We haven’t seen phytopthora be a problem in pecans since the late 1980’s and then it was primarily located in the Ft. Valley area and we have not seen it develop yet this year but I had a conversation with UGA plant pathologist, Tim Brenneman recently, and he suggested that conditions over the last 2 weeks have been ideal for this pathogen. During extended cool and wet periods the disease can get started. Phytophthora shuck and kernel rot infection usually starts at the stem end of the pecan fruit and progresses distally to encompass the entire shuck within 4 to 6 days. A distinct margin develops between dark brown necrotic tissue and healthy green tissue during rotting of the
shucks and they become water-soaked.
These symptoms can be easily confused with shuck decline, which we see commonly in years when trees have a heavy crop load. With shuck decline, the shucks will turn black and stick tight to the shells. This normally results from crop load stress on the trees, especially if conditions turn dry following kernel filling.
Phytopthora is a seprate issue from shuck decline. The confusion of symptoms between the two can be alarming and frustrating to understand. If you are concerned about the possibility of Phytopthora infection, Dr. Brenneman recommends a Phosphite application while conditions favor the disease. Once symptoms appear it will be too late to stop the infection. Bear in mind that the efficacy of phosphite on phytopthora of pecan has not been confirmed with data because we have not seen the disease since this chemistry has been used on pecan. However, phosphite works very well on phytopthora infection of other crops and there is no reason to think pecan would be any different.
