With spring weather arriving earlier, almond growers in California can expect an earlier influx of pests in their orchards — and to get started sooner on preventing them from harming their nut crops. According to UCCE Sacramento Valley Integrated Pest Management Supervisor Sudan Gyawaly, now is the time to watch out for things like navel orangeworm (NOW), peach twig borers, leaf-footed bugs and spider mites.
Navel Orangeworm (NOW)
Navel orangeworms (Amyelois transitella) are the most prominent pests in almond orchards. These moths lay their eggs on the shells after hull split, and the larvae burrow inside the shell, eating the nuts and sheltering inside. Signs of a NOW infestation in an orchard include:
· Small, flat, oval-shaped eggs outside of almond hulls
· Pinhole-sized holes in almond hulls
· Hulls that are oily in appearance
· Fungal infections of nuts
· Extensive webbing inside the hulls
· Partially eaten nuts
· Larvae that are white to pink in color, with crescent marks behind the head
To manage NOW in your orchards, be sure to continuously monitor male flight activity by using pheromone traps. Also continue to monitor NOW egg traps to establish a spring biofix (the first spring flight, which acts as the starting date for calculating growing degree days), to help you predict the timing of their later flights. The first flight usually occurs from late March through April, but earlier times are possible, depending on the weather.
According to UC IPM, prevention is key to avoiding infestation. This includes removing all mummy nuts by the start of February. To eliminate existing NOW populations:
· Establish a biofix
· Hang pheromone dispensers in the trees to disrupt mating
· Assess trap activity and begin spraying at hull split. Apply pesticides at night and early morning for optimal results
· Harvest and clean up as early as possible
· Remove mummy nuts by March 15 of the next year. Mow or disk mummies on the ground.
Peach Twig Borer
While less of a concern in mature orchards, peach twig borer — also a moth — can still be a menace for almond growers in younger fields by causing primary scaffold damage. Begin monitoring pheromone traps in April to establish a biofix and decide if a spray is necessary in May. Consult with your pest control adviser if you are unsure.
Leaf-Footed Bugs
Stink bugs and leaf-footed bugs are especially troublesome after a warm winter. Leaf-footed bugs can be trickier to spot. UC IPM lists the tell-tale signs of an infestation in your orchard as:
· Gummy nuts — nuts with exudates on the outside of the hull — a signature warning
· Nuts that have dropped prematurely
· Black spots on kernels and wrinkled, misshapen nutmeat from adult feeding
· Withered and aborted shells from bugs feeding on premature nuts
Stink bugs cause similar damage, but this is usually around May or June. Leaf-footed bug management can vary from orchard to orchard, depending on history and severity. Gyawaly advises basing spray decisions on this history plus on damage risk associated with seasonal conditions. Consult with your pest control adviser if you are unsure.
Spider Mites
Typically found in the lower parts of the canopy, spider mites may also come out earlier and in greater numbers with warmer weather. Their presence should be monitored once every two weeks. For this pest, beneficial arthropods that prey on spider mites may be one of your orchard’s best friends. These species include:
· Western predatory mites
· Spider mite destroyers
· Sixspotted thrips
· Pirate bugs
By monitoring and addressing mite and insect pests in the spring, the pest populations can be kept under control to ensure a large, high-quality almond harvest.
