Nectria twig blight and summer insect pests.

by Terence Bradshaw

We’re in a bit of a quiet window for pest management in Vermont orchards. Apple scab primary ascospore release is done, and if you have no scab in the orchard, you’re done for the year managing that disease. For anyone with a scab issue, maintaining fungicide coverage every 10-14 days or after 2″ of rain will be important until terminal bud set when leaves and fruit become less susceptible to secondary infections. I’ve seen little fire blight, despite the infection periods predicted in the pest models. I’ve said this before- cut out any fire blight strikes as soon as you see them, and feel free to contact me to evaluate any questionable strikes. I have seen several instances of Nectria twig blight this season that look much like fire blight, but are caused by a relatively weak fungal pathogen. Nectria often infects winter-damaged wood, which I am seeing a lot of this year. The most notable characteristic that identifies Nectria compared to fire blight is that Nectria-infected shoots will have a very distinct delineation between dead (brown) and live (green) tissue at the base of the dead shoot. Fire blight shoot blight will typically show a gradation between dead and living tissue as well as water soaked cambial tissue in the area of visible infection. The only management technique for Nectria is to prune it out, and maintain the orchard with good pruning and nutrition to ensure good cold hardiness. Summer diseases such as sooty blotch/flyspeck and fruit rots are the main concern now. Dr. Dave Rosenberger’s comments from June 23, 1014 issue of Scaffolds provide good insight into managing these diseases. Take home message (read the article for specifics): Captan alone or with another material will likely be in your spray program every 2-3 weeks for the next month or two, especially if this wet weather continues.

Apple maggot traps should be hung any time now to monitor for this pest. I observed my first trapped apple maggot fly at the Hort Farm yesterday in an especially problematic block, so they will be flying in commercial orchards any day now. Other insect pests of concern potentially include obliquebanded leafroller and codling moth. skingsle ASAP.