Management of Fusarium diseases in field crops with a new biopesticide
Project Code BPI10-020
Allen Xue - Agriculture and Agri-Food Canada
To determine optimal application rates and generate regulatory efficacy data with formulated Clonostachys rosea ACM941 for the management of Fusarium Head Blight in wheat and root rots in soybean
Summary of Results
Fusarium head blight (FHB), caused by Gibberella zeae (syn. Fusarium graminearum), is one of the most important wheat diseases in Canada. Infection of wheat by the pathogen results in grain yield loss, quality reduction, and kernel contamination with deoxynivalenol (DON) and other mycotoxins. Current management of this disease relies on fungicides in most wheat production areas. Multiple fungicide applications have increased the economic cost to growers and public concerns over pesticide risks and the development of pathogen resistance. Biocontrol methods represent an alternative to conventional management that can reduce pesticide risks and resistance development.
Clonostachys rosea CLO-1, a biopesticide developed by the Agriculture and Agri-Food Canada (AAFC) scientist Dr Allen Xue, was identified by growers as the biopesticide priority for the control of FHB at the Canadian Biopesticides Priority Setting Workshop in 2009. The effectiveness of this strain for the management of FHB in wheat has been evaluated in previous greenhouse and field trials in several projects supported by the Pest Management Centre (PMC; project codes BPI07-110, BPI08-020, BPI09-040 and BPI09-070). Recently, a commercial experimental formulation designated as CLO-1 was developed under project BPI09-050, in collaboration with the AAFC-PMC, ICUS Canada (a biopesticide company) and Cornell University. The aim of this project was to evaluate the efficacy of this formulated product in controlling FHB under greenhouse and field conditions.
In addition, preliminary laboratory and greenhouse experiments showed that CLO-1 significantly suppresses root rot pathogens such as F. graminearum, F. oxysporum, and F. solani all three in soybean. Therefore, the efficacy of CLO-1 was also tested against Fusarium root rot, a serious soybean disease caused by Fusarium species complex.
The current project consisted of 19 trials conducted at the Central Experimental Farm in Ottawa and trial fields in Harrow. These trials included (i) evaluation of five CLO-1 prototypes for their efficacy in greenhouse in comparison with the registered fungicide Folicur® (tebuconazole); (ii) identification of a range of concentrations of CLO-1 for the control of FHB under greenhouse and field conditions; (iii) evaluation of the effects of alternating sprays of CLO-1 with a low rate of Folicur (50% commercial rate) or BM 608 bioagent (i.e. CLO-1-Folicur, BM 608-Folicur, and Folicur-CLO-1) on control of FHB in greenhouse and fields; (iv) evaluation of the effect of wheat cultivars on the efficacy of CLO-1 in controlling FHB using five spring wheat cultivars (AC Brio, AC Foremost, AC Nass, Quantum, and Superb) representing a range of reactions to FHB from highly susceptible to moderately resistant in field trials; and (v) evaluation of the efficacy of CLO-1 in inhibiting perithecial production of G. zeae ß on residues of corn, soybean and wheat compared to Folicur under field conditions.
For all efficacy trials, the biopesticide CLO-1 was applied on plants when 50% of plants were blossoming and efficacy was evaluated against the area under the disease progress curve (AUDPC), percentage of infected spikelet (IS), Fusarium-damaged kernels (FDK), thousand kernel weight (TKW), and yield. In addition, field trials were conducted in Ottawa and Harrow to evaluate the efficacy of CLO-1 seed treatment for the control of soybean root rot caused by artificial inoculation of Fusarium graminearum (Fg), F. oxysporum (Fo), and F. solani (Fs), in comparison with the fungicide Vitaflo-280. In the assessment of CLO-1 control of Fusarium root rot, a field trial was performed to examine the proliferation and population dynamics of CLO-1 on soybean roots after soybean seed treatment.
Comparison of CLO-1 prototype efficacies
All five prototypes effectively controlled FHB, but Prototype-5 also showed a low level of phytotoxicity. There were no statistically significant differences among the 5 prototypes, but prototype-3 was numerically superior to the others, reducing the AUDPC by 82.9%, IS by 81.9% and FDK by 72.7%; and increasing wheat yield by 55.7% and TKW by 26.0%, as compared with the untreated control. These effects were less pronounced than, but not statistically different from those obtained with Folicur treatments.
