She said the gummosis left by the leaffooted bug resembles bacterial spot, but can be distinguished from that. The bacterial spot is orange or reddish while the leaffooted bug leaves clear spots.

A biological control, which parasitizes eggs, is effective in the summer, but has no benefit against over-wintering adults that migrate to almonds.

Insecticides must contact the pest. Rill said Lorsban is excellent on contact, but has a residual of only one week, while pyrethroids including Brigade and Warrior II are excellent on contact and have a residual of more than four weeks.

She said Abameticin, Agri-Mek, and others are excellent on contact, but have no residual activity. Belay, Bexar, Sivanto, Beleaf, Exirel, and Sequoia have some contact activity but no residual activity.

Discussing monitoring and management in pistachios, Kris Tollerup, an integrated pest management advisor at the Kearney Ag Center, described the leaffooted bug as a “beast” that is difficult to kill and potentially a pest in several San Joaquin Valley crops.

He said researchers are trying to find a “plant volatile” that would act as pheromone to draw the pests, which would make monitoring easier.

Tollerup also pondered whether treating overwintering aggregations could protect neighboring host crops and whether colder temperatures could reduce populations. He said it appears that temperatures of 26 or 27 degrees for hours can significantly reduce populations.

He said leaffooted bug can be distinguished from stink bugs, which lay eggs in groups that are barrel-shaped. While stink bugs have two generations per year, the leaffooted bug has three over-lapping generations per year and possibly a fourth. Its eggs are laid in a tube-shaped group.

The damage to pistachios comes in late May and early June and can include lesions, abortion of kernels, and kernel necrosis.

Tollerup recommends sampling from late April to mid-July. He said adults are hard to spot because they quickly fly away if the top branches of trees are tapped.

“But you can see their silhouettes as they fly away,” he said.