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Disease scales

DISEASE ASSESSMENT SCALES

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Dutch scab scales

Scale 1

About 50% of the number of tubers is free from scab, whereas the remaining 50% may have 1 to 2 small shallow lesions covering max. 1/32 of the tuber's surface.

Scale 1½

About 33% of the number of tubers is free from scab, whereas the remaining 66% may have 2 to 4 small shallow lesions covering max. 1/16 of the tuber's surface.

Scale 2

Nearly all tubers are affected by scab. Each tuber may have 4 to 8 scab lesions covering max 1/12 of the tuber's surface.

Scale 2½

Nearly all tubers are affected by scab. Each tuber may have 5 to 10 scab lesions covering max 1/8 of the tuber's surface.

Dutch scurf scales

Rhizoctonia 10% light

10 tubers out of 100 tubers may have light infection (max 1/20 of the tuber's surface area covered) with Rhizoctonia solani.

Rhizoctonia 25% light

25 tubers out of 100 tubers may have light infection (max 1/20 of the tuber's surface area covered) with Rhizoctonia solani.

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