Pests Affecting Native Plant Seed Production
Penstemon Seed Production Pests
Many species of Penstemon are grown in seed production fields and plots, some of which are quite large (> 10 acres). Seed production can be affected by a variety of insects which can attack the crown, stems or foliage. Impact from insect pests ranges from minor to catastrophic.
A crown boring weevil from SW CO has killed entire Penstemon fields in that region. Stem boring Penstemona clear winged moths are widespread, but have only inflicted minor damage in seed production fields. Lygus bugs feed on Penstemon plants and flowers in many production areas and can severely impact seed production.
Links to information on specific pests can be found within in the brief descriptions below.
The Penstemon borer larva lives in the crown and upper root area of any Penstemon species. They can kill plants and entire fields have been killed by them. Presently, they are known only from extreme southwestern CO. They have been tentatively identified as Coleoptera: Curculionidae: Hesperobarus ovulum, although the initial ID is currently being reviewed by a weevil taxonomist. Borer larvae can be identified by their presence within the stem at crown level. Larvae are grub-like with a distinct head capsule and no true legs.
The Penstemon clearwing Penstemonia clarkei (and other Penstemonia species) attack many Penstemon species, probably wherever they are grown near native Penstemons. The larvae are elongate whitish caterpillars which feed within the stems of the crown and lower aerial portion of the plant. Damaged plants and larvae have have been found in several plantings. There is a pheromone available for monitoring of adults.
This ebony bug, Corimelaena (Parapora) extensa Uhler was collected as it fed on Penstemon deustus near Idaho City ID. The bug was very common on plants which were at seed harvest. Not much is known about the insect, but it is probably capable of causing significant damage if infestations are large and early enough. It is a generalist, with feeding recorded on mullein, tobacco and mints. Feeding on flower buds, newly opened flowers, and foliage will appear as a wilting and general necrosis of tissue. If you see this or similar bugs attacking Penstemon, please document the damage with photographs, take a collection of mature bugs which can be stored in a freezer and contact Bob Hammon.
This page was updated on April 26, 2014