Click on any
image for a more
detailed view

Disease Management

The choice of management tactic to reduce lesion nematode damage depends upon many factors. All tactics require accurate diagnosis of the species and population levels of Pratylenchus as assessed from soil and root samples taken from any given field. Action thresholds vary among Pratylenchus species and crops depending upon geographic location, crop value, and the potential for disease complexes. Unfortunately, breeding for resistance to lesion nematodes is difficult, and thus, moderate resistance to lesion nematodes is presently limited to only a few cultivated crops (i.e. forage legumes, potato). Rotations to nonhost crops also offer limited opportunities to manage lesion nematode field populations since most Pratylenchus species have wide host ranges including both dicots and monocots. If the species of Pratylenchus is accurately diagnosed, and a suitable economic nonhost can be grown, rotations offer some promise as a management tactic. There are suggestions that microbial antagonists of lesion nematodes such as soil fungi can reduce population levels, but this has not been proven to be effective in production agriculture (Figure 18). The two most effective tactics for lesion nematode management remain sanitation and the use of nematicides.

Figure 18

Pre-plant options
The best way to manage lesion nematodes is to prevent their introduction into a field. Choosing an uninfested field site or choosing a nonhost rotation crop are two ways to avoid problems with lesion nematodes. Once lesion nematodes infest a field, it is highly unlikely that they can be eradicated. Inoculum levels can be reduced by moldboard plowing (turning over the soil layer) to expose infected roots to the elements. Planting stock should be monitored and certified to be free of lesion nematode infestation. This is especially important for seedlings of crops that will be grown perennially (i.e. fruits and ornamentals).

Pre-plant fumigation is probably the most effective tactic to reduce field population levels of lesion nematodes to below economic damage thresholds. Fumigants are usually applied by being chiseled below ground behind a tractor. The use of any chemical nematicide is dependent upon whether the nematicide is labeled for management of lesion nematodes in that crop, and if the predicted economic return on investment warrants the use of a nematicide. The multi-purpose fumigants (i.e. methyl bromide and mixtures with chlorpicrin) are rarely used specifically for lesion nematode control, although metham-sodium does provide good lesion nematode control in some cases. 1,3-dichloropropene (Telone II) is an effective and specific pre-plant soil fumigant for nematodes. Nonfumigant nematicides can also be applied pre-plant or at planting, but their efficacy may not rival that of the fumigants (Figure 19).

Figure 19

Post-plant options
Since many weeds are hosts for lesion nematodes, poor weed control will increase lesion nematode field populations and, most likely, increase crop damage. Destruction and removal of infested perennial crops, followed by soil fumigation, are drastic, but effective tactics to reduce subsequent lesion nematode-related damage. Nonfumigant nematicides represent the best tactic for remedial reduction of lesion nematode populations to reduce crop damage. Depending upon the nematicide label and crop, some of the nonfumigants include aldicarb (Temik), oxamyl (Vydate), fenamiphos (Nemacur), and carbofuran (Furadan). Some of these compounds offer systemic protection, and all are potent neurotoxins. The cost-effectiveness of nonfumigant nematicides is very dependent upon the crop, population level of nematodes, and environmental conditions. All nematicides are extremely toxic, especially the nonfumigants like Temik and Nemacur that are nerve poisons. Nematicides should only be applied by licensed applicators.

RETURN TO TOP