It’s time to consider sanitation practices that can help reduce over wintering scab inoculum. These practices should be considered an essential part of  apple IPM  programs.

In 2014 scab was once again a problem in most orchards we scouted. Even if you didn’t see scab on the fruit at harvest there still could be infected leaves in the orchard at low levels. In addition, in the northeast and other regions scab is becoming increasingly resistant to chemistries we rely upon for primary season control. Therefore, all growers should consider integrating sanitation practices into their scab control program. The recommended sanitation program involves either: fall or spring applications of Urea; flail mowing fallen leaves; or preferably both.

For a refresher we’ve linked a short video explaining this approach.

Over the past 7-10 days it has become clear that a bacterial spot epidemic is underway. It is eerily reminiscent of the epidemic of 1997, although so far it does not appear as widespread or affecting all cultivars as that year. Many blocks are dropping leaves this week, and fruit lesions are beginning to appear. Remember that it takes about a week for leaf infections to appear, and about 2 weeks for those infected leaves to start dropping. It takes about 3 weeks for those same infections to show up on the fruit. Looking back at weather records over at CoCoRaHs (choose your dates and local observations) it appears that the severe winds of May 23, and the rains over the weeks that followed set up a conducive environment for the bacteria in southern counties.  We are seeing leaf drop in many locations regardless of treatment. The coming week will tell the story of how much fruit infection there is. [Read more…]

This past season we saw elevated levels of apple scab in southern counties. Our IPM scouts found low levels of scab present in orchards where scab had not been detected for many years, even though these orchards had been carefully sprayed using effective materials. Most likely what we are witnessing is the result of an increasing pattern of wet seasons with periods of extreme rainfall and not resistance to DMI fungicides, although that is an area of great concern and cannot be ruled out. Regardless of the cause, high inoculum in the orchard will eventually lead to control failures with materials such as the DMI’s and other chemistries prone to resistance.

At any rate growers that had scab this year should integrate sanitation practices into their scab control program. The recommended sanitation program involves either: fall or spring applications of Urea; flail mowing fallen leaves: or preferably both.

Dr. Dan Cooley and Jon Clements at UMass have uploaded a short video explaining this approach.