Submitted to: Journal of Kansas Entomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2011
Publication Date: 11/30/2011
Citation: Springer, T.L., Puterka, G.J., Maas, D.L., Thacker, E.T. 2011. The southern cornstalk borer (Diatraea crambidoides (Grote), Lepidoptera: Crambidae)a new pest of eastern gamagrass (Tripsacum dactyloides (L.)L., Poaceae). Journal of the Kansas Entomological Society. 84(3):209-216. Interpretive Summary: Eastern gamagrass is recognized as a productive and palatable forage grass species and is an important component of forage and livestock production systems. As the acreage of eastern gamagrass has increased over the past 25 years, the incidence of disease and insect pests has become more evident. The southern corn stalk borer has been recognized as a pest of eastern gamagrass. An experiment was conducted at the Southern Plains Range Research Station in Woodward, Oklahoma to better understand the life cycle of this insect in eastern gamagrass. Larvae are found to overwinter within a feeding cavity located near the base of the shoot or within the proaxis. All larval instar stages were found to overwinter; but only the fourth instar stage was found to occur year round. Larvae were found to inhabit reproductive shoots 2.5 times more often than vegetative shoots, which suggest an oviposition preference of adult females for reproductive shoots. In January, the overwintering population varied from 10-15 insects per plant crown. By early June, the insect population reached a minimum, less than 5 insects per crown. Metamorphosis was completed in June when the adult insects emerged and became sexually active. By early August, the population of larvae and pupae reached a maximum of about 20 insects per crown. On the basis of these data, two generations occur annually in northwest Oklahoma.
Technical Abstract: The southern corn stalk borer [Diatraea crambidoides (Grote)] has become a serious pest to eastern gamagrass [Tripsacum dactyloides (L.) L.]. Controlling this insect will be important to the future of this forage crop in the United States. An experiment was conducted to understand the life cycle of the southern corn stalk borer infesting eastern gamagrass. For a 2-year period, four plant crowns which contained numerous shoots were randomly dug each week from a field plot located in Woodward, Oklahoma. All shoots were dissected from each crown, the number of larvae and pupae present recorded according to the shoot type in which they were found, i.e., reproductive shoot or vegetative shoot. The life stages of the southern corn stalk borer in eastern gamagrass can be described by three distinct populations in northwestern Oklahoma: the over-wintering population, the first generation population, and the second generation population. Over-wintering larvae feed within a cavity near the base of the shoot or within the proaxis. Pupation also occurs within the feeding cavity. Larvae occur in reproductive shoots 2.5 times more often than vegetative shoots, which suggest an oviposition preference of adult females for reproductive shoots. The life cycle of the southern corn stalk borer in eastern gamagrass was completed in about 911 cumulated growing degree days. Understanding the life cycle of this devastating insect to eastern gamagrass forage and seed production will help formulate methods of control.