Sequencial passages of the multiple nucleopolyhedrovirus of Anagrapha falcifera(Kirby) (Lepidoptera: Noctuidae) (AfMNPV) in Spodoptera cosmioides (Walker) (Lepidoptera, Noctuidae)

O objetivo deste trabalho foi avaliar os efeitos de múltiplas passagens do nucleopoliedrovírus de Anagrapha falcifera (AfMNPV) na biologia de lagartas de S. cosmioides, em diferentes momentos de infecção, e as alterações histológicas que o vírus poderia causar no intestino médio da lagarta, buscando correlacionar os efeitos histopatológicos e a eficácia deste vírus, como um potencial controle biológico desta praga. As lagartas foram infectadas com sete dias de desenvolvimento, utilizando três passagens diferentes do AfMNPV em S. cosmioides (F1, F4 e F7, sendo a primeira, quarta e sétima passagens, respectivamente) e o tratamento controle. Foram realizados, concomitantemente, ensaios de biologia, comparados com os mesmos tratamentos, para analisar o comportamento e mortalidade das lagartas. A morfologia do intestino médio foi comparada entre as lagartas infectadas e as não infectadas. Os tubos digestivos foram coletados com 24, 72 e 144 horas de infecção (20 tubos/tratamento/tempo de infecção). Após a coleta, os tubos foram fixados em Karnovsky, processados, corados com Hematoxilina-Eosina e analisados ao microscópio de luz. Os resultados da biologia dos tratamentos F4 e F7, mostraram uma redução drástica na locomoção e alimentação das lagartas, a partir do quarto dia pós-infecção e maior taxa de mortalidade cumulativa, em relação ao controle e F1. Morfologicamente, todos os tratamentos causaram alterações no intestino médio das lagartas de S. cosmioides, nos três tempos de infecção, sendo que as maiores alterações ocorreram no epitélio. O AfMNPV, nas três passagens testadas em S. cosmioides, provocou alterações comportamentais e morfológicas no intestino médio, indicando que pode ser um promissor agente de controle biológico desta praga.

Fluorescent Brighteners Can Enhance or Inhibit the Nucleopolyhedrovirus of the Diamondback Moth (Lepidoptera: Plutellidae)2

The nucleopolyhedrovirus of the diamondback moth, Plutella xylostella (L.), (PxMNPV) was the most potent of three viruses tested against this insect. The potency of PxMNPV could be increased by the addition of certain diaminostilbene disulfonic acid-derived fluorescent brighteners, including Blankophor P167® at a concentration of 1%. Other fluorescent brighteners, including Blankophor HRS® at 1%, reduced the activity of PxMNPV, though lower concentrations of Blankophor HRS (0.25 to 0.5%) enhanced activity. In contrast, Blankophor HRS at 1% enhanced the nucleopolyhedrovirus of the celery looper, Anagrapha falcifera (Kirby), (AfMNPV) against the diamondback moth. Similar results were found in the corn earworm, Helicoverpa zea (Boddie), and the beet armyworm, Spodoptera exigua (Hübner), which are also susceptible to both PxMNPV and AfMNPV. Consumption of foliage treated with Blankophor HRS (0.5 to 1.0%) did not differ from that of foliage treated with similar concentrations of Blankophor P167. These results indicate a negative effect of higher concentrations of Blankophor HRS on PxMNPV, rather than on the host insect.

Enhancement of Nucleopolyhedrovirus Activity in Helicoverpa zea (Boddie) and Pseudoplusia includens (Walker) Larvae with a Fluorescent Brightener

The enhancement of nucleopolyhedrovirus (NPV) activity by Tinopal® LPW (Tinopal), a stilbene fluorescent brightener, was compared in Helicoverpa zea (Boddie) and Pseudoplusia includens (Walker) using an on-diet bioassay method. Enhancement of the homologous NPV of each species was compared with three heterologous NPV that have a broad host range. In H. zea, the LC50 of H. zea NPV (HzSNPV) alone was 128 occlusion bodies (OBs)/cup, and the LC50 of it and Heliothis armigera NPV (HaMNPV) did not differ significantly. The activity of both viruses improved 18.6 fold when the OB suspension contained 1.0% Tinopal. The LC50s of Autographa californica NPV (AcMNPV) and Anagrapha falcifera NPV (AfMNPV) without Tinopal in H. zea were greater than that of HzSNPV. However, the increase in activity of AcMNPV and AfMNPV at the highest concentrations of Tinopal was two to three fold greater than the increase in activity of HzSNPV. The LC50 of P. includens NPV (PiSNPV) (856 OBs/cup) alone in P. includens was similar to that of AfMNPV and AcMNPV, and much less than that of HaMNPV (19,947 OBs/cup). The addition of Tinopal to the treatment suspension of all four viruses resulted in significantly lower LC50s at all Tinopal concentrations in P. includens. The highest concentration of Tinopal (1.0%) in the OB suspension lowered the LC50 of PiSNPV by 142.7 and AfMNPV by 89.7 fold. Tinopal in the OB suspension lowered the LC50 of AcMNPV and HaMNPV, but they remained less effective than PiSNPV with Tinopal. HaMNPV at all concentrations of Tinopal was much less active in P. includens than the other viruses with or without Tinopal.