Spring has sprung, and the season is well underway. As we progress into the crop year, scouting becomes a critical function to monitor for and keep insect pests out of the orchards. Insects such as the navel orangeworm, peach twig borer, codling moth and walnut husk fly are among the key pests that tree nut growers will want to be on the lookout for this season.
Navel Orangeworm
The navel orangeworm is a primary pest of almonds in California and is found on several agricultural and non-agricultural hosts. Many growers know firsthand just how much damage these tiny pests can do. First-generation larvae can develop in twigs during May and June, giving rise to the next flight of moths in late June or early July.
The infamous moth can generate three to four generations per year. According to University of California entomologists, orchards in warmer areas like the San Joaquin Valley generally see a fourth generation of moths, while the Sacramento Valley and San Joaquin County tend to see three generations per season.
Mature nuts are most susceptible to navel orangeworm damage during hull split. The moths’ feeding can lead to severely damaged and unusable nuts, affecting growers’ bottom lines.
Peach Twig Borer
Experts recommend scouting now for peach twig borer. You can do this by looking for “shoot strikes,” when the pest burrows into shoots and twigs, causing them to wilt.
First-generation larvae can develop in twigs during May and June, giving rise to the next flight of moths in late June or early July.
During the dormant season, pests like peach twig borer larvae can be found hibernating under the bark of young almond trees or in bark cracks. However, as soon as temperatures begin to rise, they chew their way out of their hibernaculum and work towards new shoots.
Codling Moth
One pest that might be lurking in your walnut orchard is the codling moth. The pest, which has been in North America for 200 years, is considered one of the most destructive to walnuts. The first flight typically happens between March and April and is from the overwintered generation. The flight of the overwintered generation might have two peaks and can last several months. These moths lay eggs that can signal the beginning of the first generation, according to UC IPM.
Growers and PCAs can scout for codling moth infestations by looking for frass produced by the larvae at the point of entry into the husk. Second-generation larvae often enter through the side of the husk where two nuts touch. To combat damage caused by codling moth infestations, UPL recommends an application of an insecticide spray.
Walnut Husk Fly
Typically a late-season pest, experts recommend walnut growers and PCAs have a plan in place for the walnut husk fly. With one generation per year, this pest typically emerges around July; however, some areas have seen the fly as early as May. You won’t need a magnifying glass to find the husk fly, as it is about the size of a housefly and extremely colorful with yellow spots and green eyes. Damage caused by the walnut husk fly can range from shell discoloration to kernel destruction.
ASSAIL® insecticide (IRAC 4A) is the go-to product for control of codling moth and husk fly in walnuts. ASSAIL is a standard recommendation by leading universities when it comes to controlling these two key pests and is trusted by walnut growers across California. With its translaminar activity, ASSAIL performs more like a systemic insecticide, providing weeks of control. ASSAIL has also been recognized as a bee-friendly product when good application stewardship is followed.
BIFENTURE® insecticide (IRAC 3A) is one of the most widely used insecticide/miticide products on the market — a second-generation pyrethroid that offers a high level of quality, consistency and effectiveness at an economical cost per acre. With its excellent contact and residual activity, BIFENTURE controls a wide spectrum of insects and mites in walnuts including codling moth, husk fly and spider mites.
These tiny pests can cause big problems for an orchard. To learn more on how to protect your tree nut yield this season, contact your local UPL representative.
