Harvest timing is a crucial production decision that affects the yield and quality of horticultural crops, yet little research-based information is available to guide this decision for cannabis (Cannabis sativa L.) production. The objective of this study was to quantify temporal changes in dry mass and tissue cannabinoids under an inductive photoperiod to track yield and identify optimal harvest timing. This information can be used to guide production scheduling. Two experiments were conducted that flowered cannabis ‘Southern OG’ under a 12-h photoperiod for 8 weeks (Expt. 1) or 10 weeks (Expt. 2) with weekly destructive harvest of whole plants beginning on the fourth week. Two distinct trends were revealed as flowering progressed: reproductive dry mass increased linearly each week and the cannabinoid concentration increased to a maximum and then gradually declined. On a per-crop basis, harvesting at 9 or 10 weeks resulted in maximum cannabidiol (CBD) yield or tetrahydrocannabinol (THC) yield, respectively. On an annual basis, reproductive dry yield was greatest when harvesting at 10 weeks, while cannabinoid yield declined when harvesting after 8 weeks. These results demonstrate that optimal harvest timing depends on the final product of interest (e.g., dried inflorescences or tissue extracts) because the maximum yield of reproductive mass and cannabinoids occurred in different harvest timing treatments. Commercial growers must also consider production costs and product value. Longer crop cycles are desirable to reduce variable costs, such as containers, substrate, and cuttings, but the accompanying decline in cannabinoid concentration with longer crop cycles adversely impacts the perceived quality and economic value of dried inflorescences. Therefore, optimal harvest timing depends on the interactions of yield, production cost, and product value.

In controlled-environment cannabis ( Cannabis sativa L.) production, restricting fertilizer application and maintaining low substrate electrical conductivity (EC) before harvest, which is termed “flushing,” is a standard procedure that is hypothesized to reduce inflorescence mineral nutrient concentrations, thereby improving dried inflorescence smoking quality, without impacting inflorescence yield. The objective of this study was to determine if flushing impacts yield, concentration of cannabinoids, or mineral nutrient concentrations of inflorescences. Two high-cannabidiol (CBD) cannabis cultivars, THM Jack and Southern OG, were flowered under a 12-hour photoperiod harvested at 7 weeks or 8 weeks, respectively. ‘THM Jack’ was subjected to preharvest flush durations from 0 to 3 weeks, and ‘Southern OG’ was subjected to preharvest flush durations from 0 to 4 weeks. Inflorescence dry mass (kg·m −2 ) declined as flush duration increased, but trim dry mass was unaffected. Additionally, Cannabidiol (CBD) and tetrahydrocannabinol (THC) concentrations were not impacted in ‘THM Jack’, but CBD concentration increased with flush duration in ‘Southern OG’. The increase in CBD concentration did not compensate for the decline in inflorescence mass, which resulted in a decline in CBD yield (g·m −2 ). Nitrogen, phosphorus, and potassium concentrations declined in both cultivars as flush duration increased. Collectively, these results indicate that flushing can impact dry mass and tissue concentrations of cannabinoids and mineral nutrients. Whether these changes are beneficial depends on weighing a desired outcome (e.g., reduce fertilizer costs, improve smoking quality, manipulate cannabinoid concentration) against a loss in inflorescence and/or cannabinoid yield. Future research should evaluate how restriction of specific nutrients might impact inflorescence growth or organoleptic properties as well as potential differences in cultivar sensitivity to flushing based on seasonal variation in controlled environments.

