Data/hora: 13/06/2024 06:30:12

Biblioteca(s): | Embrapa Soja.
Data corrente: | 23/10/2009
Data da última atualização: | 27/04/2011
Autoria: | NEWMAN, G. G.
Afiliação: | GARY GRANT NEWMAN.
Título: | The biology of Entomophthora gammae and its effect on populations of the soybean looper, Pseudoplusia includens, in South Carolina.
Ano de publicação: | 1975
Fonte/Imprenta: | 1975.
Páginas: | 84 f.
Idioma: | Inglês
Notas: | Dissertação (Doutorado) - Clemson University, Clemson.

Conteúdo:

Larval populations of Pseudoplusia includens (Walker) were monitored on soybeans and sweet potatoes in 1973 and on soybeans in 1974. Mortality was caused by the pathogens Entomophthora gammae (Weiser), Nomuraea rileyi (Farlow) Samson, and a nuclear polyhedrosis virus; and the parasitoids Copidosoma truncatellum (Dalman) and Lespesia alletiae (Riley). When looper populations were high, E. gammae was the most important natural control agent, often causing disease incidence exceeding 70%. In fields where looper populations were low, incidence of E. gammae was reduced. 
Incidence of E. gammae infection was higher in loopers collected by the sweep-net method of sampling than in those collected by the plant-shake method. Incidence of N. rileyi was not significantly different in larvae collected by the two sampling methods. 
The conidial form of  E. gammae killed its host in 4 days at temperatures approximating those in the field. The resting spore form had an incubation period of 5 to 8 days. Larvae infected with the conidial form of the pathogen died within a rather precise time period of the early evening (6-10 PM). Sporulation began on fresh cadavers just prior to midnight and continued until after dawn. Larvae infected with the resting spore form died at various times. 
As field epizootics of E. gammae progressed, high numbers of the conidial form gave way to high numbers of the resting spore form. Ratios of conidia to resting spores were not significantly altered when infected larvae were exposed to shortened photoperiod or to cooler temperatures. Size or age of infected larvae appeared to influence spore development, conidia being predominant in small larvae (>1.5cm) and resting spores in large larvae (<2.5 cm).
The fungus was able to sporulate at relative humidities of 80-100% but was inactivated by humidities of 50% and below. Conidia germinated at 98 and 100% RH but could not survive exposure to humidities below 75%. E gammae sporulated and germinated at 10-26.7ºC but could not survive prolonged exposure to 32.2 or 37.8ºC. When cadavers were frozen, the pathogen was inactivated in less  than 1h.
Exposure to the pesticides carbaryl, methomy1, methy1, parathion, DimilinR, and benomyl caused conidial germination to be reduced. Dimilin was less inhibitory than the other chemicals.

Thesagro: | Entomologia.
Categoria do assunto: | O Insetos e Entomologia
Registro original: | Embrapa Soja (CNPSO)
Exemplares: | CNPSO - (29806-1) - ADD - TS - PP - TS 45/1975 -  - TS 45/1975 - DIS