NUCLEAR POLYHEDROSIS VIRUS TRANSMISSION IN MULTIPLE GENERATIONS OF ANTICARSIA GEMMATALIS (LEPIDOPTERA: NOCTUIDAE) CAGED ON SOYBEAN

1989 ◽  
Vol 24 (1) ◽  
pp. 133-141
Author(s):  
S. Y. Young ◽  
W. C. Yearian

Transmission of a nuclear polyhedrosis virus (AgNPV) of the velvetbean caterpillar, Anticarsis gemmatalis Hübner, in multiple generations on caged soybeans was examined. Introduction of primary infected larvae into larval populations on soybean resulted in low levels of mortality in the initially uninfected population in generation one. Larval mortality levels increased in succeeding generations and were higher in treatments with greater larval population density. The increase in epizootic development was much less, however, when the plants were not infested for one larval generation. AgNPV concentrations on foliage and in soil generally reflected the mortality levels from AgNPV in the respective treatments.

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.


1997 ◽  
Vol 26 (1) ◽  
pp. 115-120 ◽  
Author(s):  
Lauro Morales ◽  
Flávio Moscardi ◽  
Daniel R. Sosa-Gómez ◽  
Fábio E. Paro ◽  
Ivanilda L. Soldorio

Boric acid concentrations (0.02,0.03,0.045,0.067 and 0.101 g/100 ml of diet) were evaluated in combination with the Anticarsia gemmatalis Hüb. nuclear polyhedrosis virus (AgNPV) for enhanced virali activity against the insect. Seven days after inoculation, the median lethal concentration (LC50) was 1.52 x 10(5) for the AgNPV alone and 7.95 x 10² for the NPV mixed with 0.045g of boric acid/100 ml of diet. At subsequent evaluation dates (9,11 and 14 days after inoculation) LC50's for NPV+boric acid were ca. 4x lower than those observed for the NPV alone. The median lethal time (LT50) was 13.6 days when the NPV was used alone, while, when in mixture with increasing concentrations of boric acid, LT50 values ranged from 13.7 days (boric acid at 0.02g/100 ml of diet) to 7.4 days (boric acid at 0.101 g/ml of diet). Therefore, boric acid added to the AgNPV significantly increased A. gemmatalis larval mortality and shortened mortality time by the pathogen.


1988 ◽  
Vol 120 (10) ◽  
pp. 887-892 ◽  
Author(s):  
Einar Olofsson

AbstractAn outbreak of Neodiprion sertifer (Geoffroy) was studied in a lodgepole pine plantation. It was the first tree generation on a 60-ha peatland area. The nuclear polyhedrosis virus (NPV) of N. sertifer was not found in the larval population or in the soil. Within a 1.7-ha experimental plot, a 0.35-ha block was treated with NPV and the ensuing epizootic was studied during three successive summers. The treatment caused 50% mortality of fourth- and fifth-instar larvae. The NPV persisted in the treated block and gradually dispersed into the adjacent blocks. After 2 years, larval mortality was 78% in the treated block and 21% at a distance of 110–125 m from it. The larval population remained at a high level and the outbreak expanded from the experimental plot to the entire 60-ha area in the years following the virus treatment, but few virus-diseased colonies were observed outside the experimental plot. Thus, the capability of this NPV to persist and spread was not sufficient to control and contain the sawfly outbreak.


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.


1988 ◽  
Vol 23 (4) ◽  
pp. 394-398 ◽  
Author(s):  
T. J. Kring ◽  
S. Y. Young ◽  
W. C. Yearian

The potential for transmission of a nuclear polyhedrosis virus of Anticarsia gemmatalis Hübner (AgNPV) by the striped lynx spider, Oxyopes salticus Hentz, was examined in the laboratory. Activity of the virus in excreta of O. salticus which had fed on an AgNPV - infected A. gemmatalis larva was bioassayed on alternate days over a 14 - day period. Oxyopes salticus excreta contained an average of 3.3 ± 2.2 × 104 polyhedral inclusion bodies per spider over the test period, with 95% of the active virus excreted within 24 hrs of ingestion. The amount of virus excreted was significant because only a mean of 1.2% of the total virus present in infected larva was consumed by the spider. The results suggest that O. salticus, and probably other spider predators in soybeans, may be important in dissemination of AgNPV in A. gemmatalis populations.


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