STRAWBERRY

STRAWBERRY (Fragaria x ananassa ‘Earlibrite’) J. C. Mertely and T. E. Seijo

Botrytis fruit rot; Botrytis cinerea University of Florida, GCREC

13138 Lewis Gallagher Rd

Dover, FL 33527

Evaluation of fungicides to control Botrytis fruit rot in annual strawberry, 2002-03.

Bare-root runner plants from Canada were transplanted into methyl bromide:chloropicrin (67:33) fumigated soil in plastic-mulched raised beds on 14 Oct 02. The beds were 28 in wide on 4-ft centers. Treatments were arranged in a randomized complete block design with four blocks in separate, adjacent beds. Individual plots were 8.4 ft long and contained 14 plants in two staggered rows. The transplants were irrigated by overhead sprinklers for 11 days to facilitate establishment, then irrigated and fertilized through drip tape. Fungicides were applied between 6 Nov to 5 Mar with a CO₂ backpack sprayer calibrated to deliver 100 gal/ac at 40 psi. Conventional treatments consisted of 18 weekly applications, with test products applied four times during the major bloom period (5 to 26 Feb) to protect susceptible flowers. All bloom applications were made at weekly intervals. In treatments consisting of weekly captan applications and special bloom applications of another fungicide, no captan was applied when bloom applications were made. Six additional treatments consisted of bloom applications alone. Sulfur 6L (6 pts) was applied twice in Nov to control powdery mildew in the experimental area. Fruit were harvested twice weekly from 10 Dec through 11 Mar (27 harvests) and graded for marketable yield and the incidence of Botrytis fruit rot. The incidence of Botrytis fruit rot (number of fruit with Botrytis divided by the total number of marketable and unmarketable fruit harvested, expressed in percent), and total marketable yield are reported. Botrytis incidence data were transformed (arcsine square root) before statistical analysis. The data were analyzed by two-way ANOVA and means separated using Fisher’s protected LSD (P £ 0.05). The untransformed means are reported.

The 2002-03 strawberry season was characterized by an unusually warm Oct and an unusually cold Jan. Due to the low temperatures in Jan, peak production was delayed until late Feb and early Mar, when Botrytis fruit rot appeared. Disease incidence peaked during the first week of March, and declined abruptly thereafter. All treatments reduced disease incidence relative to the untreated control. Although large differences between treatments were not found, conventional treatments with bloom applications of Elevate, Scholar, or Switch were generally more effective than treatments with captan (Captan, CapTec) or thiram (TMTD) alone. Most treatments increased marketable yield, although yields were low overall.

Treatment, rate/acre, and schedule^z	Botrytis fruit rot (%)	Marketable yield (lb/A)
Four bloom appl. of Scholar 50WP, 0.44 lb..........................................................................................	0.4 a^y	16,700 ab
Four bloom appl. of Switch 62.5WG, 11 oz...........................................................................................	0.6 ab	15,700 ab
Captan 80WP, 1.875 lb; four bloom appl. of Elevate 50WDG, 1.5 lb .........................................	0.6 ab	17,400 a
Captan 80WP, 1.875 lb; four bloom appl. of TM45002, 5.25 lb..........................................................	0.6 ab	16,800 ab
Captan 80WP, 1.875 lb; four bloom appl. of Elevate 50WDG, 1 lb + Captan 80WP, 3.75 lb^x........	0.7 ab	16,900 ab
Captan 80WP, 1.875 lb; four bloom appl. of Scholar 50WP, 0.44 lb.................................................	0.7 abc	16,000 ab
Four bloom appl. of Elevate 50WDG, 1.5 lb.........................................................................................	1.2 a-d	15,500 bc
Four bloom appl. of CX 7001, 12 fl oz....................................................................................................	1.2 a-e	16,100 ab
Captan 80WP, 1.875 lb; three appl. of Switch 62.5WG, 11 oz, (5 Feb, 19 Feb, 5 Mar); 2 appl. of Quadris 2.08F, 12.4 fl oz (12 Feb, 26 Feb) .............................................................................................	1.3 a-e	16,900 ab
Four bloom appl. of Elevate 50WDG, 1.5 lb + Kinetic surfactant 10 fl oz........................................	1.5 b-e	15,300 bc
Captan 80WP, 3.75 lb...............................................................................................................................	2.2 de	16,300 ab
TMTD 4L, 3.2 qt, 14 day, alternating with CapTec 4L 3.75 qt, 14 day.............................................	2.3 de	16,500 ab
TMTD 4L, 2.6 qt, 14 day, alternating with CapTec 4L, 3.75 qt, 14 day............................................	2.5 cde	17,200 ab
TMTD 4L, 1.3 qt.......................................................................................................................................	2.5 de	16,200 ab
Captan 80WP, 1.875 lb.............................................................................................................................	2.6 de	16,900 ab
TMTD 4L, 1.6 qt.......................................................................................................................................	2.8 e	15,400 bc
Four bloom appl. of Captan 80WP, 3.75 lb...........................................................................................	2.9 e	13,100 d
Untreated check.......................................................................................................................................	7.3 f	13,800 cd

^zApplications made weekly unless otherwise stated.

^yTreatment means within a column followed by the same letter are not significantly different using Fisher’s protected

LSD (P £ 0.05).

^xA “+” symbol indicates two or more products used in combination.