Evaluation of Fungicides to Control Powdery Mildew of Strawberry

Evaluation of Fungicides to Control Powdery Mildew 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 24 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 of 14 plants each in two rows per bed, seven plants per row. 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 either weekly or every two weeks from 16 Nov 00 through 9 Mar 01 (17 weeks) as noted in the table. For the Kaligreen treatment, Kaligreen was applied with Sil-Wet (surfactant) weekly for two weeks followed by Nova for one week then sulfur for one week, then the schedule was repeated. The two treatments with Elexa were applied on a weekly schedule as follows: Either Nova or Benlate were applied the first week, then Elexa with Joint Venture were applied the second week, then sulfur applied the third week, then Elexa and Joint Venture applied the forth week, then the application cycle was repeated beginning with Nova or Benlate applications. Bloom applications of Elevate were made on 30 Nov and 8 Dec 2000 during the first bloom period and on 26 Jan, 2, 9 and 16 Feb 2001 during the second bloom period to control gray mold fruit rot. Fruit were harvested twice weekly from 26 Dec 00 to 12 Mar 01 (23 harvests) and marketable yield determined. The number of unmarketable, powdery mildew infected, and Botrytis infected (gray mold) fruit were also determined. The percent (incidence) of fruit with either powdery mildew (number of fruit with noticeable powdery mildew mycelium on it, divided by total number of marketable and unmarketable fruit harvested) or Botrytis rot (number of fruit with Botrytis rot divided by the total number of marketable and unmarketable fruit harvested), and total marketable yield (mean pounds per plot) are reported. Disease incidence data were transformed (arcsine square root) before analysis. Data were analyzed by ANOVA and treatment means separated by Fisher’s protected LSD (P£ 0.05). Untransformed values are presented in the table.

Weather during the 2000-01 season was unusual with January being extremely cold and February being extremely warm. Little precipitation occurred during the season. Although conditions were generally favorable for the development of powdery mildew epidemics, little foliar disease developed within the experiment and no foliar ratings were made. The incidence of fruit infection was also low. Significant treatment differences were found for marketable yield and the incidence of powdery mildew and Botrytis fruit rot. Because the overall incidence of powdery mildew was low and Botrytis fruit rot high, it is difficult to draw meaningful conclusions on the control of powdery mildew from this data. Treatment differences in yield were probably due to Botrytis fruit rot or phytotoxicity. The Kaligreen treatment caused severe phytotoxic reactions (leaf necrosis) that dramatically reduced marketable yields. Sulfur at the 13 qt/A rate also damaged the foliage.

EVALUATION OF FUNGICIDES TO CONTROL POWDERY MILDEW OF STRAWBERRY, 2001
Treatment, rate/acre and schedule^*	% Powdery mildew		% Botrytis fruit rot		Marketable yield (lb)
Kaligreen 82 WP 3 lb + Sil-Wet 0.25% alt/w Nova 40W 5 oz then Sulfur 6L 13 qt, 7 day..............................................................................................................................	0.10	a^**	11.58	cde	6.75	h
QRD 131 AS 2%, 7 day............................................................................................	0.17	ab	12.44	cdef	12.74	cdef
BAS 516 UBF 38WG 0.55 lbs, 7 day.......................................................................	0.17	ab	3.01	a	15.23	ab
Valero 30% 4 qt + Joint Venture 1 pt alt/w Nova 40W 5 oz, 7 day....................	0.25	ab	12.59	def	11.71	efg
Sulfur 6L 13 qt, 7 day................................................................................................	0.34	abc	17.15	f	10.81	fg
Valero 30% 2 qt alt/w Nova 40W 5 oz, 7 day........................................................	0.25	abc	13.93	def	11.38	efg
Nova 40W 5 oz, 14 day............................................................................................	0.52	abcd	12.82	def	12.07	defg
BAS 500 02F 20WG 0.183 lb, 7 day........................................................................	0.38	abcd	6.49	b	15.79	a
BAS 510 UCF 70WG 0.367 lb, 7 day.......................................................................	0.46	abcde	3.22	a	14.68	abc
QRD 282 AS 2%, 7 day ...........................................................................................	0.64	abcdef	12.48	cdef	12.54	cdef
Nova 40W 5 oz alt/w Elexa 4% 2.5% + Joint Venture 1 pt then Sulfur 6L 13 pt, 7 day..............................................................................................................................	0.64	bcdef	12.50	cdef	14.08	abcd
Benlate 50DF 1 lb alt/w Elexa 4% 2.5% + Joint Venture 1 pt then Sulfur 6L 13 pt, 7 day..............................................................................................................................	0.73	bcdef	10.91	cd	13.12	bcde
Sulfur 6L 6.5 pt, 7 day + bloom applications of Elevate 50WDG 1 lb ...............	0.97	cdefg	11.56	cde	13.23	bcde
Sulfur 6L 6.5 pt, 7 day...............................................................................................	1.02	defg	13.50	def	11.89	defg
Procure 50W 4 oz, 14 day........................................................................................	1.15	defg	13.68	def	12.83	cdef
Benlate 50DF 1 lb, 14 day........................................................................................	1.05	defg	11.14	cd	13.41	bcde
Valero 30% 4 qt, 7 day..............................................................................................	1.25	efg	8.58	bc	10.16	g
Valero 30% 2 qt, 7 day..............................................................................................	1.32	fg	15.87	ef	10.60	fg
Procure 50W 8 oz, 14 day........................................................................................	2.30	gh	13.71	def	12.83	cdef
Untreated control......................................................................................................	2.15	gh	14.12	def	12.68	cdef
Bloom applications of Elevate 50WDG 1 lb .......................................................	3.09	h	6.47	b	13.28	bcde

* Time between applications.
** Treatment means within a column followed by the same letter are not significantly different according to Fisher’s protected LSD (P£ 0.05).

EVALUATION OF FUNGICIDES TO CONTROL POWDERY MILDEW OF STRAWBERRY, 2001