Howler EVO is a biological fungicide based on metabolites of the bacterium Pseudomonas chlororaphis strain AFS009. One of the metabolites, pyrrolnitrin, is a chemical analogue of the phenylpyrrole fludioxonil used to manage gray mold of fruit crops caused by Botrytis cinerea. Resistance to fludioxonil in B. cinerea is well documented and linked to mutations in the transcription factor mrr1, leading to overexpression of the ATP-binding cassette transporter gene BcatrB. Moderately resistant isolates are designated MDR1 and MDR1h based on the specific variation of mutations in mrr1 and the level of BcatrB expression. This study investigated concentration inhibiting 50% mycelium growth (EC50) values of 54 B. cinerea isolates sensitive and with moderate resistance to fludioxonil for sensitivity to fludioxonil and Howler EVO. The Pearson correlation coefficient indicated a strong correlation between EC50 values of fludioxonil and Howler EVO. Isolates that were moderately resistant to fludioxonil and classified as MDR strains were also moderately resistant to Howler EVO. The effect of Howler EVO and fludioxonil on BcatrB gene expression was studied by quantitative PCR. Both fungicides induced the BcatrB gene expression significantly up to 100-fold in sensitive B. cinerea isolates. Howler EVO significantly induced the BcatrB gene expression in all MDR1 isolates but not in the MDR1h isolate. In detached fruit assays on cherry, sensitive B. cinerea isolates were completely inhibited by formulated fludioxonil (Scholar) and significantly suppressed in growth by Howler EVO. However, MDR1 and MDR1h isolates produced disease in Scholar and Howler EVO treatments. Our results indicate cross-resistance between the synthetic fungicide fludioxonil and the biofungicide Howler EVO, indicating that, at least for some biofungicides, resistance management is necessary.

This study aimed to determine the relative sensitivity of poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch ‘Prestige Red’) flowering to high temperatures within a 24-hour cycle. For the first experiment, two growth chambers were used, one provided a moderate-temperature environment of 22 °C, and the other provided a high-temperature environment of 28 °C. The day length and night length in each chamber were each 12 hours. Plants were moved between chambers to provide different temperature treatments over a 2-week period. During this time, plants were exposed to high temperatures during the first 6 hours of the day, the last 6 hours of the day, the first 6 hours of the night, or the last 6 hours of the night. Additional treatments included plants that were exposed to the high-temperature environment for 12 hours of the night or day period and plants that were exposed to the moderate-temperature or high-temperature environments for the entire 24 hours. After the treatment period, all plants were moved to a 22 °C greenhouse and a 12-hour night length until flowering data were collected. The last 6 hours of the night had the highest relative sensitivity to high temperatures, followed by the first 6 hours of the day. A second experiment was conducted to provide temperatures at a broader range and higher resolution (e.g., 24, 26, 28, 30, 32 and 34 °C) while testing our hypothesis that poinsettia is highly sensitive to high temperatures during the last 6 hours of the night and the first 2 hours of the day. Plants exposed to high temperatures (≥26 °C) during the last 6 hours of the night and the first 2 hours of the day displayed a greater delay in flowering compared with plants that received 24 °C for 24 hours per day. This project demonstrated that heat delay of poinsettia is highly sensitive to temperatures ≥26 °C that occur during the last 6 hours of the night and the first 2 hours of the day during flower initiation (the first 2 weeks of inductive photoperiods) under natural day length conditions (12-hour night length).

Blue and supplemental far-red light were observed to affect in vitro shoot growth with Cannabis sativa (‘BaOx’ and ‘Cherry 1’) in RV750 vessels. A modified “hedging” and fed-batch system for multiple harvests using Oasis® foam and 120 mL DKW medium was used. Fifteen nodal and/or apical tips were planted and placed into PAR light treatments providing various red to blue ratios (polychromatic white 9:1 RB and dichromatic 2–15: 1 RB, with and without 5% far-red light). Treatments had similar light intensities (190–240 µmol · m−2 · s−1 PPFD) for a 16 h photoperiod. Shoot tips were harvested in vitro on five successive two-week cycles, with 15 mL of DKW media supplemented to each vessel following harvest. Shoot numbers, length, and fresh and dry mass were recorded at each cycle harvest. Five randomly selected shoot tips per vessel were rooted ex vitro on greenhouse mist bench for 16 days. Over multiple cycles, 5% far-red increased shoot numbers and length in both genotypes tested, regardless of polychromatic or dichromatic source. Shoots harvested per vessel increased from 15 to 28 in three cycles (6 weeks), but increased from 15 to 18 without far-red treatment. Shoot length in far-red-treated plants increased from 19 to 25 mm during cycles 1–3. Plants without far-red treatment were approximately 15 mm during the first three cycles. By cycle 5, both far-red- and non-far-red-treated plants decreased to 10 mm. Dry mass was greatest in cycle 1 for both genotypes (‘Cherry 1’ was 6 mg and ‘BaOx’ was 7 mg) under the highest amount of blue light, but 2 mg under the lowest amount of blue light. Dry mass decreased by 50% in cycle 3, to 4 mg, where it remained for the duration of the experiment. Sixty eight percent of shoots rooted ex vitro on the mist bench, regardless of any prior in vitro treatment.

