Effects of pesticidal plant extracts on non-targeted species are rare. Direct topical and residual sprays of crude aqueous extracts of three pesticidal plants: Datura stramonium L. Bobgunnia madagascariensis Kirkbr. & Wiersema and Solanum delagoense L. were assessed in laboratory bioassays and on-station experiments against the ladybird beetle, Hippodamia variegata (Goeze). The plants are routinely used by smallholder vegetable farmers to control aphids, Brevicoryne brassicae L. attacking rape, Brassica napus L. The crude extracts of D. stramonium fresh leaves, S. delagoense fresh fruits and B. madagascariensis dried pods, were applied separately at 5, 10, 15, 20 and 25% w/v under laboratory conditions. Application rates of 20% and 25% w/v of the plant extracts were further evaluated on-station. Negative (tap water) and positive (dimethoate® (36% E.C)) controls were included for comparison. The mortality of H. variegata was recorded 24, 48 and 72 h post-exposure. In on-station experiments, treatments were applied fortnightly and live H. variegata adults were counted at 1, 7 and 14 days post-application. Mortality of H. variegata in laboratory bioassays increased with increase in post-exposure time and B. madagascariensis (25% w/v) caused the highest mortality. Based on LD50 values, B. madagascariensis extracts were most toxic (LD50, 30% w/v) followed by D. stramonium (LD50, 34% w/v) and S. delagoense (LD50, 49% w/v) 24 h post-application. In on-station experiments, the synthetic chemical significantly lowered (P < 0.05) H. variegata numbers compared to the negative control and plant extracts. The results showed that D. stramonium and S. delagoense extracts at the application rates used in the study were relatively safer to H. variegata than B. madagascariensis (25% w/v); hence, the former two plants can be included in integrated pest management programmes.

Weed management programs in ‘Superior’ potato with PRE and POST rimsulfuron treatments were investigated during 1992, 1993, and 1994 in Virginia on a State sandy loam soil. Common ragweed control by PRE combinations of metolachlor with linuron or metribuzin was higher when treatments included PRE or POST rimsulfuron. Common lambsquarters control was 93 to 96% by treatments that included POST rimsulfuron. In the absence of PRE herbicides, POST applications of 35 g ai/ha rimsulfuron plus 280 g ai/ha metribuzin controlled weeds comparable to sequential applications of this combination. Potato recovered from occasional terminal leaf chlorosis caused by rimsulfuron, rimsulfuron plus metribuzin, and organophosphate insecticides combined POST with rimsulfuron plus metribuzin. These studies demonstrate that rimsulfuron can be a useful component of weed management programs that include metolachlor, linuron, and metribuzin.

Common cocklebur root and shoot interferences were investigated as factors causing soybean yield reductions in the field. Significant decreases in soybean yield resulted from common cocklebur shoot interference when the two were grown together with the common cocklebur roots confined in plastic bags. Soybean yield decreased further when common cocklebur roots were not confined, but this decrease resulted, in part, from increased common cocklebur shoot growth. Wire mesh cylinders of varying diameters, placed in gaps in the soybean rows and designed to spatially restrict soybean shoot growth, reduced yield more than did gaps alone. When similar cylinders lined with black plastic were placed next to the soybean rows to restrict both within-canopy light and space for soybean shoot growth, soybean yield was reduced most (44%) with concomitant changes in stem height, stem diameter, lodging, and branches, nodes, and pods/plant. Interference of common cocklebur with soybeans resulted primarily from shoot interference, and competition for light within the soybean canopy implicated as the major factor causing the soybean yield reduction.

Tomatoes (Lycopersicon esculentum ‘Roma VF’) and four weeds were grown in various combinations in field plots in 1973 and 1974. Season-long interference by jimsonweed (Datura stramonium L.), tall morningglory [Ipomoea purpurea (L.) Roth], and common cocklebur (Xanthium pensylvanicum Wallr.) at densities of 11, 43, and 86/m2 reduced tomato yields in 1973. In 1974, tomato yields were reduced by these three broadleaf weeds at densities of 2.7, 5.4, 8.1, and 11/m2. Season-long interference by large crabgrass [Digitaria sanguinalis (L.) Scop.] reduced tomato yield at densities of 55, 215, and 430/m2 in 1973 and 11, 22, 33, and 55/m2 in 1974. The fresh weight of tomato shoots decreased with all weed densities in both years. Total weed shoot weight increased with density and individual weed weights decreased with increasing densities. Tomato fruit quality, as measured by soluble solids, acidity, and color, was not influenced by the various weeds and densities.

