Pea yield decline syndrome in South Australia: the role of diseases and the impact of agronomic practices

Abstract

Sixty commercial pea crops were surveyed in 1995 to determine the causes of declining yields. Blackspot (Mycosphaerella pinodes and Phoma medicaginis var. pinodella) and downy mildew (Peronospora viciae) were prevalent in most crops and were identified as probable major contributors to the syndrome. Short rotation intervals (<5 years) between pea crops in paddocks were correlated with increased levels of blackspot and lower grain yields. Early sowing dates were correlated with increased levels of blackspot. A detailed survey of blackspot development was conducted in 5 commercial paddocks in 1996. The relative importance of sowing time and rotation varied between regions and seasons. The impact of a range of herbicides and the micronutrients manganese and zinc on blackspot, caused by the M. pinodes component of the blackspot complex, was investigated in a field trial during 1996. The herbicides diuron, metribuzin, and fluazifop significantly increased blackspot crown lesions compared with the nil treatment. There was a significant interaction between blackspot severity, herbicides, and the micronutrients manganese and zinc. Manganese concentration in pea plants was negatively correlated with the severity of blackspot crown lesions and positively correlated with severity of downy mildew.

Integrated disease management of ascochyta blight in pulse crops

“…In Australian farming systems, rotation interval between pea crops has recently increased from 3 to 5 years, to avoid infection from in situ inoculum. Disease severity was greater in crops sown on shorter rotations compared to those on longer rotations and yield, based on grower data, was consistently lower in the shorter rotation crops (Davidson and Ramsey 2000). Bretag et al (2001) monitored changes in populations of soil-borne ascochyta blight fungi, following different cropping sequences of field pea and barley.…”

“…In Australia, pea crops are sown two to three weeks after the agronomic optimum to avoid the peak period of ascospore release which occurs at the beginning of the growing season (Bretag 1991). Earlier sown crops have the most ascochyta and the highest percentage of infected grain at harvest particularly in the most intense pea cropping areas (Davidson and Ramsey 2000). In higher rainfall areas later planting has less impact on yield (Davidson and Ramsey 2000), but this practice risks yield loss in short growing seasons and regions where spring rain is limiting, with losses as high as 40% in some later-sown crops .…”

Combining management and breeding advances to improve field pea (Pisum sativum L.) grain yields under changing climatic conditions in south-eastern Australia

“…Alma). The major control strategy recommended from this research was to delay sowing 4-6 weeks beyond the first autumn rains to minimise ascochyta blight infection from airborne ascospores of D. pinodes (Bretag et al 2000;Davidson and Ramsey 2000;Hawthorne et al 2003). McDonald and Peck (2009) found that disease severity was more than halved and grain yield increased 6% by delaying sowing of Alma by 3-4 weeks to mid June.…”

“…Ascochyta blight has remained the most common disease affecting South Australian field pea crops (Davidson and Ramsey 2000;Bretag et al 2006). This disease is caused by a complex of fungi, viz.…”

Screening techniques and sources of resistance to rusts and mildews in grain legumes

“…Moreover, where this fungicide has been used for several years (USA, UK, New Zealand) pathogen resistance has developed (Biddle, 2001). In Australia few growers use metalaxyl either because of the perceived high cost or the deleterious effect upon Rhizobium inoculants (Davidson & Ramsey, 2000). Resistant cultivars are regarded as the best means of control.…”