The use of biorational products offers an alternative to the conventional chemical fungicide approach to manage botrytis blight caused by Botrytis cinerea . Biorationals are a broad category of products that include biological control agents (BCAs), biologically derived products, compounds that induce natural plant disease resistance mechanisms, and mineral elements. We evaluated 15 biorational products and two chemical fungicides on detached petunia ( Petunia × hybrida ) and rose ( Rosa × hybrida ) flowers inoculated with B. cinerea spores following treatments. The two chemical fungicides, Miravis Prime and Captan, were evaluated as commercial control. In the first experiment, five products showed a reduction in disease severity in petunia flowers (reduction percentages shown in parentheses are relative to the inoculated control): Zivion, a formulation of natamycin, a natural fermentation product of Streptomyces natalensis (66%); ON-Gard Calcium, a calcium chloride product delivered in soy protein (79%); Howler, a formulation of Pseudomonas chlororaphis strain AFS009 (51%); Affirm, a polyoxin D zinc salt (36%); and Regalia, an extract from giant knotweed ( Reynoutria sachalinensis ) (36%). In the second experiment, the five effective products were applied to petunia flowers individually and in combinations. The combination of Zivion + Howler and ON-Gard Calcium + Howler reduced disease severity by 77% and 79%, respectively, compared with the inoculated control, whereas ON-Gard Calcium + Zivion showed a 91% reduction in disease severity. In the third experiment, the same 15 biorational products from the first experiment were applied as a dip application on rose flowers. Applications were made 1 or 8 days before inoculation with B. cinerea spores . When biorational products were applied 1 day before inoculation, Affirm, ON-Gard Calcium, Actigard (acibenzolar-S-methyl, an inducer of systemic-acquired resistance, and Zivion showed a reduction in disease severity of 63%, 33%, 23%, and 18%, respectively. When the biorational products were applied 8 days before inoculation, Actigard, Affirm, and ON-Gard Calcium showed a reduction in botrytis severity by 16%, 54%, and 31%, respectively. In the fourth experiment, the four most effective products were evaluated as single and combination applications on rose flowers. The combinations of Actigard + ON-Gard Calcium, ON-Gard Calcium + Zivion, and Actigard + Zivion reduced botrytis blight by 66%, 62%, and 53%, respectively, whereas Actigard + Affirm, ON-Gard Calcium + Affirm, and Zivion + Affirm reduced disease severity by 85%, 77%, and 76%, respectively. This work demonstrates that tank mixes of biorational products, which provide different modes of action, can have comparable efficacy to chemical fungicides for controlling botrytis blight in petunia and rose flowers.

Postharvest Calcium dip applications help decrease Botrytis blight (Botrytis cinerea) of cut flowers. However, the extent of metabolic perturbations initiated by calcium application and its interaction with B. cinerea infection in cut roses remained unclear. The objectives of this research were to evaluate the effect of postharvest calcium dips with and without the use of the coadjuvant Capsil (R) on Botrytis blight severity and petal strength of cut roses and to assess potential metabolic pathways involved in the interaction between cut roses, calcium, and B. cinerea. During an initial experiment, calcium dips were performed on 'Orange Crush' roses at 0, 1000, and 2000 mg L-1 Ca with and without the coadjuvant 24 h prior to inoculation with B. cinerea to determine disease severity. During a second experiment, global metabolomic analysis considered three factors: coadjuvant use, B. cinerea inoculation, or calcium application. Our results show that postharvest calcium chloride dips effectively reduced Botrytis blight severity and increased calcium concentration and resistance to rupture in the petal tissue, independently of using Capsil (R). Metabolomic analysis revealed changes in the phenylalanine, tyrosine, tryptophan, flavone, and flavonol biosynthesis metabolisms for the B. cinerea inoculated samples treated with calcium chloride. Combined response to B. cinerea infection and calcium application resulted in an upregulation of sphingolipid metabolism, opposite to the response obtained with B. cinerea inoculation alone. These results prove that several metabolic perturbations occur in response to postharvest calcium dips and emphasize the importance of calcium as a management strategy for Botrytis blight.

