Powdery mildew (Leveillula taurica) on greenhouse and field peppers in Ontario – host range, cultivar response and disease management strategies

Figures & data

Table 1.  Spore dimensions for isolates of Leveilulla taurica originating from six commercial field pepper sites in Essex and Kent counties of Ontario in 2005

Isolate #	Spore type	Length (μm)	Width (μm)	Mean length/width ratio
14	pyriform^a	66.0 ± 4.71**	15.1 ± 1.40	4.4
	cylindric^b	60.4 ± 4.88	14.8 ± 1.10	4.1
23	pyriform	66.1 ± 4.71	15.8 ± 1.54	4.2
	cylindric	62.4 ± 5.02	14.6 ± 3.18	4.4
25	pyriform	65.7 ± 4.42	15.8 ± 3.59	4.2
	cylindric	61.4 ± 3.81	14.4 ± 1.68	4.3
26	pyriform	61.9 ± 4.55	14.9 ± 1.44	4.2
	cylindric	58.4 ± 4.34	13.9 ± 1.26	4.2
29	pyriform	64.2 ± 4.52	15.3 ± 1.70	4.2
	cylindric	59.9 ± 5.37	14.6 ± 1.50	4.1
30	pyriform	64.4 ± 5.21	14.4 ± 2.05	4.6
	cylindric	58.9 ± 5.46	14.0 ± 1.67	4.3
gh*	pyriform	70.8 ± 4.95	21.1 ± 2.83	3.4
	cylindric	66.3 ± 6.36	18.6 ± 2.12	3.1
*Greenhouse data reported previously (Cerkauskas et al.,1999).
^aMean length and width for field isolates is 64.7 and 15.2 μm, respectively.
^bMean length and width for field isolates is 60.3 and 14.4 μm, respectively.
**Mean ± standard deviation based on 20 spores from each of two slides.

Table 2.  Evaluation of greenhouse pepper cultivars for final per cent disease severity due to Leveillula taurica and area under the disease progress curve (AUDPC)

	Trial 1		Trial 2
Cultivar	Final % disease severity	AUDPC^2	Final % disease severity	AUDPC
Samanta	20.9	2.2	20.4	1.4
Cubico	12.6	1.2	13.8	0.9
Inia	9.0	1.2	17.1	1.2
Monster	6.8	0.7	23.9	1.6
Captain	7.9	0.6	ND	ND
Triple 4	6.8	0.5	8.8	0.6
Duplo	3.7	0.4	16.4	1.0
Bosanova	4.1	0.3	ND	ND
FLSD^1 0.05	7.6	0.6	9.9	0.5
^1Fisher's least significant difference (P = 0.05) between greenhouse pepper cultivars.
^2Area under the disease progress curve.
ND = not done.

Table 3.  Efficacy of various reduced-risk materials for control of pepper powdery mildew incited by Leveillula taurica on ‘Cubico’ greenhouse pepper at 56, 67 and 98 days after treatment application

	Days after treatment application
		56			67			98
Treatment	Rate	Diff ^a	AUDPC^b	Fds^c	Diff	AUDPC	Fds	Diff	AUDPC	Fds
H2O		2.0 a*	67.5 a	2.0 a	3.7 a	99.7 a	3.8 a	19.2 a	458.4 a	19.3 a
Milstop	3^!	0.8 bc	21.2 bc	0.8 bc	0.7 bc	30.5 bc	0.8 bc	11.2 b	217.8 bc	11.3 b
Nova	0.34^!	0.0 c	5.3 c	0.1 c	0.0 c	6.4 c	0.1 c	1.2 c	27.6 d	1.3 c
Procure	0.4^!	0.0 c	5.3 c	0.1 c	0.0 c	6.4 c	0.1 c	1.7 c	35.3 d	1.8 c
Procure	0.2^!	0.0 c	5.3 c	0.1 c	0.0 c	6.4 c	0.1 c	1.4 c	31.2 d	1.5 c
Lactosan 7.5% + (Agral 90)	75^#(1^#)	0.6 c	17.0 bc	0.6 c	0.5 c	23.7 bc	0.6 c	3.2 c	82.9 cd	3.2 c
Quintec	0.00625^#	0.0 c	5.8 c	0.1 c	0.0 c	7.2 c	0.1 c	1.9 c	41.9 d	2.0 c
Quintec	0.00375^#	0.4 c	13.3 bc	0.4 c	0.3 c	17.8 bc	0.4 c	3.2 c	73.9 cd	3.2 c
Valent-10118	0.125^#	0.0 c	6.4 c	0.2 c	0.4 c	10.3 c	0.6 c	3.9 c	80.9 cd	4.0 c
Valent-10118	0.06^#	0.2 c	9.9 bc	0.4 c	0.4 c	14.8 c	0.6 c	2.9 c	69.8 cd	3.0 c
CaCl2 + (Agral 90)	3.68^!(1^#)	1.6 ab	35.3 b	1.7 ab	2.4 ab	58.0 b	2.5 ab	11.2 b	271.3 b	11.3 b
K2HPO4 + (Agral 90)	6.97^! (1^#)	0.9 bc	23.7 bc	1.0 bc	1.0 bc	35.2 bc	1.1 bc	7.2 bc	166.0 bcd	7.3 bc
^aPer cent difference between mean final and initial disease severity values.
^bArea under disease progress curve.
^cPer cent final disease severity.
*Values followed by the same letter in each column are not significantly different (P = 0.05) according to Fisher's Protected LSD test.
^!Rate in g L^−1;
^#Rate in mL L^−1.

Fig. 1. Effect of application of reduced-risk materials upon development of powdery mildew (L. taurica) in greenhouse ‘Cubico’ pepper.

