A wide variety of insects in the order Hemiptera are known pests of almonds in the U.S., such as (left to right) the native green stink bug (Chinavia hilaris) and the invasive brown marmorated stink bug (Halyomorpha halys). A new guide in the open-access Journal of Integrated Pest Management details the biology, ecology, and management options for “true bugs” in almond orchards. (Green stink bug photo by Daren Mueller, Iowa State University, Bugwood.org; brown marmorated stink bug photo by Susan Ellis, Bugwood.org)

By Jody Green, Ph.D.

Jody Green, Ph.D.

The United States is the largest producer of almonds in the world, supplying over 80 percent of the global production. There are over 1.5 million acres in California dedicated to growing almonds, located primarily in the Central Valley region, which dominates the interior of the state of California. The Central Valley accounts for 11 percent of California’s total land area and is one of the most productive agricultural regions in the world. The valley is flat and has ideal growing conditions for crops such as almonds with mild, wet winters and hot, dry summers.

Jhalendra Rijal, Ph.D., an area IPM advisor with the University of California (UC) Cooperative Extension, has studied insect pests of almonds for six years. Due to the exclusive geographic region of almond crops, Rijal has the opportunity to study unique agricultural systems and the pests associated with them. Navel orangeworm (Amyelois transitella) is recognized as the most economically important insect pest of all major nut crops in California (which include almonds pistachios, and walnuts), but until now, little has been published about the 60 other species of insect pests that infest almond orchards.

Jhalendra Rijal, Ph.D.

Hemipteran pests are often overlooked, but their feeding as adults damages fruits, leaves, and kernels, causing direct or indirect crop problems such as gummosis, nut drop, or fruit abortion. Hemipterans are known for their piercing-sucking mouthparts used for drinking liquids from either plant or animal host. In the case of hemipteran pests of almonds, these “true bugs” insert their stylets into the host plant and inject toxic saliva that spreads into surrounding tissue.

In a profile published last week in the open-access Journal of Integrated Pest Management, Rijal and fellow UC researchers Andrea Joyce, Ph.D., and Sudan Gyawaly, Ph.D., describe the biology, life history, and management practices for 11 hemipteran pests of almonds in five families (Coreidae, Miridae, Pentatomidae, Rhopalidae, and Tingidae). Leaffooted bugs and brown marmorated stink bugs (Halyomorpha halys) can cause significant yield loss and economic damage, while others like various North American stink bug species are considered sporadic pests, and a variety of plant bugs are considered minor pests or have the potential to become pests of almonds in the future.

Among hemipteran pests of almonds, only the brown marmorated stink bug (Halyomorpha halys) can be monitored with a reliable trap, such as the one shown here. Monitoring for other bugs in almond orchards currently requires more time-consuming efforts such as visual sampling of orchard edges, beat tray sampling, and inspecting fruits for damage. (Photo by Jhalendra Rijal, Ph.D.)

Members of Jhalendra Rijal’s lab, Sudan Gyawaly (left) and Chang Vue (right), conduct beating tray sampling for hemipteran pests in an almond orchard. (Photo courtesy of Jhalendra Rijal, Ph.D.)

Integrated pest management (IPM) of hemipteran pests has included cultural management of vegetation within the orchard and overwintering shelters or alternative hosts outside of the orchard to reduce pest populations in orchards, and insecticide applications are employed to protect against significant pest pressure. At this time, no economic thresholds exist for the pests featured in this paper, the authors note, so there is much more research to be done.

Another challenge is the lack of traps available for monitoring. Aside from the fruit-feeding invasive brown marmorated stink bug, no other pest mentioned in this paper has a reliable trap used for monitoring. It is time consuming and labor intensive to conduct visual sampling of the orchard edges, beat tray sampling for insects, and inspecting fruits for damage.

Rijal knows there is both beauty and bugs to behold in the almond orchard. “In mid-February, the orchards are beautiful; the flowers are like popcorn covering the valley as far as the eye can see,” he says. “It’s a very scenic experience. In spring and summer, the trees are full of nice and green almond fruits, which resemble small peach fruits. Harvest time depends on the area and almond variety, but usually some are ready in August and September.”

As Rijal continues to make an impact as a cooperative extension IPM advisor, he considers his contribution the “tiniest sliver of the giant industry pie.” On behalf of regular consumers of almonds and almond products, we thank you!

Jody Green, Ph.D., is an urban entomology extension educator at the University of Nebraska-Lincoln and a subject editor and communications editor for the Journal of Integrated Pest Management. Twitter: @JodyBugsMeUNL. Email: jgreen17@unl.edu.