Infestation

About: Infestation is a research topic. Over the lifetime, 8308 publications have been published within this topic receiving 82305 citations.

Response of a Host-Specific Herbivore to Resource Density, Relative Abundance, and Phenology

Abstract: Ovipositing females of the host-specific herbivorous moth Frumenta nundinella Zeller discriminated among horsenettle (Solanum carolinense L.) plants in the laboratory and at five field populations. In laboratory experiments, the number of larvae that developed in high-density plant groups was not significantly greater than the number that developed in low-density groups. Conse- quently, individual plants in low-density groups were disproportionately affected; twice as many larvae developed on them as on individual plants in high-density groups. Moths also discriminated between groups of pure horsenettle (high relative abundance) and groups of horsenettle plus another naturally co-occurring species (low relative abundance). Individual plants in high relative abundance groups had a tenfold greater infestation than did plants in low relative abundance groups. Natural horsenettle populations varied in density, relative abundance, plant size, and fruit pro- duction. Plant size, fruit production, and population density were all positively correlated, so the populations with the greatest density had the largest plants, which produced the most fruits. Despite differences in these plant parameters among sites, the extent of infestation differed little, except for one site that lacked parasitoids that attack F. nundinella. Infestation within field sites was heterogeneous among plants. Virtually all large plants (those with 15 fruits), but only about half the small plants (those with < 15 fruits), became infested (one or more infested fruit per plant). However, a greater proportion of the fruit crop was infested on small plants than on large plants. Large plants remained in flower an average 2.5 wk longer than did small plants, so a smaller proportion of their flowers was available during the short period of high oviposition risk. Because of the short oviposition period, plants that flowered earlier or later than the mean flowering time of their populations appeared to have lower infestations than did plants that flowered close to the population means.

Patterns of house infestation dynamics by non-domiciliated Triatoma dimidiata reveal a spatial gradient of infestation in rural villages and potential insect manipulation by Trypanosoma cruzi.

Abstract: OBJECTIVE Chagas disease is a major vector-borne parasitic disease in Latin America, primarily transmitted to humans by triatomine vectors. Non-domiciliated triatomine species such as Triatoma dimidiata in the Yucatan peninsula, Mexico, can transiently invade houses and are emerging as a major challenge to control Trypanosoma cruzi transmission to humans. We analyzed the spatio-temporal spreading of house infestation by T. dimidiata in four rural villages. METHODS Triatomines were collected in four rural villages over a 2 years period, and the spatio-temporal patterns of infestation were analyzed. RESULTS Triatomines were consistently more abundant at the periphery of villages than in centers, indicating a much higher risk of T. cruzi transmission at the periphery. Male T. dimidiata were found further in the center of the village, while females remained closer to the periphery, suggesting differential dispersal capabilities between sexes, although the timing of dispersal appeared identical. Surprisingly, infected females were consistently collected in houses much further from the surrounding bushes than non-infected females, while the distribution of males was unaffected by their T. cruzi infection status, suggesting an increased dispersal capability in infected females. CONCLUSION The spatial structure of infestation should be taken into account for the prioritization of vector control activities within villages, and spatially targeted interventions may be explored. A potential vector manipulation by T. cruzi, observed for the first time in triatomines, may favor parasite transmission to new hosts.

The Effect of Endophytic Fusarium verticillioides on Infestation of Two Maize Varieties by Lepidopterous Stemborers and Coleopteran Grain Feeders.

Abstract: A series of experiments were conducted to test the effect of the presence of Fusarium verticillioides in the maize plant on subsequent infestation by coleopteran and lepidopteran pests. The effect of percent internodes 1 to 5 infected with F. verticillioides, time after planting, and maize variety on attacks of stem and ears by lepidopterous and coleopteran pests was assessed in field experiments in early and late season 1998 and early season 1999 in Benin Republic. Artificial inoculation of the first internode with fungal-treated toothpicks was compared with a hot-water-fungicide seed treatment and a control. In 1998, two varieties that differed in husk tightness, the improved DMRLSR-W and the local Gbogbe, were used. Percentage of node 1 to 5 and plants infected was highest with the inoculation treatment but tended to be similar in the seed treatment and the control. The infection rate tended to increase with time and, within sampling date, decreased with node level. Ear infection was strongly correlated with percent infected nodes, indicating that F. verticillioides in the stem predisposed kernel infection. F. verticillioides incidence was higher in Gbogbe than in DMRLSR-W. Stem and ear infestations by the pyralid Eldana saccharina, the major pest in the area, tended to be highest in inoculation and lowest in the protection treatment. The same trends were found for the pyralid Chilo spp., the tortricid Cryptophlebia leucotreta, and beetles pooled across species. Significant positive correlations were found between ear/stem F. verticillioides infection and E. saccharina, Cryptophlebia leucotreta, Mussidia nigrivenella, and the noctuid Sesamia calamistis, but the latter three pest species were only significantly correlated with fungal infection of the upper nodes of the plant. Similar to disease incidence, E. saccharina numbers in stem and ear were higher in Gbogbe than DMRLSR-W in late 1998, whereas for the pyralid ear feeder M. nigrivenella, it was reversed. It was suggested that some lepidopterous and coleopteran pests are attracted by and survive longer (or have lower mortality) on plants infected with F. verticillioides.

Density-Dependent and Density-Independent Mortality of the Western Corn Rootworm: Impact on Dose Calculations of Rootworm-Resistant Bt Corn

Abstract: The percentage of viable eggs of the western corn rootworm, Diabrotica virgifera virgifera LeConte, which survived to the adult stage was evaluated for the effect of egg density in 2005 and 2007 in central Missouri. In 2005, each plot was 2.44 by 3.05 m and contained 64 maize (corn), Zea mays L., plants. In 2007, plots were 3.05 by 3.05 m and again contained 64 corn plants. Seven egg densities (2,400, 1,200, 600, 300, 100, 50, and 25 viable eggs per 30.5 cm) were evaluated with four to six replications in each year in a completely randomized design. In 2007 only, an additional row was infested near each plot to evaluate plant damage. In both years, there was no correlation of infestation level and percentage of emergence between infestation levels of 25–600 viable eggs per 30.5 cm, indicating that density-dependent mortality did not occur at these egg densities. In 2005, 8.04% of the viable eggs established on a corn plant and produced an adult at these lower infestation rates. In 2007, this value was 2.9%. Regardless of egg density, ≈92–97% failed to establish and produce adults (density-independent mortality). In 2005 and in the combined analysis, as viable egg densities increased from 600 to 2400 per 30.5 cm there was a significant decrease in percentage of emergence. In a broken line analysis of the 2005 data, the point where density-dependent mortality began in the combined analysis was 851 eggs per 30.5 cm with a 95% confidence interval from 678 to 1024. That year density-dependent mortality was important at high infestations and killed 54.4% of those larvae that successfully established on a plant at the highest egg density. However, little or no density-dependent mortality occurred at infestation levels <850 viable eggs per 30.5 cm in either year of the study. Combining data from both years with all previously published data in a broken line analysis indicated that density-dependent mortality began at ≈800 viable eggs per 30.5 cm. These data are discussed in terms of dose calculations for products targeting the western corn rootworm.