2015 Summer – Research Updates

Research conducted at the University of Wyoming assessed the potential for year-round greenhouse production of cut sunflowers without the use of supplemental lighting. At 6,700 ft. elevation, Wyoming has abundant high intensity sunlight. With no cut flower wholesale business in the state of

Wyoming, the authors suggest sunflowers could be a niche market for local greenhouse producers.

Data collected included stem length and days to harvest in three sunflower cultivars: ‘Dafna’, ‘Procut Bicolor’ and ‘Sunbright Supreme’. Seeds were sown every two weeks for 14 months, starting November 16 and ending December 12, the following year. Temperature set points were 70F day and 60F night. Stems were harvested when all ray florets were open, but before the disk florets were open. Only stems at least 40 cm (15.7 in.) in length were used in data analysis and considered marketable.

The results show promising potential for year-round container production of fresh cut sunflowers in the Rocky Mountain states, integrating the crop into virtually any greenhouse operation. There were notable differences in days to harvest and stem length in different times of the year. In this study, ‘Dafna’ and ‘Sunbright Supreme’ displayed a facultative short-day response, while ‘Procut Bicolor’ showed a slight facultative long-day response. Cultivar selection or the addition of supplemental lighting can help ensure production efficiency with regard to days to harvest.

Garfinkel, A.R. and K.L. Panter, 2014. Year-round Greenhouse Production of Cut Sunflowers in the Rocky Mountain West, HortTechnology, 24(6):743-748.

Population Management of Biological Control Agents

Predatory mites have been used since the 1950s for pest control in cultivated horticultural crops. Unlike specialist natural enemies, generalist predatory mites do not depend on the pest as only a food source, but can also use an alternative food, such as honeydew, sugar solutions or egg yolk. Past research suggests a predator population can usually sustain itself for two months or more with very low populations of the intended pest prey.  In the early 1980s, research showed that the phytoseiids Amblyseius barkeri and A. cucumeris can control thrips in greenhouse crops. Furthermore, as generalists, they could be mass-produced on alternative prey that are cheap and easy to rear. Recognizing that these predators can feed and reproduce on sweet pepper pollen, they could be introduced into a flowering crop even before the occurrence of thrips.

As early as 2001, another predatory mite, Amblyseius swirskii, was introduced and shown to effectively control white flies and thrips at the same time. Although A. swirskii does not depend on the presence of one pest species, it is still desirable to introduce the predators in the crop before pests occur and supply them with alternative food, especially in ornamentals where economic damage levels are low. Several pepper plants have been identified as suitable banker plants to supply pollen as a food source to a population of beneficials in the absence of the target pest.

When predators and alternative food are introduced in a crop prior to pests presence, the densities of the predators will eventually be limited by the availability of the alternative food. Until this threshold, pest population may be allowed to temporarily increase, though the lack of food will result in the predators feeding on the pest. Research has indicated the predators sometimes perform better on a mixed diet of alternative food and target prey.

Janssen, A., M.W. Sabelis, 2015. Alternative food and biological control by generalist predatory mites: the case of Amblyseius swirskii, Experimental and Applied Acarology, 65(4):413-418.

Asiatic Hybrid Lily Production from Bulbils

A new propagation technique may significantly shorten the time required for production of Asiatic hybrid lilies. The current process takes two to three year to produce bulbs from bulblets for greenhouse forcing. The new technique reduces the time from propagation to flowering by one to two years. This research assessed the feasibility of forcing bulbils of Lilium x elegans to flower with two to three flowers per stem and a stem length of at least 60cm (23.6 in).

Lily ‘Beni no Mai’ was the cultivar selected for this research. At anthesis the inflorescence about the bracts was removed to accelerate formation of bulbils. Thirty to forty uniform bulbils formed in the middle of the stem were selected and packed in peat moss. One bulbil was planted per 10cm (4 in.) pot for continued treatments and growing. Continuous and sequential bulb cold treatments were tested. The effect of bulbil maturity, plant growth regulators and irradiance on growth and flowering were also evaluated.

Success with this technique was achieved by harvesting mature bulbils weighing about 400mg, 40-50 days after anthesis and treating with a sequential temperature treatment 14 to 20 days each at 5C, then 15C or 20C, then 5C. Plants can be produced in about 300 days from potting of the treated bulbils. Further research will need to target breeding and selection of cultivars that produce bulbils and respond to alternating temperatures before and after potting.

Keun Suh, J., M.S. Roh, 2014. New technique for cut flower production from bulbils of the Asiatic hybrid lily (Lilium x elegans Thunb.), Scientia Horticulturae, 165:374-383.