Photosynthesis and growth responses to irradiance level during growth were compared in soybean (Glycine max L. Merr. ‘Century’) and three broadleaf weeds to determine if these responses were associated with differences in shade tolerance among species. In response to reduced irradiance during growth, leaf thickness of all species decreased, while chlorophyll content per unit leaf volume and photosynthetic rate per unit leaf volume, measured at low irradiance, increased. Soybean and common cocklebur (Xanthium strumarium L. #3 XANST) also exhibited a decrease in soluble proteins on a leaf volume basis under reduced irradiance, and common cocklebur further exhibited a decrease in ribulose-1,5-bisphosphate carboxylase (RuBPcase) protein per unit leaf volume. Decreased irradiance during growth did not alter the content of RuBPcase or other soluble proteins per unit leaf volume in jimsonweed (Datura stramonium L. # DATST) or velvetleaf (Abutilon theophrasti Medic. # ABUTH). The superior shade tolerance of common cocklebur compared to the other species was attributed in part to the levels of RuBPcase and other photosynthetic proteins in leaves developed at low irradiance.

Tolerance of direct-seeded pepper under clear plastic mulch to herbicides applied pre- and post-emergence was investigated in 1991 and 1992. Weed control of herbicides applied preemergence was also studied. Paprika cultivar ‘Buketen’ and canning cultivars ‘Piquillo de Lodosa’ and ‘Pico de Mendavia’ were seeded in the field in Zaragoza, Spain, in a loamy soil. Percent emergence, plant mortality after the postemergence treatment, dry weight of plants, and fruit weight were recorded. Pepper was tolerant to diphenamid and napropamide applied preemergence but these herbicides did not control broadleaf weeds. Clomazone, when applied preemergence resulted in chlorotic seedlings and at 2 kg ai/ha reduced the final stand, but was selective when applied at the 6 to 8-leaf stage of the crop. Pepper was tolerant to diethatyl-ethyl when applied preemergence. However, diethatyl-ethyl applied postemergence caused severe phytotoxicity symptoms, and when mixed with diphenamid, fruit ripeness in 1992 was delayed. Weed control during the crop emergence period was better when diethatyl-ethyl was used mixed with diphenamid or napropamide.

In 1992 and 1993, rimsulfuron alone at 17, 35, and 70 g ai/ha, and at 35 g/ha plus metribuzin at 280 g ai/ha, respectively, was evaluated PRE and POST for weed control in potato. Rimsulfuron at 35 g/ha PRE and POST controlled common lambsquarters and giant foxtail and when combined with 280 g/ha metribuzin, controlled common ragweed and jimsonweed. Rimsulfuron and rimsulfuron with metribuzin caused slight to moderate chlorosis in new terminal growth of potato but chlorosis disappeared within 3 wk. Potato height, tuber yields, and tuber quality were not affected by rimsulfuron alone or with metribuzin.

Field experiments were conducted in 1994 and 1995 to evaluate weed control in imidazolinone-resistant corn with postemergence applications of imidazolinone and sulfonylurea herbicides. Imazethapyr controlled 100% of redroot pigweed, jimsonweed, and eastern black nightshade. Control of fall panicum with imazethapyr was inconsistent, with control ranging from 42 to 85%. Imazethapyr provided less than 55% control of common lambsquarters and 43% of large crabgrass. Imazethapyr plus either atrazine, 2,4-D, or dicamba increased control of common lambsquarters compared to imazethapyr alone. Fall panicum control was > 95% with nicosufluron. CGA-152005 and MON 12000 did not control eastern black nightshade. In 1995, corn yield was greater with the hand-weeded check compared to all herbicide treatments. The greatest return over herbicide cost with imazethapyr was obtained with imazethapyr plus atrazine. Nicosulfuron plus CGA-152005 provided the greatest return over herbicide cost when averaged across years.

Application of 112 to 336 kg/ha N as ammonium nitrate [NH4(NO−3)] failed to affect population numbers of common lambsquarters (Chenopodium album L.), giant foxtail (Setaria faberi Herrm.), velvetleaf (Abutilon theophrasti Medic.), jimsonweed (Datura stramonium L.), or redroot pigweed (Amaranthus retroflexus L.). Common lambsquarters seeds harvested from NO−3-treated plots were less dormant than control seeds. Seed germination in the laboratory increased from 3.0% for control seeds to 34.0% for seeds harvested from plots treated with 280 kg/ha N as NH4(NO−3). Nitrate concentration in common lambsquarters seeds increased as nitrogen fertilization increased. Seeds from nonfertilized plots contained 18.7 μg/g NO−3, while seeds from plots fertilized with 280 kg/ha N contained 126.3 μg/g. Adding exogenous NO−3 to the germination medium brought the germination of most seed lots to a similar level, except for control seeds which germinated at a lower rate. In contrast to common lambsquarters, nitrogen fertilization did not greatly affect dormancy or NO−3 accumulation in velvetleaf seeds. Exogenous NO−3 failed to stimulate velvetleaf germination because dormant velvetleaf seeds did not imbibe.