Table 4.  Efficacy of various rates of JMS Stylet-Oil for control of powdery mildew incited by Leveillula taurica on greenhouse pepper in three separate experiments

			Disease severity*
Treatment	Rate^a	Number of applications	Final %	AUDPC ^b
Experiment 1
Stylet-Oil	125	1	2.2 b^c	0.22 b
	250	1	2.4 b	0.14 b
	500	1	1.8 b	0.17 b
Check – uninoculated			0.3 b	0.03 b
Check – inoculated			67.2 a	9.42 a
Experiment 2
Stylet-Oil	12.5	1	1.1 b	0.17 b
	25	1	2.0 b	0.28 b
	50	1	1.3 b	0.19 b
Check – inoculated			58.3 a	7.06 a
Experiment 3
Stylet-Oil	12.5	1	32.7 b	3.87 bc
	12.5	2	20.9 bc	5.10 ab
	12.5	3	10.2 cd	2.05 d
	25	1	50.0 a	5.92 a
	25	2	7.1 cd	2.69 cd
	25	3	5.6 d	4.19 bc
Check – inoculated			56.2 a	4.02 bc
*Evaluated 23, 30, and 36 days after spray application in separate experiments corresponding to experiment 1, 2, 3 respectively. All experiments were repeated once.
^aRate is mL of Stylet-Oil per 20 L of water.
^bArea under the disease progress curve.
^cMeans within each column within each sub-table followed by the same letter are not significantly different (P = 0.05) according to Fisher's Protected LSD test.

Table 5.  Efficacy of various products for control of pepper powdery mildew in the greenhouse

			Disease severity*
Product	Type of material	Rate	Final %	AUDPC ^a
Experiment 1
Check	Water	—	6.7 a^b	56.7 a
Kaligreen	Potassium bicarbonate	3.4 ^!	2.7 bc	22.1 bc
Sporodex	Sporothrix flocculosa	10.0 ^!	4.9 ab	41.3 ab
Serenade	Bacillus subtilis	18.8 ^#	1.9 c	16.9 cd
Quadris	Strobilurin derivative	0.52 ^#	0.4 c	3.4 cd
Actigard	Plant resistance activator	0.1 ^!	0.6 c	5.9 cd
Sulphur	Micro-fine sulphur	0.82 ^!	0.5 c	3.2 cd
Flint	Strobilurin derivative	0.14 ^!	0.2 c	1.4 d
Experiment 2
Check		—	50.6	3.28
Copper soap	copper octanoate	10.0 ^#	12	0.59
Sovran	Strobilurin derivative	0.45 ^!	3.6	0.18
Nova	myclobutanil	0.34 ^!	0.1	0.01
FLSD0.05			10.7	0.7
*Evaluated 50 and 37 days after spray application for experiment 1 and 2, respectively.
^aArea under the disease progress curve.
^bMeans within each column are not significantly different (P = 0.05) according to Fisher's protected LSD test.
^!Rate in g L^−1; ^# Rate in mL L^−1.

Table 6.  Effect of reduced-risk spray treatments on development of Leveillula taurica on ‘Early California Wonder’ pepper in field plots at GPCRC, Harrow, Ontario in 2006–2007

		2006		2007
Spray treatment	Rate	AUDPC ^a	Final % Disease Severity ^a	AUDPC	Final % Disease Severity	Yield ^a,b
Inoculated - Water check	—	10.97 a	27.5 a	29.38	70.0 abc	0.753
Un-inoculated check	—	3.58 b	16.2 ab	27.79	85.0 a	1.134
Nova	1.36 ^!	0.12 b	1.9 c	27.28	54.4 cd	0.709
Lactosan + Agral 90	75 ^#	0.16 b	0.6 c	30.38	81.2 ab	0.94
Pristine	1.37 ^!	0.55 b	5.0 bc	28.75	70.6 abc	1.306
Prev-Am	3.5 ^#	1.26 b	6.2 bc	27.6	48.8 d	0.784
Procure	0.458 ^!	1.83 b	5.0 bc	28.99	58.1 dc	0.872
Milstop	3.0 ^!	2.69 b	16.2 ab	28.41	45.6 d	0.688
Quintec	0.006 ^#	ND	ND	25.53	69.4 abc	1.064
V-10118	0.125 ^#	ND	ND	29.55	61.9 bcd	0.852
^aMeans within the column followed by the same letter are not significantly different (P = 0.05) according to Fisher's protected LSD test.
^bWeight in kg of marketable fruit (red and green) from two plants of the centre row of each subplot.
ND = not done.
^!Rate in g L^−1; ^# Rate in mL L^−1.

Table 7.  Survival of L. taurica after storage of symptomatic ‘Cubico’ pepper leaves at 10 °C, 4 °C or −10 °C for varying periods of time

	Days in storage
Expt. 1 – Treatment	0	2	8	16		33	64
10 °C – Inoculated	3^a+	2+	+, tr	3+		+, tr	tr
4 °C – Inoculated	3+	3+	3+	3+		3+	2 tr
−10 °C – Inoculated	3+	2+	2 tr	2+, tr		+, 2 tr	3 tr
Expt. 2 – Treatment	0	4	7	17	32	62	128
10 °C – Inoculated	3+	3+	3+	0	0	2+, tr	2 tr
4 °C – Inoculated	3+	3+	3+	3+	0	2+, tr	tr
−10 °C – Inoculated	3+	0	0	3+	0	+	0
^aThree inoculated ‘Cubico’ pepper plants evaluated per treatment/storage period.
3 + denotes three plants with some mycelial growth evident on each.
tr = trace amount of mycelial growth on a single plant.

Cerkauskas , R.F. , Brown , J. , Ferguson , G. and Khosla , S. 1999 . First report of powdery mildew of greenhouse pepper caused by Leveillula taurica in Canada . Plant Dis , 83 : 781

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