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Larval Damage (larval + damage)
Selected AbstractsDiamondback moth females oviposit more on plants infested by non-parasitised than by parasitised conspecificsECOLOGICAL ENTOMOLOGY, Issue 5 2008YASUYUKI CHOH Abstract 1.,When offered a choice, female diamondback moths (Plutella xylostella) oviposited more eggs on plants with non-parasitised conspecific larvae than on plants with parasitised larvae. 2.,The leaf area consumed by parasitised larvae was significantly lower than that by non-parasitised larvae. However, this quantitative difference in larval damage did not explain the female's ability to discriminate between plants with parasitised and non-parasitised larvae, as females showed an equal oviposition preference for plants infested by higher or lower densities of non-parasitised larvae. 3.,Pupal weight and duration of the larval stage of P. xylostella were independent of whether larvae were reared on plants that were previously infested by either non-parasitised or parasitised larvae. 4.,The larval parasitoid Cotesia vestalis did not distinguish between plants infested by non-parasitised larvae and plants infested by larvae that had already been parasitised by conspecific wasps. 5.,Based on these data, it can be concluded that the moth oviposition preference for plants infested by non-parasitised conspecifics relative to plants infested by parasitised conspecifics was not explained by plant quality or by the attractiveness of plants towards wasps. It is hypothesised that one of the reasons for this preference is avoidance of plants where a relatively high risk of parasitism is expected due to the emergence of parasitoids from the parasitised host larvae. [source] Interactions between nutrient status and weevil herbivory in the biological control of water hyacinthJOURNAL OF APPLIED ECOLOGY, Issue 1 2000Tim A. Heard Summary 1.,Despite the widespread release of effective biocontrol agents, water hyacinth remains the world's most problematic aquatic weed, particularly in eutrophic waterbodies. However, understanding of the interaction between control and trophic status is still incomplete. 2.,Growth of water hyacinth plants was measured at two water nutrient concentrations (high and medium) and in the presence and absence of two insect biocontrol agents in a large circulating hydroponic system in a glasshouse. 3.,At the high nutrient concentration (1·6 mg l,1 N and 1·0 mg l,1 P), plants multiplied more quickly, attaining greater biomass. Both insect species reduced plant growth at both nutrient concentrations. Neochetina bruchi, however, performed better than N. eichhorniae at the high nutrient concentration by inflicting more damage on the plants and reducing biomass by a greater extent. 4.,Insect damage reduced the concentrations of nitrogen and phosphorus found in plants growing in high nutrient water but not in medium nutrient water (0·4 mg l,1 N and 0·025 mg l,1 P). 5.,The developmental and reproductive performance of N. bruchi was determined at both nutrient concentrations. Water hyacinth plants grown at higher nutrient concentration were superior hosts to N. bruchi than plants grown at medium concentrations. Net reproductive rate and intrinsic rate of increase were significantly greater at the high concentrations. Greater damage by N. bruchi to water hyacinth at the high nutrient concentration was due to the greater production of offspring, and hence greater larval damage. 6.,We predict that water hyacinth problems will be greater in eutrophic waterbodies, where N. bruchi will be a superior biocontrol agent to N. eichhorniae. In low-nutrient waterbodies, local nutrient enrichment of water may assist the establishment of control agents. These results illustrate the importance of wider ecological factors on the success of biological control. [source] An ecological study of the relationship between two living fossils in Malawi: the Mulanje Tiger Moth (Callioratis grandis) and the Mulanje Cycad (Encephalartos gratus)AFRICAN JOURNAL OF ECOLOGY, Issue 2 2010Julian Bayliss Abstract The Mulanje tiger moth (Callioratis grandis) has recently been discovered feeding solely on the Mulanje Cycad, Encephalartos gratus. In its type locality Encephalartos gratus is severely threatened through habitat destruction and human population growth. As a result the first detailed demographic survey of Encephalartos gratus on Mount Mulanje was undertaken with particular emphasis on the relationship between E. gratus and Callioratis grandis. What is unusual about C. grandis is that the males exhibit lekking behaviour, for which aposematism may be a