spore maturity has not progressed to a point yet where spores are ready to be released in our area. Chances are they will not be until later in the week. To keep track of apple scab spore maturity close to your operation, click one of the links below and look under the heading ‘Weekly Apple Scab Spore Maturity and Discharge Report’ halfway down the page. There you can track both estimated spore maturity (M) and discharge (D).

Apple Scab Casco               Apple Scab Southern Door               Apple Scab Sturgeon Bay

Apple Scab Egg Harbor               Apple Scab W Jacksonport               Apple Scab Sister Bay

 

APPLE

Disease Pressure – Apple Scab is now an issue on susceptible varieties like McIntosh & Cortland. Keep these varieties covered with fungicide treatments through the end of primary scab season; typically mid to end of June in Northeast WI.

Insect Pressure – Green fruit worm have begun to fly, but do not yet pose a damage threat. Scout for presence of their larva as well as overwintering oblique banded leafroller larva starting at the half inch green stage of development through petal fall.

CHERRY

Disease Pressure – none at this time; check back of updates.

Insect Pressure – Green fruit worm have begun to fly, but do not yet pose a damage threat. Scout for presence of their larva as well as overwintering oblique banded leafroller larva starting at the half inch green stage of development through petal fall.

GRAPE

Disease Pressure – none at this time; check back of updates.

Insect Pressure – none at this time; check back of updates.

 

Links to individual Enviro-Weather stations:

Casco   Southern Door   Sturgeon Bay   Egg Harbor   W Jacksonport   Sister Bay