Efficacy of sterol-inhibiting fungicides and SAR chemicals for control of black root rot of cotton in the absence and presence of nematodes Harun Toksoz

Outline Black root rot Sterol-inhibiting fungicides & SAR chemicals Objective Materials and methods Results Conclusions

Black Root Rot Caused by Thielaviopsis basicola Found in almost all major production areas Pathogen has a host range of more than 230 species Rarely kills plants Causes stunting Results in less vigorous plants Delays flowering Reduces yield

Sterol-inhibiting fungicides and SAR chemicals Myclobutanil and triadimenol Triadimenol (Arthur, 1991) Myclobutanil (Butler et al. 1996) Bion (Acibenzolar-S-methyl) Mondal et al. 2005

Effect of Bion on Disease Severity and Shoot Height (Mondal et al. 2005)

Objective Evaluate the efficacy of sterol-inhibiting fungicides and SAR chemicals alone and in combination on black root rot. Systhane (Myclobutanil) Bion (Acibenzolar-S-methyl)

Materials and Methods Artificially infested experiments Controlled environmental experiments Naturally infested experiments Field experiments

Artificially Infested Experiments Controlled environmental experiments 15 °C night 24 °C day 14 h daylight period Infested with M. incognita (16 eggs per g soil) T. basicola (100 chlamydospores per g soil) Both pathogens None 15 different seed treatments Terminate 28 DAP 2 experiments

Naturally Infested Experiments 1. Controlled environmental experiments 7 different treatments 4 replications 3 different soils 2. Field experiments 11 different treatments

Data Collection Disease assessments % Root discoloration (0-10) Hypocotyl discoloration (1-4) Galling (on root system and tap roots) Percent colonization (0-10) / incidence

Results Artificially infested experiments Naturally infested experiments Controlled environmental experiments Field experiments

Effect of seed treatments, artificially infested soil Root Discoloration Untreated 5.40 A Dynasty CST 4.91 BA Dynasty CST + Systhane 3.12 CDE Dynasty CST + Bion 3.80 DCB 2.66 E 3.20 CDE Dynasty + Avicta + Systhane 2.00 E Dynasty + Avicta + Bion 3.72 BCD 3.83 BCD 3.41 DE Dynasty + Avicta 4.51 ABC

Effect of seed treatments, naturally infested soil; Tb+RN RDI Seed treatment 3.75 A Systhane 2.87 B Systhane (2x) + Avicta 2.94 B Systhane + Avicta + Bion (0.6) 2.36 B Systhane + Avicta + Bion (1.0) 2.31 B Systhane (2x) + Avicta + Bion (0.6) 1.26 C 24 ppg

Effect of seed treatments, naturally infested soil; Tb+RKN RDI Seed treatment 5.66 A Systhane 5.00 A Systhane (2x) + Avicta 4.82 A Systhane + Avicta + Bion (0.6) 5.28 A Systhane + Avicta + Bion (1.0) 5.25 A Systhane (2x) + Avicta + Bion (0.6) 5.27 A 113 ppg

Effect of seed treatments, naturally infested soil; Tb+RKN Node Seed treatment 1.45 B Systhane 1.75 A Systhane (2x) + Avicta Systhane + Avicta + Bion (0.6) 1.91 A Systhane + Avicta + Bion (1.0) 1.88 A Systhane (2x) + Avicta + Bion (0.6) Soil 3: 113 ppg

Effect of seed treatments, field experiment 2007 RDI Seed treatment 4.60 a Systhane 4.50 a Systhane (2x) + Avicta 3.73 a Systhane + Avicta + Bion (0.6) 4.17 a Systhane + Avicta + Bion (1.0) 4.00 a Systhane (2x) + Avicta + Bion (0.6) 4.33 a Systhane (2x) + Avicta + Bion (1.0) 3.77 a Systhane + Temik 4.27 a

Effect of seed treatments, field experiments Incidence Seed treatment 88.0 a Systhane 60.0 b Systhane (2x) + Avicta 57.3 b Systhane + Avicta + Bion (0.6) Systhane + Avicta + Bion (1.0) 52.0 b Systhane (2x) + Avicta + Bion (0.6) 62.7 ab Systhane (2x) + Avicta + Bion (1.0) 53.3 b Systhane + Temik

Effect of seed treatments, field experiments Galling Seed treatment 3.27 a Systhane 2.73 ab Systhane (2x) + Avicta 1.83 cd Systhane + Avicta + Bion (0.6) 2.13 bc Systhane + Avicta + Bion (1.0) 2.10 bc Systhane (2x) + Avicta + Bion (0.6) 2.03 bc Systhane (2x) + Avicta + Bion (1.0) 1.97 bcd Systhane + Temik 1.13 d

Conclusions Sterol-inhibiting fungicides are effective Bion is effective Population of pathogen Plant growth, incidence…