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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPMENT & EVALUATION OF BIOLOGICAL CONTROL AGENTS FOR INVASIVE SPECIES THREATENING THE EVERGLADES & OTHER NATURAL AND MANANGED SYSTEMS

Location: Invasive Plant Research Laboratory

Title: Host specificity of Ischnodemus variegatus, 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: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 16, 2008
Publication Date: August 12, 2008
Citation: Diaz, R., Overholt, W.A., Cuda, J.P., Pratt, P.D., Fox, A. 2008. Host specificity of Ischnodemus variegatus, an herbivore of West Indian marsh grass (Hymenachne amplexicaulis). Biocontrol Science and Technology. 54:301-312.

Interpretive Summary: West Indian marsh grass, Hymenachne amplexicaulis, is an emergent wetlands weed that is native to South/Central America and the Caribbean, and is invasive in Florida and Australia. The neotropical bug, Ischnodemus variegatus was found feeding on H. amplexicaulis in Florida in 2000. The host specificity of I. variegatus was studied under laboratory and field conditions. Developmental host range was examined in 57 plant species compromising seven plant families. Development to adult was obtained on the target weed H. amplexicaulis (23.4%) and non-targets P. repens (0.4%), P. anceps (2.2%) and T. geniculata (0.3%). Adults survived 1.6 times longer and laid 6.6 times more eggs on the target weed than in the non-targets. Oviposition in non-target species was positively related to I. variegatus density under multiple choice conditions. Field experiments indicated that H. amplexicaulis had higher population densities of I. variegatus than non-targets species. Spill-over to non-target hosts occurred in an area where the target weed was growing in poor conditions and had high I. variegatus density compared to healthier stands. This study indicated that I. variegatus has a narrow fundamental host range that closely matched the ecological host range. However, under poor host conditions, nearby grasses could serve as temporary hosts of I. variegatus populations. The ultimate long-term establishment of this insect on non-target plants should be evaluated through periodic sampling of insect densities, feeding damage and plant population variables.

Technical Abstract: West Indian marsh grass, Hymenachne amplexicaulis (Poaceae), is an emergent wetlands weed that is native to South/Central America and the Caribbean, and is invasive in Florida and Australia. The neotropical bug, Ischnodemus variegatus (Signoret) (Hemiptera: Blissidae) was found feeding on H. amplexicaulis in Florida in 2000. The host specificity of I. variegatus (Hemiptera: Blissidae) was studied under laboratory and field conditions. Developmental host range was examined in 57 plant species compromising seven plant families. Development to adult was obtained on the target weed H. amplexicaulis (23.4%) and non-targets P. repens (0.4%), P. anceps (2.2%) and T. geniculata (0.3%). Adults survived 1.6 times longer and laid 6.6 times more eggs on the target weed than in the non-targets. Oviposition in non-target species was positively related to I. variegatus density under multiple choice conditions. Field experiments indicated that H. amplexicaulis had higher population densities of I. variegatus than non-targets species. Spill-over to non-target hosts occurred in an area where the target weed was growing in poor conditions and had high I. variegatus density compared to healthier stands. This study indicated that I. variegatus has a narrow fundamental host range that closely matched the ecological host range. However, under poor host conditions, nearby grasses could serve as temporary hosts of I. variegatus populations. The ultimate long-term establishment of this insect on non-target plants should be evaluated through periodic sampling of insect densities, feeding damage and plant population variables.

Last Modified: 7/27/2014
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