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| Introduction Symptoms Disease Cycle Diagnosis/Sampling Management |
| DIAGNOSIS/SAMPLING WHEN: Six to ten weeks after planting, when the corn is mid-thigh to waist high (the 6 leaf stage). SAMPLING: 1. Walk through your field on a transect. With a shovel, dig up a root ball chosen at random. 2. Knock the soil off the root ball by hitting the root ball on your shoe or shovel. You may need to wash the roots. 3. Turn the root ball upside down and look down into the root ball. 4. Pluck out the radicle (the root growing directly from the seed) and place in a plastic bag (Fig. 7). 5. Repeat this 9 more times, so you have 10 radicles. 6. Wash the radicles. |
 Fig. 7. Plucking the radicle. |
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| DIAGNOSIS: Rate each radicle on a 0-4 scale: 0 = completely healthy 1 = 1-10% of radicle has lesions 2 = 11-50% of radicle has lesions 3 = 51-99% of radicle has lesions 4 = 100% of the radicle has lesions Add up all the ratings and divide by 10 or the number of radicles rated to get an average rating for your field (0-4) (Figs. 8a-8c). |
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 Fig. 8a. Healthy radicles (average rating 0.2) |
 Fig. 8b. Moderately diseased radicles (average rating 1.8) |
 Fig. 8c. Severely diseased radicles (average rating 3.2) |