Seed Wasp on Multiflora Rose, Rosa multiflora, in Virginia

1988 ◽  
Vol 2 (3) ◽  
pp. 265-268 ◽  
Author(s):  
Warren T. Mays ◽  
Loke-Tuck Kok
Keyword(s):  
Biological Control ◽  
Sex Ratio ◽  
Biological Control Agent ◽  
Control Agent ◽  
Rosa Multiflora ◽  
Severe Winter ◽  
Winter Temperatures ◽  
Weed Distribution ◽  
Multiflora Rose ◽  
Chalcid Wasp

Multiflora rose is a major weed in pastures, highway embankments, and recreational areas. A chalcid wasp, Megastigmus aculeatus (Swederus) (Hymenoptera: Torymidae), which feeds on the multiflora rose seeds, is a potential biological control agent for this weed. Distribution of multiflora rose and the seed wasp was studied from 1983 to 1986 in Virginia. Multiflora achenes collected from 58 sites in 51 counties showed that M. aculeatus was present in all but one of the counties surveyed; female:male sex ratio was high (94:1), indicating parthenogenesis. Infestation rates of the achenes averaged 26.5% in 1985 and 23.9% in 1986. Severe winter temperatures appear to affect the wasp population adversely.

Mind the gap: the delayed recovery of a population of the biological control agent Megamelus scutellaris Berg. (Hemiptera: Delphacidae) on water hyacinth after winter

2020 ◽  
Vol 111 (1) ◽  
pp. 120-128 ◽  
Author(s):  
Benjamin E. Miller ◽  
Julie A. Coetzee ◽  
Martin P. Hill
Keyword(s):  
Biological Control ◽  
Water Hyacinth ◽  
Biological Control Agent ◽  
Population Decline ◽  
Growing Season ◽  
Control Agent ◽  
Population Recovery ◽  
Control Effort ◽  
Developmental Threshold ◽  
Winter Temperatures

AbstractCold winter temperatures significantly affect the biological control effort against water hyacinth, Pontederia ( = Eichhornia) crassipes Mart. (Pontederiaceae), in more temperate regions around the world. The population dynamics of the planthopper Megamelus scutellaris Berg. (Hemiptera: Delphacidae), a newly released biological control agent of water hyacinth, were recorded on the Kubusi River in the Eastern Cape Province (South Africa) over 15 months to determine the population recovery post-winter. Megamelus scutellaris incurred a severe population decline at the onset of winter when the water hyacinth plants became frost damaged. The combined effect of a population bottleneck and low minimum winter temperatures (6.12°C) below the agent's lower developmental threshold (11.46°C) caused a post-winter lag in agent density increase. Subsequently, the maximum agent population density was only reached at the end of the following summer growing season which allowed the water hyacinth population to recover in the absence of any significant biological control immediately post-winter. Supplementary releases of agents from mass-reared cultures at the beginning of the growing season (spring) is suggested as a potential method of reducing the lag-period in field populations in colder areas where natural population recovery of agents is slower.

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