Assessment of fennel aphids (Hemiptera: Aphididae) and their predators in fennel intercropped with cotton with colored fibers.

The fennel aphid, Hyadaphis foeniculi (Passerini) (Hemiptera: Aphididae) is a major pest of fennel, Foeniculum vulgare Miller in northeast region of Brazil. We hypothesize that intercropping can be used as an alternative pest management strategy to reduce aphid yield loss in fennel. Thus, we investigated the severity of fennel plant damage in relation to infestation by the fennel aphid and predation by Cycloneda sanguinea (L.) (Coleoptera: Coccinellidae) (spotless lady beetle), green lacewing, Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae), and Scymnus spp. (Coleoptera: Coccinellidae) in sole fennel plots and plots of fennel intercropped with cotton with colored fibers. The fennel aphid populations in nontreated plots were significantly larger in sole fennel plots than in intercropped plots. The highest densities of C. sanguinea, green lacewings and Scymnus spp., associated with the suppression of fennel aphid populations was found in fennel in the intercropping systems. Fennel aphids reduced the fennel seed yield by 80% in the sole fennel plots compared with approximately 30% for all intercropping systems. The results obtained in this research are of practical significance for designing appropriate strategies for fennel aphid control in fennel-cotton intercropping systems. In summary, intercropping fennel with cotton with colored fibers apparently promoted biocontrol of fennel aphid in fennel.

Within-plant distribution of cotton aphids, Aphis gossypii Glover (Hemiptera: Aphididae), in Bt and non-Bt cotton fields.

Knowledge of the vertical and horizontal distribution of Aphis gossypii Glover (Hemiptera: Aphididae) on genetically modified cotton plants over time could help optimize decision-making in integrated cotton aphid management programs. Therefore, the aim of the present study was to determine the vertical and horizontal distribution of A. gossypii in non-transgenic Bt cotton and transgenic Bt-cotton over time during two cotton seasons by examining plants throughout the seasons. There was no significant interaction between years and cotton cultivar treatments for apterous or alate aphids. Considering year-to-year data, analyses on season-long averages of apterous or alate aphids showed that aphid densities per plant did not differ among years. The number of apterous aphids found per plant for the Bt transgenic cultivar (2427 apterous aphids per plant) was lower than for its isoline (3335 apterous aphids per plant). The number of alate aphids found per plant on the Bt transgenic cultivar (12.28 alate aphids per plant) was lower than for the isoline (140.56 alate aphids per plant). With regard to the vertical distribution of apterous aphids or alate aphids, there were interactions between cotton cultivar, plant age and plant region. We conclude that in comparison to non-Bt cotton (DP 4049), Bt cotton (DP 404 BG (Bollgard)) has significant effects on the vertical, horizontal, spatial and temporal distribution patterns of A. gossypii, showing changes in its distribution behaviour inside the plant as the cotton crop develops. The results of our study are relevant for understanding the vertical and horizontal distribution of A. gossypii on Bt cotton cultivar (DP 404 BG (Bollgard)) and on its isoline (DP 4049), and could be useful in decision-making, implementing controls and determining the timing of population peaks of this insect.

População de artrópodes benéficos em algodoeiro afetado por inseticidas em sistemas de manejo integrado e convencional / Beneficial insect population affected by pesticides in ipm and conventional cotton systems

Com o objetivo de estudar o impacto de inseticidas na redução da entomofauna benéfica na cultura algodoeira, conduziu-se um experimento na região Oeste da Bahia nos anos de 2002/2003. Dois sistemas de manejo foram adotados, o Manejo Integrado de Pragas (MIP) e o sistema convencional realizado na fazenda onde o experimento foi instalado. As populações de Orius spp., Chrysoperla externa, Sirfideos e Coccinelideos foram monitoradas por 19 semanas consecutivas, utilizando-se o pano de batida, com 100 batidas de pano por levantamento em cada um dos sistemas de cultivo. Estimou-se uma regressão linear para cada espécie monitorada, em cada sistema, tomando-se como variável independente o tempo, número de semanas, e como variável dependente a população de insetos, representada pela média das contagens dos 100 pontos de batida de pano em cada levantamento. Para as espécies em estudo, constatou-se que as taxas de crescimento representadas nas inclinações das retas de regressão foram sempre superiores no MIP.

Aiming to study the impact of insecticides on beneficial insects in the cotton crop, we conducted an experiment in the western region of state of Bahia, Brazil, in the 2002/2003 season. Two management systems were compared: the Integrated Pest Management (IPM) and the conventional system, conducted at the farm where the experiment was installed. The populations of Orius spp, Chrysoperla externa, syrphid flies (Diptera: Syrphidae) and coccinellids (Coeloptera: Coccinellidae) were monitored for 19 consecutive weeks, using a beat cloth, beat 100 times per week at each cropping system. The evaluation was made based on linear regression for each species monitored in each system, taking "time," the number of weeks, as the independent variable, and, as the dependent variable, the insect population, represented by the average of the counts of the 100 beat cloth points in each survey. For these species, it was found that the growth rates given by the slopes of regression lines were always higher in the IPM.