Ascochyta Shows Up In Montana

BOZEMAN - Jun 18/07 - SNS -- This season's first cases of Aschochyta blight have been identified on chickpeas in Montana, near Bozeman, Billings and Sidney.

The rapidly spreading disease is favored by cool, wet conditions such as Montana has been experiencing, said Mary Burrows, Montana State University Extension plant pathologist.

Burrows said that producers with chickpeas should be prepared to spray at least twice with fungicides during the growing season to control the blight. Because the disease can spread very rapidly, producers should spray a fungicide at the first sign of disease.

"Producers should scout early and often for symptoms of ascochyta blight," she said. Those symptoms include circular lesions with black specks that are visible with a magnifying glass. The lesions appear on leaves and stems, and stem girdling and breakage can also be present.

Since fungicide-resistant ascochyta blight has been identified in North Dakota, it is important to rotate the chemistry used to treat the blight in Montana, Burrows said. No fungicide-resistant ascochyta has been identified in Montana so far.

The North Dakota strain is resistant to strobilurins, and North Dakota has recommended against using any strobilurins to control ascochyta this year.

"Once a fungus is resistant to one strobilurin, it generally is resistant to all strobilurins, and we could loose these as a tool to control ascochyta," Burrows said. To avoid that problem, it is important for growers near North Dakota to avoid using the strobilurin or "QoI" fungicides on chickpea this year.

Strobilurins include fungicides such as Quadris (azoxystrobin) and Headline (pyraclostrobin), some of the most effective fungicides we have against ascochyta blight. In fungicide trials in Montana, Bravo (chlorothalonil) and Manex (maneb) have not performed well. Other non-strobilurin fungicide options include Endura (boscalid) and Proline (prothioconazole). Consider tank mixing Endura with a protectant fungicide such as chlorothalonil or maneb for added protection to foliage not infected with the disease, or using a fungicide mix with more than one mode of action. Currently, Proline is not labeled for tank mixing.

Other options to control ascochyta blight generally occur before planting, she said. Use disease-free seed (0 percent tolerance for kabuli chickpeas). Treat seed with thiabendazole (also known as LSP or Mertect) to manage seed-borne ascochyta, even if they have tested disease-free. This seed treatment should be used in addition to a seed treatment for control of damping off such as Apron MAXX.

Small kabuli and desi chickpeas are generally less susceptible to ascochyta blight, so fewer fungicide applications may be necessary than for large kabuli chickpeas, Burrows said. Ascochyta blight also attacks lentils and peas, but the fungi causing ascochyta blight in chickpea is different from that which causes blight in lentils and peas.