Rain is forecasted for the coming week. Many growers are wondering “Should I apply another fungicide?”
Foliar diseases of concern at this time of year are scab, shothole, and anthracnose. Conditions of leaf wetness and mild conditions favor growth of these fungi, which can infect and kill leaves, nuts, spurs, and shoots.
Currently, the forecast calls for 2-3 days of rain. If it rains all three days, there would be ample time for these fungi to infect your trees. Post-rain event weather conditions should also be considered when making this decision. If the weather looks to be warm and breezy, a spray might not be necessary as the conditions will dry out the trees. Some level of disease may occur, but the rate of secondary spread would be reduced to improper environmental conditions. A rain event following 4-5 days later, however, would increase the disease pressure within the orchard.
Since spring rain events tend to be one to two days in length, broad spectrum fungicides are a viable alternative for orchard applications. Applications of Captan, Captevate, Maneb, and/or Ziram can provide a cheaper treatment option than some of the other fungicides. These products provide moderate to good control of scab, shothole, and anthracnose and reduce the chance of resistance formation. For more information of treatment options and fungicide efficacy, please see the Fungicide Efficacy and Timing Charts for Almond.