Damage potential of Argentine stem weevil in Lincoln dairy pasture: has biological control by Microctonus hyperodae altered the balance?

Abstract

<jats:p>To measure the impact of biological control of Argentine stem weevil, Listronotus bonariensis (ASW) by Microctonus hyperodae in dairy pasture, a research site was established in the autumn of 1997 on a dairy farm near Lincoln, where the parasitoid had been present since 1994. Existing pasture was killed with glyphosate and four ryegrass cultivar treatments consisting of three perennial (Nui, Embassy, Vedette) and one hybrid mixture (Marsden/Greenstone), each containing either low or high levels of Neotyphodium lolii endophyte, were sown by direct drilling. A third main plot treatment was low endophyte plus insecticide. Between 1997 and 1999, seasonal pasture production was measured in all plots. Herbage composition was also measured in all plots for the first 2 years but only in the Nui treatments in 1999. ASW adult and larval densities, larval damage to ryegrass, parasitism by M. hyperodae and ryegrass tiller density were measured on Nui plots in spring and again in summer, coinciding with periods of peak ASW egg laying and larval development. Between 1997 and 2000, ASW adult densities in Nui were highest in the first summer (26 January 1998) following establishment. Thereafter, densities did not rise above c. 60 ASW/m2. Densities of adults, larvae, levels of larval damage to ryegrass, and parasitism by M. hyperodae were significantly higher in summer than spring (P</jats:p>

Ryegrass production in Wairarapa, New Zealand: is biological control of Argentine stem weevil important?

“…The relatively higher numbers of L. bonariensis on wild-type most probably reflected the moderate proportion of endophyte-infected tillers (52%) in these pastures, as AR1 and wild-type infected ryegrass tillers provide an equivalent high level of feeding deterrence to L. bonariensis adults through the production of peramine (Popay et al 2003). Furthermore, ryegrass densities measured in this study were far higher than that measured by Barker et al (1989) in Waikato, but similar to those measured under irrigated pasture in Canterbury (Goldson et al 1998, McNeill et al 2001. Therefore, it is highly probable that in the Wairarapa wild-type pastures, endophyte-free tillers were not limiting to L. bonariensis oviposition and subsequent adult recruitment.…”

“…Furthermore, low adult numbers were observed in a study examining the relationship between endophyte, L. bonariensis and its parasitoid M. hyperodae (Goldson et al 2000), leading to the suggestion that parasitism may have suppressed weevil numbers. McNeill et al (2001) reported a similar result on a dairy farm near Lincoln, where adult numbers were high in the first summer following pasture establishment (c. 128 /m 2 ) but thereafter, were less than 40 /m 2 .…”

Response to clover root weevil outbreaks in South Canterbury, Otago and Southland; the agricultural sector and government working together

“…McNeill et al 1996) or following pasture renewal, as has been observed for the Argentine stem weevil parasitoid in New Zealand dairy pasture (e.g. McNeill et al 2001).…”

Endophytes improve ryegrass persistence by controlling insects

“…In cooler climates and where there is little pest damage, infection rates in pastures sown as endophytefree can stabilise at low levels (e.g. Eerens et al 1998;McNeill et al 2001McNeill et al , 2007.…”