Photoperiodism and seasonality in neotropical population of Plutella xylostella L. (Lepidoptera: Yponomeutidae)

Abstract

Fotoperiodismo e Sazonalidade em População Neotropical de Plutella xylostella L. (Lepidoptera:Yponomeutidae)RESUMO -Populações neotropicais de Plutella xylostella L. possuem ciclos sazonais de crescimento e declíneo e a migração é um fator-chave na geração da dinâmica populacional. Devido à previsibilidade sazonal das oscilações populacionais, o fotoperíodo poderia agir como o sinal que desencadea o comportamento migratório do inseto. Migrações de insetos são geralmente precedidas por diapausa reprodutiva, uma típica resposta fotoperiódica caracterizada por alterações morfológicas, fi siológicas e comportamentais que possibilitam discriminar as formas migratórias das não-migratórias. Neste estudo, foi testado se o desenvolvimento pré-imaginal e reprodutivo de P. xylostella, proveniente de Minas Gerais, é inibido por fotoperíodos equivalentes aos comprimentos de dias em que ocorrem as fases de crescimento ou de declínio das populações naturais. Nenhuma evidencia de resposta fotoperiódica foi encontrada para os insetos criados em laboratório sob cinco regimes constantes de fotoperíodos, variando de oito a dezesseis horas-luz-dia. Não houve variação signifi cativa na sobrevivência e na duração dos estágios de ovo, larva e pupa. O peso das pupas também não foi afetado, assim como o tamanho, a fecundidade e a longevidade dos adultos. Embora algumas espécies de insetos possuam respostas fotoperiódicas geografi camente diferenciadas, a sugestão de alguns autores de que a cosmopolita P. xylostella responde ao fotoperíodo em regiões de clima temperado foi questionada. Os dados experimentais não suportaram a hipótese de que a sazonalidade migratória e populacional de P. xylostella dependem do fotoperíodo como sinal de anúncio de mudanças temporais na qualidade do habitat.PALAVRAS-CHAVE: Diapausa, dinâmica populacional, fotoperíodo, migração ABSTRACT -Neotropical populations of the diamondback moth Plutella xylostella L. have seasonal cycles of growth and decrease, and moth migration plays a fundamental role in generating such population dynamics. Since the oscillation of these populations is predictable, photoperiod might operate as a signal that triggers the migratory behaviour of the insect. Migration in insects is usually preceded by reproductive diapause, a photoperiodic response that can be characterised by morphological, physiological and behavioural alterations that permit to discriminate between migratory and nonmigratory forms. In this study, I tested whether the pre-imaginal and reproductive development of P. xylostella from Minas Gerais (Brazil) is affected by artifi cial day-lengths that are equivalent to the periods of natural population growth or decrease. No evidence of photoperiodic response was found for the insect reared in laboratory on fi ve different constant photoperiods, from 8h to 16h of light per day. There was no signifi cant variation in survival and duration of egg, larva, and pupa stages or in pupal weight, adult size (forewing length), fecundity, and longevity. Although some species have geog...

Development and Age-Specific Mortality of Diamondback Moth on Brassica Host Plants: Pattern and Causes of Mortality Under Laboratory Conditions

“…The effect of different canola cultivars on developmental time and adult longevity of P. xylostella (Tables 2 and 3) were similar to those reported for P. xylostella on canola (Ebrahimi et al 2008, Golizadeh et al 2009), cabbage (Campos 2008), and some Brassica vegetables (Syed and Abro 2003) in previous studies. Our developmental time data were much lower than those reported for P. xylostella on cabbage (28.84 Ϯ 1.85 d) (Ahmad et al 2008).…”

“…Highest peak in each graph reveal the early stage cause-speciÞc mortality (d x is part of original cohort dying between two consecutive days). study were greater than those reported by Campos (2008) for cabbage (4.4 d) and was similar to those reported by Golizadeh et al (2009) on canola PF under the same environmental conditions (male longevity, 6.40; female longevity, 8.33 d), by Ahmad et al (2008) for cabbage (8.46 d), and these differences can be attributed to host plant type, although different geographical region may be a signiÞcant factor.…”

“…The mean larval period was 8.29 d, which is lower than the value reported by Ahmad et al (2008) on cabbage (11.29 d), by Ebrahimi et al (2008) for rapeseed (11.03 d), and by Syed and Abro (2003) for some Brassica vegetable (Ͼ9 d), whereas our data were greater than those reported by Golizadeh et al (2009) for canola PF (7.82 d), and similar to values reported by Campos (2008) on cabbage (8.8 d). These differences may be due to physiological differences depending on the type of the host plant, genetic variation as a result of laboratory rearing or variation due to geographic sources of the pest.…”

The Biology and Ecology of the Diamondback Moth, Plutella xylostella (L.) in Eastern Ontario Revisited

“…Atwal (1955) and Shirai (1993) found that larval development was slower under shorter (9:15 hours, (Atwal, 1955;Campos, 2008). Although studies in the past have demonstrated extended development time and decreased fecundity as a result of photoperiod, Campos (2008) proposed that indirect effects of photoperiod is the likeliest explanation for these observations. In addition, there is the potential for the effects to be population dependent; the effects of photoperiod should be revisited in the context of temperate and tropical populations as well as, overwintering.…”

“…The consensus in the literature is that the diamondback moth does not overwinter in diapause (Hardy, 1938;Frost, 1949;Atwal, 1955;Harcourt and Cass, 1966;Butts, 1979;Smith and Sears, 1982;Kimura et al, 1987a;Saito, 1994b;Campos, 2008;Kim et al, 2015); instead it likely survives unfavourable conditions in a state of quiescence Campos, 2008). This is demonstrated by: (1) the slowing of development in response to decreasing temperature with no indication of arrested development (Atwal, 1955;Liu et al, 2002); (2) the ability to become active immediately when placed back in favourable conditions despite long durations at 0…”