1 How do nematodes cause turf damage?
A: Plant parasitic nematodes have needle-shaped mouthparts that allow them to draw nutrients from plant cells. Most nematodes feed on turf roots, reducing the depth and density of root growth. Nematodes rarely kill turf outright, but instead make it more prone to drought, heat, mechanical wear, nutrient deficiency and disease.
2 How are nematode problems diagnosed?
A: Nematode problems can be difficult to diagnose since symptoms are so variable. Areas that are constantly weak, lack root growth or are prone to other stresses may be infested with nematodes. These areas should be sampled to determine if nematodes are present. Visit www.GreenCastOnline.com/NematodeKnowledge for a video and downloadable PDF guide about collecting nematode samples, and a list of 30 labs to submit samples to.
Nematode assay results are usually expressed as a number per 100 cubic centimeters of soil, and compared to threshold values for each nematode species on each turf type. If populations are above the threshold, turf is likely to benefit from a nematicide application.
Assay results are often inconclusive if populations are borderline, or if multiple nematodes are present in moderate amounts. A more definitive way to diagnose a nematode problem is to apply a nematicide to see if it improves turf health and quality.
3 When is the best time to apply a nematicide?
A: Nematodes have the greatest impact during periods of turf root growth. This is the key time to manage populations with a nematicide like Divanem®. Even though symptoms of nematode damage are most common in mid-summer, spring and fall are the best times to apply nematicides in most climates. We generally recommend three to four Divanem applications (12.2 fl. oz./A) on a 28-day interval in spring and early summer when root growth is occurring. These applications keep nematode populations under control, allowing turf to grow a deeper, denser root system in preparation for summer stress.
4 How do I tell if a nematicide is working?
A: Nematode counts are a valuable diagnostic tool, but aren’t a good judge of nematicide performance. Nematode populations naturally ebb and flow with root growth and weather conditions, so comparing assay results before and after a nematicide application can be misleading. You must sample untreated areas at the same time to determine how the background population changed, and how the nematicide influenced it.
The goal of a nematicide program is to increase root growth and create turf that is more stress-tolerant and resilient. Focus on turf health and quality as primary indicators of nematicide performance, and leave an untreated area for comparison.
5 Why do you recommend tank-mixing fungicides with nematicides?
A: Diseases are an additional stress that contribute to the decline of nematode-infested turf. Wounds created by nematode feeding are susceptible to infection by root diseases like take-all, summer patch and Pythium. Compared to applications of Divanem alone, tank-mixing Divanem with a fungicide like Heritage® Action™ or Velista® consistently provides better turf quality and root growth.