Western Colorado Insects

Pests Affecting Native Plant Seed Production

Great Basin Native PlantsUncomphagre Plateau Project
Penstemon angustifoliusPenstemon palmeriPenstemon strictus

Scientific Name: Penstemon sp.
Common Name:
Penstemon (many species)
Plant Abbreviation:
PE**; P. angustifolius - PEAN; P. palmeri - PEPA; P. strictus - PEST
Penstemons are some of our showiest wildflowers. Many species of Penstemon are grown for seed in western North America. They are used for reclamation, restoration, and landscape purposes. Seed production has been relatively pest free, but borers and Lygus have caused significant local problems.

The Penstemon Clearwing

Scientific Name: Lepidoptera: Sessiidae; Penstemonia spp.

There are at least 5 species of Penstemonia in North America. Larval feeding is probably limited to Penstemon or closely related plant species in the Scrophulariaceae. We have observed clearwing feeding in PEPA, PEBA, and PEAN in Colorado.

Damage appears as a wilting or dieback of individual stems. Heavily infested plants will die, but we have seen no more than occasional infested plants in Penstemon fields to this point. Penstemon clearwings can be expected wherever there are native Penstemons present.

Adult Clearwing borerAdult

Adult moths are wasp mimics with clear wings. The species I have experience with, P. clarkei, is about 1 cm in length, with dark blue, almost black coloration of the body and wing margins. The broad portion of the wings is clear.


Eggs will probably be laid at the base of plants. There is no description available.

Penstemon Weevil LarvaLarva

The larva will be found within a stem at crown level. They are whitish in color, with true legs and prolegs. The segments of the abdomen will appear divided by intersegmental incisions. The head is narrower than the prothorax. Prolegs on abdominal segments bear two transverse lines of uniordinal crochets, while the anal prolegs have only one row of uniordinal crochets.


Pupation is probably in the soil at the base of plants, but there is no description of them.


There are pheromones available at Great Lakes IPM (Clearwing borer complex; SC-L103) to monitor adult flights. The pheromone is generic for many clearwing borers, so it is essential that you learn to identify Penstemonia if they are used. Pheromoen traping can help determine if moths are present, give some idea of the intensity of flights, and help determine timing if control ever need to be applied.

Should sprays be necessary, they must be preventative in nature. Sprays would target newly hatched larvae as they hatch from eggs. A residual insecticide would be used. The choice of insecticide will be determined by timing. There would be a wider range of options for a post bloom application than pre or during-bloom applications.

If you have questions about clearwing management in Penstemons, please contact Bob Hammon.


San Diego Natural History Museum Penstemonia hennei Page
Penstemonia Pheromone Information

This page was updated on April 26, 2014