How to Manage Pests
UC Pest Management Guidelines
The false chinch bug is an occasional pest of young walnut orchards. It hibernates as an adult and moves in late winter to preferred weeds, primarily mustard family weeds such as London rocket, shepherd's purse, and common peppergrass, where it stays to lay eggs in early spring. Nymphs are dull gray or brownish red and collect in great numbers on the host plants.
When weed hosts dry up in late spring, chinch bugs move into orchard trees where they may kill new foliage. This damage can occur within hours because the nymphs apparently inject a toxin while feeding. The leaves dry up and are covered with fecal spots. Damage may be substantial on trees that are 1 to 3 years old. Several generations are produced each year, but damage in orchards usually occurs only in spring.
Where damage has occurred, control weed hosts in and adjacent to the orchard to prevent populations from developing in future years. Begin checking weed hosts for false chinch bug in late February and early March, especially in years when moisture is abundant. Mowing and discing cover crops before walnut trees begin to leaf out prevents false chinch bug development and migration. If potentially harmful populations are found on weeds or cover crops after walnut trees have leafed out, consider spraying the weeds or cover crop; avoid mowing or discing at this time to prevent migration to walnut foliage.
UC IPM Pest Management Guidelines: Walnut