The susceptibility of Heliothis armigera larvae to three nuclear polyhedrosis viruses

Abstract

SUMMARY Quantitative bioassay techniques were used to measure the susceptibility of Heliothis armigera to three nuclear polyhedrosis viruses (NPVs): H. armigera singly‐enveloped NPV (HaSNPV), H. zea SNPV (HzSNPV) and H. armigera multiply‐enveloped NPV (HaMNPV). Viruses were identified by EcoRI restriction endonuclease analysis. Electrophoretic profiles of DNA fragments revealed that the HaSNPV isolate was a previously undescribed genotypic variant. Bioassays with neonate and 6‐day‐old larvae measured small but significant differences in virulence between the three viruses. HzSNPV was the most virulent for neonate larvae with a median lethal dose (LD50) of five polyhedra. HaMNPV was least virulent for 6‐day‐old larvae, with a LD50 of 1400 polyhedra compared with 640–670 polyhedra for HaSNPV and HzSNPV. In addition, the median lethal time (LT50) for infection with HaMNPV in neonate larvae was approximately 1·7 days longer than for the other viruses. Although they varied in virulence, each of the three viruses was sufficiently virulent to have considerable potential as a microbial control agent of H. armigera.

Diversity of Iberian nucleopolyhedrovirus wild-type isolates infecting Helicoverpa armigera (Lepidoptera: Noctuidae)

“…MTD values were also lower than those obtained by Teakle et al (1985), who reported a LT 50 value of 4.1-4.5 days for second instars. In contrast, our results were more similar to those of Williams and Payne (1984) with neonates and third-instar larvae.…”

Variation in Cydia pomonella Granulosis Virus Isolates and Physical Maps of the DNA from Three Variants

“…Although C. pomonella is a widely distributed pest which is highly susceptible to infection with GV, there appears to be very little genotypic variation between virus isolates that have so far been obtained, unlike the situation with some other baculoviruses where many variants have been isolated, e.g.A, caliJbrnica multiple nucleocapsid NPV (Smith & Summers, 1979), Heliothis single and multiple nucleocapsid NPVs (Gettig & McCarthy, 1982;Williams & Payne, 1984), SpodopteraJkugiperda multiple nucleocapsid NPV (Maruniak et al, 1984) and Pieris GV (Crook, 1981 a, b). This may indicate that CpGV has a particularly stable genome but it seems more likely that most of the virus in laboratories today has originated knowingly or unknowingly from a single isolation made in Mexico in 1963.…”

Biochemical identification and comparative insecticidal activity of nucleopolyhedrovirus isolates pathogenic for Heliothis armigera (Lep., Noctuidae) larvae

“…The cotton bollworm Heliothis armigera is an economically important pest of various food and fibre crops in Southern Europe and in many other areas of the world ( Cayrol 1972). Several single and multiple NPV (HearMNPV and HearSNPV) have been isolated in different geographical regions from H. armigera larvae ( Kelly 1980 ; Gettig 1982 ; Hamm 1982; Flattery 1983; Ignoffo 1983 ; Williams 1984) . Some of these isolates showing different DNA restriction endonuclease (REN) profiles also differed significantly in their insecticidal activity ( Hughes 1983 ; Williams & Payne 1984).…”