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This review considers the cascade of events that link injuries caused by plant pathogens on crop stands to possible (quantitative and qualitative) crop losses (damage), and to the resulting economic losses. To date, much research has focused on injury control to prevent this cascade of events from occurring. However, this cascade involves a complex(More)
ABSTRACT Spatial and temporal patterns of foliar disease caused by Phoma ligulicola were quantified in naturally occurring epidemics in Tasmanian pyrethrum fields. Disease assessments (defoliation incidence, defoliation severity, incidence of stems with ray blight, and incidence of flowers with ray blight) were performed four times each year in 2002 and(More)
Integrating remote sensing and geographic information systems (GIS) technologies offers tremendous opportunities for farmers to more cost effectively manage the causes of crop stress. Initial soybean cyst nematode (SCN) population densities from 995 2-x-3-m quadrats were obtained from a soybean field near Ames, Iowa, in 2000. The percentage of sunlight(More)
Temporal dynamics of soybean sudden death syndrome (SDS) root and foliar disease severity were studied in growth chamber experiments on susceptible plants exposed to different inoculum densities (0, 100, 101, 102, and 103 conidia g−1 soil) of Fusarium virguliforme. The monomolecular model provided the best fit to describe the progress of root and foliar(More)
Field studies were conducted in Iowa during 2001 and 2002 to determine the optimal sampling height and orientation for using yellow sticky cards to monitor populations of Chaetocnema pulicaria Melsheimer, the vector of the bacterial pathogen Pantoea stewartii subsp, stewartii, the causal organism of Stewart's disease of corn, Zea mays L.. Sticky cards were(More)
In 1999 and 2000, yellow sticky cards and sweep net samples were used to document the occurrence of an overwintering adult generation of Chaetocnema pulicaria Melsheimer, corn flea beetle, followed by two distinct populations peaks during the growing season in Iowa Emergence of the overwintering adult generation started in mid-April and continued until(More)
ABSTRACT The germination and sporulation of Colletotrichum acutatum were characterized over time on strawberry leaves (cv. Tristar) and plastic coverslips incubated at 26 degrees C under continuous wetness. Conidia germinated within 3 h after inoculation and formed melanized appressoria with pores by 9 h after inoculation. Host penetration was not observed(More)
ABSTRACT Soybean lines transformed with the coat protein (CP) gene of Soybean mosaic virus (SMV) were evaluated for SMV resistance by quantifying the temporal and spatial spread of SMV strain AL-5 released from a point source in the field. The temporal spread of SMV within field plots during 1999 and 2000 was quantified by enzyme-linked immunosorbent assay.(More)
ABSTRACT Strawberry leaves (cv. Tristar) inoculated with Colletotrichum acuta-tum conidia were incubated at 10, 15, 20, 25, 30, and 35 degrees C under continuous wetness, and at 25 degrees C under six intermittent wetness regimes. The number of conidia and appressoria was quantified on excised leaf disks. In order to assess pathogen survival, inoculated(More)
ABSTRACT In order to better understand the epidemiology of the Stewart's disease of corn pathosystem, quantitative information concerning the temporal dynamics of the amount of pathogen inoculum present in the form of Pantoea stewartii-infested corn flea beetles (Chaetocnema pulicaria) is needed. Temporal changes in the proportion of P. stewartii-infested(More)