Effect of Biopesticides on Foliar Diseases and Japanese Beetle ( Popillia japonica) Adults in Roses ( Rosaspp.), Oakleaf Hydrangea ( Hydrangea quercifolia), and Crapemyrtle ( Lagerstroemia indica)
M.T. Mmbaga and J.B. Oliver
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.
Keywords: Black spot; fungicides; insecticides; Japanese beetle; pest management; powdery mildew; Xanthomonas leaf spot.