Influência de tricomas do algodoeiro sobre os aspectos biológicos e capacidade predatória de Chrysoperla externa (Hagen) alimentada com Aphis gossypii Glover

Abstract

RESUMOOs tricomas do algodoeiro atuam como um dos fatores de resistência a Aphis gossypii Glover, e podem afetar também seus inimigos naturais, reduzindo a eficiência desses agentes de controle e aumentando o tempo de procura pela presa. Neste trabalho, em condições de laboratório, avaliou-se a influência da densidade de tricomas das cultivares de algodoeiro Antares (pouco pilosa), CNPA 7H (hirsuta) e Deltapine Acala 90 (pilosa) sobre os aspectos biológicos e a capacidade predatória de Chrysoperla externa (Hagen) alimentada com A. gossypii criado em plântulas da cultivar de algodoeiro IAC 22. Verificou-se que a duração e a viabilidade das fases de desenvolvimento de C. externa não foram influenciadas pelos tricomas das cultivares. O período de oviposição de C. externa foi maior quando suas larvas se alimentaram de A. gossypii sobre folhas da cultivar Antares. A capacidade diária e a total de oviposição de C. externa não sofreram influência das cultivares de algodoeiro nas quais essa espécie foi mantida durante a fase larval. Fêmeas de C. externa, alimentadas durante a fase larval com A. gossypii e mantidas sobre folhas da cultivar Antares, apresentaram maior longevidade. Durante o período larval, C. externa consumiu respectivamente, 544,0; 494,3 e 454,8 pulgões, quando mantida sobre folhas das cultivares CNPA 7H, Antares e Deltapine Acala 90. As cultivares de algodoeiro demonstraram compatibilidade com esse predador, o que indica a possibilidade de integração de cultivares resistentes com diferentes níveis de densidade de tricomas com C. externa para controle do pulgão A. gossypii. Palavras-chave: resistência de plantas, pulgão, interação tritrófica, predador. ABSTRACT INFLUENCE OF COTTON TRICHOMES ON BIOLOGICAL ASPECTS AND PREDATORY ABILITY OF CHRYSOPERLA EXTERNA (HAGEN) FED WITH APHIS GOSSYPII GLOVERCotton trichomes, acting as a resistance factor to Aphis gossypii Glover, can also affect its natural enemies, reducing the efficacy of the control agents and increasing prey searching time. The effects of different trichome densities, observed in three cotton cultivars (Antares -low pilosity; CNPA 7H -hirsute and Deltapine Acala 90 -high pilose), on biological aspects and predatory ability of Chrysoperla externa (Hagen), fed on A. gossypii reared on IAC-22 cotton seedlings, were evaluated. Developmental period and viability of C. externa larva were not significantly affected by trichome densities. However, C. externa oviposition period was longer when larva were fed on A. gossypii reared on Antares leaves. Also, daily and total egg numbers laid by C. externa were not influenced by any cotton cultivars on which it was maintained during the larval phase. Highest longevity of C. externa females was observed when they were fed, during the larval phase, on leaves of the lowest pilosity cultivar (Antares). During larval period, C. externa consumed, respectively, 540.0; 494.3 and 454.8 aphids, when it was maintained on CNPA 7H, Antares and Detapine Acala 90 cultivars leaves. Cotton cultivars showed good compatibilities w...

Factors affecting colonization and abundance of Aphis gossypii glover (hemiptera: aphididae) on okra plantations

“…The A. gossypii population attack preferentially in young leaves, which are generally located on the apical parts (CHAU et al, 2005;SANTOS et al, 2003). However, in the present study, we observed higher attack of this insect in the bottom and medium rather than in the apical part of okra plants.…”

“…(CHAU et al, 2005;MEN et al, 2004;RHAINDS & MESSING, 2005;SANTOS et al, 2003;SOGLIA et al, 2002SOGLIA et al, , 2003, leaf N and K, leaf organic compounds analyzed and trichomes were apparently not important in this study. The trichomes (% non-glandular) found in okra were of low density and did not contain toxic compounds, which could present antibiotic and nonpreference effects.…”

“…Rhainds & Messing (2005) Although no significant effects (P > 0.05) of plant age, total rainfall and median temperature on aphid population were observed, in June and October, when plants were 86 and 140 days old respectively, there was a drastic decrease in the insect population, probably due to, besides natural enemies, plant senescence and/or associated with rainy season (total rainfall = March: 189 mm, April: 25 mm, May: 0 mm, June: 24 mm, July: 0 mm, August: 0 mm, September: 32 mm, October: 125 mm and November: 509 mm). High rainfall is an important mortality factor of A. gossypii in the field (MCDONALD et al, 2003;RHAINDS & MESSING, 2005) and this insect is considered to be initial pest due to changes in plant quality as the crop gets older (MEN et al, 2004;RHAINDS & MESSING, 2005;SANTOS et al, 2003;SOGLIA et al, 2002).…”

“…However, in the present study, we observed higher attack of this insect in the bottom and medium rather than in the apical part of okra plants. A plausible explanation, besides leaf areas (RHAINDS & MESSING, 2005;SECHSER et al, 2002), for the non-occurrence of attack preferentially on the apical leaves is that these leaves have more trichomes, which can make locomotion, feeding and reproduction of A. gossypii difficult (SANTOS et al, 2003;SOGLIA et al, 2002SOGLIA et al, , 2003, despite the absence of significant relationship between them.…”

“…Also, plant phenology such as leaf position on plant canopy, plant age, leaf areas, and trichomes besides natural enemies and weather can influence population of A. gossypii (CHAU et al, 2005;338 Ciênc. agrotec., Lavras, v. 31, n. 2, p. 337-343, mar./abr., 2007MEN et al, 2004RHAINDS & MESSING, 2005;SANTOS et al, 2003;SATAR et al, 2005;SECHSER et al, 2002;SOGLIA et al, 2002SOGLIA et al, , 2003. Since effects of such factors on okra plants are little known, the aim of the present investigation was to evaluate the effects of predators, parasitoids, leaf organic compounds, levels of N and K, leaf trichome density, canopy height, plant age, leaf areas, rainfall and temperature on attack intensity of A. gossypii on successive okra plantations under field conditions.…”