The invasive brown marmorated stinkbug is in the Central Valley and has caused significant damage in some almond orchards.
The brown marmorated stinkbug (BMSB) is a polyphagous insect native to Asia (i.e., China, Japan, Korea, and Taiwan) that feeds on fruit, nut, and vegetable crops. BMSB established in the mid-Atlantic states during the 1990s and since the initial detections, has spread to more than 42 states, and more than 170 agricultural and ornamental host plants have been recorded.
Almond growers and farm managers who know BMSB infestations occurred in their orchards last year should be on the look out for signs of their return, said Dr. Jhalendra Rijal, area UCCE Integrated Pest Management Advisor in Modesto. Those signs include significant early drop of nuts and multiple gumming sites on nuts later in the season.
The majority of those nuts does not drop, but have signs of interior damage to kernels at harvest. Kernel damage includes gummy nuts, shriveled and dumpling nuts.
Rijal, who has been tracking BMSB infestations and conducting research since 2016, said this pest has been slowly moving into nut and fruit tree orchards.
Orchards that border BMSB overwintering sites such as houses, barns, etc. and have alternate hosts such as trees of heaven (i.e., Ailanthus trees) are more prone to high level of BMSB damage because of the BMSB ‘supply’ there. Rijal said in the past two years in the Modesto/Turlock area more damage occurred in orchards with known BMSB source nearby compared to orchards without overwinter signs nearby.
Sticky panel traps with BMSB pheromone lures are advised for detection of BMSB in orchards early in the growing season. Rijal said the traps should be placed on orchard edges on the ground using a 1-2 inch thick wooden stake (i.e., 4 feet-tall aboveground), The best time to detect movement of adult BMSB into an orchard is early in the spring to prevent the early-season damage to the developing nuts. Besides traps, it is critical to do visual sampling of the trees to detect live insects and/or any damage to the nuts. Visual sampling should focus on trees in edges. This year, Rijal said adult BMSB movement began in April in the northern San Joaquin Valley.
UCCE IPM advisor Kris Tollerup said BMSB has not been detected in commercial orchards in the southern San Joaquin Valley, but it has been detected in urban Fresno County Pest control advisors are being vigilant about signs of the pest, but Tollerup said he believes the hotter summer temperatures in the southern San Joaquin Valley are keeping BMSB from further expansion.