1. Dithiopyr Plus Fenoxaprop for Postemergent Crabgrass (Digitaria species) Control
Michael W. Melichar, Anita L. Alexander, Daniel L. Loughner and Michelle S. Smith
Dow AgroSciences LLC

2. Dithiopyr Plus Fenoxaprop for Postemergent Crabgrass Control
Research Justification
Dithiopyr is labeled for preemergent crabgrass control in turfgrass
Typical applications occur in spring prior to or just after (1-5 leaf stage) crabgrass emergence
Fenoxaprop is labeled for postemergent crabgrass control in turfgrass
Typical applications occur in late spring or early summer after crabgrass emergence
Little research has been conducted with early postemergent (1-3 and 3-5 tiller stage) application of reduced rates of dithiopyr and fenoxaprop for crabgrass control

3. Dithiopyr Plus Fenoxaprop for Postemergent Crabgrass Control
Key Question – Will postemergent application of reduced rates dithiopyr + fenoxaprop provide crabgrass control comparable to X rate of fenoxaprop?
Trial Locations
CT, IN, MI, NJ, NC, PA (2)
Methods
Plots; 1.5M X 1.5M
Replications; 3
Application Equipment; CO2 Backpack Sprayer
Statistical Analysis
Combined data from three trials
ANOVA with Tukey means comparison test to determine differences between treatment means (p<.05)

4. Dithiopyr Plus Fenoxaprop for Postemergent Crabgrass Control
Key Findings
1 to 3 Tiller Stage
Reduced rates of 140 g ai/Ha + fenoxaprop @ 70 g ai/Ha and 140 g ai/Ha + fenoxaprop @ 100 g ai/Ha provided comparable crabgrass control to the X rate of 140 g ai/Ha
3 to 5 Tiller Stage

5. Dithiopyr Plus Fenoxaprop for Postemergent Crabgrass Control
Treatment List
- 200 g 1 – 3 Tiller
- 280 g 1 – 3 Tiller
- 140 g 1 – 3 Tiller
- 140 g ai/Ha + 70 g 1 – 3 Tiller
- 140 g ai/Ha g 1 – 3 Tiller
- 200 g Tiller
- 280 g Tiller
- 140 g Tiller
- 140 g ai/Ha + 70 g 3 – 5 Tiller
- 140 g ai/Ha g 3 – 5 Tiller

6. Crabgrass (Digitaria species)

7. Crabgrass growth stages
4 leaves
1st tiller

8. Parts of a Box-Plot + Extreme Value Upper 25% 75th Percentile
Response
120
100
Upper 25%
75th Percentile
Center 50% 80
Median l
Mean
25th Percentile 60
Lower 25% 40 20 +
Extreme Value

9. B A A A A A A B B B

10. B A A A B

11. A A A B B

12. Dithiopyr Plus Fenoxaprop for Postemergent Crabgrass Control
Conclusions
Reduced rates of dithiopyr + fenoxaprop applied at the 1 to 3 and 3 to 5 tiller stage of crabgrass development provided comparable crabgrass control to the X rate of fenoxaprop
Professional lawn care operators and golf course superintendents can confidently apply reduced rates of dithiopyr + fenoxaprop for crabgrass control resulting in savings from the X rate of fenoxaprop