Farm406

FIGURE 8. Stemphylium blight on lentil causes brown lesions that expand to a characteristic rolling of the leaves, left. Plants are defoliated, right. FIGURE 9. Circular lesions on pods due to Septoria blight of pea, left. Note the lesions are sunken and pycnidia are not organized in concentric rings like Ascochyta blight. Irregular shaped leaf lesions on a pea leaf due to Septoria blight, right. Ascochyta also can blow in as spores from other pulsegrowing areas. Environmental conditions favoring disease development include cool temperatures (59 to 77°F) and high humidity. e decision to spray a foliar fungicide will depend on the crop and variety, the timing of infection, the incidence (percent of plants infected) and severity (percent of tissue area with symptoms) of infection. Many foliar fungicides are effective against Ascochyta blight. Examples of strobilurin fungicides include pyraclostrobin (Headline) and azoxystrobin (Quadris). Additional fungicide options include chlorothalonil (Bravo) as a protectant early in the season, prothioconazole (Proline), boscalid (Endura), and fluxapyroxad (Xemium + Headline = Priaxor) for inseason control. Fungicides should be applied at bloom initiation or canopy closure, or when the first symptoms are seen. Additional applications may be necessary. Please pay aention to label restrictions and rotate Fungicide Resistance Action Commiee (FC) groups to prevent the development of resistance to these chemical classes. Stemphylium blight (chickpea, lentil), caused by Stemphylium botryosum, is an emerging disease of importance on lentil in Canada (Garvey, 2009) and is known to occur on chickpea worldwide (akur et al. 2010) and is present in Montana and North Dakota. It causes leaf spots that begin as small, water-soaked lesions, become blackish-brown, and are divided by leaf veins. ey oen start at the edge of the leaflet, fuse with adjacent lesions and become large, causing defoliation of the plant (Figure 8). ey are oen oval or irregular in shape, sunken, dark brown with lighter centers and a yellow halo. Older spots on chickpea may develop concentric rings, resembling a target. In lentil, lesions tend to be more beigecolored, and dead leaves develop a characteristic rolled and twisted appearance (Figure 8). e pathogen can be transmied by residue, soil, seed, wind and stubble. It prefers warm (about 77°F), moist (85 percent relative humidity and eight hours of leaf wetness) conditions for disease development. Infected seed has a significantly lower germination rate. ere are no fungicides registered for control of this disease, and standard applications for disease control have not been effective thus far. Septoria blight of pea does occur in Montana and is easily confused with Ascochyta blight due to the formation of small black spots (pycnidia) in the lesions. Lesions can be yellowed, sunken and circular or irregular in shape (Figure 9). Unlike Ascochyta blight lesions, pyncnidia caused by Septoria blight are not arranged in concentric circles and not all lesions are circular in shape. e disease is considered of minor importance and there are no fungicides registered for use. Photo: Michael Wunsch Photo: Michael Wunsch Photo: Mary Burrows, Montana State University Photo: Mary Burrows, Montana State University farm406 56

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