Effects of nitrogen availability and spore concentration on the biocontrol activity of Ascochyta caulina in common lambsquarters (Chenopodium album)

Common lambsquarters is an annual weed of many important crops Ascochyta caulina is a plant pathogenic fungus that causes necrotic lesions on the leaves and stems of common lambsquarters The objective of the present study was to estimate the effect of plant N supply on the biocontrol activity of A caulina isolates against common lambsquarters; In greenhouse experiments replicated groups of common lambsquarters plants raised with different N supplies were sprayed with various isolates and concentrations of A caulina 3 wk after planting Height, number of leaves, total leaf area, fresh and dry weight, and tissue N concentration of common lambsquarters 4 wk after emergence increased significantly with increasing N supply Disease development was positively related to increasing plant tissue N and also to increasing spore concentration Fungal spore concentration also had a positive effect on the plant tissue N percentage Ascochyta caulina isolate W90-1 caused a greater dry weight reduction in common lambsquarters than isolates I-001 and NW-6 did.