Scientific Research Journal Update

By: Susan Switras and Jeff Gillman

The published research we are reporting on this month addresses a wide range of nursery industry concerns from pesticides for the Japanese beetle to the timing of nutrient storage for Freeman maple. Once again, we ask you to remember that we are reporting the results of other peoples' research and neither endorse nor refute the methods which they use or the results which they report. It should be remembered that frequently this research is conducted elsewhere and that often conditions in Minnesota are very different from conditions in other parts of the US. As we write these reports we try to do so as accurately as possible, however, we recommend looking up these articles for yourself if you have any questions regarding the research. A full citation of each article is included. Due to the frequency of publication of some of the journals surveyed, reviews from the most recent issues may appear in the next installment of this column instead of the current one. In some of these articles information regarding a particular compound or pesticide is given which does not necessarily follow label recommendations. We strongly discourage the use of these compounds and pesticides in a way that is inconsistent with the label.

• Theo J. Bloom and Wayne Brown at the Vineland Station in Ontario, Canada found that pre-plant treatment of rhizomes and bulbs with copper-based bactericides resulted in decreased incidence of Erwinia carotovra sp. soft rots in Calla Lilies (Zantedeschia elliotiana 'Yellow'). At the time that this research was submitted for review there was no registered, effective, pre-plant treatment for field bacterial soft rot prevention. Of the four bactericides tested (Physan-20, Fixed Copper, Phyton 27 and Virkon), those that contained copper (Fixed Copper and Phyton 27) were more effective than other treatments.⁽¹⁾

  As with all chemicals, read the label before using this product.

• The effects of cyclic irrigation and media on irrigation application efficiency and growth in pot-in-pot production of Acer rubrum 'Franksred' (Red Sunset ^TM) was studied by Fain, Tilt, Gilliam, Ponder and Sibley at Auburn University. Growth was greater when irrigation was applied multiple times during a day (cyclic) instead of as a single application. Cycled irrigation also cut down on the total nitrogen lost from each pot. The concentration of inorganic nitrogen was greater in the leachate from the cyclicly irrigated pots, but, since those pots also lost less water, the quantity of N lost was higher with a single daily irrigation. This study also reported that using pinebark:coconut coir (4:1) as a growing media increased irrigation application efficiency.⁽²⁾
• •In another study done on a maple species, Freeman maple (Acer × freemanii 'Jeffersred'), Mary Ann Rose and Barbara Biernacka at The Ohio State University observed seasonal patterns of N, P, and K accumulation in order to improve fertilization efficiency. The nutrient contents of the whole plant were found to increase until mid-October. Most of the nutrients and dry weight went to the leaves until early September, at which time they (with the exception of K) were redirected to the roots until October and the onset of leaf abscission. Fertilizer rate did not affect the seasonal accumulation patterns of these maples. This research does not support the theory that late summer and early fall fertilizer applications adversely affect Freeman maple.⁽³⁾
• •Steve McNamara and Harold Pellet at Minnesota Landscape Arboretum developed cold hardiness profiles for 18 different container grown cultivars of Weigela sp.. Some cultivars show winter injury in northern climates because of limited cold hardiness. According to their results, late hardening and insufficient mid-winter hardiness appear to be the cause of winter injury exhibited by susceptible cultivars. 'Centennial', 'Java Red', and 'Samba' were the most cold hardy cultivars in this study, while 'Boskoop Glory' , 'Bristol Snowflake' and 'Variegata' were the least hardy.⁽⁴⁾
• •A study performed at North Carolina State University examined vegetative propagation of Thuja × 'Green Giant'. This particular cultivar is a hybrid of the western red cedar and Japanese arborvitae. Griffin, Blazich and Ranney found that, regardless of the cutting type (terminals or laterals), growth stage (softwood, semi-hardwood or hardwood), or IBA concentration applied (.15%, .3%, .6% or .9%), all cuttings rooted at high percentages. In general, highest rooting percentages came from hardwood cuttings treated with 0.3%, 0.6% or 0.9% IBA.⁽⁵⁾ This particular arborvitae is only hardy through USDA hardiness zone 5, but there are a number of arborvitae species that are hardy in our zone and may behave similarly.
• •David Nielsen and Richard Cowles from Ohio State University tested different treatments for the prevention of white grub establishment in container stock. Their experiments were done on container grown Cotoneaster apiculatus 'Coral Beauty', Juniperus chinensis and Briza maxima (quaking grass). Their results show that pre-plant media incorporation of Talstar 0.2 G (10 ppm) and Fireban 1.5 G (15 ppm), as well as a drench of Talstar 0.67 F immediately after planting controlled the larvae of the Japanese beetle, the Oriental beetle and the European chafer beetle effectively for two growing seasons.⁽⁶⁾ Fireban 1.5 G is labeled only for control of fire ants. Read the labels before attempting to use any of these compounds.
• •A study done at the Swedish University of Agricultural Sciences by Hans Lindqvist examined the importance of lifting date in combination with cold storage on one-year-old seedlings of four deciduous species. European white birch (Betula pendula Roth.), red-osier dogwood (Cornus sericea 'Flaviramea'), singleseed hawthorn (Crataegus monogyna) and English oak (Quercus robur) were lifted at intervals over the fall and placed in cold storage for four months. Early lifting followed by cold storage had negative effects on the survival of all four species, as did extended periods of cold storage after early lifting. Early-lifted plants of all four species showed more die-back damage the following season. The ideal lifting date may vary between species, but dormant plants that have achieved sufficient hardiness will survive the process best.⁽⁷⁾

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1. Blom, T. J. and W. Brown. 1999. Preplant Copper-based Compounds Reduce Erwinia Soft Rot on Calla Lilies. HortTechnology. 9(1):56-59.

2. Fain, G. B., K. M. Tilt, C. H. Gilliam, H. G. Ponder and J. L. Sibley. 1998. Effects of Cyclic Micro-irrigation and Substrate in Pot-in-pot Production. Journal of Environmental Horticulture. 16(4): 215-218.

3. Rose, M. A. and B. Biernacka. 1999. Seasonal Patterns of Nutrient and Dry Weight Accumulation in Freeman Maple. HortScience. 34(1): 91-95.

4. McNamara, S. and H. Pellet. 1998. Cold Hardiness of Weigela Cultivars. Journal of Environmental Horticulture. 16(4): 238-242.

5. Griffin, J. J., F. A. Blazich and T. G. Ranney. 1998. Propagation of Thuja X 'Green Giant' by Stem Cuttings: Effects of Growth Stage, Type of Cutting, and IBA Treatment. Journal of Environmental Horticulture. 16(4): 212-214.

6. Nielsen, D. G. and R. S. Cowles. 1998. Preventing White Grub Infestation in Container-Grown Nursery Stock. Journal of Environmental Horticulture. 16(4): 202-207.

7. Lindqvist, Hans. 1998. Effect of Lifting Date and Time of Storage on Survival and Die-Back in Four Deciduous Species. Journal of Environmental Horticulture. 16(4): 195-201.