In field studies in 1991, 1992, and 1993, rimsulfuron at 26 and 35 g ai/ha, sequentially at 26 g/ha, at 26 g/ha plus metribuzin at 280 g ai/ha, and metribuzin at 280 g/ha were evaluated POST for weed control in transplanted ‘Agriset’ tomato. Common lambsquarters was controlled by rimsulfuron at 35 g/ha. Rimsulfuron plus metribuzin gave consistent control of common ragweed, but jimsonweed control was inconsistent and goosegrass control was generally low. Rimsulfuron treatments caused slight (< 12%) temporary injury to new terminal growth of tomato. Yield of tomato fruit was consistently high in the metribuzin, metribuzin plus rimsulfuron, and rimsulfuron sequential treatments. In greenhouse studies, giant foxtail and large crabgrass control by rimsulfuron was above 95 and 85%, respectively, but goosegrass was not controlled. Height of four tomato cultivars was not reduced, but dry weight of ‘Floradade’ and ‘Sunbeam’ was reduced by rimsulfuron.

Tomatoes (Lycopersicon esculentum ‘Roma VF’) and weeds were seeded at two locations in 1973 and 1974. In separate plots, jimsonweed (Datura stramonium L.), tall morningglory [Ipomoea purpurea (L.) Roth.], and common cocklebur (Xanthium pensylvanicum Wallr.) seedlings were thinned to densities ranging from 2.7 to 86 plants/m2. Densities of large crabgrass [Digitaria sanguinalis (L.) Scop.] ranged from 11 to 430 plants/m2. There were a few instances of difference in nutrient concentrations in tomato and weed leaf tissue, but no clear relationship was evident between concentration of N, P, K, Ca, Mg, and S and weed density. Considerably more fruit weight was produced per kilogram of total assimilated N, P, and K in the weed-free than in the weed-infested tomato plots.

Common cocklebur (Xanthium pensylvanicum Wallr. ♯ XANPE), velvetleaf (Abutilon theophrasti Medic. ♯ ABUTH), and jimsonweed (Datura stramonium L. ♯ DATST) are weeds that grow taller than soybeans [Glycine max (L.) Merr.] and compete for limited resources such as light. These weeds have an average area of influence of 0.5 m2, thus a density of 1 to 2 plants/m2 forms a full canopy of weed leaves above the soybeans that intercept 44 to 56% of the sunlight. Shade of 44 to 56% without weeds, placed above soybeans late in the season corresponding to times of weed shading, reduced soybean yield 19 to 26%. Since reported soybean yield reductions at weed densities of 0.7 to 2.5 plants/m2 were 18 to 54% for common cocklebur and 12 to 31% for jimsonweed and velvedeaf, it was concluded that most of the interference from jimsonweed and velvetleaf infestations in soybeans could be ascribed to competition for light, but only about one-half the interference was due to competition for light for common cocklebur. Soybean photosynthesis in the field was reduced about twice as much as soybean yield at equivalent levels of shading.

Acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} and bentazon [3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] were applied singly, in combination at various rates, with and without a crop oil concentrate to common lambsquarters (Chenopodium album L. # CHEAL), redroot pigweed (Amaranthus retroflexus L. # AMARE), jimsonweed (Datura stramonium L. # DATST), and velvetleaf (Abutilon theophrasti Medic. # ABUTH) grown in containers in the greenhouse and outdoors. Without crop oil concentrate, synergistic responses to the combinations were measured in common lambsquarters and velvetleaf. Antagonistic responses were measured in jimsonweed. Redroot pigweed response was antagonistic in the greenhouse and synergistic outdoors. The addition of a crop oil concentrate tended to mask the interactions. Crop oil concentrate also increased the droplet size for common lambsquarters, velvetleaf, jimsonweed, and redroot pigweed 53, 41, 28, and 27%, respectively. Neither herbicide at any rate or combination influenced droplet size. Radiolabeled studies showed reduced uptake of 14C-acifluorfen when bentazon was present in common lambsquarters and redroot pigweed by 15 and 10%, respectively. Radiolabeled bentazon uptake was reduced 3% in jimsonweed and increased 20% in redroot pigweed when acifluorfen was present.

