The Sphaeralcea Weevil
A seed increase planting of scarlet globemallow, Sphaeralcea coccinea, near Hotchkiss, CO (Delta County) was found to be infested with seed feeding straight-snouted weevils (Apionidae). A suction sample was taken on May 11, 2007 while the field was in full bloom, and adult weevils were common. A plant sample was taken on May 21, and eggs, larvae, pupae and adult weevils were present. Twenty-five percent of the developing seed in the sample had been destroyed on that date. Globe mallow are indeterminate bloomers, and the weevils are feeding on developing seed pods while the plant is still producing new flowers. It appears that there will be multiple generations of the weevil and the damage potential is high.
Two species of weevils were present in the field. Anthonomus sphaeralciae Fall (Coleoptera: Apionidae) was the dominant species, with an unidentified Apion sp. (Coleoptera: Apionidae) also present.
Sphaeralcea weevils were also found in a planting of globe mallow in Montezuma Co. CO. Populations were much smaller that those observed in Delta Co. Weevils are probably widespread across western states where Sphaeralcea is native.
The first step in management is to monitor for their presence. Use a sweep net or suction sampler to sample for adult weevils. Inspect developing fruits for the presence of damage, larvae, and pupae.
If adult control is an option insecticides should be applied to prevent egg laying. If larvae are present, a systemic insecticide application may be an option. Any insecticide application should be carefully considered since they will be applied during bloom and precautions should be taken to protect pollinators. If you wish to discuss control options, please e-mail Bob Hammon.
This page was updated on January 31, 2015