Cypermethrin, quinalphos, endosulfan and methomyl were bioassayed against strains of Helicoverpa armigera collected from field crops in Andhra Pradesh and Tamil Nadu, South India, during the 1989‐90 and 1990‐91 cropping seasons. In 1989, high levels of resistance to cypermethrin were recorded in strains from cotton in the cotton‐growing regions of Guntur, Andhra Pradesh and Coimbatore, Tamil Nadu, and from pigeon pea near Hyderabad. There was no evidence for resistance to quinalphos or methomyl at that time. In 1990‐91 sampling was more extensive and although tolerance to cypermethrin was lower than the previous season, the survey indicated that pyrethroid‐resistant populations were present throughout much of Andhra Pradesh. Tolerance to quinalphos had increased slightly in 1990‐91, while resistance to methomyl had increased substantially, particularly in the cotton‐growing area of Guntur. Endosulfan tolerance had increased slightly compared to strains tested in 1986‐88 in an earlier study. The geographic and temporal variations in severity of pyrethroid resistance in H. armigera in Andhra Pradesh are believed to arise because of dynamic interactions between local selection pressure and immigration of resistant and susceptible moths at certain times of the year.
Helio this armigera collected in October 1987 from Juzzuru in the coastal cotton growing district of Krishna in Andhra Pradesh (Eastern India) were highly resistant to cypermethrin and fenvalerate and moderately resistant to endosulfan. Prior to this, in 1986, H. armigera in the Hyderabad area were resistant to DDT but not to pyrethroids or endosulfan. By late 1987 these latter populations were highly resistant to pyrethroids and mildly resistant to endosulfan. Concurrently, the resistance to DDT increased. It is suggested that resistant moths from the east coast migrated downwind in a northwesterly direction with the prevailing winds which occur at that time of year. The level of pyrethroid resistance in H. armigera infesting pigeon‐pea and chick‐pea fields around Hyderabad increased steadily up to March 1988. These results are discussed with special reference to the resistance mechanisms likely to be involved.
Virgin females of Distantiella theobroma (Dist.) produced a sex attractant capable of attracting males, which was emitted only during the late afternoon. Females first became attractive 3 to 5 days after the final moult when the first eggs matured in the ovarioles. Few wild males were caught in specially designed traps each containing a virgin female, and females had to adopt a characteristic calling position as a pre‐requisite to male attraction. Female age affected attractiveness: a large catch of males on the day after calling began was followed by a decline before the numbers captured increased to maximum about 9 days later. No males were captured after the 18th day of calling. Few marked males were recaptured, and these in traps closest to the point of release. The capture of wild males was enhanced by a slight breeze but depressed in dim light and rain. The degree of trap exposure to the sun did not significantly affect the numbers captured although the positioning of traps may be important. No sex attractant was found in the related cocoa capsid Sahlbergella singularis. Résumé ÉTUDES SUR L'ATTRACTION SEXUELLE CHEZ LA CAPSIDE DU CACAOYER, DISTANTIELLA THEOBROMA Les femelles vierges de la Capside du Cacaoyer Distantiella theobroma se révèlent produire un attractif sexuel capable d'attirer les mâles; seules les femelles qui prennent une posture caracTÉristique d'appel sont attractives. Cet appel apparaît 3 à 5 jours après la dernière mue et ne se manifeste que dans la fin de l'après‐midi, de 15h30 jusqu'au crépuscule. Les mâles seuls sont alors attirés. Un piège appâte avec une femelle vierge a éTÉ conçu pour capturer vivants les mâles attirés. Pendant deux mois de piègeage sexuel (en Octobre et Novembre 1970) correspondant à 893 jours de piègeage, on a capturé seulement 73 mâles de D. theohroma. On a noTÉ une légère tendance à un accroissement du nombre des captures quand le piège renfermait 2 femelles vierges, au lieu d'une seule, mais la différence n'est pas significative; en outre cellesci mouraient plus précocement. Les captures sont les plus nombreuses le jour même où la femelle commence à appeler, vient ensuite un déclin suivi d'un second maximum du 10e au 13e jour. Il n'y a plus de captures de mâles 18 jours après le début de la manifestation d'appel sexuel, bien que certaines femelles non accouplées continuent à prendre la position d'appel jusqu'à leur mort, soit 34 jours. Deux mâles seulement ont éTÉ recapturés sur approximativement 125 qui avaient éTÉ lâchés à partir d'un arbre fonctionnant comme marqueur radioactif. Ces 2 mâles ont éTÉ capturés dans un des pièges les plus proches du point de lâcher. L'avantage d'une légère brise sur les captures et l'orientation de vol des mâles face au vent suggèrent que ce dernier intervient sur la dispersion d'un attractif chimique. Ce n'est que dans le cas de très faibles éclairements, conséquence de nuages épais habituellement accompagnés de pluie, que la capture des mâles est réduite de façon significative. Les femelles deviennent attractives quand leurs ova...
