Charles Krasnow

Pythium root rot, caused by the pathogen Pythium ultimum, is a destructive disease of snapdragon in greenhouse production. Symptoms include stunting, chlorosis of lower leaves, and wilting. Eventually, plants wilt completely, and plant death may occur. This report evaluates the efficacy of fungicide drenches with conventional fungicides for the management of Pythium root rot. The trial was conducted in 2026 on greenhouse-grown snapdragon ‘Rocket Red’ in Storrs, CT. Results from this trial will help in developing management programs for this disease.

Botrytis blight, caused by Botrytis cinerea, is one of the most destructive diseases of poinsettia in greenhouse production. On bracts, leaves, and stems, Botrytis blight typically develops as rapidly expanding water-soaked lesions that become necrotic with characteristic gray sporulation. This article reports on the evaluation of the efficacy of spray programs with conventional fungicides for the management of Botrytis blight. The trial was conducted in 2025 in Storrs, CT, on greenhouse-grown ‘Christmas Eve Red’ poinsettias. Results from this trial will aid in developing management programs for this disease.

Geranium rust, caused by the fungal pathogen Puccinia pelargonii-zonalis, is a destructive disease of geranium in greenhouse production. On leaves, geranium rust typically develops as small chlorotic spots on the upper leaf surface with raised, rust pustules on the underside of the leaf. Eventually, leaves become necrotic and may abscise. This report evaluates the efficacy of spray programs with conventional fungicides for the management of geranium rust. The trial was conducted in 2025 in Storrs, CT, on greenhouse-grown geranium ‘Americana Salmon’. Results from this trial will help in developing management programs for this disease.

Geranium ‘Black Velvet’ seeds were planted in 72-cell flats at the research greenhouses of the University of Connecticut. Seedlings with three to four true leaves were transplanted on 31 August into 4.5-in. pots into PRO-MIX BX potting mixture containing 1 g/liter of Pythium-infested millet. Sterilized millet was infested with Pythium ultimum (isolate 024P, originally from geranium) prior to use as inoculum. Each pot was fertilized with 1 g of Osmocote and received weekly applications of 20-20-20 liquid fertilizer. No fungicides or insecticides were applied as maintenance sprays. There were six pots per treatment arranged in a completely randomized design. Immediately after transplant, the plants were drenched with 120 ml of fungicide solution, which was sufficient to displace 10% water in each pot. A second drench application was made 7 days after treatment A on 7 September. The greenhouse was maintained between 15.5 to 29.5°C. The plants were rated for disease severity and phytotoxicity, and fresh weights of aboveground plant parts were recorded at the conclusion of the trial. Data were analyzed using an analysis of variance (ANOVA) with means separation preformed using Fisher's protected least significant difference (LSD) test using JMP software.

Connecticut has a robust greenhouse industry that produces a wide range of ornamental crops. Bedding plants are an important category and bring in significa ...

When an ornamental crop is ready for sale (finish time) is the result of many interconnected factors. The theoretical optimal finish time is often not reach ...

Bedding plants comprise an important segment of the Connecticut greenhouse industry, worth close to $350 million annually. These crops, which include pansy, ...

The oomycete Phytophthora capsici is a destructive pathogen infecting more than 50 plant species and is one of the most serious threats to cucurbit production. Phytophthora blight caused by Phytophthora capsici can affect all plant growth stages, and fungicides and cultural controls are used to limit losses. Dissecting pathogen virulence and fungicide resistance can provide insights into pathogenic mechanisms and inform effective management practices to control P. capsici. In this study, we assessed virulence, mefenoxam sensitivity, and genetic diversity of nine P. capsici populations collected from Cucurbitaceae, Solanaceae, and Fabaceae host families in Michigan from 2002 to 2016. We developed 992 simple sequence repeats (SSRs) in the P. capsici genome and identified 60 SSRs located within or close to RXLR-class (Arginine-any amino acid-Leucine-Arginine) effectors and 29 SSRs within or close to effector CRN (CRinkling and Necrosis) family protein, which represent 62 RXLR and 34 putative CRNs. Population structure analysis shows that mefenoxam resistance was not associated with the year of collection, host type, or location, but there were significant differences in virulence among the populations. Using the general linear model and mixed linear model-based association analyses with all effector-related SSR markers, we identified four SSR markers significantly associated with at least one of the virulence-related parameters. Of these, one (Pce_SC18) was in a predicted CRN effector and had high identity with the putative PhCRN37 effector in the pathogen Plasmopara halstedii, which can be further verified for virulence identification in P. capsici.