Improving fungicide-based management of Cercospora leaf spot in table beet in New York, USA

Figures & data

Fig. 1 Frequency of azoxystrobin-sensitive and -resistant Cercospora beticola isolates collected from conventional and organic table beet fields in 2015 (a), 2016 (b), and 2017 (c) based on in vitro conidial germination assays.

Table 1. Effect of fungicides (benzovindiflupyr, difenoconazole, benzovindiflupyr + difenoconazole, and propiconazole [conventional fungicide standard]) and frequency of applications on Cercospora leaf spot (CLS) disease severity and epidemic progress, canopy reflectance at 830 nm, and table beet yield components in a small-plot, replicated trial at Geneva, New York in 2017.

Fungicide (number of applications)	CLS lesions per leaf (76 DAP) ^a	AUDPS ^b	Canopy reflectance at 830 nm (77 DAP)	Dry weight of foliage (g m^−1; 80 DAP)	Roots m^−1 (80 DAP)	Fresh weight of roots (g m^−1; 80 DAP)	Average root shoulder diameter (cm; 80 DAP)
Benzovindiflupyr (1)	50.3 bc	871 bc	22.6 d	206.1 e	46.0	1,640.0 cd	4.32
Benzovindiflupyr (2)	52.1 bc	798 c	23.9 d	243.5 cde	46.8	1,640.1 cd	4.24
Benzovindiflupyr (3)	48 bc	836 c	26.7 cd	245.2 cde	38.2	1,710.0 bcd	4.57
Difenoconazole (1)	42.3 c	493 d	29.8 bc	222.0 d	44.0	1,630.1 cd	4.42
Difenoconazole (2)	18 d	272 e	36.2 a	308.7 bcd	48.0	2,040.0 ab	4.57
Difenoconazole (3)	4.9 e	122 ef	39.8 a	343.9 ab	45.2	2,150.1 a	4.59
Benzovindiflupyr + Difenoconazole (1)	14.9 de	241 ef	31.6 b	300.2 bcd	44.5	1,810.4 abc	4.42
Benzovindiflupyr + Difenoconazole (2)	9.2 de	181 ef	37.0 a	316.4 abc	43.8	1,890.1 abc	4.49
Benzovindiflupyr + Difenoconazole (3)	3.6 e	110 f	39.7 a	407.7 a	58.2	2,157.9 a	4.34
Propiconazole (1)	58.9 b	997 b	26.3 cd	309.9 bcd	48.2	1,719.9 bc	4.34
Propiconazole (2)	49.7 bc	788 c	30.1 bc	250.6 bcde	56.5	1,759.9 bc	4.42
Propiconazole (3)	41.3 c	722 c	29.8 bc	251.2 bcde	49.0	1,710.0 bcd	4.37
Non-treated	78.9 a	1583 a	22.6 d	111.7 f	48.8	1,340.1 d	4.01
LSD ^c	12.4	149.9	4.4	93.8	-	369.9	-
P	<0.001	<0.001	<0.001	<0.001	0.206 (ns) ^e	0.004	0.162 (ns)
CV ^d (%)	13.0	17.0	2.5	24.2	18.6	14.4	5.9

^a DAP = Days After Planting.

^b AUDPS = Area Under the Disease Progress Stairs (measure of epidemic progress). Larger values indicative of higher disease severity and faster spread.

^c LSD = Least Significant Difference.

^d CV = Coefficient of Variation.

^e ns = not significant.

Fig. 2 Temporal changes in the average number of cercospora leaf spot (CLS) lesions per leaf from 43 to 76 days after planting (DAP) in plots receiving up to three applications (number of applications in parentheses) of benzovindiflupyr (a), benzovindiflupyr + difenoconazole (b), difenoconazole (c), and propiconazole (d) in a small-plot, replicated trial conducted at Geneva, New York in 2017.

Table 2. Effect of fungicides (benzovindiflupyr + difenoconazole, difenoconazole, pydiflumetofen + difenoconazole, and propiconazole) and the number of applications on cercospora leaf spot (CLS) disease severity and epidemic progress, canopy reflectance at 830 nm, and table beet yield components in a small-plot, replicated trial at Geneva, New York in 2018.

Treatment (Application Frequency)	CLS lesions per leaf (93 DAP) ^a	AUDPS ^b	Canopy reflectance at 830 nm (93 DAP)	Dry weight of foliage (g m^−1; 94 DAP)	Roots m^−1 (94 DAP)	Fresh weight of roots (g m^−1 94 DAP)	Average root shoulder diameter (cm; 94 DAP)
Pydiflumetofen + Difenoconazole (1)	20.3 ef	306 f	34.56 d	170.7 ab	39.1	4,010	5.51
Pydiflumetofen + Difenoconazole (2)	3.9 g	41 g	40.06 ab	189.2 ab	39.5	4,250	5.83
Pydiflumetofen + Difenoconazole (3)	1.7 g	21 g	40.17 ab	173.4 ab	30.5	3,921	6.09
Difenoconazole (1)	17.4 f	304 f	33.56 de	184.9 ab	30.5	3,874	5.85
Difenoconazole (2)	26.9 e	409 e	36.56 cd	152.0 b	38.2	3,762	5.82
Difenoconazole (3)	5.0 g	83 g	38.32 bc	162.5 b	35.2	3,688	5.71
Benzovindiflupyr + Difenoconazole (1)	37.6 d	536 d	30.53 e	148.4 b	31.8	4,055	6.01
Benzovindiflupyr + Difenoconazole (2)	6.9 g	83 g	40.69 ab	210.3 a	43.2	4,201	5.77
Benzovindiflupyr + Difenoconazole (3)	5.3 g	82 g	42.81 a	172.5 ab	39.5	3,834	5.49
Propiconazole (1)	65.0 b	1113 b	24.69 f	151.2 b	33.2	3,833	6.78
Propiconazole (2)	39.3 cd	714 c	34.16 d	173.7 ab	46.8	4,192	5.46
Propiconazole (3)	46.3 c	741 c	34.69 cd	168.2 ab	34.2	3,723	6.10
Non-treated	76.9 a	1573 a	25.07 f	71.2 c	33.2	3,674	5.80
LSD ^c	8.1	118	3.36	47.5	-	-	-
P	< 0.001	< 0.001	< 0.001	< 0.001	0.243 (ns) ^e	0.826 (ns)	0.342 (ns)
CV ^d (%)	6.3	4.8	2.6	8.3	14.5	7.5	6.3

^aDAP = Days After Planting.

^bAUDPS = Area Under the Disease Progress Stairs (measure of epidemic progress). Larger values indicative of higher disease severity and faster spread.

^cLSD = Least Significant Difference.

^dCV = Coefficient of Variation.

^ens = not significant.

Fig. 3 Temporal changes in the average number of cercospora leaf spot (CLS) lesions per leaf from 51 to 93 days after planting (DAP) in plots receiving up to three applications (number of applications in parentheses) of benzovindiflupyr + difenoconazole (a), pydiflumetofen + difenoconazole (b), difenoconazole (c), and propiconazole (d) in a small-plot, replicated trial conducted at Geneva, New York in 2018.