| Apple -- Nematode (Dagger) |
| See Also: Apple -- Virus Diseases |
| Cause: The dagger nematode (Xiphinema spp.) transmits the Tomato ringspot virus to apples causing the Flat Apple disease. Both the nematode and virus are required for this disease to occur. Damage caused by the virus affects fruit production. The nematode is an extoparasite (see Nematodes) found only in soil. Nematode populations are highest in fall, at the end of the growing season. |
| Symptoms: No known symptoms occur from nematode feeding alone. Fruits on Flat-Apple-infected trees are smaller, flatter, and the calyx end tends to be open. |
| Sampling: It is best to sample in late summer or early fall when nematode populations are higher than in early spring. At the tree drip-line, remove the top 2 to 3 inches of soil; using a shovel, sample to a depth of 1 ft or to the point that feeder roots are present. Put a handful of soil in the bucket. Take 10 to 20 subsamples from a given area, mix soil thoroughly, and combine into one sample. When sampling single trees, take two to five subsamples depending on the size of the tree. |
| Chemical
control: Preplant soil fumigation in fall is highly recommended; However, spring fumigation is effective provided criteria for fumigation conditions are met. Generally, soil temperatures and moisture for fumigation is better in fall than in spring. In addition, nematode populations are more active in fall and, therefore, more susceptible. Also, cool, wet conditions in spring slow the fumigant's diffusion rate, thus delaying planting.
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| Content edited by: Jay W. Pscheidt on January 1, 2009 |
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