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ARS Home » Southeast Area » Poplarville, Mississippi » Southern Horticultural Research » Research » Publications at this Location » Publication #256867

Title: Effects of Biopesticides on Foliar Diseases and Japanese Beetle (Popillia japonica) Adults in Roses (Rosa spp.), Oakleaf Hydrangea (Hydrangea quercifolia), and Crapemyrtle (Lagerstroemia indica)

item MMBAGA, M - University Of Tennessee
item OLIVER, JASON - University Of Tennessee

Submitted to: Journal Of Arboriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2007
Publication Date: 5/1/2007
Citation: Mmbaga, M.T., Oliver, J.B. 2007. Effects of Biopesticides on Foliar Diseases and Japanese Beetle (Popillia japonica) Adults in Roses (Rosa spp.), Oakleaf Hydrangea (Hydrangea quercifolia), and Crapemyrtle (Lagerstroemia indica). Journal of Arboriculture. 33:210-219.

Interpretive Summary: Alternative products for pest management, which are environmentally friendly and safer for workers, would be a valuable addition to nursery production systems and landscape industry. In this study, we evaluated a number of biopesticides that are U.S. Environmental Protection Agencyregistered as pesticides and other nonregistered products that are commercially available and have previously shown potential to control foliar diseases and pests. Among the products evaluated, the neem-based product (Triact 70) was effective in reducing foliar diseases on roses in agreement with reports by Horst et al. and Locke. Other neem-based material (Neem Gold) was not as effective. Weekly applications of conventional fungicides such as strobilurines, triazoles, and benzimidazoles are typically used to manage powdery mildew, whereas bimonthly applications are used on black spot. In our study, all products evaluated, including household soaps (Ajax and Equate), bicarbonate salt (Armicarb), neem seed oil extract (Triact 70 and Neem Gold), and kaolin clay (Surround) were more effective than the nontreated control and as effective as the conventional fungicides in reducing powdery mildew and black spot in roses. Only Surround was consistently effective in controlling bacterial leaf spot on oakleaf hydrangea, and it was the best product for controlling powdery mildew in crapemyrtle. Surround, UltraFine, Sunspray oil, Armicarb, and M-Pede are registered biopesticides for ornamental plants. Household soaps are not registered for use as biopesticides, but they are considered safe enough for household use and have repeatedly shown potential for controlling foliar diseases. The slight leaf burn problem associated with soap use on hot sunny days may be eliminated by concentration adjustments. Recently, a lower soap concentration at 0.5% to 1.0% was shown to be as effective as a conventional fungicide program in controlling powdery mildew fungi in apple, cherry, and grape. These results support previous reports that biopesticides may be incorporated in disease management and reduce the dependence on conventional fungicides

Technical Abstract: This study evaluated efficacy of biopesticides for reducing foliar diseases and feeding damage from Japanese beetle adults on hybrid T rose (Rosa spp.), oakleaf hydrangea (Hydrangea quercifolia), and crapemyrtle (Lagerstroemia indica). The materials tested included household soaps with Triclosan active ingredient (Equate and Ajax), kaolin clay (Surround), neem seed oil extract (Triact 70 and Neem Gold), potassium salt of fatty acids (M-Pede), horticultural oil (UltraFine Sunspray oil), and bicarbonate salt (Armicarb) applied to plants grown under greenhouse, shadehouse, and field conditions. Two fungicides, trifloxystrobin (Strobilurin) and triadimefon (Triazole), and the insecticide carbaryl were included for comparison. All materials tested were effective in controlling black spot (Marssonina rosae, anamorph Diplocarpon rosae) and powdery mildew (Sphaerotheca pannosa) of roses. Kaolin was effective in reducing disease severity of bacterial leaf spot (Xanthomonas campestris) on oakleaf hydrangea and powdery mildew of crapemyrtle. Based on data from repeated trials, the biopesticides were as effective as conventional fungicides in suppressing foliar diseases. Kaolin clay was as effective as carbaryl in controlling Japanese beetle adult feeding damage on oakleaf hydrangea, roses, and crapemyrtle, but other products were not effective. Results from this study indicate kaolin clay may be an alternative product to conventional pesticides in foliar diseases and insect pest management for roses, oakleaf hydrangea, and crapemyrtle.