ABSTRACT
Cotton aphid (Aphis gossypii) is a key pest of cotton crop. The indiscriminate use of insecticides and pesticides during 1930’s and latter to control insects pests, developed resistance in cotton aphid against these chemicals resulting in outbreak of this pest. Cotton aphid has a major impact on quality and yield of cotton which emphasizes the need to manage this notorious pest. The main goal of this review is to highlight various strategies viz., biological, chemical and cultural control for cotton aphid management. The selection of suitable control strategy is made on by viewing the severity of cotton aphid outbreak. Furthermore, the role of transgenic crops in lowering cotton aphid population is also described. However, the preservation of the cotton aphid's natural enemies could be an ecologically sustainable method of maintaining the aphid population below threshold level.
ABSTRACT
Objective To investigate the existence of genetic divergence of sympatric populations of Anopheles sinensis of different feeding preferences based on the rDNA-ITS2 sequence differences. Methods A large number of wild anopheles popu-lations were trapped all night by man-baited net and calf-baited net that had been set up between high-density natural villages of An. sinensis populations and vector-breeding sites,from which two groups of An. sinensis were separated by morphological iden-tification and brought back to the lab for conventional breeding. A large closed greenhouse which temperature and humidity was appropriate was selected as research settings of mark-release-recapture methods by female mosquitoes ,in the center of which above An. sinensis populations baited by man and calf and respectively correspondingly marked by red and yellow phosphors were released in together,in each side of which An. sinensis were recaptured simultaneously by man-baited net and calf-baited net. An. sinensis populations trapped by man twice were brought back to the lab and bred with man-blood,correspondingly ones trapped by calf with calf-blood. Man-preferring and calf-preferring strains were screened respectively from An. sinensis which had been baited by man and calf by the mark-release-recapture methods after parent and F1 mosquitoes,and sequencing and aligning of both rDNA-ITS2 were conducted via PCR amplification. Results The recapture ratios of wild parental mosquitoes An. sinensis of man-preferring group by man-baited net and calf-baited net were 54.07%(339/627)and 45.93%(288/627)re-spectively,and ones of calf-preferring group by man-baited net and calf-baited net were 58.01%(409/705)and 41.99%(296/705)respectively. Two groups of parental mosquitoes trended towards selecting the original blood hosts in host-seeking prefer-ence(χ2=19.42,P<0.01). The recapture ratios of F1 mosquitoes An. sinensis of man-preferring group by man-baited net and calf-baited net were 63.43%(765/1 206)and 36.57%(441/1 206),and ones of calf-preferring group by man-baited net and calf-baited net were 68.22%(1 039/1 523)and 31.78%(484/1 523). Two groups of F1 mosquitoes had more significant characteris-tics of selecting the original blood hosts in host-seeking preference(χ2=271.69,P<0.01)and showed the genetic differentia-tion phenomenon,but the results of sequencing and aligning of the rDNA-ITS2 via PCR amplification showed no difference in base sequence between the two strains and both were 469 bp. Conclusions The genetic divergence based on the rDNA-ITS2 se-quence does not happen in An. sinensis sympatric populations of different feeding preferences.
ABSTRACT
The importance of age and feeding on the performance of Cephalonomia stephanoderis (Hymenoptera, Bethylidae), a parasitoid of the coffee berry borer, Hypothenemus hampei (Coleoptera, Curculionidae) was investigated in the laboratory. Groups of female parasitoids were subject to the following treatments: a group fed during one, five and ten days after emergence of adults with coffee borer larvae; another group fed only with honey solution during five days after emergence; and as a control, a third group was kept without food for five days. At the end of each treatment, survivorship, parasitoid activity (walking and flying capacity in an arena), search capacity for finding coffee borer-infested berries, host feeding and oviposition (on immature hosts), were assessed. Unfed females showed a significant decrease in survivorship compared to individuals that were fed. The type of meal (insects or honey) did not significantly influence parasitoid activity, search and oviposition capacities. Females fed with honey solution significantly consumed less immature coffee borers. Younger females (one day old) walked and flew out of the arena significantly faster than older ones (5 and 10 days old). Implications of these results are discussed on the performance of C. stephanoderis as a biological control agent of the coffee berry borer.
