The role of seed infection level and fungicide seed treatments in control of net blotch in barley

The effect of seed-borne net blotch infection in barley on the agronomic characters yield, thousand kernel weight, grain volume weight, protein, starch and plant density was investigated in field trials using six net blotch infection levels (100/0, 80/20, 60/40, 40/60, 20/80 and 0/100 % high/low infected seed) and four fungicide seed treatments. The untreated trials showed significant differences between infection levels only for some agronomic characters, years and levels. Seed treatment with Anchor (carboxin + thiram) reduced net blotch by nearly 100 %, compared to 81 % by Fungazil A 25 (imazalil), 60 % by Rancona i-MIX (ipconazole + imazalil) and 54 % by Rubin TT (triticonazole + prochloraz + pyrimethanil). Anchor significantly increased yield 3-7 %, thousand kernel weight 3-13 %, grain volume weight 3-9 % and protein content 1-7 % in the first year, but not in the second. Fungazil A 25 had a low positive effect on agronomic characters, while Rancona i-MIX and Rubin TT had a positive, negative or no effect. The correlation between percent infected kernels in the conventional osmotic method and real-time PCR results was high, showing a potential for complementing traditional plate test methods with molecular methods that needs further optimization. The development of net blotch and its effect on agronomic characters thus depended on many other factors than the seed infection level. The current recommendations for seed treatment could be considered a preventative measure.