Florida is the “land of flowers.” Surely, one of the things that Florida is known for is the beauty of its vegetation. Due to the tropical and subtropical environment, color can abound in Florida landscapes year-round. Unfortunately, plants are not the only organisms that enjoy the mild climate. Due to warm temperatures, sandy soil, and humidity, Florida has more than its fair share of pests and pathogens that attack bedding plants. Plant-parasitic nematodes (Figure 1) can be among the most damaging and hard-to-control of these organisms.

Nematodes are unsegmented roundworms, different from earthworms (https://edis.ifas.ufl.edu/in946) and other familiar worms that are segmented (annelids) or in some cases flattened and slimy (flatworms). Many kinds of nematodes may be found in the soil of any landscape. Most are beneficial, feeding on bacteria, fungi, or other microscopic organisms, and some may be used as biological control organisms to help manage important insect pests. Plant-parasitic nematodes are nematodes that feed on live plants (Figure 1).

Plant-parasitic nematodes are very small and most can only be seen using a microscope (Figure 2). All plant-parasitic nematodes have a stylet or mouth-spear that is similar in structure and function to a hypodermic needle (Figure 3). The stylet is used to puncture plant cells and then inject digestive juices and ingest plant fluids. Most of the plant-parasitic nematodes that are important on ornamental plants in Florida feed on roots. Some plant-parasitic nematodes, called ectoparasites, remain in the soil and feed by inserting only their stylet into the root. Other nematodes enter the plant with part or all of their body and are called endoparasites. Some endoparasites, called migratory endoparasites, continually burrow around inside the root (Figure 4). Other endoparasites, called sedentary endoparasites, establish permanent feeding sites inside the root and remain in one place. As it matures, a sedentary endoparasites body changes shape and adult females are usually swollen (Figure 5).

How do nematodes damage plants?

As plant-parasitic nematodes feed, they damage a plants root system and reduce its ability to obtain water and nutrients from the soil. When nematode numbers increase, and/or when environmental stresses occur, aboveground symptoms may become evident. Aboveground nematode symptoms often resemble nutrient deficiencies or drought stress. Symptoms include yellowing, wilting, thinning, and stunting (Figure 6). These symptoms occur because the damaged roots cannot take up water and nutrients from the soil properly. If planted into beds that already have high numbers of plant-parasitic nematodes, plants may become stunted and slowly die. Nematode damage usually occurs in localized areas that may enlarge slowly over time. While other types of nematodes may damage bedding plants on occasion, in Florida the most common are root-knot, sting, awl, and stubby-root nematodes. Be aware that similar conditions may be caused by other factors such as localized soil conditions, fungal diseases, or insects.

Root-knot nematodes are the most well-known of the plant-parasitic nematodes. These are sedentary endoparasites. Although other species are known to occur, four species are common in Florida on bedding plants: Meloidogyne incognita, M. arenaria, M. javanica, and M. enterolobii. These nematodes inject hormones into plants roots that cause knots or galls to form (Figure 7). These galls are typically easy to recognize. In addition to galls, root-knot nematodes cause other physical and physiological changes in the plant. These changes can make plants more prone to fungal and bacterial plant diseases such as root rot or vascular wilt. Sometimes the damage caused by the nematodes and the other organisms together is worse than that caused by both organisms separately.

Root-knot nematodes are one of the most destructive plant parasites. High infestations can kill many types of bedding plants. Table 1 lists some of the annual bedding plants common in Florida, and their susceptibility to several species of root-knot nematodes. This is not an exhaustive list; the majority of plants may occasionally be affected by root-knot nematodes. Different cultivars of the same plant species may react differently to the nematodes. Table 2 shows the reactions of several different cultivars of Vinca (periwinkle), and Salvia to several species of root-knot nematodes.

How do I know if nematodes are my plants’ problem?