Botrytis blight in cut-flower roses is a devastating disease caused by Botrytis cinerea. Calcium (Ca) applications have shown great potential as alternative disease management strategies for different crops. This research aimed to evaluate the effect of preharvest calcium sprays and postharvest calcium dips on rose flower susceptibility to Botrytis blight, petal tissue calcium concentration, and petal strength. Calcium chloride spray applications (0, 500, 1000, and 1500 mg.L-1of Ca) during greenhouse production and postharvest calcium chloride dips (0, 1000, and 2000 mg.L- 1 of Ca) were evaluated and compared with commercial controls, including hydrogen peroxide, captan, and pydiflumethophen + fludioxonil. Calcium chloride sprays during production reduced Botrytis blight severity at 500 and 1000 mg . L- 1 of Ca; however, no concentration of calcium chloride spray solution increased calcium in the petal tissue. Postharvest calcium chloride dip applications at 1000 and 2000 mg . L- 1 of Ca effectively reduced Botrytis blight compared to the untreated control. Calcium chloride dip applications at 2000 mg . L- 1 of Ca were effective for increasing the calcium concentration in the epidermis and mesophyll of the petal tissue in comparison to the 0 mg . L- 1 treatment and resulted in increased petal strength and reduced Botrytis severity in comparison to captan and hydrogen peroxide treatments. These results show that postharvest calcium chloride dip applications are more effective than spray applications during production in improving calcium concentration and petal strength on roses and result in a reduction of Botrytis blight severity greater than captan and hydrogen peroxide commercial treatments. This underscores the importance of calcium chloride applications as an alternative management approach for Botrytis blight on roses.

In vitro hedging; combined with the fed-batch liquid media process is an innovative system that generates multiple sterile plants without the use of exogenous cytokinin. This combined process was demonstrated with Cannabis sativa (‘Cherry1’, ‘BaOx’, ‘T1’, ‘Peach’) grown in vessels of three different physical states—stationary agar (A); stationary Oasis® infused with liquid (OILs); and agitated Oasis® infused with liquid (OILa). Vessels were pre-selected as control or supplemented; where supplement vessels received 15 mL DKW liquid media each cycle harvest. The number of shoot tips harvested; shoot length; and dry shoot mass from repeated cutting cycles was recorded. In a single harvest; ‘BaOx’ and ‘Cherry 1’ produced one shoot per plant from the original 15 planted on all treatments. ‘Peach’ and ‘T1’ produced less shoots on average; but the most in OIL treatments. All shoots harvested were longer in OIL compared to A; regardless of genotype. Over multiple cycles; ‘Peach’ and ‘T1’ were unable to reliably produce shoots on a repeated schedule and were, therefore, eliminated from the experiment. By cycle 3; maximum number of plants were produced; regardless of supplementation (‘Cherry 1’; 30; ‘BaOx’; 22). Shoot length was above 10 mm (planting standard) for both genotypes until after the third cycle (10 weeks) where number and quality decreased (nodes and internodes easily discerned). By the end of the experiment; the only shoots that remained productive for over 16 weeks and multiple repeated harvest cycles were those in OIL treatments with supplements.

Mixtures of fungicides with different modes of action are commonly used as disease and resistance management tools, but little is known of mixtures of natural and synthetic products. In this study, mixtures of metabolites from the rhizobacterium Pseudomonas chlororaphis strain ASF009 formulated as Howler EVO with below-label rates (50 µg/ml) of conventional sterol demethylation inhibitor (DMI) fungicides were investigated for control of anthracnose of cherry (Prunus avium) caused by Colletotrichum siamense. Howler mixed with metconazole or propiconazole synergistically reduced disease severity through lesion growth. Real-time PCR showed that difenoconazole, flutriafol, metconazole, and propiconazole induced the expression of DMI target genes CsCYP51A and CsCYP51B in C. siamense. The addition of Howler completely suppressed the DMI fungicide-induced expression of both CYP51 genes. We hypothesize that the downregulation of DMI fungicide-induced expression of the DMI target genes may, at least in part, explain the synergism observed in detached fruit assays.

