Bug of the Day: Sting Nematode
Depending on how you define the term “bug,” sting nematodes might not be bugs at all. Yes, they’re small invertebrates (animals without backbones), and might give you the heebie-jeebies when you think about them. But unlike insects or spiders or scorpions, nematodes are not members of the phylum called Arthropoda. Instead, they have their own phylum, Nematoda. Nematodes are sometimes called “unsegmented round worms,” but they’re not closely related to the earthworms in your garden – those organisms are part of yet another phylum called Annelida.
The term “sting nematode” is often used as a catch-all common name for any species from the nematode genus Belonolaimus, but it particularly refers to one species, Belonolaimus longicaudatus. As nematodes go, this one is unusually large – a full-grown adult is 2 or 3 millimeters long and only about one-tenth of a millimeter wide. That’s huge for a nematode, but on a human scale it’s still so small that many people would be unable to spot one with the naked eye.
The sting nematode is native to Florida, and it parasitizes plant roots, including the roots of many grasses and agricultural crops. It’s a particularly significant problem for the state’s golf industry, because the sting nematode loves sandy, well-drained soil and the subsurface of a putting green is a perfect habitat.
Check out the STING NEMATODE acrostic below to find out more about these pests:
S – Stylet
A stylet is a slender probe that forms part of the sting nematode’s mouth. It uses the stylet to feed on cells in a plant’s roots, inserting the stylet like a hypodermic needle into one cell, injecting enzymes to liquefy the contents, and then consuming the liquid that results. When multiple sting nematodes begin feeding on a single root tip, it can cause the entire root to stop growing. If this happens to multiple roots simultaneously, it can deprive the plant of nutrients and water, weakening and eventually killing the plant.
T – Turfgrass
Turfgrass is the sting nematode’s favorite food. Though this pest has a wide host range – fruits, vegetables, forages, grains, agronomic crops, even weeds – the sting nematode is most commonly known as a pest to the grasses we grow in our lawns, such as St. Augustinegrass, Bermudagrass, zoysia, centipede, and seashore paspalum. Nematode damage causes reduced tolerance to stress (drought or flooding), which, in turn, leads to patches of wilting and dead grass.
I – Integrated Pest Management
Integrated Pest Management, also known as IPM, is a holistic approach to pest control that emphasizes prevention, scouting and conservative use of pesticides. Usually the best way to discourage a pest is through a combination of cultural practices (mowing or irrigation), chemical practices (the use of insecticides), and biological control (development of resistant cultivars or the introduction of predators). There are several biological control methods already in use, including a resistant cultivar of Bermudagrass called Celebration, and a pathogenic bacterium, Pasteuria usgae.
N – Nematode Phylum
It’s been estimated that there are more individual nematodes on Earth than there are multi-celled animals of any other type. Supposedly, it’s not uncommon for there to be one million nematodes present in a square meter of surface area and its accompanying topsoil. Nematodes exist in almost every Earthly environment you can imagine. About 25,000 species have been formally described by scientists and given a scientific name, and estimates suggest that there may be as many as 1 million nematode species on Earth. About half of the described nematode species are parasitic on plants and animals.
G – Golf Courses
Sting nematodes dwell in very sandy soils; they don’t usually live in heavier clay soils. Their preference for sandy soils combined with their love of turfgrass makes golf courses and putting greens the perfect homes for sting nematodes. Because of this, many golf courses have begun using a Bermudagrass cultivar called Celebration – as mentioned previously, it has improved tolerance to sting nematodes.
N – Nematicides
Nematicides are insecticides that target nematodes. Chemical nematicides can be used to control sting nematode populations but they must be applied by a licensed pest-control operator.
E – Ectoparasite
An ectoparasite is a type of parasite that lives on the outside of its host. For sting nematodes, that means that they spend their entire life cycle in the soil, feeding on the outside of plant roots, particularly at the elongation of the root where cell division occurs.
M – Methyl Bromide
Methyl bromide is soil fumigant that was once widely used in Florida to prepare outdoor fields for planting, by reducing populations of sting nematodes, insects and plant pathogens, prior to planting crops. In recent years, the chemical has been phased out by the federal Environmental Protection Agency, leading to increased research into new chemicals and biopesticides that might stop sting nematodes.
A – Amphimictic
Sting nematodes are amphimictic, which means that males and females can interbreed freely and produce fertile offspring. In any given population, there is an abundance of both male and female nematodes, and they must be attracted to each other in order to reproduce.
T – Temperatures
When usually high or low air temperatures threaten, the sting nematode moves deeper into the soil to protect itself. This is called seasonal vertical migration. By digging deeper to avoid the extreme hot or cold, the sting nematode can also avoid any fumigants applied to the upper portions of the soil, making them difficult to control.
O – Ornamentals and Agricultural Crops
In addition to turfgrasses, the sting nematode also attacks ornamentals and agricultural crops including citrus, cotton, and forages. Beans, carrots, corn, crucifers, potatoes, strawberries, peanuts, sorghum, soybeans and even pine trees are all plants that the sting nematode will feed upon.
D – Damaged roots
When sting nematodes feed on the roots of plants, they cause the roots to become stunted, making it difficult for the roots to absorb water and nutrients from the soil. This, in turn, leads to symptoms showing up in the aboveground portions of the plants, and reduced crop yields. For example, the foliage of plants might turn yellow or red because of nutrient deficiencies. Sometimes the plants will grow lateral roots to counteract the attack of the sting nematodes, but the sting nematodes will migrate to feed on the lateral roots as well.
E – Economic Pest
Sting nematodes feed on a wide range of plants, particularly economically important plants like the fruits and vegetables that we eat and the grasses we use on our lawns, athletic fields and golf courses. This makes them extreme economic pests, costing farmers and gardeners lots of money from reduced yields or destroyed plants, as well as the money and resources needed to control sting nematodes.
S – Sunn Hemp and Crop Rotation
Sting nematodes are unable to survive for long periods without plant roots to feed on. Therefore, crop rotation can be used to control sting nematodes. Since sting nematodes eat a wide range of plants, it can be difficult to find a non-host plant with which to rotate. Sunn hemp, however, has been shown to be resistant to sting nematodes and can be used as a summer cover crop. (LINK TO SUNN HEMP DOC AT https://edis.ifas.ufl.edu/ng043)
You can learn more about the sting nematode at this “Featured Creatures” document, from the UF/IFAS Entomology and Nematology Department. http://entnemdept.ufl.edu/creatures/nematode/sting_nematode.htm
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UF/IFAS Photo by Tyler Jones