Influence of Seed Head–Attacking Biological Control Agents on Spotted Knapweed Reproductive Potential in Western Montana Over a 30-Year Period
Abstract Five insect biological control agents that attack flower heads of spotted knapweed, Centaurea stoebe L. subsp. micranthos (Gugler) Hayek, became established in western Montana between 1973…
Decline of spotted knapweed density at two sites in western Montana with large populations of the introduced root weevil, Cyphocleonus achates (Fahraeus)
Cause and Extent of Predation on Urophora spp. Larvae (Diptera: Tephritidae) in Spotted Knapweed Capitula
Field studies were conducted at 19 sites in western Montana to determine the cause and extent of predation on Urophora spp.
Voltinism and Phenological Synchrony of Urophora affinis and U. quadrifasciata (Diptera: Tephritidae), Two Seed Head Flies Introduced Against Spotted Knapweed in Montana
The distinct differences in voltinism and associated survival strategies serve as key factors in the niche separation of the two species, and U. affinis will likely become the dominant species at sites where the two flies coexist.
Effects of the Interaction of the Biocontrol Agent Agapeta zoegana L. (Lepidoptera: Cochylidae) and Grass Competition on Spotted Knapweed
Agapeta zoegana is a Eurasian root-mining moth introduced for biological control of spotted knapweed, Centaurea maculosa, in North America and it became comparably well established at a check site, 140 m away, by 1994, and appeared to reduce the number of bolted Knapweed plants in plots with low grass density by 39% and increase the density ofknapweed seedlings in the spring by 65%.
Impacts of the biological control agent Cyphocleonus achates on spotted knapweed, Centaurea maculosa, in experimental plots
The Population Age Structure of Spotted Knapweed (Centaurea maculosa) in Montana
Spotted knapweed communities were sampled to determine the relationship between age and the number of root rings, and the population age structure, and in 1984, popula- tions were expanding with high densities of individuals in the early age classes, followed by a steady decline in the older classes.
Relationship Among Growth Attributes of Spotted Knapweed (Centaurea maculosa) in Western Montana1
A study was conducted near Corvallis, MT, during 1992 to 1994 in order to assess the relationship among the growth attributes of spotted knapweed to identify a minimum set of measurable plant characteristics that are representative of spottedknapweed vigor.
Propagation ofCyphocleonus achates(Fahraeus) (Coleoptera: Curculionidae) for Biological Control of Spotted Knapweed: Procedures and Cost
The described field-corral approach is effective and the cost appropriate for providing C. achates for initial colonization in the western United States.