The use of conventional fungicides to control Botrytis blight of ornamentals caused by Botrytis cinerea has its limitations due to increasing resistance to site-specific fungicides. Calcium propionate (CaP) has suppressive action against this disease, and resistance in B. cinerea to CaP has not been reported. This study evaluated the efficacy of postharvest dip applications of 0.1% CaP (pH 6.0) to control Botrytis blight in four cut rose (Rosa x hybrida) cultivars and analyzed gene expression of CaP-treated rose petals. CaP reduced Botrytis blight symptoms in rose 'Alive' but not in 'Freedom', 'Momentum', and 'Orange Crush', and no change in gene expression in 'Orange Crush' was detected following CaP treatment. Aerial spray applications at 0.1, 0.2, 0.3, 0.4, and 0.5% CaP made twice a week for 5 weeks caused minimal phytotoxicity damage to calendula (Calendula officinalis), carnation (Dianthus sp.), dahlia (Dahlia sp.), pansy (Viola x wittrockiana), and snapdragon (Antirrhinum majus) leaves; however, CaP spray applications generated residues at all CaP concentrations in all species except for dahlia, where no residue was observed. The results suggest that CaP will suppress Botrytis blight in some but not all rose cultivars and establish a reference for phytotoxicity symptoms and visible CaP residues on ornamental plants. Copyright (c) 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Two common challenges reported by cannabis growers are low yields and small profit margins. Although recent research of cannabis yield has focused on lighting and nutrition, little research has examined how changes in other cultivation practices may be beneficial. The objective of this study was to evaluate the following two techniques to potentially improve yield: fertilizer restriction (FR) to reduce plant size and, thus, increase plant density and shoot number manipulation (SNM) to reduce shoot length and improve biomass partitioning. The FR technique involves leaching the substrate and providing only tap water for 0, 1, or 2 weeks at the start of flower initiation, whereas SNM involves pinching shoot tips 2, 3, or 4 times to produce 4, 8, or 16 shoots/plant, respectively. This study used a full factorial treatment design for a total of nine treatments (three FR × three SNM). Plants were flowered under 12-hour photoperiods for 8 weeks and then destructively harvested for data collection. The results demonstrated that both techniques improve plant productivity in different ways. The FR technique reduced all mass measurements (g/plant) and decreased plant area (m2/plant); therefore, the yield metrics (kg·m−2) increased with the increasing FR treatments. The SNM technique did not affect plant area, but more pinching events resulted in a decrease in reproductive shoot length (cm/shoot) and an increase in inflorescence to trim the dry mass ratio (inflorescence:trim). Shorter shoot lengths are desirable for eliminating trellis support netting, which helps growers reduce material costs and improve labor efficiency during harvest. Increasing the inflorescence:trim may also reduce labor costs related to trimming, which comprise the largest cost of production by many growers. Although both techniques offer advantages, there are trade-offs that must be considered in the context of overall profitability.

Previous studies have demonstrated the efficacy of calcium (Ca) spray applications derived from Ca chloride for reducing botrytis (Botrytis cinerea) infection severity on petunia (Petunia ×hybrida) flowers. This study examines the effects of six Ca sources for their efficacy in reducing Botrytis blight on petunia flowers and their potential to cause spray damage or phytotoxicity. In the first experiment, the six Ca sources evaluated were laboratory-grade and commercial-grade Ca chloride, Ca nitrate, Ca ethylenediaminetetraacetic acid chelate, Ca amino acid chelate, and Ca silicate. In the second experiment, petunia flowers that were 0, 1, 3, 5, or 7 days old at the time of the Ca spray applications were evaluated for spray damage severity. For both experiments, treatments were applied to flowering plants. For the evaluation of Botrytis blight efficacy, flowers were excised and inoculated with botrytis spores 24 hours after the Ca spray application, and were evaluated every 12 hours for 72 hours. Laboratory-grade and commercial-grade Ca chloride at 1250 mg⋅L–1 Ca were the most effective Ca sources evaluated for decreasing Botrytis blight severity while not causing spray damage at any flower age. Spray damage to the flowers from the Ca chloride application increased when Ca concentrations increased to 2000 mg⋅L–1, but no additional benefit was observed for reducing Botrytis blight severity compared with the 1250-mg⋅L–1 Ca application. The results demonstrate that several Ca sources reduce Botrytis blight severity significantly; however, selection of the Ca source is important for minimizing the risk of spray damage.