Prepupae from a population of P. forficalis larvae reared at 16 h photoperiod and 20°C produced a continuous distribution of emerging adults; no clear distinction between diapause and non‐diapause was evident. At 16‐h photoperiod adult emergence distributions from the progeny of individual pairs having different prepupal lengths varied widely. Under photo‐periods of 20 and 24 h all individuals emerged within a few days of each other, following a short prepupal period, and pupal stage of 14 days. At 14 and 12 h photoperiods emergence was protracted and rarely began before 40 days after the start of the prepupal stage. Emergence before 40 days was therefore taken as the criterion for non‐diapause. Under 16 h at 20° pre‐40‐day emergence varied from 10% to over 80%; this photoperiod must therefore be near to critical for P. forficalis. Selections for tendency to diapause and rapid emergence, based on time of emergence at respectively long and short photoperiods, were successful. There was a significant correlation between F1% emergence at 16 h and that of the male parental family at 16 h photoperiod. When the rearing photoperiod, % emergence and prepupal length of both parents and grandparents were examined for their effects on F3 emergence, a multivariate regression analysis showed that all these factors together accounted for 46% of F3 emergence variance at 16 h. All those partial regressions of factors associated with the male parent were significantly correlated with F3 emergence. Possible causes for these relationships were examined and the nature of diapause in P. forficalis and the significance of its intrinsic variation are discussed. Résumé NATURE HÉRÉDITAIRE DE LA DIAPAUSE ET SON INDUCTION PAR LA PHOTOPÉRIODE CHEZ PIONEA FORFICALIS (LEPIDOPTERA PYRALWAE) Dans une population naturelle de larves de P. forficalis élevées sous une photopériode de 16 à ä 20°, l'émergence des adultes se produit à un rythrne continu, présentant d'abord un maximum après une durée d'enviroo 3 semaines de la périod pré‐nymphale et nymphale, et s'achevant par quelques éclosions sporadiques étalées sur plus de 30 semaines. II n'y a done pas ici de distinction nette entre individus à diapause et individus. sans diapause. La descendance de couples éléves à 16 h montrait une grande variation, dans la proportion des émergences précoces et dans la distribution de ces emergences; celle‐ci tendait Dependant à être parfois bimodale. Pour une photopériode de 20 et 24 b, tous les adultes sont éclos dans un délai de 30 jours après le début du Stade pré‐nymphal, alors qu'avec une photopériode de 12 et 14 h il n'y a pas ou très peu d'émergence d'adultes avant 40 jours. Avec une photopériode de 16 h la proportion d'émergence avant 40 jours varie de moins de 10% ä plus de 80%; cette photopériode représents done une valeur critique. La durée d'émergence avant on après 40 heures servira done de enTÈre pour distinguer lee conditions de non diapause ou de diapause. Il a éTÉ possible de sélectkmner la tendance à la diapause ou le développement sans diapau...
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