Xiuming Hao

Impact of western flower thrips (Thysanoptera: Thripidae) on growth, photosynthesis and productivity of greenhouse sweet pepper

Low, medium and high densities of western flower thrips [Frankliniella occidentalis (Pergande)] were established in three greenhouses, in 1994 and 1995, to investigate the effects of thrips on growth, photosynthesis and productivity of greenhouse sweet pepper. Sweet pepper fruit was very susceptible to cosmetic injury which resulted in a reduction of the commercial grade of the fruit (quality). Damage by western flower thrips (WFT) on the fruit was direct and instant. Short periods of high thrips densities resulted in cosmetic damage to the fruit. The major period for fruit damage occurred in the 3rd to 5th weeks before harvest, when the fruit was growing rapidly. Approximately seven thrips per sticky trap per day from weeks #3 to #5 before fruit harvest will result in fruit being downgraded from commercial grade #1 to #2. Impact of WFT on plant growth, photosynthesis and marketable yield was indirect and cumulative. Leaf photosynthesis was reduced when plants were exposed to more than 1200 accumulated larval-days per plant and marketable yield was reduced when exposed to more than 1800 accumulated larval-days per plant. Plants recovered slowly from the thrips damage once yield loss had been detected. Therefore, thrips abundance should be maintained below 1200 larval-days per plant to prevent the negative impact of WFT on plant physiology and yield. The importance of these findings on pest management programs for WFT is discussed.

Effects of three greenhouse cover materials on tomato growth, productivity, and energy use

Abstract Effects of single-layered glass (glass), double inflated polyethylene film (D-poly), and rigid-twin wall acrylic panels (acrylic), as greenhouse covers on tomato ( Lycopersicon esculentum Mill) growth, productivity and energy use were investigated over two spring seasons in 1993 and 1994. There was no significant difference in early marketable yield (harvested until April 30) between the D-poly and glass houses. Early marketable yield in the acrylic houses was similar to that in the glass houses, but higher than that in the D-poly houses in 1994. Mid-season yield in the D-poly houses was lower than in the glass houses. Final marketable yield in the D-poly and acrylic houses was similar to that in the glass houses. Fruit size during the early and mid-season in the D-poly houses was smaller than in the glass or acrylic houses. This reduction in fruit size shifted 6–12% of grade # 1 fruit from extra large to large. Fruit size in the glass and acrylic houses was similar. In 1993, there was a higher BER (blossom-end rot) incidence in the glass houses than in D-poly or acrylic houses, but a higher percentage of grade #1 fruit in the D-poly houses than in the glass or acrylic houses. The D-poly and acrylic houses saved 30% in heating energy compared to the glass houses.

Effects of greenhouse covers on seedless cucumber growth, productivity, and energy use

Effects of single-glass (glass), double inflated polyethylene film (D-poly), and rigid twin acrylic (acrylic) panels, as greenhouse covers, on seedless cucumber growth, productivity and energy use were investigated over three spring seasons (1988, 1990 and 1992). The early and final marketable yields of plants grown in D-poly houses were similar to or higher than those grown in glass houses. Also, plants grown in D-poly houses produced a similar or higher percentage of large and a lower percentage of small fruits than the plants grown in glass houses. The early and final marketable yield and percentages of fruit grades were similar in D-poly and acrylic houses; an exception was the early marketable yield in 1992 which was higher in the acrylic houses. Light transmission was the highest in glass houses, intermediate in acrylic houses and the lowest in D-poly houses. Relative humidity was highest in D-poly, intermediate in acrylic, and the lowest in glass houses. The plants in D-poly houses grew and developed faster (more leaves and flowers) than those in glass houses. The leaf size of plants in D-poly houses and glass houses was similar, but the dry matter content and specific leaf weight of plants grown in D-poly houses were significantly lower (40% less) than those in glass houses. Plants in D-poly houses might have acclimated to the low light conditions by reducing specific leaf weight and increasing their light interception efficiency. Plant growth and development in acrylic and D-poly houses was similar. For cucumber production in climatic conditions similar to South Western Ontario, the D-poly greenhouse is strongly recommended, because there is no loss of productivity in comparison with a glass house, while great savings on initial investment and energy use are achieved.

Impact of western flower thrips on growth, photosynthesis and productivity of greenhouse cucumber

Abstract Low, medium and high densities of western flower thrips ( Frankliniella occidentalis (Pergande)) were established in three greenhouses in 1996 and 1998 to investigate effects of thrips on growth, photosynthesis, yield and quality of greenhouse cucumber. Cucumber fruit were very susceptible to direct cosmetic damage by western flower thrips (WFT). High densities of WFT for short time periods significantly increased the number of fruit downgraded from grade #1 to #2. The most vulnerable stage to cosmetic damage was 4–10 days before fruit harvest, when the fruit were growing rapidly. WFT also increased fruit curvature and reduced plant growth, photosynthesis and marketable fruit yield. However, the impact of WFT on plant growth, photosynthesis and marketable yield was mainly cumulative; the impact was less dependent on the density or exposure duration alone, but more on thrips abundance (integration of thrips density over time). Leaf growth, leaf photosynthetic rate, marketable yield were reduced when plants were exposed to more than 700–2000, 2800, 3000 accumulated thrips-days per sticky card, respectively. It was very difficult for cucumber plants to recover from thrips damage once yield loss had taken place. Therefore, it is recommended to control thrips abundance below 700 accumulated thrips-days per sticky card to prevent a negative thrips impact on plant physiology or yield. The impact of WFT on fruit curvature was smaller than on fruit appearance, but more serious than on plant growth and yield. Five-hundred accumulated thrips-days per sticky card would significantly increase fruit curvature. The implications of experimental results from this study for WFT control are discussed.

