Raymond F. Cerkauskas

Long-term evaluation of cover crop and strip-tillage on tomato yield, foliar diseases and nematode populations

A 6-yr (1987–1992) experiment, continuous on the same site, evaluated potential problems for yield, nematodes and diseases with tomatoes (Lycopersicon esculentum Mill.) grown in a strip-till system. Treatments consisted of conventional tillage (CT) and strip tillage (ST), rye (Secale cereale L.), wheat (Triticum aestivum L.) and perennial ryegrass (Lolium perenne L.) cover crops and a 2-yr rye-tomato rotation. Results of the first 5 yr indicated a decrease in tomato yield over time for both tillage treatments and cover crops. However, yield rebounded overall for treatments in 1992 with the highest yield in the rye-tomato rotation. We suspect this was a result of high populations of root-knot nematodes which collapsed over the winter of 1991/1992. Tomato yields were lower following wheat and perennial ryegrass than rye. In only 1 yr out of 6, strip-tillage reduced yield compared with conventional tillage. Bacterial speck/spot symptoms on foliage, although minor, were significantly greater in ST than in CT ...

Fungicidal suppression of symptomless latent infections of Monilinia fructicola in European plums

European plums (Prunus domestica “Stanley”) with a high incidence of symptomless latent infections of Monilinia fructicola, were harvested soft-ripe or firm-ripe, surface disinfested in NaOCl, soaked for 4 min in fungicide suspensions at 20°C and incubated for 7-11 days at >95% RH at 20°C. Using soft-ripe fruits, all 12 fungicides reduced brown rot relative to the water check after 7 days incubation, with tebuconazole and flusilazole being numerically superior. Using firm-ripe fruits, five sterol-inhibiting fungicides and iprodione reduced brown rot infections after 7 days incubation, with tebuconazole, flusilazole and myclobutanil being numerically superior. Fruits were soaked for 4 min in suspensions of tebuconazole and flusilazole at 33, 67, and 100 mg a.i./L, and incubated for 7-8 days. Treatments were moderately effective with no rate response except for soft-ripe plums soaked in flusilazole. Five sterol-inhibiting fungicides were applied twice at mid-season to Stanley trees having fruits with a high...

Management of powdery mildew (Podosphaera xanthii) on greenhouse cucumber in Ontario

Abstract Cucumber powdery mildew (Podosphaera xanthii) causes significant annual yield and quality losses in greenhouse production in Canada. Management of the disease was evaluated in various research trials conducted at Harrow, ON from 1999–2007 and at two commercial greenhouse operations in Leamington, ON in 2005–2006. Products evaluated included biological control agents, new classes of fungicides, and materials derived from natural products as well as several traditional fungicides with multi-site modes of action. Best control in the research greenhouse was obtained with applications of Nova, Quintec, strobilurin derivatives (Quadris, Flint, Sovran), Procure, Pristine, JMS Stylet-Oil®, V-10118, Prev-AM, copper soap, Actigard and sulphur. Disease control was also obtained with Milstop, two fermented milk by-products (Lactosan, Yo-K-San) + surfactant formulations (Agral 90), and Agral 90 only. Applications of K2HPO4 + Agral 90, CaCl2 + Agral 90, and Siliforce were significantly better than the water check while fumed silica was not effective. Among biological control products, Sporodex (Pseudozyma flocculosa) was effective in control of P. xanthii while Serenade (Bacillus subtilis) was not. Actinovate (Streptomyces lydicus) provided control also. Under commercial greenhouse conditions, Milstop, and Lactosan + Agral 90 when applied weekly suppressed powdery mildew development at least equal to that of Nova. Resistance in P. xanthii to high rates of Nova and Pristine was detected in 3 of 17 and 2 of 8 commercial greenhouse cucumber operations, respectively, near Leamington. None of the locations had resistance to both fungicides at commercial rates of application, although one site showed consistently greater resistance of P. xanthii to both fungicides.

