2018 BARLEY DISEASE SURVEY IN THE SOUTH PEACE REGION OF ALBERTA

In 2018, 19 producer fields were surveyed for leaf diseases at the milk to early dough stage of crop development. Growing season temperatures were generally above normal, while moisture conditions were initially dry in the spring, but were greater than normal in July and August. Scald and the net-form of net blotch were most common, although severity levels for all diseases were generally low. METHODS: Nineteen producer fields in the South Peace Region of Alberta were surveyed for leaf diseases from Aug 1 to Aug 10, 2018 when crops were at milk to early dough stage. Fields were traversed in a diamond shaped pattern with samples taken at the vertices. At each vertex, 25 leaves were randomly sampled from a circle of 5 m radius. Equal numbers of penultimate (flag leaf - 1) and the next lower (flag leaf - 2) leaves were removed and placed in envelopes and air-dried for disease assessment later in the summer and fall. The percentage of diseased leaf area (DLA) was assessed for scald (Rhynchosporium commune), the net-form of net blotch (Pyrenophora teres f. teres), leaf blotch (Parastagonospora nodorum) and other leaf spots such as spot-form net blotch (P. teres f. maculata) and spot blotch (Cochliobolus sativus). Disease assessments were aided by the use of standard area diagrams. Leaf pieces with typical lesions were surface sterilized (10% bleach/10% alcohol) for 1-2 minutes, placed on water agar, and incubated under light at 18 degrees C for 3-14 days. Diseases were identified on the basis of symptoms, sporulation structures and conidia in lesions. Plating was repeated for samples with non-sporulating lesions and/or if overgrown by Cladosporium and/or Alternaria spp. RESULTS AND COMMENTS: In May and June, average temperatures generally were warmer than the 20-year normal for the 1991 to 2011 period, and trended towards normal in July and August. Dry conditions were prevalent in May followed by greater than normal precipitation in July and August. Results of the disease survey are shown in Table 1. Although there was high field disease incidence for scald and net blotch at 84%, average disease severity per field was low for both scald (2.4% with two fields greater than 10% DLA) and net blotch (0.9%). Leaf blotch was also prevalent affecting 57% of fields with an overall low disease severity (1%). Other leaf spot diseases accounted for low disease levels. Spot-form net blotch was found at low levels (<1 to 1.5%) in three fields. Trace levels of stripe rust were found in one field and trace to 1% incidence of loose smut in six fields. [GRAPHICS]