Effects of day and night air temperature on growth, productivity and energy use of long English cucumber.

To determine the optimum air temperature regime for greenhouse seedless cucumber production under North American conditions, the cvs. Corona (in the spring of 1990 and 1992) and Aramon (in the spring of 1992) were grown under nine day/night temperature regimes composed of a factorial combination of three day (18, 21 and 24 °C; DT) and three night (16, 18 and 20 °C; NT) heating temperatures, at a common 24 °C ventilation temperature. Plant development rates (leaf and flower number) were linearly increased with increasing daily average air temperature (MT), but not affected by day–night air temperature difference (DIF), indicating that plant development rates increased with increasing air temperature regardless of DT or NT. Specific leaf weight decreased with increasing DT or NT, and leaf photosynthesis rates decreased with increasing DT. Therefore, high DT or NT promoted the growth rates of young cucumber plants mainly through increasing leaf area ratios. Early and final yields of Corona were mainly affect...

Effects of day and night air temperature in early season on growth, productivity and energy use of spring tomato

Effects of air temperature on tomato (Lycopersicon esculentum Mill) growth, yield and heating energy consumption were investigated in spring of 1993 and 1994. Tomato plants were grown under nine day/night air temperature regimes formed by factorial combination of three day (19, 20 and 21°C) and three night (16, 17 and 18°C) heating temperature set points. Early (until 30 April) fruit yield increased but early fruit size decreased with increasing daily average air temperature (MT, 24-h mean). The plants grown under high daily average air temperature early in the season had lower fruit yield late in the season. Plants grown under high night air temperature (NT) and low day air temperature (DT) during the early production period achieved high fruit yield in early season and avoided the negative effects of high MT on early fruit size; these plants also had high yield and large fruit size late in the season. The different day and night heating temperature regimes studied caused no more than 10% in heating ener...

Effect of elevated CO2 and spectral quality on whole plant gas exchange patterns in tomatoes

In controlled environment plant production facilities, elevating either light or CO2 levels generally has led to increased biomass and yield due to enhanced canopy photosynthesis. Today, advancements in light-emitting diodes (LEDs) have made this technology a viable option for both supplementary lighting in greenhouses and a sole lighting source in controlled environment chambers. Our study used tomato plants grown under both ambient CO2 (AC) and elevated CO2 (EC) conditions then exposed them to various CO2 and lighting treatments during both whole plant and leaf level measurements. Plants grown under EC reached the first flower developmental stage 8 days sooner and were approximately 15cm taller than those grown under AC. However, under AC plants had more leaf area while their dry weights were similar. Of note, under EC chlorophyll a and b were lower, as were carotenoids per unit leaf area. Whole plant analyses, under all CO2 challenges, showed that plants exposed to high-pressure sodium (HPS), red-blue LED, and red-white LED had similar photosynthesis, respiration, and daily carbon gain. Under different light qualities, day-time transpiration rates were similar among CO2 conditions. Day-time water-use efficiency (WUE) was higher in plants grown and exposed to EC. Similarly, WUE of plants grown under AC but exposed to short-term elevated CO2 conditions was higher than those grown and tested under AC during all light treatments. Under all CO2 conditions, plants exposed to red-white and red-blue LEDs had lower WUE than those exposed to HPS lighting. Assessing alterations due to CO2 and light quality on a whole plant basis, not merely on an individual leaf basis, furthers our understanding of the interactions between these two parameters during controlled environment production. Principle component analyses of both whole plant and leaf data indicates that increasing CO2 supply has a more dramatic effect on photosynthesis and WUE than on transpiration.

Energy Saving Achieved by Retractable Liquid Foam between Double Polyethylene Films Covering Greenhouses

Heating is a major cost component in greenhouse crop production. A retractable liquid foam insulation technology was developed recently in Canada to reduce energy use for greenhouse heating. The system dynamically generates and injects liquid foam into the cavity between two polyethylene films in the greenhouse roof. Several experiments were conducted in southwestern Ontario, Canada, from December 2007 through May 2008 to evaluate the energy saving potential of this technology. The liquid foam system was installed in two independent greenhouses; in one of them, the system was shut off to serve as control. The foam was used only during the night for greenhouse insulation. In December 2007, no crop was grown inside the greenhouses. During the first five months of 2008, tomato (Lycopersicon esculentum) and sweet pepper (Capsicum annuum) plants were grown inside both greenhouses. Natural gas consumption for heating, and inside microclimate and outside climatic conditions (air and leaf temperature, humidity, solar radiation, and wind speed) were recorded. Heat loss from the roof with or without liquid foam was calculated. During December 2007, the liquid foam reduced the heat loss through the roof by 31%. During 2008, the heat loss was reduced by 29%, 36%, and 42% for January, February, and March, respectively. A larger reduction in roof heat loss (higher energy saving) was recorded during spring nights: 62% and 58% in April and May 2008, respectively. Therefore, the liquid foam showed a good energy saving potential (29% to 62%), but its energy saving decreased with low outside temperature. Further improvement in liquid foam formulation may be needed to increase its energy saving potential during the winter under low outside temperature conditions. Finally, liquid foam insulation resulted in higher greenhouse air temperature and plant leaf temperature; this should benefit plant growth and development and promote early yield.