A importância da idade e da alimentação no desempenho de Cephalonomia stephanoderis (Hymenoptera, Bethylidae) parasitóide da broca-do-café, Hypothenemus hampei (Coleoptera, Curculionidae) foi investigada em laboratório. Grupos de parasitóides fêmeas foram submetidos aos seguintes tratamentos: um grupo alimentado durante um, cinco e 10 dias após a emergência dos adultos sobre as larvas da broca-do-café; outro grupo foi alimentado apenas com uma solução de mel, durante cinco dias após a emergência; e como controle, um terceiro grupo foi mantido sem alimento por cinco dias. No final de cada tratamento de sobrevivência, a atividade do parasitóide (capacidade de andar e voar numa arena), a capacidade de busca (de encontrar frutos de café infestados com a broca), consumo do hospedeiro e oviposição (em hospedeiros imaturos), foram avaliados. Fêmeas em jejum mostraram uma diminuição significativa na sobrevivência de indivíduos em relação à alimentação. O tipo de alimento (insetos ou mel) não influenciou significativamente a atividade de busca do parasitóide e capacidades de oviposição. As fêmeas alimentadas com solução de mel consumiram significativamente menor número de imaturos da broca-do-café. Fêmeas mais jovens (um dia) andaram e voaram da arena significativamente mais rápido que as mais velhas (5 e 10 dias de idade). Implicações desses resultados são discutidas sobre o desempenho de C. stephanoderis como um agente de controle biológico da broca-do-café.
ABSTRACT
Host feeding plants of adult boll weevils (Anthonomus grandis Boheman) were determined within the period: January 1997 - December 1999. This took place through the identification of pollen grains, isolated from the digestive tracts of boll weevils captured in pheromone traps placed in a transect line which passes through the localities of Montecarlo, San Ignacio, Candelaria and the Capital in the province of Misiones. Cotton has not been cultivated for five years in that province, nevertheless important populations of weevils still remain during the whole year. About 1,360 weevils were dissected and 5,325 pollen grains were found; these were assigned to 28 species. Only those that presented percentages above 1%, which were 20 (4,183 pollen grains), were used. They belonged to five botanical families: Malvaceae, Compositae, Solanaceae, Euphorbiaceae and Leguminosae. Pollen of alternative plants provides the necessary energy for the survival of adult weevil in the absence of cotton pollen. The variation in the levels of relative abundance of pollen was analyzed with the study of the time of capture, sex, color, type of corporal fat, and reproductive status, using a log linear model (P<0.01).The following third order significant interactions were observed: time of capture x sex x reproductive status; color x corporal fat x reproductive status; levels of pollinic abundance x corporal fat x reproductive status. The ingesta level varied significantly with the corporal fat and the reproductive status, which are some determinants of the physiologic status of adult weevils. The grouping and ordering analyses showed the period of time, selectivity and use of the availability of pollen, since gender and species varied in the different seasons of the year, but they always belonged to the five mentioned families.
Se determinaron las plantas hospedantes alimenticias del picudo del algodonero adulto (Anthonomus grandis Boheman) en el período enero 1997- diciembre 1999. La misma se llevó a cabo mediante la identificación de los granos de polen aislados de los tractos digestivos de picudos capturados en trampas con feromonas ubicadas en una transecta que atraviesa los departamentos de Montecarlo, San Martín, San Ignacio, Candelaria y Capital de la provincia de Misiones, Argentina. Esta provincia no cultiva algodón desde hace cinco años, pero mantiene importantes poblaciones de picudo durante todo el año. Se disecaron 1360 picudos y se hallaron 5325 granos de polen asignados a 28 especies. Solo se utilizaron las que presentaron porcentajes superiores al 1%, que fueron 20 (4183 granos de polen), pertenecientes a cinco familias: Malvaceae, Compositae, Solanaceae, Euphorbiaceae y Leguminosae. El polen de plantas alternativas provee de la energía necesaria para la sobrevivencia del picudo adulto en ausencia de polen de algodón. Se analizó la variación en los niveles de abundancia relativa de polen, a través del estudio de la estacionalidad, sexo, color, tipo de grasa acumulada, y estado reproductivo, usando un modelo loglinear (P< 0,01). Se observaron las siguientes interacciones significativas de tercer orden: época de captura x sexo x estado reproductivo; color x grasa corporal x estado reproductivo; nivel de abundancia polínica x grasa corporal x estado reproductivo. El nivel de ingesta varió significativamente con la grasa corporal y el estado reproductivo, que son algunas determinantes del estado fisiológico de los picudos adultos. Los análisis de agrupamiento y ordenamiento demostraron la estacionalidad, selectividad y aprovechamiento de la disponibilidad de polen, ya que variaron géneros y especies en las diferentes estaciones del año, pero siempre pertenecientes a las cinco familias citadas.