Yellow Woollybear Caterpillar and Saltmarsh Caterpillar

Eggs and small larvae of the yellow wollybear caterpillar were being reported from soybean fields in the Garden City area this week. And high numbers of apparently these moths were also reported from Pratt. In addition, moths of the Saltmarsh caterpillar were observed and some later instar larvae of the Saltmarsh caterpillar were reported crossing the roads in some areas. These woollybear caterpillars can also be a pest of sunflowers.


Eggs and small larvae	Yellow wollybear caterpillar


Moth	Picture 2 of moth

Woollybears are very hairy (woolly), yellowish or brown caterpillars ranging up to 2 inches in length. Populations are often overestimated because the larvae and damage are very striking. The smaller larvae often are observed feeding in groups on the underside of the leaves which quickly become skeletonized and die. The larger, very showy, larvae tend to feed exposed on the upper leaf surfaces.


Woollybear caterpillar	Larvae and damage are very striking

Many fields are probably far enough along that the late season defoliation will not threaten yields, however fields in early to mid pod fill could be damaged if populations are heavy and widespread throughout the field. In some cases populations may be heavier along field edges.

In soybeans treatments may be justified if defoliation approaches 40% in the vegetative stage or 20% in the pod-forming or pod-filling stage, if the insects are still small and defoliation is expected to continue to increase.

Another factor to consider may be the spider mite situation. If mites are present use special caution in selecting treatment options some compounds labeled for caterpillar control may flair mite populations. Might consider using Chlorpyrifos which has some activity against mites or Methoxyfenozide (Intrepid 2F) and Spinosad (Tracer) which may be safer on beneficial organisms.

Information on control in Soybeans can be found at: http://www.entomology.ksu.edu/DesktopDefault.aspx?tabindex=367&tabid=570 and for Sunflowers at: http://www.entomology.ksu.edu/DesktopDefault.aspx?tabindex=361&tabid=555

Phil Sloderbeck

Sincerely,

Phil Sloderbeck
Southwest Research and Extension Center
Entomology - Garden City, KS
phone: 620/275-9164
email: psloderb@ksu.edu