This study examined the interaction between constant liquid fertilization (CLF) concentrations and plant growth regulator (PGR) application concentrations on petunia ( Petunia × hybrida ) growth and flowering in the production and post-production environments. Paclobutrazol application is a common practice in bedding plant production to achieve a compact plant that increases greenhouse space-use efficiency, shipping density, and tolerance to physical handling stresses in the post-production environment. The objective of this research was to determine the best strategy for balancing CLF and PGR application concentration in the greenhouse environment so that growth and flowering can be maximized in the post-production environment. A two-factorial combination of four CLF concentrations [50, 100, 150, or 200 ppm nitrogen (N)] and four paclobutrazol drench concentrations (0, 5, 10, or 20 ppm) were provided to plants during the production phase, and plant growth and flowering were recorded in the production and post-production environments. From a sustainability perspective, the ideal PGR concentration was 5 ppm paclobutrazol, since this concentration resulted in the best combination of production and post-production characteristics and performance. At this PGR concentration, all plant growth and flowering measures increased as CLF increased from 50 to 200 ppm N; however, all CLF concentrations also produced commercially acceptable plants. Therefore, the ideal CLF concentration depends on the size of plant desired; that is, CLF concentrations as low as 50 to 100 ppm N can be provided depending on the market size requirements of the plants being grown. Based on our results, a combination of 50 ppm N CLF with 0 ppm paclobutrazol or 100 ppm N CLF with 5 ppm paclobutrazol both demonstrated adequate growth control during both production and post-production phases.

Cut roses are highly valuable ornamentals and their profitability depends on the flower postharvest performance. Bent neck symptoms in roses make them unmarketable and are typically related to physiological disorders, bacteria accumulation in the vase solution, and Botrytis cinerea infection. Unusual bent neck symptoms were observed in 4.7% of ‘Orange Crush’ roses from two commercial shipments, resulting in complete flower collapse. This research was aimed to determine the causal agent of the bent neck symptoms. Following incubation in a humid chamber, symptomatic roses evolved in water-soaked lesions with the presence of white mycelium and sclerotia development. Fungal isolations and molecular characterization were performed and Sclerotinia sclerotiorum was identified as the causal agent of rose bent neck. Therefore, when bent neck symptoms are observed, S. sclerotiorum incidence should be considered to avoid possible outbreaks.

Commercial poinsettia production in the United States (US) begins with the propagation of unrooted cuttings that are harvested from stock plants. Unrooted cuttings are produced in Mexico and Central America and shipped to the US via airfreight. During propagation, Botrytis blight caused by Botrytis cinerea can reduce the quality and viability of poinsettia cuttings, leading to leaf loss and tissue collapse. Cuttings appear to be more prone to the development of Botrytis blight during the initial days in propagation; however, there are no data to support this observation. The objective of this project was to evaluate if the susceptibility of poinsettia cuttings to Botrytis blight changes during propagation. Two experiments were conducted with three repetitions over time for each. During the first experiment, poinsettia cuttings were inoculated with a spore suspension of Botrytis cinerea (1x10(4) spores mL(-1)) after 0, 2, and 4 d in propagation. For the second experiment, cuttings were inoculated after 0, 3, 6, and 9 d in propagation. For both experiments, the cuttings were placed in humid chambers following inoculation, and Botrytis blight development was assessed over a period of 15 d. Additionally, non -inoculated cuttings of each treatment were placed in the humid chambers simultaneously with the inoculated cuttings to evaluate ambient disease pressure. For both inoculated and non -inoculated cuttings, Botrytis blight severity decreased linearly as cutting time in propagation increased. Overall, 9 -day-old cuttings showed 54% of reduction in Botrytis blight severity in comparison to 0 -dayold cuttings. These results indicate that the age of poinsettia cuttings is linked to the susceptibility to Botrytis blight severity, and cuttings are most susceptible to Botrytis infection immediately following harvest. Further investigations are required to elucidate the physiological, biochemical, and molecular mechanisms behind this response, which may reveal alternative approaches for disease management.

