Field studies were conducted in 1986 and 1987 to determine the critical period for weed control in white bean grown in Ontario. The treatments consisted of either allowing weeds to infest the crop for increasing durations after planting or maintaining plots weed free for increasing durations after planting. The beginning of the critical period was defined as the crop stage by which weed interference reduced yields by 3%. Similarly, the end of the critical period was defined as the crop stage to which the crop had to be weed free to prevent a 3% yield loss. The critical period of weed control occurred between the second-trifoliolate and first-flower stages of growth for all cultivars and years, with the exception of the cultivar ‘OAC Seaforth’ in 1986. The average number of pods per plant for both cultivars was reduced by increasing durations of weed interference after planting in both years. However, pod number of the cultivar OAC Seaforth was reduced at a greater rate in 1986 than ‘Ex Rico 23’. The beginning of the critical period corresponded with the beginning of a rapid increase in total weed biomass.

The response of ‘C-20’ navy bean and ‘Frankenmuth’ soft white winter wheat grown in rotation to clomazone, imazethapyr, bentazon, and acifluorfen was examined. Clomazone at 560 and 430 g ai ha−1 plus 800 g ai ha−1 pendimethalin and 2000 g ai ha−1 chloramben visibly injured navy bean in 1 of 2 yr. However, navy bean seed moisture at harvest and yield was not reduced compared to the weed-free control. PPI and PRE treatments of 70 g ai ha−1 imazethapyr did not injure navy bean or reduce yield. Imazethapyr applied POST at 70 g ha−1 plus nonionic surfactant visibly injured navy bean. The addition of urea ammonium nitrate to imazethapyr enhanced visible injury and seed moisture compared to nonionic surfactant alone in 1 of 2 yr. However, seed yield was not reduced. Seed moisture at harvest was greater following treatment with 430 g ai ha−1 acifluorfen plus nonionic surfactant or urea ammonium nitrate and 140 and 280 g ha−1 acifluorfen plus 840 g ai ha−1 bentazon in 1 of 2 yr compared to the weed-free control, but yield was not reduced. Wheat yield was reduced in 2 of 2 and 1 of 2 yr by 560 g ha−1 and 430 g ha−1 clomazone, respectively, plus pendimethalin plus chloramben compared to the weed-free control. Wheat yield was not reduced by imazethapyr, bentazon, or acifluorfen.

Field experiments were conducted at the Elora Research Station, Elora, Ontario, in 1988 and 1989 to quantify the inherent competitive ability of three white bean cultivars: OAC Gryphon, OAC Sprint, and OAC Laser growing with a naturally occurring population of annual weeds. An attempt was made to increase the competitive ability of these cultivars by altering row spacing and seeding density. Uncontrolled populations of weeds reduced white bean yields by 70%. OAC Gryphon and OAC Laser reduced weed biomass by 10 to 35% compared to OAC Sprint. The ability of cultivars to reduce weed biomass was further enhanced in medium and narrow rows compared to traditional wide rows. Cultivar, row spacing, and seeding density combinations which maximized leaf area index when grown under weedy conditions also had significantly less weed biomass. However, cultivar selection, row spacing, and seeding density did not reduce weed density. A significant negative correlation was observed between weed biomass accumulation and final yield of white bean. For each kg ha−1 increase in weed biomass the corresponding white bean yield loss averaged 0.380 kg ha−1. Season-long weed competition significantly reduced total number of pods per plant, number of seeds per pod, and 100-seed weight.

White bean producers have a limited number of herbicide options available for annual grass and broadleaf weed control. Tolerance of two white bean cultivars to preemergence (PRE) applications of S-metolachlor, S-metolachlor + imazethapyr, flumetsulam + S-metolachlor, cloransulam-methyl, clomazone, clomazone + imazethapyr, and clomazone + S-metolachlor at the maximum labeled rate in soybean (1×) and twice the labeled rate (2×) were studied at two Ontario locations (Exeter and Ridgetown) in 2001 and 2002. S-Metolachlor, clomazone, and clomazone + S-metolachlor generally had no negative effect on plant height, dry weight, maturity, and yield. S-Metolachlor + imazethapyr and clomazone + imazethapyr reduced plant height, dry weight, and yield as much as 21, 42, and 24%, respectively. Flumesulam + S-metolachlor and cloransulam-methyl reduced plant height, dry weight, and yield as much as 39, 58, and 43%, respectively. White beans are tolerant to PRE applications of S-metolachlor, clomazone, and clomazone + S-metolachlor. White beans are sensitive to PRE applications of S-metolachlor + imazethapyr, flumetsulam + S-metolachlor, clomazone + imazethapyr, and cloransulam-methyl.

