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Funny what a difference only a few days can make – even with cooler temperatures. Since Wednesday’s first pest update of the year, more areas are reporting signs of green tissue. Some even moving quickly to what looks like 1/4″ green.
In addition to my comments from Wednesday on the importance of applying:
- Fixed copper between dormant to 1/4″ green (possibly 1/2″ green, depending on product) for fire blight and early season scab activity.
- Urea and flail mowing overwintering leaves for scab inoculum reduction.
- Horticultural oil between dormant to tight cluster for scale and mites. Reminder – the earlier, the better for scale control!
… are you prepared to keep green tissue protected from scab?
- Leaves are susceptible to infection as soon as green tissue is present, especially if you had scab in your orchard last year.
- Green tip to tight cluster is a period of extensive new growth. Keep covered with a good protectant fungicide program and re-apply every 5-7 days during periods conducive to disease development or following heavy (greater than 1”) rain.
- Protectant fungicides such as captan, mancozeb or metiram do not provide effective post-infection or anti-sporulant activity.
- That means if sprays are applied in less than ideal conditions, ie., windy, alternate rows, or washed off in rain, the risk of scab infection is increased.
- New use patterns for Supra Captan /Maestro 80 WSP have restrictions on re-entry, preharvest intervals and allowable applications per season depending on canopy width. Refer to the label for more information.
- Ascospores mature slowly early season, peaking over bloom period so plan to save your systemic scab products for when infection risk is greatest.
- For example, more than 20 hours of leaf wetness are required for primary ascospore infection at an average temperature of 5C. This goes down to only 6 hours during average temperatures of 15-25C.
- During cool, wet springs, protectant fungicides may not be enough. Consider tank-mixing with post-infection products such as Syllit, Scala, Inspire Super, Luna Tranquility or Buran.
If powdery mildew has been a problem, include 3-5 kg/ha sulphur (Microthiol Disperss, Microscopic Sulphur, Kumulus, Cosavet DF Edge) with your protectant sprays until tight cluster when more effective mildew products will be used.
Keep an eye on those trees and be prepared to cover that green tissue as it shows up. In the coming week, it looks like we may be seeing some rain in the forecast and it’s possible with the right temperatures, it could bring a scab infection.