prerequisite. Cycads were surveyed in a systematic manner. Both the biotic and abiotic parameters were recorded from 532 wild Encephalartos gratus. Results showed the morphological range of measurements differed from that of previously published literature on this species. Results also showed that the incidence of Callioratis larval damage was related to the maturity of the wild cycads , moth damage was greater on more mature plants. Approximately 50% of surveyed cycads showed evidence of Callioratis moth damage, however, there was no apparent preference from the moth to select either male or female cycads as food plants for the larvae. In some cases there was severe damage to cycad fronds, but this did not seem to affect the production of reproductive cones or even the survival of individual cycads. Résumé On a découvert récemment que le papillon du Mulanje (Callioratis grandis) ne se nourrit que sur le cycadale Mulanje Encephalartos gratus. Dans son milieu type, Encephalartos gratus est gravement menacé dans la nature à cause de la destruction de l'habitat et de la croissance de la population humaine. Par conséquent, la première étude démographique détaillée d'Encephalartos gratus réalisée sur le mont Mulanje fut entreprise en insistant particulièrement sur la relation entre Encephalartos gratus et Callioratis grandis. Ce qui est inhabituel chez C. grandis, c'est que les mâles présentent un comportement territorial (lek). Les cycadales ont été systématiquement surveillées. On a enregistré les paramètres biotiques et abiotiques pour 532 Encephalartos gratus poussant dans la nature. Les résultats ont montré que l'amplitude des mesures morphologiques différait de ce que la littérature existante décrit sur cette espèce. Ils ont aussi montré que l'incidence des dommages causés par les larves de Callioratisétait liée à la maturité des cycadales sauvages , les dégâts causés par les papillons étaient plus graves sur les plants plus matures. Environ 50% des cycadales suivis montraient des traces de dommages causés par ce papillon, mais il n'y avait pas de preuve qui aurait pu montrer que le papillon sélectionnait des cycadales mâles ou femelles pour en nourrir ses larves. Dans certains cas, il y avait des dégâts sérieux dans les feuilles de cycadales; cependant, cela ne semblait pas affecter la production de cônes reproducteurs, pas plus que la survie des individus. [source] Responses of Corcyra cephalonica (Stainton) to pirimiphos-methyl, spinosad, and combinations of pirimiphos-methyl and synergized pyrethrins,PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2004Fangneng Huang Abstract Field control failures with pirimiphos-methyl against the rice moth, Corcyra cephalonica (Stainton), in Weslaco, Texas, USA, led us to investigate the susceptibility of this particular strain to pirimiphos-methyl, spinosad, pyrethrins synergized with piperonyl butoxide, and pirimiphos-methyl combined with synergized pyrethrins. In laboratory bioassays, 50 eggs of C cephalonica were exposed to untreated and insecticide-treated corn and sunflower seeds to determine larval survival after 21 days, egg-to-adult emergence after 49 days, and larval damage to seeds at both exposure periods. Pirimiphos-methyl at both 4 and 8 mg kg,1 did not prevent larval survival or egg-to-adult emergence of C cephalonica on either corn or sunflower seeds, and seed damage was evident at both rates. The C cephalonica strain was highly susceptible to spinosad at 0.5 and 1 mg kg,1. At both spinosad rates, reduction in larval survival, egg-to-adult emergence, and seed damage relative to the control treatment was ,93% on both corn and sunflower seeds. Pirimiphos-methyl and spinosad were generally more effective against C cephalonica on corn than sunflower seeds. The C cephalonica strain was completely controlled on corn treated with 1.5 mg kg,1 of pyrethrins synergized with 15 mg kg,1 of piperonyl butoxide. Many larvae survived and became adults on corn treated with synergized pyrethrins at ,0.75 mg kg,1. Corn treated with pirimiphos-methyl at 4, 6 or 8 mg kg,1 in combination with 0.38 to 1.5 mg kg,1 of synergized pyrethrins reduced larval survival by ,95%, egg-to-adult emergence by ,97%, and seed damage by ,94%. Our results suggest that the C cephalonica strain can be controlled on corn by combining pirimiphos-methyl with synergized pyrethrins or with synergized pyrethrins at the labeled rate. Although spinosad is not currently labeled for use on stored corn and sunflower seeds, it appears to be effective against C cephalonica on both commodities at very low rates. Copyright © 2004 Society of Chemical Industry [source] | ||||||||||