Photoperiodism is best studied through the use of live plant material in the laboratory so that students can observe a progression of developmental stages. This paper describes photoperiod compartments which are simple and easy to construct, inexpensive, and require only a modest amount of greenhouse bench space. The compartments can be used to demonstrate various photoperiod responses including flower initiation and development, pigment production, leaf fall, onset of dormancy, runnering, and the formation of underground food storage organs.
Landscape architects occupy a strategic position in the landscape industry; yet, they have not been generally considered an important customer group by nurserymen. They influence selection of plant material for commercial, government, and residential landscapes and are generally the first to know what will be in demand. A recent survey of Georgia landscape architects found they specify $85 M of plants. This compares to the $200 M estimate for the 1989 wholesale value of nursery stock produced in Georgia. In addition, 60% of the landscape architectural firms influence which production nursery supplies plants by determining or recommending the production nursery where the landscape contractor obtains plants. More importantly, 92% of the large firms, which account for 67% of the dollar value, are involved in selection of the production nursery. The results provide the first quantitative estimate of the influence of landscape architects on nurserymen and suggest that nurserymen should view landscape architects as important customers.
The effect of age on CO2 exchange rates of cucumber (Cucumis sativus L.) cotyledons was measured. A biphasic process was noted, with a period of relatively high exchange rates up to 17-18 days from planting, when the first true leaf was nearly fully expanded, followed by a decline in exchange rates thereafter. The relative contribution of cotyledons versus leaves to photosynthesis as a function of age was measured. At 16 days from planting, the cotyledons accounted for 80% of the total net CO2 exchange and slightly more than 50% of the total foliage area. Twenty-four days after planting, the cotyledons still accounted for about one-fourth of the total net CO2 exchange and 20% of the total foliage area. The use of cotyledons in chilling injury studies of cucumber is justified by both the large photosynthetic contribution of cotyledons to growth and development, and the presence of cotyledons during early growth when chilling is most likely to occur.
Photosynthesis was measured in excised cucumber (Cucumis sativus L. cv. Marketer) cotyledons subjected to chilling temperatures in the presence or absence of photo synthetically active radiation (PAR), under conditions that precluded water stress. Cotyledon CO2 exchange rates (CER) were reduced after chilling in the light, but not after chilling in the dark. In the light, reduction occurred more rapidly at lower than at higher chilling temperatures. The level of PAR had little or no effect on CER reductions at lower temperatures within the chilling range, but at higher chilling temperatures, reduction occurred more rapidly at higher PAR levels. Recovery of photosynthesis following chilling in the light occurred more rapidly in the dark than in the light, and this difference in recovery rate was greater with longer exposure to light and chilling conditions. The removal of light during the recovery phase accelerated the rate of recovery to a level comparable to the dark control.
A national survey of the greenhouse and nursery industries was conducted to determine the current status of pest management practices. This study covers the trends in chemical and nonchemical pest control measures and factors that affect adoption of nonchemical control measures. For the 5-year period 1988-93, there appeared to be a decrease in chemical use for disease and insect control and for plant growth regulators. During the same period there was an increase in chemical weed control. The adoption of nonchemical pest control measures was concentrated in the area of insect control. The primary factors limiting use of nonchemical pest control measures were 1) availability of effective materials/biological agents, 2)availability of information, and 3) management complexity. The primary information sources on nonchemical pest control used by growers varied by size of firm and region of the country. For all respondents the primary sources were 1) industry trade journals, 2) other growers in the industry, 3) cooperative extension service, and 4) industry-sponsored seminars.
A national survey of the commercial ornamental industry was conducted to determine the current status of pest control including chemical and nonchemical disease control practices. The fungicides thiophanate methyl, chlorothalonil, mancozeb, and metalaxyl were used in the greatest quantity and by the largest percentage of growers. Metalaxyl was used in greenhouse and field operations by the highest percentage of growers, primarily to control root diseases but many growers reported using metalaxyl to control foliar disease. Overall, more fungicides were used in the field for foliar diseases, whereas almost equal amounts of fungicides were used for foliar and root diseases in the greenhouse.
Growers in the American Association of Nurserymen and the Society of American Florists were queried as to their use of plant growth regulators (PGRs) and nonchemical alternative practices during 1993. Daminozide (B-Nine SP) and chlormequat chloride (Cycocel) accounted for 78% of the total pounds active ingredient and were used by 20% and 17% of the respondents, respectively. In contrast, the rooting compounds indolebutyric acid (Dip `N Grow, Rootone, and Hormoroot) and naphthaleneacetic acid (Dip `N Grow, and Hormodin I, II, and III) were used by 53% and 24% of the respondents, respectively, but combined accounted for less than 3% of total pounds active ingredient. Pruning/pinching was used by the greatest number of respondents (82%) and was the only alternative to PGRs rated as very effective by more than 60% of the respondents. Use of chemical PGRs and nonchemical alternative practices was influenced by region and firm size. In the northeastern United States, growers reported relatively low use of PGRs (frequency and total pounds) and the lowest use of mechanical brushing as an alternative practice. In contrast, mechanical brushing was used most in the western United States. Large firms (more than $2 million in annual sales) reported the greatest use of chemical and nonchemical means of regulating growth.
Members of the American Association of Nurserymen and the Society of American Florists were surveyed as to their use of herbicides and nonchemical alternative weed control practices for 1993. Glyphosate was the top-ranking herbicide among the total of 37 reported, in terms of number of respondents and estimated total amounts of active ingredients applied. It was used by all but two of the respondents that used herbicides in their operations. Oryzalin was the top-ranked preemergent herbicide, and was second only to glyphosate in number of respondents and amount of active ingredient applied. The highest estimated use in amounts of active ingredient applied was in the southeastern (43% of total) and north-central (27% of total) regions, nearly two to three times the estimated use in the northeastern or western regions. However, there were only about 50% more respondents in the southeastern or north-central regions compared to the other regions. About 56% of herbicide active ingredients used were in field sites, 22% in container sites, 19% in perimeter areas, and 3% in green-houses. Large firms (annual sales more than $2,000,000) used the greatest estimated total amount of active ingredients, while small firms (annual sales more than or equal to $500,000) tended to use nonchemical alternatives the most. Nearly all respondents used handweeding or hoeing as part of their weed control program. Mowing was used by 84% of the respondents, 71% used tractor cultivation, and 66% used mulches (includes gravel and black plastic). Alternative methods were rated as somewhat effective to very effective by 65% or more of the respondents who used them.
A national survey of the greenhouse and nursery industry provided data on insecticide/miticide use in 1993. Respondents reported using 46 different compounds, and the industry used an estimated 2.8 million pounds of active ingredients to control insect and mite pests. The most frequently used material was acephate: 52% of the respondents reporting use in 1993. The most heavily used material was a miticide, dienochlor, with an estimated 643,281 lb (292,400 kg) applied, or 28% of the total. Only three other compounds represented more than 5% of the total use—carbaryl (498,073 lb or 22%) (226,397 kg), diazinon (326,131 lb or 14%) (148,242 kg), and propargite (143,888 lb or 6%) (65,404 kg). Of the top four products, two (dienochlor and propargite) are miticides. Together these represented 34% of the total estimated insecticide/miticide use, demonstrating the importance of mites as pests in the industry.