Development, reproduction, voltinism and host synchrony of Meteorus trachynotus with its hosts Choristoneura fumiferana and C. rosaceana

Abstract

The form and variability of temperature‐dependent development responses were measured for the braconid parasitoid Meteorus trachynotus (Vier.), developing in Choristoneura fumiferana (Clem.) and C. rosaceana (Harr.). It was found that parasitism reduces the duration and variability of postdiapause development in C. rosaceana larvae, and that the development of the parasitoid does not resume until its host emerges from diapause. M. trachynotus development and entry into diapause are controlled by the host. In large, nondiapausing hosts, the parasitoid can complete one generation in about 348 degree‐days above 5.9 °C. Male and female adults live an average of 22.0 and 23.8 days at 20 °C, and the preoviposition period is 1.7 days. Total fecundity averages 194.2 eggs per female and is reduced considerably by low host density. Under our experimental conditions, female M. trachynotus lay a maximum of 14.3 eggs per day, with a maximum of 3.7 eggs per host, on average. Simulations based on degree‐day accumulation in 13 locations in eastern Canada showed that the parasitoid was well synchronized with its two alternative hosts, that M. trachynotus could complete three generations in most locations, and that voltinism was essentially determined by entry of C. rosaceana larvae into diapause. Overlap between adult parasitoids and larvae of the spruce budworm is incomplete, and inadequate synchrony seems to be an important aspect of the ecological interactions between these two organisms. Résumé Nous avons mesuré la forme et la variabilité des réactions de cause à effet entre la température et le développement de la braconide Meteorus trachynotus (Vier.) se développant à l'intérieur de larves de Choristoneurafumiferana (Clem.) et de C. rosaceana (Harr.). Le parasitisme réduit la durée et la variabilité de la postdiapause de C. rosaceana, et le développement du parasitoîde ne reprend qu'une fois l'hôte émergé de diapause. Le développement et l'entrée en diapause de M. trachynotus sont sous le contrôle de l'hôte. Dans des larves‐hôtes agées et non diapausantes, le parasitoîde peut engendrer une génération en moins de 348 degrés‐jours au‐dessus de 5,9 °C. Les adultes mâles et femelles vivent en moyenne 22,0 et 23,8 jours à 20 °C, et la période de préoviposition est de 1,7 jour. La fécondité totale est de 194,2 oeufs par femelle, et une faible densité d'hôtes la réduit considérablement. Dans nos conditions expérimentales, les femelles de M. trachynotus pondent au plus 14,3 oeufs par jour, la moyenne maximale étant de 3,7 oeufs par hôte. Des simulations basées sur l'accumulation de degrés‐jours pour 13 endroits dans l'est du Canada ont indiqué que le parasitoîde est bien synchronisé avec ses deux hôtes alternants, que M. trachynotus peut engendrer jusqu' à trois générations par année dans la plupart des endroits, et que son voltinisme est déterminé essentiellement par l'entrée en diapause des larves de C. rosaceana. Le chevauchement entre la période de vol des adultes du parasitoîde et celle de la disponibilité des larves ...

Causes of polymorphic melanism and its thermoregulatory function in a parasitoid wasp Meteorus pulchricornis (Hymenoptera: Braconidae)

“…In contrast, because high body temperature has been shown to have a negative effect on adult survival in a related species Meteorus trachynotus Viereck (Thireau & Regniere, 1995), being light coloured in summer would presumably be to some extent advantageous in terms of extending longevity. The temperature-dependent melanism observed in this species probably plays a significant role in thermoregulation, with basking during cool conditions.…”

“…A better understanding of the effects of body colour on the thermoregulation and activity of natural enemies is important for successful biological control and the effects of ambient temperature on flight activity (Barbosa & Frongillo Jr., 1977;Cox et al, 2007) and adult longevity (Thireau & Regniere, 1995) have been investigated in parasitoid wasps. It is well-known that some parasitoid wasps show a temperature dependent phenotypic variation in body colour (Genieys, 1925;Narayanan et al, 1954;Shu-Sheng & Carver, 1982;Quicke, 1997;Bernardo et al, 2007), which might indicate that the colour of the body could be important in thermoregulation.…”

Exigências térmicas de Brevicoryne brassicae e previsão de picos populacionais

“…As temperaturas utilizadas nesse estudo foram registradas na Estação Agroclimatológica da FCAV/Unesp. A precisão do modelo de graus-dia empregado foi estimada de duas maneiras: a) comparando-se os resultados da previsão do modelo com o tempo do desenvolvimento da fase ninfal nos experimentos em campo, que foi contado em dias, desde o surgimento das ninfas de primeiro ínstar até o dia em que 50% atingiram a fase adulta; b) estimandose a porcentagem do erro entre a ocorrência de adultos prevista pelo modelo e a observada no campo (West & Laing, 1984). O erro foi estimado pela fórmula: E = 100(GDA -K)/K, onde GDA: graus-dia acumulados e K: constante térmica de B. brassicae.…”

“…Cabe ressaltar que modelos de graus-dia têm sido úteis na previsão de ocorrência de adultos de insetos, possibilitando a indicação mais precisa da época de controle ou de amostragem (Wilson & Barnett, 1983), na construção de modelos de simulação por computador (Higley et al, 1986) e no entendimento de interações ecoló-gicas de insetos-praga e de inimigos naturais (Raffa et al, 1992;Thireau & Regniere, 1995).…”

Temperature-dependent survival, development, and adult longevity of the koinobiont endoparasitoid Venturia canescens (Hymenoptera: Ichneumonidae) parasitizing Plodia interpunctella (Lepidoptera: Pyralidae)

“…This result is justified by the fact that low temperatures reduce metabolic rate of insects and as a result, adults survive for a longer period of time in relation to adults that live in habitats with higher temperatures (Davidowitz and Nijhout 2004). In the case of the parasitic wasp Meteorus trachynotus (Hymenoptera: Braconidae), female adults lived for a significantly longer period of time when reared at 15°C (40 days) compared to those reared at 30°C (10 days) (Thireau and Régnière 1995). The same trend was observed to adult individuals of the egg parasitoid Trichogramma cacoeciae (Hymenoptera: Trichogrammatidae), which lived for a shorter period of time as temperature increased (Pizzol et al 2010).…”