Pepper is grown on ≈1200 ha with farm gate receipts close to $12 million in 2005 in Ontario (Mailvaganam, 2006). Bell pepper is not a competitive crop and yield reductions can result in significant financial loss if weeds are not properly controlled (Eshel et al., 1973; Frank et al., 1992); therefore, broadleaf weed control is one of the most important weed management considerations in pepper production. Current problem weeds include velvetleaf (Abutilon theophrasti Medic.), redroot pigweed (Amaranthus retroflexus L.), common ragweed (Ambrosia artemisiifolia L.), common lambsquarters (Chenopodium album L.), and eastern black nightshade (Solanum ptycanthum Dun.).
Napropamide, trifluralin, chlorthal dimethyl, and s-metolachlor are the currently registered soil-applied herbicides for pepper production in Ontario [Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), 2006a]. Although napropamide can provide good control of redroot pigweed and common lambsquarters early in the season, it does not provide long-term residual control of these weeds. Additionally, it is weak on common ragweed, velvetleaf, and eastern black nightshade. Trifluralin is used primarily as a grass herbicide, although it will provide early-season control of redroot pigweed and common lambsquarters. Chlorthal dimethyl will give good control of common lambsquarters and suppresses redroot pigweed, but it provides poor control of velvetleaf, common ragweed, and eastern black nightshade. S-metolachlor controls redroot pigweed and eastern black nightshade and was recently registered for use in pepper in Ontario. S-metolachlor, because of availability, grower experience, and cost, is the primary pretransplant graminicide used for weed control in pepper in Ontario. As a result, s-metolachlor was used as the tank mixture partner with sulfentrazone in these trials. Finally, dimethenamid-p was included to compare an alternate graminicide, which offers some control of common ragweed, redroot pigweed, and eastern black nightshade. Dimethenamid-p is not currently registered in pepper but could be an effective option to control troublesome weeds for pepper growers in Ontario. It would also be of significant benefit to growers in Ontario to have a tank mix to control weed species that s-metolachlor is weak on, specifically velvetleaf, common ragweed, and common lambsquarters.
The first objective of this research was to identify pretransplant herbicides with activity on velvetleaf, common ragweed, and common lambsquarters with an acceptable level of tolerance in pepper. The second objective of this research was to determine weed control and tolerance of these pretransplant herbicides applied as a tank mixture.
Frank, J.R., Schartwz P.H. Jr & Potts, W.E. 1992 Modelling the effects of weed interference periods and insects on bell peppers Weed Sci. 40 308 312
Grey, T.L., Bridges, D.C. & NeSmith, D.C. 2002 Transplanted pepper (Capsicum anuum) tolerance to selected herbicides and method of application Journal of Vegetable Crop Production 8 27 39
Mailvaganam, S. 2006 Farm value and harvested area of vegetable crops, Ontario, 1980–2005 25 May 2007 <http://www.omafra.gov.on.ca/english/stats/hort/value_veg.html#3>.
Ontario Ministry of Agriculture. Food and Rural Affairs (OMAFRA) 2006a Guide to weed control 2006–2007 Publication 75. Ontario Ministry of Agriculture, Food and Rural Affairs Toronto, Ontario 243 244
Ontario Ministry of Agriculture. Food and Rural Affairs (OMAFRA) 2006b Vegetable production recommendations 2006–2007 Publication 363. Ontario Ministry of Agriculture, Food and Rural Affairs Toronto, Ontario 144 145