Tolerance of eight market classes of dry beans (black, brown, cranberry, kidney, otebo, pinto, white, and yellow eye beans) to the PRE application of linuron at the rate of 2.25 and 4.50 kg ai/ha was studied at two locations in Ontario, Canada, in 2003 and 2004. The eight market classes differed in their response to linuron. Linuron PRE caused as much as 43, 20, 7, 17, 54, 36, 56, and 12% visual injury in black, brown, cranberry, kidney, otebo, pinto, white, and yellow eye beans, respectively. Linuron PRE at 2.25 kg/ha reduced plant height 38% in otebo beans and 31% in white beans. Linuron PRE at 4.50 kg/ha reduced plant height 24 to 56% in black, brown, otebo, pinto, and white beans. Shoot dry weight was reduced in otebo beans by 56% and in white beans, by 46% at the low rate. Shoot dry weight was decreased 26 to 92% in black, otebo, pinto, white, and yellow eye beans at the high rate. There were no differences in the shoot dry weight of the other market classes. Linuron PRE at the low rate reduced otebo bean yield 42% and at the high rate reduced yields by 56, 74, and 61% in black, otebo, and white beans, respectively. There was no effect on the yield of other market classes. Differences in dry bean market class tolerance to linuron exists and may be summarized for these cultivars as cranberry > kidney > brown > yellow eye > pinto > black > white > otebo. Additional research is needed to determine if cultivars within a dry bean market class differ in their response to linuron.

There is little information on the sensitivity of dry beans to flumioxazin. Tolerance of eight cultivars of dry beans representing four market classes (black, cranberry, kidney, and white beans) to preplant incorporated (PPI) and preemergence (PRE) applications of flumioxazin at the rate of 52.5, 70, and 140 g ai/ha were studied in three field experiments in Ontario in 2002 and 2003. There were no differences (P < 0.05) between two cultivars within a market class in their responses to flumioxazin. However, the four market classes differed in their responses to flumioxazin. Black and white beans were more sensitive to the PRE application of flumioxazin than cranberry and kidney beans. Flumioxazin applied PRE at 140 g/ha caused as much as 34% visual injury and reduced plant height by 23 to 28%, shoot dry weight by 35 to 39%, and yield by 20 to 30% in black and white bean market classes. Flumioxazin-applied PPI did not injure any market class. On the basis of this research, there is an acceptable margin of crop safety in these black and white bean cultivars only when flumioxazin is applied PPI. The two cranberry and kidney bean cultivars were tolerant to all rates of flumioxazin applied both PPI and PRE.

Resource-poor farmers often have diverse but small quantities of materials available that might be used to manage soil fertility. Opportunity costs of money are very high and farmers often opt to invest their scarce financial resources elsewhere rather than in fertilizer. This paper presents an approach to adaptive research and technology dissemination that was applied in Uganda and is applicable for improvement of integrated nutrient management (INM) in resource-poor farming systems. While little information may be available from research conducted in a particular agroecological zone (AEZ), information on INM components from diverse sources may be applicable for major crops in that AEZ. This information must be compiled and subjected to agronomic and economic analysis. A conceptual framework, e.g., in the form of a tentative decision guide, is then constructed, with consideration of interactions among nutrient sources, given the farmers' situations. Researchers estimate the most likely rates of application and substitution ratios, and then judge their confidence in the estimates. Priority actions are then identified for research and extension. When confident of their estimates, researchers formulate recommendations for promotion through extension means. If confidence is lacking, on-farm verification trials or other research may be needed. The approach is illustrated by work done for one AEZ in Uganda for maize and dry bean production, but is intended for application to other resource-poor farming systems in eastern Africa.

This study was conducted to identify the individual biochemical factors involved in the resistance observed in a few Mexican bean accessions against the bean weevil, Acanthoscelides obtectus (Say) (Coleoptera: Bruchidae). Soluble proteins from different bean genotypes were separated by fractionated acetone precipitation. Insects were reared on artifical seeds composed of a susceptible background bean flour enriched with the different protein fractions. At low doses (2% w/w), the 0–20% and 20–40% acetone fractions of the resistant bean accessions G 12954 and G 12880 inhibited larval growth of the bean weevil, but not of a related species, the Mexican bean weevil, Zabrotes subfasciatus (Boheman). The 0–20% fraction caused the highest mortality of first instar larvae. The 60–80% acetone fraction contains general resistance factors, like α-amylase and protease inhibitors, which when enriched in artifical seeds led to a strong depression of insect growth for resistant and susceptible bean accessions alike. These factors should also be taken into account in breeding for multigenic, durable resistance, in order to exploit the synergism between general and specific resistance factors.