Evaluation of Fungicides to Control Anthracnose 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 30 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.  The 10-foot long plots consisted of 16 plants in two rows per bed, eight 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).  Weekly applications of the Captan, Thiram, UCB9906 and Rovral treatments were made from 29 Nov 00 to 14 Mar 01 (16 applications).  The early season Captan treatment was applied from 29 Nov 00 to 10 Jan 01 (7 applications).  The late season captan treatment was applied from 17 Jan to 14 Mar 01 (9 applications).  Quadris, Switch and Benlate were applied as late season treatments beginning on 17 Jan 01 on a 14 day schedule (5 applications).  For the late season Quadris/Switch treatment, applications of  fungicides were alternated weekly beginning on 17 Jan 01.  The Captan plus late season Quadris treatment consisted of weekly applications of Captan for the whole season with Quadris applied every 14 days beginning on 17 Jan 01.  Fruit were harvested twice weekly from 5 Jan 01 through 16 Mar 01 (21 harvests) and anthracnose and Botrytis fruit rot incidence recorded.  Because little anthracnose fruit rot developed, the experiment was inoculated with a conidial suspension  (1 x 10⁵ conidia/ml, 5 to 10 ml /plant) of Colletotrichum acutatum on 16 and 22 Feb 2001 and overhead sprinkler irrigated to initiate an epidemic.  Overhead sprinkler irrigation was then applied to the experiment once or twice weekly to provide disease-conducive conditions until the end of the experiment.  The percent of fruit harvested with anthracnose (C. acutatum) (number of berries with anthracnose divided by total number of marketable and unmarketable fruit harvested), and total marketable yield (mean grams / plot) are reported.  Anthracnose incidence data were transformed (arc sine square root) before analysis.  A two way ANOVA was conducted and means separated by Fisher’s protected LSD (P£ 0.05).

Weather during the 2000 to 2001 strawberry season was warmer and dryer than normal.  This resulted in less than ideal conditions for the development of anthracnose fruit rot.  No Colletotrichum crown rot (C. gloeosporioides) was observed in the experiment.  Significant treatment differences (P£0.05) in marketable yield, incidence of anthracnose fruit rot and Botrytis fruit rot occurred.  The best control was provided by late season or whole season weekly applications of Captan.  Weekly applications of UCB9906 and a late season program of Quadris alternating with Switch also provided excellent control of anthracnose.  Late season applications of Quadris provided only limited control of anthracnose fruit rot.  

x      Incidence of anthracnose fruit rot (number of anthracnose fruit / total number of marketable and unmarketable fruit).

y      Incidence of Botrytis fruit rot (number of Botrytis fruit / total number of marketable and unmarketable fruit).

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