`Sunny' tomato (Lycopersicon esculentum Mill.), `Black Beauty' eggplant (Solanum melongena var. esculentum L. Nees.), or `Sugar Baby' watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] were nontreated, subjected to brushing (20 strokes twice daily) or drought conditioning (2 hours daily wilt), or maintained undisturbed using ebb-and-flow irrigation. One week after brushing or drought conditioning, plants were inoculated with western flower thrips (Frankliniella occidentalis Pergande) or green peach aphid (Myzus persicae Sulzer). Brushing and drought conditioning reduced plant height and shoot dry weight of all crops. Brushing of all three species generally reduced the number of thrips, as indicated by number of feeding scars or percent leaf area damaged. Drought conditioning did not affect thrips populations consistently. Undisturbed plants grown with ebb-and-flow irrigation exhibited the greatest damage from thrips. Brushing reduced the number of aphids on tomato relative to the nontreated controls. Drought did not reduce aphid populations consistently on any crop. Brushing for height control may be advantageous in an integrated pest-management program to control aphids and thrips.
Joyce G. Latimer and Ronald D. Oetting
Joyce G. Latimer and Ronald D. Oetting
During greenhouse production in Spring 1995, conditioning treatments were applied to columbine (Aquilegia×hybrida Sims `McKana Giants'), New Guinea impatiens (Impatiens hawkeri Bull. `Antares'), marigold (Tagetes erecta L. `Little Devil Mix') and ageratum (Ageratum houstonianum Mill. `Blue Puffs') plants. Treatments included: mechanical conditioning (brushing 40 strokes twice daily); moisture stress conditioning (MSC) (wilting for ≈2 hours per day); undisturbed ebb-and-flow irrigation; overhead irrigation; high (500 mg·L-1 N) or low (50 mg·L-1 N) 3×/week N fertilizer regimes; daminozide (5000 mg·L-1); or paclobutrazol (30, 45, or 180 mg·L-1). One week after initiation of treatments, individual plants in separate greenhouses were inoculated with two adult green peach aphids (Myzus persicae Sulzer) or five two-spotted spider mites (Tetranychus urticae Koch). A natural infestation of western flower thrips (Frankliniella occidentalis Pergande) in the mite-inoculated greenhouse provided an additional insect treatment. Brushing was the only treatment that consistently reduced thrips and mite populations. Aphid populations were lower on low-N than on high-N plants, but thrips and mite populations were not consistently affected by plant fertilization. Moisture stress conditioning tended to increase aphid populations on New Guinea impatiens and marigold, but had little effect on spider mite or thrips populations. Ebb-and-flow irrigation reduced the mite population on ageratum relative to that on overhead irrigated (control) plants. Plant growth regulators did not consistently affect pest populations. Chemical names used: butane-dioic acid mono(2,2-dimethylhydrazide) (daminozide); β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-1-ethanol (paclobutrazol).
Joyce G. Latimer and Ronald D. Oetting
Two weeks after planting, plugs of New Guinea impatiens (Impatiens × hybrida), marigold (Tagetes erecta), or ageratum (Ageratum Houstonianum) were subjected to eight conditioning treatments: untreated, low N (50 ppm), high N (500 ppm), ebb/flow watering, drought, brushing (40 strokes twice daily), daminozide (5000 ppm), or paclobutrazol (45 ppm). Fertilizers were applied three times per week at 250 ppm N for all plants not treated with high or low N. Five adult twospotted spider mites were placed on each plant 1 week after treatment. New Guinea impatiens height was reduced by low N, brushing, or paclobutrazol at 4 weeks after treatment. Spider mite populations were reduced only by brushing. Marigold height was reduced by low N, drought, or brushing, but spider mite counts were reduced by brushing or paclobutrazol. Height of ageratum was reduced by low N, daminozide, or paclobutrazol, but spider mite counts were reduced by ebb/flow or brushing at 4 weeks after treatment.
Joyce G. Latimer and Ronald D. Oetting
Four-week-old salvia (Salvia splendens F. Sellow `Red Pillar') seedlings were treated with 0 or 50 ppm paclobutrazol, followed 5 h later by 0, 1, 2, or 4 times (0×, 1×, 2×, or 4×, respectively) the recommended label rate of bendiocarb (0.6 g a.i./liter), a carbamate insecticide. Seven days after treatment (DAT), phytotoxicity ratings increased with bendiocarb rate on all plants, but 50 ppm paclobutrazol reduced damage at 1× and 4× bendiocarb. Paclobutrazol also improved plant recovery from phytotoxicity damage at 21 DAT. Bendiocarb decreased the height of plants not treated with paclobutrazol at 7, 14, and 21 DAT. Plants treated with 40 ppm paclobutrazol had lower maximum phytotoxicity damage at 14 DAT, and even better recovery at 21 DAT than plants treated with 20 or 60 ppm paclobutrazol. Plants treated with paclobutrazol 4 days before applying bendiocarb had lower maximum phytotoxicity ratings relative to controls than plants treated 8 days before, the same day as, or 4 days after bendiocarb application. Chemical names used: β- [(4-chlorophenyl)methyl]- α -(1,1-dimethylethyl)-1 H- 1,2,4-triazole-1-ethanol (paclobutrazol); 2,2-dimethyl,1,3-benzodioxol-4-yl-methylcarbamate (bendiocarb).
