Latin name: Xiphinema americanum
Reason for Concern:
1) Nematodes, when present in large numbers, cause stunting and reduce vigor by feeding on the roots.
2) Dagger nematodes can transmit viruses, such as tomato ringspot.
Usual symptoms are areas of distorted or stunted plants. Most nematodes are microscopic though a few species can be seen without magnification. Most plant-parasitic nematodes range in size from 0.02” to 0.04” in length. A great many nematodes have a wormlike or eel like shape. Females of some kinds grow swollen at maturity and resemble tiny beans, lemons, or pears.
Nematodes commonly have 6 developmental phases including an egg, four juvenile stages, and an adult nematode stage. Each juvenile stage is completed by a developmental process called a molt. Except for size, juveniles usually resemble adults. Reproductive organs normally do not appear until after the nematode has undergone four molts. Nematodes are present and active in the soil all year, although the level of activity will be the least in winter when soils are cold.
- As a vector for Tomato ring spot virus, can cause economic injury at very low population levels.
- In spring, scout for Tomato Ringspot symptoms in areas of low vigor. Leaves will often show a characteristic chevron or mottled pattern.
- Feeding by high concentrations of Dagger nematodes can cause roots to deform and swell.
- Sampling for Daggers should be done between December and April when their populations are highest.
- Nematodes have contagious or clumped distributions.
- Sample field in 2-5 acre blocks (max). Partition fields by soil type, stand vigor, drainage, crop history & etc.
- Collect 20 core (minimum) to depth of 10”—12” per block.
- Preplant sampling systemically in each block, “W” pattern is good.
- Sample established plantings in the plant row or hill and within 12-15” of the crowns, sample systematically throughout the block.
- Send labeled samples to laboratory for testing.