Evaluation of Fungicides to Control Botrytis Fruit Rot of Strawberry

Evaluation of Fungicides to Control Botrytis Fruit Rot of Strawberry, 2001.

Bare root plants from Canada were transplanted into plastic-mulched raised beds on 4 ft centers (28 in wide and 7 in high at the center and 6 in high at the edge), in methyl bromide: chloropicrin (98:2) fumigated soil on 9 Oct, 2000. Each bed contained two rows of plants spaced 15 in apart within row and 12 in apart between rows. The experiment consisted of a randomized complete block design with four replicates, with plots consisting of 14 plants in two rows per bed, seven plants per row. Fruit were harvested twice a week from 1 Dec 2000 through 6 Mar 2001 (28 total harvests) and graded for marketable yield and Botrytis fruit rot incidence. The transplants were irrigated by overhead sprinkler for 10 days to facilitate establishment, then irrigated and fertilized through drip tape. Fungicide treatments were applied with a CO₂ backpack sprayer (100 GPA). Treatments were applied weekly from 1 Nov 2000 to 29 Feb 2001except for bloom applications and treatments including BAS 500, BAS 510 and BAS 516, which began on 22 Nov 2000. Bloom applications were timed to provide coverage either during the first two peak bloom periods (split bloom) or only during the second peak bloom period (late bloom). Fungicides were applied to the first peak bloom beginning on 22 Nov, and on the second peak bloom beginning on 24 Jan. The bloom applications were applied 7 days apart, with two applications made during the first bloom period and/or four applications during the second bloom period. In the treatment with late bloom applications of both Switch and Quadris, applications of each fungicide were alternated weekly until the end of the season beginning with the Switch application on 24 Jan. Treatments with weekly or bloom applications that alternated two fungicides began with applications of the first product listed. The percent of fruit harvested with Botrytis fruit rot (B. cinerea) (number of fruit with Botrytis divided by the total number of marketable and unmarketable fruit harvested), and total marketable yield (mean pounds per plot) are reported. Botrytis incidence data were transformed (arcsine square root) before statistical analysis. The data were analyzed with ANOVA and means separated using Fisher’s protected LSD (P£ 0.05).

Weather during the 2000-01 season was extremely cold in January and unusually warm in February. Little precipitation occurred during the season. Despite the unusual weather, extended dew periods occurred throughout the season and a moderate Botrytis fruit rot epidemic developed. Significant treatment differences (P£0.05) in Botrytis fruit rot and marketable yield were observed. The most effective treatments included weekly applications of TMTD 4L-c or BAS 516, or weekly applications of Captan supplemented with bloom applications of Elevate or Switch.

EVALUATION OF FUNGICIDES TO CONTROL BOTRYTIS FRUIT ROT OF STRAWBERRY, 2000
Treatments, rate/A and schedule*	% Botrytis fruit rot		Marketable yield (lb)
TMTD 4L-c 3 qt..............................................................................................................	2.49	a^**	16.98	a
Captan 80W 1.88 lb + late bloom applications of Elevate 50WDG 1.5 lb ..............	2.51	ab	14.88	bcde
Captan 80W 3.75 lb + late bloom applications of Switch 62.5WG 11 oz alternating with Quadris 2.08F 12.4 fl oz ....................................................................	2.57	ab	14.57	cdef
Captan 80W 3.75 lb + split bloom applications of Elevate 50WDG 1 lb ................	2.76	ab	15.09	bcd
Captan 80W 3.75 lb + late bloom applications of Elevate 50WDG 1.5 lb...............	3.00	abc	14.33	def
BAS 516 UBF 38WG 0.55 lb .........................................................................................	3.48	abc	16.09	ab
Thiram 65WSB 3 lb alt/w Captan 80W 3.75 lb ...........................................................	3.81	abc	14.85	bcde
Thiram 65WSB 4 lb alt/w Captan 80W 3.75 lb ...........................................................	3.85	abc	15.82	abc
Elevate 50WDG 1.5 lb....................................................................................................	4.42	bcd	13.49	efhi
Thiram 65WSB 2 lb alt/w Captan 80W 3.75 lb ...........................................................	4.77	cd	15.15	bcd
BAS 510 UCF 70WG 0.367 lb .......................................................................................	4.84	cde	14.86	bcde
Elevate 50WDG 1.0 lb, split bloom applications........................................................	4.98	cdef	13.48	efhi
UCB9906 50WP 2 lb ......................................................................................................	6.13	defg	13.30	fhij
ECB-151 6.67 oz until first bloom 14 day then Captan 80W 3.75 lb ........................	7.00	efgh	13.05	hij
Captan 80W 3.75 lb .......................................................................................................	7.01	efgh	14.80	bcde
Captan 80W 1.88 lb .......................................................................................................	7.34	fghi	14.41	cdef
Captan 80W 3.75 lb + late bloom applications of Quadris 2.08F 12.4 fl oz ...........	7.38	ghi	14.74	cdef
UCB9906 50WP 1 lb ......................................................................................................	8.00	ghij	12.18	ijk
BAS 500 02F 20WG 0.183 lb .........................................................................................	8.30	ghij	13.86	defh
ECB-151 6.67 oz alt/w Captan 80W 3.75 lb .................................................................	8.82	ghij	14.07	def
QRD 132 8 lb ...................................................................................................................	9.03	hijk	12.48	hijk
QRD 131 WP 2%.............................................................................................................	9.40	hijk	11.24	kl
ECB-151 4.45 oz alt/w Captan 80W 3.75 lb .................................................................	10.00	ijk	13.58	efhi
ECB-151 9 oz alt/w Captan 80W 3.75 lb ......................................................................	10.57	jk	13.10	hij
Untreated control...........................................................................................................	10.78	jk	11.98	jkl
QRD 282 AS 2%..............................................................................................................	11.95	k	10.56	l

* Applications made weekly unless otherwise stated

** Treatment means within a column followed by the same letter are not significantly different using Fisher’s protected LSD (P£0.05). Analysis of the gray mold incidence was done on arc sine square root transformed data.