Biology of the Diamondback Moth, Plutella maculipennis (Curt.) (Lepidoptera: Plutellidae), in Eastern Ontario III. Natural Enemies

Abstract

The diamondback moth, Plutella maculipennis (Curt.), is a sporadic pest of cruciferous crops throughout Canada. It is normally held in check by a multiplicity of environmental factors, chiefly biotic; however, serious outbreaks do occur (MacNay, 1948, 1953, 1957, 1959). In eastern Ontario it has been extremely numerous since late 1951, and during the present study, 1952 – 1956, it was more abundant than the imported cabbageworm, Pieris rapae (L.), or the cabbage looper, Trichoplusia ni (Hbn.) . Two earlier papers (Harcourt, 1956, 1957) presented the history, distribution, and synonymy of the insect, giving general descriptions of the stages and many aspects of its biology in eastern Ontario. This article gives the relative abundance of its parasites and predators, and discusses certain population relationships.

Biological control of the diamondback moth,Plutella xylostella: A review

“…This large genus of Campoleginae comprises about 200 species worldwide (Yu & Horstmann 1997), with the majority (about 118 species) being described from temperate regions (Delvare 2004). Diadegma insulare is a solitary, host-specific larval endoparasitoid of DBM and is one of its most important biocontrol agents in the Nearctic to the northern Neotropical regions (Harcourt 1960(Harcourt , 1986Fitton & Walker 1992;Mukenfuss et al 1992;Idris & Grafius 2001). On average, it can parasitize 70 Á/90% of DBM larvae and parasitized larvae consume 35 Á/80% less food than nonparasitized larvae (Mukenfuss et al 1992;Mitchell et al 1997;Sourakov & Mitchell 2000;Monnerat et al 2002).…”

“…In the absence of a host plant (or leaf), female wasps rarely parasitize DBM larvae (Sourakov & Mitchell 2000). Under laboratory conditions, the ratio of males to females is usually extremely high (about 10:1) due to frequent haploid parthenogenesis; in the field this ratio is equivalent (about 1.1:1.0) (Harcourt 1960). The proportion of male wasps from young parasitized DBM larvae (L 2 ) is greater than females while larvae parasitized at L 3 and L 4 stages yield more females (Fox et al 1990;Monnerat et al 2002).…”

“…Microplitis plutellae is also a primary larval endoparasitoid of DBM especially in North America. Initially it was listed only from Iowa, Colorado, Idaho, and California, but now it has also been recorded from Utah, South Carolina, New York, Alberta, Saskatchewan, Ontario (Harcourt 1960;Braun et al 2004), Taiwan, Laos and Cambodia . A congeneric species, M. mediator (Haliday) is also known to parasitize DBM and can be quite common in Romania .…”

“…The mature parasitic larva emerges from the membranous area between the fourth and fifth abdominal tergites of the final instar host and spins its own brown, oval cocoon that adheres to any available surface (e.g., stem, leaf, wall of a cage, etc.) a short distance from the dying host (Harcourt 1960;Putnam 1968;Gharuka et al 2004).…”

“…Although both D. insulare and M. plutellae parasitize all four instars of P. xylostella (with very low parasitism of first instars), M. plutellae kills and emerges from fourth instars, whereas D. insulare kills and emerges from the prepupal stage and spins its own cocoon inside the loosely woven cocoon of its host (Harcourt 1960;Putnam 1968). The number of generations per year of both parasitoids corresponds to the number of generations of DBM as one host larva supports only one parasitoid larva (Sourakov & Mitchell 2000).…”