Farm406

FIGURE 6. Ascochyta blight causes stem lesions that can lead to stem breakage, (left). Pod infection, (right), can lead to discoloration and shrivelling of seed as well as seed transmission of the pathogen. FIGURE 7. Ascochyta blight lesions on chickpea usually have a characteristic ring pattern. Lesions coalesce and cause defoliation. In the photo on the (right), chickpeas resistant to Ascochyta blight (left) are not defoliated by the disease compared to the susceptible variety (right). Management of Ascochyta blight begins at planting. is is a residue-borne disease, therefore we recommend a minimum of three to four years between the same legume crop (ie. two crops of chickpea) to allow residue decomposition. P. pinodella and M. pinodes can also survive long periods in soil as thick- walled chlamydospores. is pathogen can be seedborne at high levels (Table 1), and both North Dakota and Montana seed labs will test for Ascochyta. Please contact them directly for submission and fee instructions (contact information can be found on the outside back cover). We recommend zero percent seed-borne infection for Ascochyta in chickpea, and below five percent for pea and lentil. ese levels are based on recommendations from other pulse-growing areas as well as the relative susceptibility of the crop. iabendazole (Mertect), azoxystrobin (Dynasty), and pyraclostrobin (Stamina) have shown efficacy against seedborne Ascochyta. Fluxapyroxad (Xemium) has also shown efficacy in preliminary trials, but is not currently formulated as a seed treatment for pulse crops. Due to the presence of strobilurin- resistant strains of Ascochyta in chickpea crops in Montana and North Dakota, we do not recommend the use of azoxystrobin or pyraclostrobin on chickpea. In North Dakota, resistant populations went from less than ten percent of detections to almost 100 percent in a single year (2005- 2006) due to overuse of strobilurin fungicides. (Markell: personal communication) Photo: Sam Markell Photo: Sam Markell Photo: Mary Burrows, Montana State University Photo: Mary Burrows, Montana State University 55 farm406

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