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Raymond A. Cloyd and Amy Dickinson

Fungus gnats (Bradysia spp.) are major insect pests in greenhouses. The adult stage is primarily a nuisance whereas the larval stage is directly responsible for plant injury by feeding on plant roots or tunneling into stems. Insecticides are used to deal with fungus gnat larvae in growing medium, although sometimes with limited success. This study evaluated the potential of using a soil amendment—diatomaceous earth (DE) incorporated into growing media—for controlling the fungus gnat Bradysia sp. nr. coprophila. Two experiments were conducted by testing a series of growing media containing various concentrations of diatomaceous earth, and several without diatomaceous earth. The effects of the growing media containing diatomaceous earth on both the 2nd and 3rd instars of fungus gnat larvae were determined by recording the number of adults captured on yellow sticky cards (2.5 × 2.5 cm). Based on the results obtained from both experiments, the addition of DE to growing medium, at the concentrations tested, did not negatively affect or increase efficacy against both the 2nd and 3rd instars. This suggests that incorporating DE into commercially available growing medium may not be beneficial to greenhouse producers. However, further research is needed to assess whether differential larval susceptibility and moisture content influence the ability of DE to control soil-dwelling arthropods.

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Alan W. Meerow and Timothy K. Broschat

Growth of Hibiscus rosasinensis L. `President' under daily irrigation and decreasing irrigation frequency was compared in a 5 pine bark : 4 sedge peat : 1 sand (by volume) medium amended further with 0%, 10%, 20%, or 30% (by volume) Axis, a kiln-fired diatomaceous earth granule. Half of each substrate treatment also was drenched three times with Agroroots, a kelp extract. Shoot and root dry weights were compared after 4.5 months of growth. Container media amended with Axis at 10% volume yielded hibiscus plants with higher shoot dry weights than nonamended media. Root-zone drenches with Agroroots increased shoot dry weights of plants subjected to decreasing irrigation frequency and grown without Axis, but did not significantly affect plants receiving daily irrigation. Shelf-life effects of Axis treatment revealed that all plants reached the permanent wilting point 5 days after cessation of daily irrigation. Both products may allow container plant production with less irrigation. Further tests should be conducted with a broader range of species.

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Xiuling Tian and Youbin Zheng

rate of six pathogens grown in vitro after varying incubation times by three compost teas (pine bark, manure, and vermicasting), Root Rescue, waste diatomaceous earth (DE), and reused greenhouse nutrient solution (RNS). Data are means ± se (n = 10

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Edward L. McCoy

(CC) products such as Profile (Profile Products, Buffalo Grove, IL), clinoptilolite zeolite (CZ) products such as Ecolite (Western Organics, Tempe, AZ), and diatomaceous earth (DE) products such as Axis (EnviroTech Soil Solutions, Oregon City, OR

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Rose A. Ogutu, Kimberly A. Williams, and Gary M. Pierzynski

clay and collapsing of micro- and mesopores by intra- and interparticle sintering caused a rapid decrease in specific surface area and specific micromesopore volume as the temperature increased. Diatomaceous earth (DE) is not derived from clay, but

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Tanja Mucha-Pelzer, Reinhard Bauer, Ekkehard Scobel, and Christian Ulrichs

. Naturally occurring silicas [e.g., diatomaceous earth (DE)] have already been verified for their insecticidal properties in the field of stored product protection by numerous authors ( Athanassiou et al., 2003 ; Dowdy, 1999 ; Ebeling, 1971 ; Fields and

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Vickie Murphy, Kimberly Moore, M. Patrick Griffith, and Chad Husby

/20)/50% Profile (1:1); 7) PermaTill: calcined slate (Carolina Stalite Company, Salisbury, NC); 8) Axis: calcined diatomaceous earth (EnviroTech Soil Solutions, Oregon City, OR); or 9) Fafard potting mix #2: sphagnum peatmoss (70%), perlite (20%), vermiculite (10

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Masoume Amirkhani, Anil N. Netravali, Wencheng Huang, and Alan G. Taylor

, and diatomaceous earth (DE) obtained from Perma-Guard, Inc., Albuquerque, NM. Coating treatments designated as “SCD” consisting of different proportions by weight of soy flour, cellulose fibers, and DE (00:00:100, 20:00:80, 30:00:70, 40:00:60, 50

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Julie A. McIntyre, Douglas A. Hopper, and W.S. Cranshaw

Chemical and physical methods were tested to determine their effectiveness in controlling Western Flower Thrips, Frankliniella occidentalis (Pergande), in greenhouses. Comparisons were made between abamectin (Avid); Spinosyn A and D, formulated from the soil Actinomycete, Saccharopolyspora spinosa (Spinosad); azadirachtin (Margosan-O); and diatomaceous earth, a physical control aimed at deterring pupation. Results based on the number of thrips counted in gerbera (Gerbera jamesonii L.) flowers indicate that the chemical treatments were significantly more effective in reducing populations than the diatomaceous earth. Over time, the population of thrips in both the Avid and Spinosad treatments was reduced to zero. Diatomaceous earth treatments reduced populations almost 50% as compared to the control, while reductions from Margosan-O ranged 50-90%.

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Grady L. Miller

The effects of several soil amendments, following a single filling of core aerification holes, on growth and transpiration of `Tifdwarf' bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy] were examined during drought stress. Soil amendments had variable effects on turf quality. In general, turf grown in ZeoPro®- and Profile®-amended sand had the highest quality. Data indicated that the evaluated soil amendments have the potential to influence soil water content, ultimately influencing transpirational response to drought stress. Amended sand contained 1% to 16% more transpirable water compared with non-amended sand. Turfgrass grown in Axis®- and Isolite®-amended sand required 0.4 to 1.4 days longer to reach the endpoint (transpiration rate of drought stressed plants <12% of well-watered plants) during a period of rapid water depletion. Data from this study suggest that the total volume these amendments occupied in the root zone, following a single filling of core aerification holes in sand, may positively influence soil moisture status, resulting in an increase in drought avoidance.