Franz Niederholzer0 commentsDecember 11, 2017Diseases

New pesticide labels available to help control pruning wound infections

Topsin® M WSP and Rally® 40WSP now have 2EE labels to protect pruning wounds on almonds (and other stone fruit trees and/or grapes) from canker disease infection. These products should be especially helpful in protecting young trees where disease infection of relatively large pruning cuts may cause extensive damage.   —-Canker diseases listed on the Topsin®M and Rally® labels—-   Topsin®M WSP Rally® 40WSP Eutypa Eutypa Cytospora Cytospora Calosphaeria pulchella Calosphaeria pulchella Lasiodiplodia theobromae Lasiodiplodia theobromae Botryosphaeria Botryosphaeria* Phomopsis Phomopsis* *suppression, only   The labels are very similar in many regards.  The following are recommended on both labels: Application within 24 hours of pruning is highly recommended. Assure complete coverage of all cut surfaces. Add a registered spray dye to better assess coverage. Additional application after about 2 weeks, especially if rain, irrigation, or high humidity occurs. Product combination (tank mixing) for best results and resistance management (Topsin M is a FRAC 1 fungicide, Rally a FRAC 3, and both have single site – high resistance risk – activity). Use of an organosilicone surfactant to improve pesticide penetration into pruning wound surfaces. (It is up to the grower to select and use a crop-safe organo-silicone with these products on pruning wounds).   There are some differences in the labels that limit how they can be used separately or combined. While the labels recommend tank mixing for best results and resistance management, consider the following: The Rally label does not allow painting the product on pruning wounds, while the Topsin M label does allow painting In addition, at the labeled rate (1.5 lb/acre), Topsin M is limited to 2 applications/year (max of 3 lbs/acre/year), while Rally is permitted a max of 3 applications/season (max of 1.5 lb/season). Therefore, if the two products are combined, painting is out and only 2 applications

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David Doll3 CommentsNovember 30, 2009Diseases

Pruning Wound Cankers Found in Almond Trees

Making pruning cuts on almond trees is risky business. Every cut provides the opportunity for fungal/bacterial pathogens to enter the tree (Think: a cut on you hand can allow bacteria to enter). Once the pathogens enter the tree and successfully colonize, poor tree performance and shortened orchard life can be expected. Figure 1: Fungal canker associated with a pruning wound on a young tree. Upon bark removal, canker growth and damage is evident. Fungi are the most commonly found pathogens invading tree wounds. In figure 1, a large pruning cut was made on a super-vigorous first leaf almond. The pruning wound became infected with the fungi Eutypa which grew through the tree causing a large canker. This canker did not become noticeable until the third leaf. Upon bark removal, it is clear that the canker grows outward from the point of origin. As the canker continues to grow, it has the ability to kill branches by girdling (Figure 2), weaken scaffolds which then break (Figure 3), and/or killing the tree by girdling the trunk (Figure 4). Botryosphaeria is another fungi that may cause this problem. Figure 2: Scaffold killed by fungal canker girdling the vascular tissues of the branch. Figure 3: Scaffold split caused by weakening of crotch angle by invading fungi. Figure 4: Tree killed by wood fungal canker girdling the vascular tissue of the tree trunk. Bark removal shows the advancement of the canker. Irregardless of the possible infection by fungi, trees need to be pruned to shape (young trees), remove unwanted branches, and remove dead/diseased tissue. Knowing this, how can we prune the tree and reduce the chance of fungal infection? Most fungi require moisture/high humidity/rain event to produce spores. These spores are usually transferred by wind-blown rain. The “window of opportunity” for these fungi to infect

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