With any plant problem, having an accurate diagnosis is important to address the problem, and to avoid wasting effort and unnecessary pesticide applications. Generally, nematode symptoms resemble the symptoms of other disorders, so visual inspection is not enough. The only reliable way to determine if plant-parasitic nematodes are causing or contributing to a plant problem is to have a nematode assay conducted by a professional nematode diagnostic lab. The Florida Nematode Assay Lab, at University of Florida, will evaluate nematode samples for a cost of $20.00 each. See the Florida Nematode Assay Lab website at https://entnemdept.ufl.edu/nematology-assay-lab/ for information on forms, fees, and sample submission. The lab staff will assign a level of risk to the sample based on what kind of nematodes they find, how many nematodes there are, and the type and age of the plants involved. To make an accurate nematode diagnosis, the lab must have a quality sample. Whether you are submitting a sample to the Florida Assay Lab or another lab, following the guidelines below can help ensure that the results will be as accurate as possible.

Sometimes samples are collected before planting to find out if nematodes are a potential problem and, if so, to take protective measures. Pre-plant samples will typically only consist of soil. After planting, samples are collected from sick plants to determine if nematodes are the cause of plant decline. Samples taken after planting require both soil and roots.

Before planting: Collect soil from 8 to 12 locations in a planting bed. Samples should be taken about 6 to 8 inches deep. If the soil is dry, dig down to where there is some soil moisture to collect the samples and do not include the dry soil. A small handful of soil from each location is adequate. Combine all the soil into a single plastic bag. The total volume of soil from the samples should be about 1 pint. Samples may be taken with a shovel, trowel, or other device. If you use a shovel, you can put part of the soil from 8 to 12 shovels full into a bucket. Thoroughly mix the soil in the bucket, and then take out a pint to submit for analysis.

After planting: Often a nematode assay is needed to determine if nematodes are causing a plant to get sick. This type of sample requires both soil and roots! Dig soil and roots from underneath the canopy of the symptomatic plants. Sample depth depends on the size of the plant. For most bedding plants, 6 inches deep is adequate. Do not include the top 1 inch of soil. If multiple plants are affected, collect some soil and roots from several plants. Place the soil and roots together in the same plastic bag. A minimum of 1 pint of soil and 1 to 2 cups of roots are required. For small bedding plants, entire plants with the soil from around their roots can be submitted.

• Nematode samples should be kept in plastic bags to keep the sample moist. Do not send samples in soil test bags. Soil testing bags are designed to dry soil out, and dried-out samples are no good for nematode diagnosis. If using a self-sealing bag, tape the seal shut so that the bag does not come open in the mail.
• If submitting more than one sample, make sure that the outside of each bag is labeled with a permanent marker. You can also write on masking tape stuck to the bag. Do not put paper labels inside of bags because they tend to decompose and become illegible.
• Keep samples out of direct sunlight or heat. Heat and ultraviolet light kill nematodes. Even a few minutes on the dashboard or in the back of a pickup can invalidate assay results. Keep the samples in an air conditioned room until they can be shipped.
• Handle the sample gently and pack it well. The more the soil gets banged around, the more the nematodes may get destroyed.
• Fill out the information on the forms with as much information as possible. The diagnostician needs detailed information about the type of plant or plants in question and the cultivar, if known. Make sure that the information on the form matches the identification on the sample bag (i.e., front yard, back yard, coleus bed).

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FAQ

What kills nematodes instantly?

How do you get rid of nematodes in plants?

What can be applied to the soil to stop nematodes?

What repels nematodes?

How do you care for autumn sage?

Autumn sage is a fairly easy-going plant. Here are the main care requirements for growing autumn sage. Plant in a spot that gets lots of sunlight, ideally at least six hours. Place in dry, well-drained soil, but do not plant in wet, clay-based soil. Water moderately, though autumn sage is fairly drought-tolerant once established.

How do you grow autumn sage?

In most regions, this plant will thrive in a site with full sun, but in very hot climates it will appreciate some shade during the heat of the day. Give the plant moderately fertile, well-drained soil. Autumn sage does well in gravely, rocky soil, but may not tolerate dense clay-based soil. Water regularly after planting.

How do you get rid of nematodes?

Solarizing involves thoroughly irrigating the soil and then putting down sheets of clear plastic to let the sun heat up the soil and cook the nematodes. To do this, till the moist soil first, then put down a sheet of two- to four-millimeter-thick clear plastic.

Does turning up soil kill nematodes?

Turning up the soil will also bring many nematodes to the surface, leaving them exposed and vulnerable. Solarizing is the process of using heat from the sun to raise the temperature of soil in a garden. The sharp temperature increase will kill nematodes in the worked-through portion of the soil. Spray the overturned soil lightly with a hose.