Periodicity and gradients in dispersal ofAlternaria linicola in linseed crops

Abstract

Conidia of Alternaria linicola produced on infected linseed crops were mainly dispersed by wind. The numbers of conidia in the air above linseed crops collected by a Burkard spore sampler were greatest between 12:00 h and 13:00 h, when the relative humidity was lowest. Although numbers of conidia collected decreased with increasing height within and above the crop canopy, air-borne A. linicola conidia were present up to 80 cm above the crop canopy. Conidia of A. linicola were transported by wind up to at least 40 m downwind from an artificial line inoculum source, but their numbers decreased with increasing distance from the source. In 1991In , 1992In , and 1993, the dispersal of A. linicola conidia above linseed crops followed a seasonal periodicity which was influenced by weather conditions and cultural practices. The greatest numbers of conidia were collected during July, August and early September and coincided with periods favourable for sporulation and with an increase in the incidence of the disease in the senescent crop. Air-borne A. linicola conidia produced on point or line inoculum sources (naturally infected linseed stern'debris) were responsible for the spread of the disease in linseed crops. In 1992 and 1993, the disease was first detected downwind from the sources, but by the end of the growing seasons, it had spread in all directions and up to 20 m and 60 m from the sources, respectively. Disease gradients were initially steep near the inoculum sources but they became flatter with time due to the secondary spread of the disease.

Patterns of airborne conidia of Stemphylium vesicarium, the causal agent of brown spot disease of pears, in relation to weather conditions

“…In Alternaria species, seasonal periodicity and abundance of airborne spores are related to environmental conditions that favour their production and release into the air, but also to the abundance of infected host tissue that serves as inoculum source (Eversmeyer and Kramer, 1975;Lagenberg et al, 1977;Datar and Mayee, 1982;Bashan et al, 1991;Rotem, 1991;Vloutoglou et al, 1995). The same occurs for S. vesicarium conidia in garlic and leeks (Suheri and Price, 2001;Prados-Ligero et al, 2003).…”

Characterization of the fungal community in the canopy air of the invasive plant Ageratina adenophora and its potential to cause plant diseases

“…Previously, there have been verified the occurrence of more fungal spores in the air in the low part of the canopy, which is close to plant leaves (i.e., the important release source of fungal spores), compared with the number of spores in the air of the high part of the canopy [20,59]. Several reports from crop systems have also verified this trend [27][28][29]. We did not found a higher fungal diversity and abundance in low part than high part of the canopy S2 Table).…”

“…Pathogens in the canopy air can infect plants under optimal microclimate conditions and in turn, release their spores into the air to complete their life cycle; meanwhile, the host can change the canopy microclimate to affect pathogen spread and disease development [26]. Some studies for the monoculture crop also have shown that numbers of conidia collected decreased with increasing height within and above the crop canopy [27][28][29]. Similarly, for the monoculture invasive plant, its canopy air would harbor diverse fungal spores released from leaf spots, which in turn, may infect host itself as well as neighboring species.…”

Distribution of Airborne Fungal Propagule Concentrations in an Irrigated Cropland Zone

“…The sampling procedure at a given site on a given day consisted of exposing two portable Burkard volumetric traps (Hirst 1952) for 5 min each, at a separation of 2–4 m, within the respective crop area, between 10 : 00 and 13 : 00 local time, always sampling in the same sequence of farms with a time interval of 15–20 min between each so that they were sampled at the same time for each crop for the results to be comparable. The most suitable time of day for sampling was chosen on the basis of previous studies and the literature (Vloutoglou et al. 1995; Paredes 1997) which showed the highest concentrations to occur about midday.…”