Powdery mildew (Leveillula taurica) on greenhouse and field peppers in Ontario – host range, cultivar response and disease management strategies

Abstract Leveillula taurica was observed on field pepper at various sites in south-western Ontario in 2005–2007. The field isolates collected from these sites were similar to a greenhouse isolate based on morphological observations. Host range of greenhouse and field isolates was similar, with minor sporulation on potato, carrot and several weeds. The greenhouse pepper cultivar ‘Samanta’ was the most susceptible to L. taurica while ‘Triple 4’, ‘Duplo’ and ‘Bosanova’ were the least susceptible to infection. Best control of pepper powdery mildew in the greenhouse was obtained with applications of myclobutanil, triflumizole, pyraclostrobin + boscalid, quinoxyfen, strobilurin derivatives (azoxystrobin, trifloxystrobin, kresoxim-methyl), copper soap, JMS Stylet-Oil®, Valent-10118, acibenzolar-S-methyl and sulphur. Disease reduction was also obtained with applications of potassium bicarbonate, citrus oil + borax, Bacillus subtilis and a fermented milk byproduct + surfactant. K2HPO4 + surfactant was effective in reducing disease whereas CaCl2 + surfactant, fumed silica and Sporothrix flocculosa were not effective. In field plots, best disease control was achieved with applications of myclobutanil and the fermented milk byproduct + surfactant in 2006 whereas in 2007, citrus oil + borax and potassium bicarbonate were most effective. There were no significant differences in pepper yield among the treatments in field plots. In vitro survival studies showed that the fungus was able to survive in infected pepper leaves after exposure to temperatures of −10 °C for 2 months.

Aspects of the epidemiology and control of powdery mildew (Oidium neolycopersici) on tomato in Ontario, Canada

Abstract The epidemiology and control of powdery mildew (Oidium neolycopersici) of tomato (Solanum lycopersicum L.) was studied in greenhouse, growth chamber, and field experiments at Harrow, Ontario. Greenhouse environmental conditions were more favourable for disease development, with higher disease progress rates than in the field. Symptoms were more severe on older, lower leaves where the air temperature was slightly lower and relative humidity higher than on young leaves at the top of the canopy. A temperature of 22°C with 16 or 24 h of leaf wetness was optimal for disease development in a growth chamber experiment. Early inoculation resulted in significantly greater final disease severity and area under the disease progress curve than later inoculations. Disease progress in greenhouse and growth chamber trials was best described by the Gompertz model, while the logistic model was best for disease progress in field studies and for sections of plants in greenhouse studies. No yield loss occurred in field studies. The best disease control was obtained with acibenzolar-S-methyl (Actigard®), trifloxystrobin (Flint®), JMS-Stylet Oil®, azoxystrobin (Quadris®) and sulphur applied as protectants. Some phytotoxicity occurred with Actigard in greenhouse studies. Serenade® (Bacillus subtilis) was less effective while Kaligreen, Sporodex® (Pseudozyma flocculosa), copper octanoate and fumed silica were ineffective. Quinoxyfen was phytotoxic at the rate applied. Several tobacco cultivars, jimsonweed, American and black nightshade were susceptible to infection by O. neolycopersici. Eggplant, hairy nightshade and bittersweet were less susceptible, while no visible symptoms developed on pepper, potato and tomato ‘Grace’, and only trace levels of sporulation occurred on cucumber.

Etiology and management of Fusarium crown and root rot (Fusarium oxysporum) on greenhouse pepper in Ontario, Canada

