The trademarked bactericide Kasumin has received Environmental Protection Agency Section 18 approval for use in almonds in 2021.
The kasugamycin product for control of bacterial blast can be used on a maximum of 100,000 acres of almond in Butte, Colusa, Fresno, Glenn, Madera, Merced, San Joaquin, Stanislaus, Sutter, Tehama, Yolo and Yuba counties.
The bactericide acts mainly as a preventative and is applied to coincide with early shoot emergence and bloom, which places a protective layer of the bactericide on emerging green tissue and blossoms.
Under the Section 18 approval, Kasumin can be applied up to two times at a use rate of 64 fluid ounces per acre. The application should be made when conditions favour disease development from bud break to petal fall. Application is not allowed after petal fall.
This bactericide is the lone member of FRAC Group 24. According to the manufacturer, UPL, Kasumin is most effective as part of a rotation program due to no cross resistance to other bactericides. The product has a 12-hour restricted entry and a 100-day pre-harvest interval.
UC Riverside plant pathologist Jim Adaskaveg prepared the Section 18 request for Kasumin in almond. He said outbreaks of bacterial blast are caused by the bacteria Pseudomonas syringae. The bacteria colonize plant tissue in a cold and wet environment. Bacterial blast was found in 2019 to be most severe in some self-pollinating varieties of almond as well as other cultivars that bloomed during cold weather.
Bacterial blast infections affect almond varieties depending on their stage of bloom when cold, wet weather hits. In early blooming Independence, Aldridge and Monterey, the disease affects blossoms and leaves, which wilt and die.
Blast infections of dormant buds result in bud death. Blossoms may wither suddenly and turn dark brown. When there are multiple blasted flowers, the shoot tip may become necrotic and exude gum.
Blast infections are most severe in the lower part of the tree canopy and in low places in an orchard where colder air has settled. Growers who experienced previous bouts with this disease now know which varieties of almonds are most susceptible and orchard locations where trees are most vulnerable due to environmental conditions.
Production losses due to bacterial blast infections can reach 30% to 40%. Non-bearing trees can also be infected as the subsequent dieback of fruiting wood can delay production.