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United States Department of Agriculture

Agricultural Research Service

Title: Temperature-dependent development, survival and potential distribution of Ischnodemus variegatus (Hemiptera: Blissidae), an herbivore of West Indian marsh grass (Hymenachne amplexicaulis)

Authors
item Diaz, Rodrigo - UFL
item Overholt, William - UFL
item Cuda, Jim - UFL
item Pratt, Paul
item Fox, Alison - UFL

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 11, 2008
Publication Date: May 15, 2008
Citation: Diaz, R., Overholt, W.A., Cuda, J.P., Pratt, P.D., Fox, A. 2008. Temperature-dependent development, survival and potential distribution of Ischnodemus variegatus (Hemiptera: Blissidae), an herbivore of West Indian marsh grass (Hymenachne amplexicaulis). Annals of the Entomological Society of America,May 2008 : Volume 101 Issue 3, pps. 604-612.

Interpretive Summary: The bug Ischnodemus variegatus has invaded south Florida and attacks the exotic grass Hymenachne amplexicaulis. This grass is a problematic weed in Florida and Australia but a highly valued forage in Mexico, Cuba and Venezuela. We studied the influence of nine constant temperatures (8-380C) on the developmental time and survival of I. variegatus. Complete egg and nymphal mortality occurred at temperatures =20.50C and at 380C. Developmental time decreased linearly with temperature until an optimum between 28-300C and increased at 330C. Mortality of first, second and third instars was high across all temperatures. Developmental time across all temperatures was greatest for eggs, first and fifth instars as compared to other stages. Linear and Brière-1 nonlinear models were used to determine the lower temperature threshold at which the developmental rate (1/D) approaches zero. The lower thresholds to complete development (egg to adult) estimated with the linear and nonlinear model were 14.6 and 17.40C, respectively. The total degree-days required to complete development estimated by the linear model was 588. Using temperature data from Florida, a GIS map was generated to project a prediction grid of I. variegatus generations/year. Based on these predictions, the insect will complete 3-5 generations per year in areas currently invaded in Florida. Results of this study will be used to understand the potential distribution and population growth of I. variegatus in H. amplexicaulis infested regions.

Technical Abstract: The bug Ischnodemus variegatus (Signnoret) (Hemiptera: Blissidae) is a fortuitous herbivore of the invasive grass Hymenachne amplexicaulis (Poaceae). This grass is a problematic weed in Florida and Australia but a highly valued forage in Mexico, Cuba and Venezuela. We studied the influence of nine constant temperatures (8-380C) on the developmental time and survival of I. variegatus. Complete egg and nymphal mortality occurred at temperatures =20.50C and at 380C. Developmental time decreased linearly with temperature until an optimum between 28-300C and increased at 330C. Mortality of first, second and third instars was high across all temperatures. Developmental time across all temperatures was greatest for eggs, first and fifth instars as compared to other stages. Linear and Brière-1 nonlinear models were used to determine the lower temperature threshold at which the developmental rate (1/D) approaches zero. The lower thresholds to complete development (egg to adult) estimated with the linear and nonlinear model were 14.6 and 17.40C, respectively. The total degree-days required to complete development estimated by the linear model was 588. Using temperature data from Florida, a GIS map was generated to project a prediction grid of I. variegatus generations/year. Based on these predictions, the insect will complete 3-5 generations per year in areas currently invaded in Florida. Results of this study will be used to understand the potential distribution and population growth of I. variegatus in H. amplexicaulis infested regions.

Last Modified: 10/21/2014
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