Influence of soil-water matric potential on the control of Pythium root infection of wheat with metalaxyl in two contrasting soils of South Australia

Abstract

Under prevailing climatic conditions, treatment of winter-sown wheat with metalaxyl (seed dressing, granule, or soil drench applications) significantly limited seed infection by Pythium species but did not give a significant yield response in separate field trials conducted on 2 contrasting soil types in South Australia. However, following irrigation of trial plots (which raised the soil-water matric potential from about -0.09 MPa to -0.02 MPa) during the first 3 weeks of wheat growth in 1989, metalaxyl granule treatment was effective in limiting seed and root infection by the 2 dominant Pythium species present, P. irregulare and P. echinulatum, and gave a significant increase in grain yield on both soil types. This effect of soil-water matric potential was confirmed in growth cabinet experiments in which metalaxyl was shown to be more effective in controlling infection of wheat by P. irregulare in both soil types when the soil-water matric potential was maintained at -0.02 MPa than at a soil-water matric potential of -0.1 MPa.

In vitro somatic growth and reproduction of phenylamide‐resistant and ‐sensitive isolates of Phytophthora erythroseptica from infected potato tubers in Idaho

“…Phytophthora species are generally sensitive to 0·01 to 1 mg L −1 of metalaxyl‐M (Erwin & Ribeiro, 1996). EC 50 values of natural MR isolates (not laboratory‐induced) of species in the order Peronosporales are commonly over 100 times more resistant than those of MS isolates (White et al ., 1988; Ferrin & Kabashima, 1991; Klein, 1994; O’Brien & Weinert, 1995; Pankhurst et al ., 1995; Sujkowski et al ., 1995; Timmer et al ., 1998), and EC 50 values of MR isolates of P. erythroseptica from Idaho in the present study were on average 380 times more resistant than MS isolates.…”

Relationship of Soil Moisture With The Incidence of Pod Rot In Peanut in West Texas1

“…The negative correlation between soil moisture and pod rot incidence observed in field 22 is contrary to that predicted by controlled experiments on the effect of Pythium spp. and soil matric potential, where the severity of infection was greater under wet soil conditions (Bhatti and Kraft, 1992;Hering et al, 1987;Pankhurst et al, 1995;Pieczarka and Abawi, 1978;Stanghellini et al, 1983). High soil moisture content favors the development of oospores and prevented the formation of sporangia by Pythium ultimum (Bainbridge, 1970).…”