Evaluation of a Biological Control Agent for Control of Root-Knot Nematode,
Meloidogyne marylandi, on Turfgrass
Rachel A. McGregor and Travis R. Faske
Department of Environmental and Agricultural Management, Tarleton State University, Stephenville, TX
Turfgrass color, density, and root quality were similar among
treatments at all sample dates in this study. All treatments averaged
6.8 quality index for color and density; however a quality index above
8 was observed for all plots after fertilization and aeration.
Furthermore, these observations were similar to those collected with
a chlorophyll meter. The average chlorophyll index increased from
199.2 (before treatment) to 453.0 (90 days after treatment), which
was consistent with fertilization and turfgrass management.
The average root quality rating was similar among treatments
(Fig. 4). Numerically, turfgrass treated with Nortica at all rates
averaged longer root length than water control.
Introduction
Meloidogyne marylandi, root-knot nematode, is a widely distributed pest
of turfgrass in Texas (Starr et al., 2007). This root-knot nematode is frequently
associated with turfgrass exhibiting various symptoms of decline and poor
growth (Fig. 1). Female root-knot nematodes are located on turfgrass roots
which can exhibit slight galling (Fig. 2). Despite its distribution and importance
on turfgrass few studies have investigated practices to manage this nematode
species. Bacillus firmus, a biological control agent, has been reported to
reduce root-knot nematode populations (Giannakou and ProphetouAthanasiadou, 2004); however, no study has evaluated the effects of Bacillus
firmus on M. marylandi.
Figure 2. Root-knot nematode females (yellow arrows) on bermudagrass root.
Results
The initial population density of root-knot nematode (RKN) was similar
among plots and averaged 192.9 eggs/g of root. Thus, all plots had a moderate
population density of RKN on turfgrass. No phytotoxicity was observed on plots
treated with Nortica or DiTera.
Nematode reproduction increased 90 days after treatment among all
treatments; however no difference was observed among treatments (Fig. 3).
Numerically, turfgrass treated with Nortica at 90 lb/A and DiTera at 50 lb/A had a
lower reproduction index than water control.
Figure 1. Decline and poor growth caused by root-knot nematode on a golf course putting
green in Stephenville, Texas.
Objectives
1.
Evaluate B. firmus to control M. marylandi on turfgrass
2. Determine the effect of B. firmus on turfgrass quality
Figure 4. Length of root development treated with two biological control agents 90
days after treatment.
Methods and Materials
This study was conducted on a golf course putting green (cv. Mini Verde,
bermudagrass) naturally infested with root-knot nematodes. Based on esterase
and malic dehydrogenase isoenzymatic pattern this species was identified as M.
marylandi. Nortica (Bayer Environmental Sciences), B. firmus was applied at 0, 50,
75, 90 lb/acre, and Myrothecium verrucaria, (DiTera DF, Valent Biosciences
Corporation) applied at 50 lb/acre served as the industry standard. Each treatment
was replicated four times in a randomized complete block design. Each treatment
was applied in late March to a 25 sq. ft. (5 ft x 5 ft) plot and irrigated with 0.25 in
of water. Reproduction was determined based on eggs produced on turfgrass
roots. Turf response to treatment was based on a turf color rating (chlorophyll
meter) turf quality rating (1=poor to 9=excellent based on color and density) and
root quality (quantitative measurement, root length, and weight).
Conclusion
Nematode population density and turfgrass quality varied in response
to all rates of Nortica in this study. Further investigation will continue in the
fall to assess B. firmus for control of M. marylandi and determine effects on
turfgrass quality.
Literature Cited
Figure 3. Reproduction of M. marylandi on bermudagrass treated with two biological control
agents. Reproduction index was calculated by dividing the final population (Pf= 90 days after
treatment) by the initial population (Pi= before treatment) of nematodes sampled.
Starr, J. L., Ong, K. L., Huddleston, M., and Handoo, Z. A. 2007. Control of
Meloidogyne marylandi on bermudagrass. Nematropica 37:43-49.
Giannakou, I. O. and Prophetou-Athanasiadou, D. 2004. A novel non-chemical
nematicide for the control of root-knot nematodes. Applied Soil Ecology 26:
69–79.