2019 ASHS Annual Conference

Selected biological products for control of black root rot (Rhizoctonia spp.) in strawberries grown on two plasticulture systems (high tunnel [HT] and open field low tunnels [OFLT]) were applied October 2017 through June 2018 at the Texas A&M AgriLife Research & Extension Center at Lubbock. Treatments included untreated and chemically-treated (mefenoxam + azoxystrobin) controls, caliente mustard pellets applied in-furrow, and the biologicals Actinovate® (Streptomyces lydicus strain WYEC 108), AmyProtec 42 (Bacillus amyloliquefaciens strain FZB 42), DoubleNickel® (Bacillus amyloliquefaciens strain D747), Regalia® (extract of Reynoutria sachalinensis) and RootShield Plus® (Trichoderma harzianum Rifai strain T-22 + T. virens strain G-41). Treatments were first applied by drenching strawberry plugs at transplanting (except caliente mustard), followed by applying products through a CO₂-pressurized system that delivered treatments through drip irrigation in each microplot at 8 + 16 weeks after transplanting (WAT) or 4 + 8 + 12 + 16 + 20 WAT. Microplots measured 2.5-feet by 10-feet with 20 plants replicated four times and randomized within each plasticulture system. Crop fertilization and pest control were equivalent in both systems. Data were statistically analyzed using the JMP version 14 software (SAS Institute Inc., Cary, NC). While the biological treatments showed no differences, there were differences (p<0.05) between the plasticulture systems. Except percent culls by weight, all other parameters measured including total marketable and cull weights, total fruit weight, plant vigor, biomass and crown number were significantly higher in the high tunnel system. There was a 322% increase in average marketable berry yields in the HT system compared to OFLT plots, which was due to an increased number of harvests in the HT system. Average plant weight and crown numbers were 86% and 67% higher, respectively, in the HT compared to the OFLT plots. However, the number of Rhizoctonia-infected plants was 2.3 times higher in OFLT plots compared to those in the HT. These results indicate that the strawberry harvest season was extended in the HT compared to OFLTs, and that the type of plasticulture system influenced Rhizoctonia infections, strawberry plant growth, and marketable yield more than did the biological treatments. While HT plots had higher average berry yields and plant growth, they also had fewer Rhizoctonia-infected plants suggesting that the HT environment was less conducive to Rhizoctonia root rot in this trial. A second year of this study is currently under investigation.