Skip to main content

First Symptoms of Apple Bitter Rot Visible in The Shenandoah Valley (Martinsburg WV)

First signs of apple bitter rot disease on fruit of apple cultivar ‘Wolf River’ have been found in the Shenandoah Valley, more exactly in Martinsburg WV, Berkeley County (Fig.1). Rot started from the fruit side (Fig. 1 bottom) indicating that it probably started as an established quiescent Colletotrichum infection at bloom or petal fall, that then expressed recently. We found that bitter rots were almost always on fruit in dense clusters with many fruit together indicating on the conducive moisture conditions on these clusters and lack of fungicide coverage on fruit penetrating in between the fruit (Fig. 1 top). Bitter rot fungi can infect any fungicide-uncovered areas on fruit, especially when warm wetting events occur, and we had severla of these in the last 15 days. Extreme heat and the rain that "came" back this week has and will extremely favor this disease in the weeks preceding harvest. Start scouting for bitter rot symptoms to make sure you are free of this disease and to make sure how well was your fungicide coverage during the early summer cover sprays.


Figure 1. First signs of bitter rot on ‘Wolf River’ apple fruit near Martinsburg WV (Photo by Aćimović S. G. 2021).

We hope you will NOT see any bitter rot in your blocks and that your fungicide coverage was satisfactory. If by you see bitter rot on some fruit, especially on highly valuable crop like 'Honeycrisp', our recommendation is to protect the whole block by immediately spray applying the full rate of captan plus higher rate of Pristine or Merivon or other QoI containing fungicides such as Sovran, Flint, Luna Sensation or similar. We would also recommend to include a surfactant such as LI-700 to enhance fruit coverage (use low rate for coverage only!). This will help both to inactivate spores on the decay lesions and to protect the remaining healthy fruit from infection until they can be harvested. We warn that if fruit will be sold for pick-your-own, then the full rate of captan close to harvest may be a problem and one might get by with a half-rate of Captan 80 plus a full rate of either Pristine or Merivon (read the labels and PHI limits of these fungicides). After harvest, strive to pick all of the decayed fruit from the the orchard floor before winter and destroy it by burying the fruit. If the bitter rot affected block was a block that had fire blight last year or this year, it will also be important to cut out and remove all of the dead fire blight wood because bitter rot likes to colonize old fire blight strikes.

Comments

Post a Comment

Popular posts from this blog

First Symptoms of Apple Blotch Disease Visible on Leaves in Winchester VA

On 26 July we visited a classic training system orchard in south part of Winchester, VA, with trees of apple cv. 'Ginger Gold' and detected symptoms of  Apple Blotch Disease (ABD), also known as Marssonina Leaf Blotch (MLB). The symptoms were found on the lower scaffolds in the canopy and are visible in Figure 1 . This disease primarily expresses on apple leaves and is  caused by a pathogenic fungus  Diplocarpon coronariae . Even though we  recently  experienced dry weather periods in the Shenandoah Valley, e xcessive rains we received in May and June 2021 favored the development of ABD.  Leaf symptoms express as grey to brown large round spots (blotches) that can merge. This leads to  leaf yellowing.   Figure 1. Apple Blotch Disease (aka Marssonina Leaf Blotch) on apple cultivar 'Ginger Gold' in Winchester, VA.  If effective fungicides are not applied timely, continued infections by  D. coronariae  can occur during summer and until the leaves are present on the trees.
Post a Comment
Read more

This Blog Post is no longer active and has permanently moved to a new URL: https://treefruitpathology.spes.vt.edu/posts/

This blog post platform is no longer in use or active - please go to the https://treefruitpathology.spes.vt.edu/posts/ and subscribe to Tree Fruit Disease Updates using a Subscribe to box on that website as seen in the Figure below. Thank you!  
Post a Comment
Read more

More Rain = More Apple Bitter Rot: Late Maturing Apple Cultivars Need Continued Fungicide Protection up Until Harvest (!)

Bitter rot incidence is high in some Virginia and West Virginia apple orchards as hot summer days with drought mid- summer   preceded  rains in August and September. Bitter rot emerged at an increasing rate where fungicide was stopped in June or July or coverage until harvest was less frequent then necessary after many small rain events that in the end summed up to 2 inches of rain or more (Fig. 1). In addition, we had a severe 3 inches of rain brought in by the hurricane Ida that were highly favorable for infections by bitter rot fungi from genus Colletotrichum   . If you spray every row (full orchard coverage), your fungicide  cover spray is worth 14 days or 2 inches of rain, whichever comes first. Under this spray scenario, if you do not get rain for 14 days, you can extend the spray interval to 21 days, under the condition that you do not get rain during the 7 additional days. However, if you spray every second row every 14 days ( alternate row middle) , f ruit rots will be or have
Post a Comment
Read more