Apple bloom in California means that growers will want to be monitoring for signs of fire blight in their orchards. While apple cultivars can vary in their susceptibility to the disease, the disease prevents a significant threat for some rootstocks. Technical Services Manager for Northern California for UPL, Katie Driver said that left untreated, the bacteria can move beneath the bark towards the core of the tree. Once infection reaches the core, the tree can eventually die.
“Fire blight has been around for a very long time. It’s caused by a bacteria and it infests trees via new buds or cracks or cuts on leaves and branches, which then develop into oozing cankers and infected foliage turns a necrotic red-brown as though it has been burned,” said Driver. “While the disease attacks many different parts of the tree, blossom is when the trees are most susceptible, and the disease is most prevalent in warm or rainy humid weather early in the season. Infections most commonly occur at bloom and the weeks following petal fall.”
The disease can cause blossom clusters to wilt and collapse, which growers will want to be monitoring for. Driver said that the tips of infected shoots will rapidly wilt and curve into what’s known as a “shepherd’s crook.” Overwintering cankers that are black, grey, or violet in color can also be indicative of infection. Driver explained that growers will want to keep these signs and symptoms in mind so that can act accordingly to combat the disease.
“Using a product like KASUMIN will give growers the help that they need. Kasugamycin is the unique active ingredient in KASUMIN and it features a high level of preventative activity, making it effective on a wide variety of plant pathogenic bacteria, including fire blight,” Driver explained. “KASUMIN is available as a liquid formulation. Its field testing has shown that it can be effectively tank-mixed with other fungicides to increase the spectrum of disease control.”
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