Transmission of Nuclear Polyhedrosis Virus by the Parasitoid Microplitis croceipes (Hymenoptera: Braconidae) to Heliothis virescens (Lepidoptera: Noctuidae) on Soybean

1990 ◽  
Vol 19 (2) ◽  
pp. 251-256 ◽  
Author(s):  
S. Y. Young ◽  
W. C. Yearian
1989 ◽  
Vol 24 (4) ◽  
pp. 500-506 ◽  
Author(s):  
S. Y. Young ◽  
W. C. Yearian

Heliothis nuclear polyhedrosis virus (HNPV) transmission by Microplitis croceipes (Cresson) [Hymenoptera: Braconidae] that emerged from HNPV-infected Heliothis virescens (F.) (Lepidoptera: Noctuidae) larvae was investigated in the laboratory and in single plant cage tests on field grown soybean. In the laboratory a small percentage of the M croceipes adults (13.3%) from infected larvae transmitted Heliothis HNPV. The mortality from HNPV in larvae exposed as late second instars to female parasitoids was 20.0%. In a single plant cage test on soybean conducted in the field, however, the percentage of mortality from HNPV in larvae did not differ significantly from that in the control group. When larvae were caged with females that had been artificially contaminated with HNPV up to 79.2% of the H. virescens larvae died of HNPV.


1992 ◽  
Vol 27 (2) ◽  
pp. 126-134 ◽  
Author(s):  
S. Y. Young ◽  
W. C. Yearian

Nabis roseipennis Reuter nymphs that preyed on larvae of the nuclear polyhedrosis virus (NPV) infected velvetbean caterpillar, Anticarsia gemmatalis (Hübner), excreted the virus (AgNPV) for several days thereafter. Based on bioassays, fifth instar and second instar nymphs excreted 84.7 × 105 and 9.7 × 105 polyhedral inclusion bodies (PIB) per nymph, respectively. The AgNPV-contaminated nymphs effectively disseminated the virus via the feces over soybean plants where it served as inoculum to initiate disease in larval populations of A. gemmatalis caged in the field. Larval mortality from AgNPV ranged from 11.4 to 48.5% over treatments in two tests. Larval mortality in treatments where the source of virus inoculum was AgNPV-contaminated fifth instar nymphs was similar to that in treatments where the source of viral inoculum was diseased larvae. Larval mortality resulting from AgNPV dissemination by the nymphs was usually higher in treatments containing fifth instar nymphs than in those with second instar nymphs. Dissemination of NPV by fifth instar nymphs was higher in mixed-age than in uniformed-age A. gemmatalis larval populations. This was not the case with the smaller second instar nymphs.


1991 ◽  
Vol 26 (1) ◽  
pp. 69-75 ◽  
Author(s):  
M. R. Bell

The effects of viral inoculum and incubation period on virus yield in a method of in vivo production of the multicapsid nuclear polyhedrosis virus of Heliothis armigera (Hübner) were examined utilizing Heliothis virescens larvae reared in multicellular containers. Trays of diet were surface contaminated with virus levels ranging from 54 to 2708 polyhedral inclusion bodies (PIB) per mm2 of diet at 7 days after egg infestation. The virus was harvested either at 6 or 7 days after treatment. Within the ranges of this study, the greatest quantity virus was obtained when the diet was inoculated with the 54 PIB level, and the virus was harvested at 7 days. This combination resulted in an average production of 2919 × 109 PIB per tray, with 5.7 × 109 PIB per larvae and 523 collectable larvae per tray. It also represented an increase in polyhedra of 2.43 × 105× compared to the inoculum. The costs of the production were estimated based on prevailing wages and current costs of materials.


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