Abstract Infection of greenhouse pepper plants (Capsicum annuum L.) by Fusarium oxysporum was observed in two commercial operations in Ontario, causing plant death and yield losses. The pathogen was identified based on cultural, morphological and pathogenicity tests supplemented by PCR amplification of TEF primers. Following inoculation, symptoms of mild stunting occurred within 5–6 weeks, followed by more severe stunting later. Other symptoms, such as chlorosis, wilting and necrosis of the lower foliage, did not become readily evident until about 60 days after inoculation. At 77 days after inoculation, there was considerable brown-black discolouration and decay of crown tissue but little internal stem discolouration or damage beyond the crown portion was observed. Roots were dark brown to black, severely decayed, and easily separated from the surrounding rock wool medium. The fungus was not pathogenic to greenhouse tomato, cucumber or eggplant, nor to field crops such as bean, chickpea or zucchini squash. There were no significant differences in virulence among isolates but differences in resistance/susceptibility among pepper cultivars were observed. The fungicides Medallion® (fludioxonil) and Senator® (thiophanate-methyl) were as effective as bio-control products Mycostop® (Streptomyces griseoviridis) and Prestop® (Gliocladium catenulatum) in limiting Fusarium crown and root rot in greenhouse pepper. Aspects of an integrated disease management strategy are discussed.

Management of phytophthora blight (Phytophthora capsici) on vegetables in Ontario: some greenhouse and field aspects

Abstract Phytophthora blight (Phytophthora capsici) affecting greenhouse vegetable production in Canada is reported for the first time. Aspects of the epidemiology and management of P. capsici in relation to greenhouse and field vegetable production in Ontario are discussed. Identification of the pathogen was based on cultural, morphological and molecular approaches, the latter using primer set PC1/2. The pathogen caused 10% plant population losses in a greenhouse pepper operation in Leamington, ON in 2006–2007, and 5%, 5% and 10% losses in commercial greenhouse tomato operations at sites in 2007, 2008 and 2011, respectively, with 1000 greenhouse tomato plants affected in 2012. Phytophthora blight occurred in 2006 in Haldimand-Norfolk and Essex counties on field cucumber and pepper, respectively, and in Essex county in 2007 on field pepper, squash and tomato. The disease was not observed on field pepper, tomato or cucumber plants in fungicide efficacy trials near Harrow, ON in 2005–2006 or near St. Williams, ON in 2007 where the disease had occurred previously. Symptom development was most rapid on greenhouse cucumber and least rapid on greenhouse tomato. Virkon® disinfectant at 0.25%, 0.5%, 1% and 2% commercially formulated product was 100% effective in preventing zoospore germination of P. capsici while Chemprocide™ disinfectant was not fully effective at 0.04%, 0.4% and 4%, and Virucidal Extra® was intermediate in efficacy. The fungicides fluazinam, mandipropamid, cyazofamid and fluopicolide were effective in controlling P. capsici on greenhouse tomato, cucumber, and pepper plants for at least a 14-day period. Metalaxyl was less effective, possibly due to partial resistance in the fungus to this chemical.

Diseases, pests, and abiotic disorders of greenhouse-grown water spinach (Ipomoea aquatica) in Ontario and California

Water spinach, a specialty vegetable and a member of the sweet potato family, is cultivated for Asian markets in California (United States) and Ontario (Canada). Foliar diseases of this vegetable observed in commercial greenhouses of Ontario in 1993 and 1994, as well as in greenhouses of California in 1998, were attributed respectively to Phyllosticta ipomoeae, Cercospora ipomoeae, and Pseudomonas syringae pv. syringae in the present study. In Ontario, C. ipomoeae infected less than 1% of plants, with less than 25% of the foliage affected, while Phyllosticta ipomoeae occurred on 100% of plants in some greenhouses, with leaf spotting affecting up to 25% of the foliage. In California, Pseudomonas syringae pv. syringae occurred on less than 25% of plants with up to 25% of the foliage affected. In Ontario, no virus was detected in eight suspect foliage samples while damage from vectors of plant viruses such as the green peach aphid (Myzus persicae) was minor and from Western flower thrips (Frankliniella occidentalis) was moderate. Edema affected water spinach at four sites in Ontario in 1994, with both the incidence and severity exceeding 75% at one site. For fungal and bacterial pathogens, Kochs postulates were fulfilled by inoculation and reisolation. Morphological characteristics of isolates in vitro and in vivo were used to identify the fungal pathogens, and LOPAT tests and fatty acid analyses were applied to identify the bacterial pathogen. Symptoms and etiology are discussed. This is the first report of these diseases, pests, and abiotic disorders on water spinach in Ontario and California.