Conventional fungicides are used in IPM programs to manage fungal plant pathogens, but there are concerns about resistance development in target organisms, environmental contamination, and human health risks. This study explored the potential of calcium propionate (CaP), a common food preservative generally recognized as safe (GRAS) to control fungicide-resistant plant pathogens, mainly Botrytis cinerea, and botrytis blight in ornamentals. In-vitro experiments using mycelium growth inhibition indicated a mean EC50 value for CaP (pH 6.0) of 527 mg/L for six isolates of Botrytis cinerea as well as 618, 1354, and 1310 mg/L for six isolates each of Monilinia fructicola, Alternaria alternata, and Colletotrichum acutatum. In vitro efficacy tests indicated CaP equally inhibited mycelium growth of fungal isolates sensitive and resistant to FRAC codes 1, 2, 3, 7, 9, 11, 12, and 17 fungicides. CaP at 0.1% (pH 6.0-6.5) reduced infection cushion (IC) formation in vitro, botrytis blight on petunia flowers, and botrytis blight of cut flower roses with little to no visible phytotoxicity. Although higher concentrations strongly inhibited infection cushion formation, they did not improve efficacy and exhibited phytotoxicity. We hypothesize that high concentrations may create tissue damage that facilitates direct fungal penetration without the need for infection cushion and subsequent appressoria formation. This study indicates the potential usefulness of CaP for blossom blight disease management in ornamentals if applied at concentrations low enough to avoid phytotoxicity.

During the propagation of unrooted cuttings of floriculture crops, water is applied to the cuttings in the form of mist to reduce transpiration, reduce leaf temperature, and maintain cutting turgidity until roots are initiated in the propagation substrate. Seventeen commercial propagators throughout eastern North America were surveyed about their greenhouse facilities and propagation schedules, and measurements were taken to quantify the volume of water being applied to vegetative annual and zonal geranium cuttings during the first 10 days in propagation. The survey indicated that the primary distinctions between commercial propagation systems were how the nozzles were mounted, e.g., a fixed-position system or a tracking-boom system, and how the frequency of mist events was controlled, e.g., a time clock (static) or a vapor pressure deficit (VPD) (dynamic) system. The water volume per mist event ranged from 34 to 128 mL m(-2) for vegetative annual species and 37 to 354 mL m(-2) for zonal geraniums. The total number of mist events over a 10-day propagation cycle ranged from 65 to 909 for vegetative annuals and from 38 to 1008 for zonal geraniums. The total mist volume over 10 days ranged from 2.8 to 64.3 L m(-2) for vegetative annuals and 3.2 to 134.1 L m(-2) for zonal geraniums. The wide range of water volume applied during propagation suggests that there is ample opportunity for some propagators to reduce the water volume applied. The results suggest a benchmark target of 20 L m(-2) of water for vegetative annuals and 10 L m(-2) for zonal geraniums over a 10-day propagation cycle during late winter can provide sufficient water for successful propagation while reducing excess runoff.

The objective of this study was to identify the specific weeks and night lengths when poinsettia ( Euphorbia pulcherrima Willd. ex Klotzsch) flowering is most sensitive to high temperatures. One experiment was conducted in greenhouses under natural daylength (ND) conditions at lat. 34.7°N starting on 4 Sep, and a second experiment was conducted in growth chambers with an initial night length (NL) of 11 hours 01 minutes that was increased by 2 min/d to simulate ND conditions through September and October. Each week, one group of plants was moved from a moderate-temperature environment [22 °C average daily temperature (ADT)] to a high-temperature environment 28 °C ADT. Each group of plants spent 1 week in the high-temperature environment before returning to the moderate-temperature environment. The temperature treatments lasted for 7 or 8 weeks for the growth chamber and greenhouse studies, respectively. Additional groups of plants were kept in either the moderate- or high-temperature environment for the entire treatment period as controls. Four cultivars were used in the greenhouse study: Advent Red, Freedom Red, Prestige Red, and Tikal Red; only Prestige Red was used in the growth chamber study. Advent Red was identified as the most heat-tolerant cultivar followed by Tikal Red, Freedom Red, and Prestige Red. ‘Advent Red’s’ period of sensitivity to high temperatures ranged from 4 Sep to 1 Oct. ‘Tikal Red’s’ period of sensitivity to high temperature ranged from 11 Sep to 8 Oct. ‘Freedom Red’ had a longer period of high-temperature sensitivity: from 11 Sep to 22 Oct. ‘Prestige Red’ had the longest period of sensitivity to high temperatures encompassing 4 Sep to 29 Oct, and 11 hours 01 minute to 12 hours 37 minutes NL for the greenhouse and growth chamber studies, respectively. Within periods of sensitivity to high temperatures, time to visible bud and anthesis were most affected by high temperatures in earlier weeks, and final bract color development and time to first bract color were more affected by high temperatures during the latter weeks. As cultivars varied in their duration of sensitivity to high temperatures, duration, as well as magnitude of response to high temperature, should be considered in future breeding projects.