Effects of varying concentrations on efficacy
Consistent and significant concentration effects were observed in both greenhouse and field trials. In the greenhouse, CLO-1 at concentrations of 8 × 106 to 1 × 108 cfu/mL significantly reduced the AUDPC by 65.4-83.2%, IS by 6.6-8.9%, FDK by 67.8-91.6% and DON by 51.4-95.1%; and increased yield by 85.7-88.1% and TKW by 47.2-57.6%. Under field conditions, significant effects were observed at or above 3 × 106 cfu/mL. On average, CLO-1 reduced the AUDPC by 25.4-37.1%, FHB index by 30.1-46.3%, FDK by 30.7-38.5%, and DON by 21.6-32.5% at concentrations of 3 × 106 to 1 ×108 cfu/mL. These effects were not significantly different from those obtained with Folicur.
Effects of alternating CLO-1 sprays with a low rate of Folicur on efficacy In greenhouse trials, two CLO-1 applications at a 5-day interval was the most effective treatment, and significantly better than the others at reducing IS. However, alternating treatments (CLO-1-Folicur, BM 608-Folicur, and Folicur-CLO-1) were the most effective treatments for other parameters, thus reducing the AUDPC by 74.4-89.0%, FDK by 79.9-89.0% and DON by 86.7-97.6%; and increasing yield by 76.8- 80.6% and TKW by 53.6-60.6%. Compared with two applications of Folicur, enhanced efficacy was observed with Folicur-CLO-1 and CLO-1-Folicur treatments in reducing the AUDPC, IS and DON.
Effects of wheat cultivars on efficacy of CLO-1
Results indicated that CLO-1 was most effective on the moderately resistant cultivar AC Nass and least effective on the highly susceptible cultivar AC Foremost. On average for the five cultivars, CLO-1 significantly reduced the AUDPC and FHB index by 19.2% and 32.6%, respectively. These effects were better but not significantly different from those of Folicur. Neither CLO-1 nor Folicur significantly reduced FDK or DON in these trials.
Effects of CLO-1 on perithecial production
CLO-1 significantly suppressed daily perithecial production on crop residues, with a reduction in perithecia of 96.6% on corn residue, 98.5% on soybean, and 97.4% on wheat. When CLO-1 was applied on the residues in the previous fall, perithecial production was delayed by 2-3 weeks the next spring compared to untreated residues, and daily perithecial production was reduced by 59.3% on peduncles, 53.2% on spikelets, and 55.7% on stems. These effects of CLO-1 on perithecia production were numerically better but not significantly different from those observed with Folicur.
Efficacy of CLO-1 on the control of Fusarium root rot in soybean
The field trial indicated that CLO-1 can propagate and quickly establish colonization on the surface of hypocotyls and roots as the seed germinates and the seedling plant develops and grows. CLO-1 density was greater on buds than on seeds where the bioagent was applied. During the growing season from July to October, a generally higher density of CLO-1 was observed on secondary roots than on taproots. On the taproots, density was lowest at the beginning of the season, peaked in August, and decreased again in September and October. On the secondary roots, trends were not clear, but density was consistently high over the entire growing season. Although the field trial showed that CLO-1 is a good root surface colonizer, it did not show significant efficacy in the field for the control of Fusarium root rot of soybean caused by Fusarium spp.
Results of this research project indicate that CLO-1 is an effective microbial biocontrol product that can be used for foliar application at concentrations of 5 x 106 to 1 x 10 8 cfu/mL for the control of FHB, or used for the spray treatment of crop residues to inhibit G. zeae perithecial production, thereby reducing the initial inoculum of FHB. It seems that prototype 3 formulated by ICUS provided the best efficacy.
To validate the efficacy of CLO-1 in controlling FHB in wheat at the on-farm scale, additional field trials may be needed at multiple sites in diverse environments. CLO-1 may exhibit better efficacy in combination with a forecasting model for FHB in wheat or in an Integrated Pest Management (IPM) program. Therefore, further research may be needed to determine how to integrate CLO-1 into an IPM program, or how to apply it based on a forecasting model. In addition, further research is needed to evaluate the efficacy of CLO-1 as a seed treatment for the control of Fusarium root rot and seedling blight of soybean.
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