STRAWBERRY

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

Anthracnose fruit rot; Colletotrichum acutatum University of Florida, GCREC

13138 Lewis Gallagher Rd

Dover, FL 33527

Evaluation of fungicides to control anthracnose 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 21 Oct 02. The beds were 28 in wide on 4-ft centers. Each bed contained two staggered rows of plants spaced 15 in apart within row and 12 in apart between rows. Treatments were arranged in a randomized complete block design with four blocks, each in a separate bed. Individual plots were 8 ft long and contained 12 plants. Experimental beds were separated by single untreated beds planted to ‘Strawberry Festival’ to facilitate the natural increase and spread of inoculum. The transplants were irrigated by overhead sprinkler for 12 days to facilitate establishment, then irrigated and fertilized through drip tape. Fungicides were applied weekly up to 18 times from 13 Nov to 12 Mar using a CO₂ backpack sprayer calibrated to deliver 100 gal/ac at 40 psi. Four treatments consisted of 18 weekly applications of Captan combined with Quadris or Switch during a 5-week interval coinciding with early (27 Nov to 25 Dec) or late (5 Feb to 5 Mar) season periods. Elevate was also tested in conjunction with Captan as a late season treatment (four applications). In another treatment, Captan was applied after significant rain events (12 applications). Topsin M was tested without captan as a late season treatment (five applications at weekly intervals). Fruit were harvested twice weekly from 3 Jan through 14 Mar (21 harvests) and evaluated for anthracnose fruit rot caused by C. acutatum. The incidence of anthracnose fruit rot (number of diseased fruit divided by total number of marketable and unmarketable fruit, expressed in percent), and total marketable yield (lbs/A) are reported. Disease incidence data were transformed (arc sine square root) prior to a two way ANOVA. Treatment means were compared using a Fisher’s protected LSD test (P £ 0.05). The reported means are untransformed.

The 2002-03 strawberry season was characterized by an unusually warm Oct and an unusually cold Jan. Due to low temperatures in Jan, the second peak bloom occurred in February, and peak production in early Mar. A mild epidemic of anthracnose fruit rot coincided with this peak production period. No Colletotrichum crown rot (C. gloeosporioides) was observed in the experiment. However, Botrytis fruit rot incidence was 11.3% in the control, 5.4% in the Topsin M treatment, and less than 2.3% in the other treatments. Weekly applications of Captan or Thiram significantly reduced anthracnose fruit rot. Late season applications of Switch, but not Quadris, significantly improved the level of control provided by a weekly Captan program. With the exception of Topsin M, all treatments significantly improved yields of marketable fruit compared to the check.

Treatment, rate/acre, and spray interval^z	Anthracnose fruit rot (%)	Marketable yield (lb/A)
Captan 80WP, 3.75 lb, 7 day + five late appl. of Switch 62.5WG, 11 oz, 7 day^x.................	1.0 a^y	16,900 a
Captan 80WP, 3.75 lb, 7 day + five late appl. of Quadris 2.08F, 12.4 fl oz, 7 day...............	1.3 ab	18,200 a
Captan 80WP, 3.75 lb, 12 appl. after significant rain events................................................	1.8 ab	15,600 ab
Captan 80WP, 3.75 lb, 7 day + five early appl. of Switch 62.5WG, 11 oz, 7 day................	2.1 abc	18,200 a
Captan 80WP, 3.75 lb, 7 day + five early appl. of Quadris 2.08F, 12.4 fl oz, 7 day............	2.4 abc	16,900 a
Captan 80WP, 3.75 lb, 7 day + four late appl. of Elevate 50WDG, 1.0 lb, 7 day................	3.7 abc	16,900 a
Captan 80WP, 3.75 lb + Brotomax 2.1 pint, 14 day, alternating with Captan 80WP 3.75 lb, 14 day ...............................................................................................................................................	3.9 abc	17,700 a
Captan 80WP, 3.75 lb, 7 day......................................................................................................	4.1 bcd	17,500 a
Thiram 65WSB, 4 lb, 7 day........................................................................................................	5.2 cd	17,200 a
Five late appl. of Topsin M 70WP, 1 lb, 7 day.......................................................................	9.6 de	13,800 bc
Untreated check..........................................................................................................................	13.3 e	12,000 c

^zEarly season applications (early appl.) were made from 27 Nov to 25 Dec; late season applications from 5 Feb to 5 Mar.

^xThe “+” symbol indicates products used in combination.

^yTreatment means within a column followed by the same letter are not significantly different using Fisher’s protected LSD (P ≤ 0.05).