jan-feb-2021

IN YOUR ORCHARD (Propiconazole/Azoxystrobin, FRAC 3 and 1 1 ), Merivon (Pyraclostrobin/Fluxapyroxad, FRAC 7 and 1 1 ) and Rhyme (Flutriafol, FRAC 3) provided moderate disease control, with efficacy ranging from 40 percent to 70 percent. Acrylic paint was shown as being poorly effective overall as a pruning wound protectant against all the various canker pathogens, achieving only 20 to 40 percent. Pruning Wound Susceptibility Recent research conducted in our laboratory investigated the susceptibility of almond pruning wounds to fungal canker pathogens according to the month of pruning, i.e. September, October, November, December and January. While pruning wounds are susceptible to infection during all months between September and January, pruning wounds appear to heal faster when pruning is performed in late January versus sometime between September and December. Also, pruning wounds are most susceptible to infection by canker pathogens immediately after pruning through the first two weeks following pruning; a steady decrease in pruning wound susceptibility is observed two weeks post-pruning. It is also important to note that in the absence of rain (for example, in September), chances of pruning wound exposure to fungal inoculum are reduced, limiting the risk of infection. The high susceptibility of pruning wounds immediately following pruning and up to two weeks after stresses the need for protecting these wounds right after pruning. Interestingly, the two-week susceptibility window of pruning wound overlaps with the two-week residual activity of most chemical fungicides. This suggests that a single application of a pruning wound protectant right after pruning suffices to reduce infection. In comparison to chemical fungicides and physical barriers such as paint, biological control agents such as Trichoderma , when applied on the surface of a pruning wound, can colonize wood and establish durably in the host tissues, providing long-term protection of trees against canker pathogens. Adopt Cultural Practices to Reduce Risk of Diseases It is common knowledge that trees subjected to any type of stress become more susceptible to infection by canker pathogens. Conversely, maintaining good nutrition and water status in trees generally minimizes tree stress and can help trees overcome canker pathogens. Also, proper training of young trees will create strong branch attachment and help ensure branches will not split as the tree matures, which can help reduce infection. When pruning, growers should avoid making horizontal pruning cuts as they may allow for an accumulation of water. Overall, pruning should not be conducted during or following rainfall, as doing so would permit the release of fungal spores. As for Ceratocystis canker, the disease may be managed by avoiding bark injuries from mechanical shakers. Ultimately, if the bark is injured, the damaged tissue should be removed to the edge of the injury to promote callus formation. Dead almond trees, including stumps, as well as dead wood from other susceptible woody crops such as apricots, grapevines, pistachios, prunes, sweet cherries, and walnuts next to commercial almond orchards should be removed and destroyed to reduce inoculum. Finally, adjusting sprinkler irrigation locations so that tree trunks are not wetted will help reduce the incidence of canker diseases. Final Tips Combined results of pruning wound protection and susceptibility experiments provided strong evidence that successful protection of almond trees against fungal canker pathogens can be achieved. While pruning should always be avoided during and following rainfall, late- January pruning combined with a single application of a protective fungicide or biological control agent applied immediately after pruning is recommended to reduce the risk of infection caused by canker pathogens. Our research indicates that both Topsin M and Vintec can provide great protection of almond pruning wounds against a broad spectrum of fungal canker pathogens including those responsible for band canker, Ceratocystis 4 2 A L M O N D F A C T S