The sting nematode is a microscopic roundworm averaging about 1/12 inch in length. It is found almost exclusively in soils with a sand content of 80 percent or higher and thrives best in irrigated cropland where there is a constant supply of moisture. Sting nematodes do not enter plant roots'. All life stages remain in the soil, feeding at or near root tips. Even small populations can cause serious damage because of a powerful toxic chemical injected into the roots during feeding.
Plant roots
Sting nematodes typically feed on root tips. In response to this feeding, root tips cease to grow, causing an abbreviated or stubby-appearing root system. The roots may appear cropped-off just below the soil surface. With high population densities, complete root destruction can occur. Damaged roots have a greatly reduced ability to take up water and nutrients from the soil, and this leads to expression of aboveground symptoms and yield reductions.
Chemical control
Sting nematodes can be effectively managed with nematicides. Unlike many of the endoparasitic nematodes that spend a majority of their life within roots, contact nematicides often work well on sting nematode. Both carbamate (aldicarb, carbofuran) and organophosphate (fenamiphos, ethoprop, turbufos) nematicides and fumigants (methyl bromide, 1,3-dichloropropene, metam sodium) are currently registered and can be effectively used to reduce sting nematode populations. On annual crops, nematicides applied either before or at planting usually provide acceptable levels of control by protecting newly developing root systems. On perennial crops such as turfgrasses, seasonal application of post-plant nematicides during times of root growth may be required.
Cultural practices
When possible, avoid use of infested planting material. Sting nematodes and other pathogens can be moved in the soil adhering to the sod. It is believed that this is the primary way that the sting nematode has become established in new areas, especially outside of its native geographical range.
Relieving additional stresses by raising mowing height, increasing irrigation frequency, improving aeration to roots, and reducing traffic can improve tolerance to sting nematodes. The addition of organic, and some inorganic, amendments to soil also can improve tolerance to sting nematodes by improving the water and nutrient-holding capacity of the soil. Organic amendments have also been shown to reduce population densities of sting nematodes in some studies. This may be due to direct effects of these additives on the nematodes or due to stimulation of antagonistic microorganisms in the soil.
Biological control
Pasteuria usgae, an endospore-forming bacterium, is an obligate parasite of B. longicaudatus. Pasteuria usgae was successfully introduced into a previously non-infested putting green resulting in the suppression of sting nematodes. Presently, the only method for infesting a field site with P. usgae is by adding soil from a site that already has sting nematodes infected with the bacterium. Unfortunately, this method is not economically feasible for commercial use. However, in vitro production of P. usgae is being attempted at this time. If these efforts are successful, P. usgae may become a viable inoculative biological control agent for sting nematodes in the future.
Symptoms
Primary damage from the sting nematode is to the roots of the plant. The degree of injury to the roots varies with the age of the plant when attacked. Symptoms are most severe when the feeding occurs during the first few weeks after planting.
In general, symptoms consist of greatly reduced root systems with short, stubby roots having dark, shrunken lesions, particularly at the tips. If the root tip is destroyed, new roots may be produced above the damaged area, resulting in a highly-branched appearance. Plants which are not severely damaged by the initial feeding may recover and produce near-normal yields under optimum growing conditions.
In general, symptoms consist of greatly reduced root systems with short, stubby roots having dark, shrunken lesions, particularly at the tips. If the root tip is destroyed, new roots may be produced above the damaged area, resulting in a highly-branched appearance. Plants which are not severely damaged by the initial feeding may recover and produce near-normal yields under optimum growing conditions.
Plant roots
Sting nematodes typically feed on root tips. In response to this feeding, root tips cease to grow, causing an abbreviated or stubby-appearing root system. The roots may appear cropped-off just below the soil surface. With high population densities, complete root destruction can occur. Damaged roots have a greatly reduced ability to take up water and nutrients from the soil, and this leads to expression of aboveground symptoms and yield reductions.
Above-ground
With moderate initial population densities of sting nematodes, young plants may experience reduced vigor, slow growth, and stunting. With high initial population densities, young plants may stop growing completely following seed germination or transplanting and eventually die. The foliage of affected plants may turn yellow or red due to nutrient deficiencies in the foliage resulting from an impaired root system or to physiological responses in the plant in response to nematode feeding.
Control
Sting nematodes can be effectively managed with nematicides. Unlike many of the endoparasitic nematodes that spend a majority of their life within roots, contact nematicides often work well on sting nematode. Both carbamate (aldicarb, carbofuran) and organophosphate (fenamiphos, ethoprop, turbufos) nematicides and fumigants (methyl bromide, 1,3-dichloropropene, metam sodium) are currently registered and can be effectively used to reduce sting nematode populations. On annual crops, nematicides applied either before or at planting usually provide acceptable levels of control by protecting newly developing root systems. On perennial crops such as turfgrasses, seasonal application of post-plant nematicides during times of root growth may be required.
Cultural practices
When possible, avoid use of infested planting material. Sting nematodes and other pathogens can be moved in the soil adhering to the sod. It is believed that this is the primary way that the sting nematode has become established in new areas, especially outside of its native geographical range.
Relieving additional stresses by raising mowing height, increasing irrigation frequency, improving aeration to roots, and reducing traffic can improve tolerance to sting nematodes. The addition of organic, and some inorganic, amendments to soil also can improve tolerance to sting nematodes by improving the water and nutrient-holding capacity of the soil. Organic amendments have also been shown to reduce population densities of sting nematodes in some studies. This may be due to direct effects of these additives on the nematodes or due to stimulation of antagonistic microorganisms in the soil.
Biological control
Pasteuria usgae, an endospore-forming bacterium, is an obligate parasite of B. longicaudatus. Pasteuria usgae was successfully introduced into a previously non-infested putting green resulting in the suppression of sting nematodes. Presently, the only method for infesting a field site with P. usgae is by adding soil from a site that already has sting nematodes infected with the bacterium. Unfortunately, this method is not economically feasible for commercial use. However, in vitro production of P. usgae is being attempted at this time. If these efforts are successful, P. usgae may become a viable inoculative biological control agent for sting nematodes in the future.
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