Joyce G. Latimer, Ronald D. Oetting and Paul A. Thomas
Denise L. Olson, Ronald D. Oetting and Marc W. van Iersel
Coconut coir dust is being marketed as a soilless medium substitute for sphagnum peat moss that inhibits fungus gnat (Bradysia sp.) development. However, little information is available on the effects of coconut coir dust on Bradysia sp. In a laboratory study we examined the effect of substituting coconut coir dust for peat moss, with or without a food source, on the development of fungus gnats. An average of less than one adult emerged when 20 fungus gnat eggs were provided with pure or sterilized peat moss or coconut coir. A significantly higher number of adults (11.5-13) emerged when a food source of 1 g of yeast was added to either soilless potting medium type. The adults required up to 10 fewer days to emerge when food was provided, compared to sterilized and pure media, except for the pure peat moss. In a greenhouse study examining the effects of coir and peat at different textures and different moisture levels on fungus gnat survival, there were significant differences at the different levels of moisture. There was a higher population of larvae in the coarse medium containing peat. In the coir-based media, the fine-textured medium had the highest population level of fungus gnats. There were no significant effects on fungus gnat populations among the different levels of moisture within a medium type. However, there was a tendency for lower populations in the most moist and the driest media and the highest survival in the media that were maintained at 52.5% moisture. Plant growth was best in the media with the lowest number of fungus gnats (coarse coconut coir dust-based and fine and medium peat-based media). These results suggest that it is possible to select growing media that minimize fungus gnat populations, while optimizing plant growth. However, contrary to claims made by growing media producers, coconut coir dust does not necessarily inhibit fungus gnat development.
William G. Hudson, Melvin P. Garber, Ronald D. Oetting, Russell F. Mizell, Ann R. Chase and Kane Bondari
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.
Joyce G. Latimer, Reuben B. Beverly, Carol D. Robacker, Orville M. Lindstrom, S. Kristine Braman, Ronald D. Oetting, Denise L. Olson, Paul A. Thomas, Jerry T. Walker, Beverly Sparks, John M. Ruter, Wojciech Florkowski, Melvin P. Garber and William G. Hudson
Optimizing growing conditions and, thereby, plant growth reduces the susceptibility of plants to many disease and insect pest problems. Educating lawn or landscape management professionals and homeowners about plant health management reduces the need for chemical intervention. Pesticides combined with N and P fertilizers contribute to water pollution problems in urban areas; thus, it is important to manage the amount, timing, and placement of chemicals and fertilizers. To educate consumers applying pesticides and fertilizers in residential gardens, we must educate the sales representatives and others who interact most closely with consumers. Evidence suggests that knowledge about the effects of chemicals is limited and that warning labels are not read or are ignored. Integrated pest management (IPM) offers alternatives to conventional chemical treatments, but such methods are not used commonly because of their relatively high cost and their uncertain impact on pests. Pest detection methods and using pest-resistant plants in landscapes are simple and, in many cases, readily available approaches to reducing the dependence on chemical use. Research on effective, low-cost IPM methods is essential if chemical use in landscape management is to decrease. Current impediments to reducing the pollution potential of chemicals used in the landscape include the limited number of easily implemented, reliable, and cost-effective alternative pest control methods; underfunding of research on development of alternative pest control measures; limited knowledge of commercial operators, chemical and nursery sales representatives, landscape architects, and the general public concerning available alternatives; reluctance of the nursery industry to produce, and of the landscape architects to specify the use of, pest-resistant plant materials; lack of economic or regulatory incentive for professionals to implement alternatives; inadequate funding for education on the benefits of decreased chemical use; and the necessity of changing consumer definition of unacceptable plant damage. We need to teach homeowners and professionals how to manage irrigation to optimize plant growth; use sound IPM practices for reducing disease, weed, and insect problems; and minimize pollution hazards from fertilizers and pesticides.
Joyce G. Latimer, Reuben B. Beverly, Carol D. Robacker, Orville M. Lindstrom, Ronald D. Oetting, Denise L. Olson, S. Kristine Braman, Paul A. Thomas, John R. Allison, Wojciech Florkowski, John M. Ruter, Jerry T. Walker, Melvin P. Garber and William G. Hudson
Pesticides have been the primary method of pest control for years, and growers depend on them to control insect and disease-causing pests effectively and economically. However, opportunities for reducing the potential pollution arising from the use of pesticides and fertilizers in environmental horticulture are excellent. Greenhouse, nursery, and sod producers are using many of the scouting and cultural practices recommended for reducing the outbreak potential and severity of disease and insect problems. Growers are receptive to alternatives to conventional pesticides, and many already use biorational insecticides. Future research should focus on increasing the effectiveness and availability of these alternatives. Optimizing growing conditions, and thereby plant health, reduces the susceptibility of plants to many disease and insect pest problems. Impediments to reducing the use of conventional pesticides and fertilizers in the environmental horticulture industry include 1) lack of easily implemented, reliable, and cost-effective alternative pest control methods; 2) inadequate funding for research to develop alternatives; 3) lack of sufficient educational or resource information for users on the availability of alternatives; 4) insufficient funding for educating users on implementing alternatives; 5) lack of economic or regulatory incentive for growers to implement alternatives; and 6) limited consumer acceptance of aesthetic damage to plants. Research and broadly defined educational efforts will help alleviate these impediments to reducing potential pollution by the environmental horticulture industry.