In growth chamber studies, we measured the movement of cotyledons and leaves or leaflets in seedlings of nine weed species to determine: the magnitude of movement, whether movements followed a rhythmic pattern, and if rhythmic movements were endogenously controlled. Seedlings were always entrained under a 15-h light:9-h dark regime. Measurements were made at 3-h intervals for 3 to 4 days under four light regimes: alternating 15-h light:9-h dark; continuous light; one 15-h light:9-h dark span, followed by continuous light; and a 15-h light:9-h dark regime, in which the dark span was advanced 9 h (phase shift) when measurements were begun. No clearly defined pattern of leaf movement was found in wild mustard [Brassica kaber (DC.) L. C. Wheeler var. pinnatifida (Stokes) L. C. Wheeler]. Daily rhythmic leaf movements that did not appear to be endogenously controlled were found in redroot pigweed (Amaranthus retroflexus L.) and black nightshade (Solanum nigrum L.). Circadian rhythmic leaf movements that appeared to be under endogenous control were found in jimson-weed (Datura stramonium L.), common lambsquarters (Chenopodium album L.), common cocklebur (Xanthium pensylvanicum Wallr.), prickly sida (Sida spinosa L.), sicklepod (Cassia obtusifolia L.), and coffee senna (Cassia occidentalis L.).

2,4-D [(2,4-dichlorophenoxy)acetie acid] and dalapon (2,2-dichloropropionic acid) were applied to a natural stand of annual weeds at a time near flowering to determine effects on seed production and the dormancy and viability of seeds produced. At rates of 0.6 and 1.1 kg/ha, 2,4-D reduced, respectively the seed production of common lambsquarters (Chenopodium album L.) 99 and 99%, redroot pigweed (Amaranthus retroflexus L.) 77 and 84%, and jimsonweed (Datura stramonium L.) 64 and 100%, while giant foxtail (Setaria faberi Herrm) seed production was increased to 307 and 381% of the control, respectively. Dalapon at rates of 2.2 and 4.5 kg/ha reduced respectively seed production of giant foxtail 100 and 100%, and jimsonweed 100 and 91%. Before and after overwinter burial in the soil, common lambsquarters seeds from plants treated with 4.5 kg/ha dalapon were less dormant than control seeds. After overwintering, redroot pigweed seeds from dalapon-treated plants were less dormant than controls, and more seeds survived the winter burial. Common lambsquarters and redroot pigweed seeds from plants treated with 1.1 kg/ha 2,4-D were more dormant than control seeds before overwintering,’ while giant foxtail seeds from 2,4-D treated plants were less dormant than controls after overwintering. Viability of seeds produced by herbicide-treated plants, as determined by germination in KCN, was not greatly different from control seeds. Treatment with 2,4-D or dalapon resulted in the production of common lambsquarters seeds which produced seedlings about half as vigorous as controls. Jimsonweed seedlings grown from seeds from 2,4-D-treated plants showed phenoxy herbicide injury symptoms.

Black nightshade was selectively controlled along with other annual weeds in direct-seeded tomatoes by BAY SMY 1500 applied preemergence. BAY SMY 1500 was also found selective for transplanted tomatoes when applied prior to transplanting or soon after planting prior to black nightshade emergence. Black nightshade control and crop selectivity were obtained with BAY SMY 1500 at 0.75 and 1.25 kg ai ha-1 applied on sandy loam and clay loam soils, respectively.

Soybean seed yield losses due to interference from common cocklebur, velvetleaf, and jimsonweed, with and without a PPI application of 0.42 kg ai ha-1 metribuzin, were determined in 1986, 1987, and 1988. Damage functions were calculated based on weed density, weed leaf density, and relative weed leaf area index, respectively. Functions relating crop yield losses to weed density varied significantly among treatments and years for each species. Weeds which escaped soil-applied metribuzin were shorter with fewer leaves at 3 wk after planting, and caused lower crop yield losses than control plants at equal densities. Yield loss estimates based upon relative weed leaf area at 3 wk after planting showed least variation between years and treatments.

In field studies, in 1993, 1994, and 1995, clomazone at 390 g ai/ha and rimsulfuron at 35 g ai/ha were evaluated preplant incorporated (PPI) and postemergence (POST), respectively, for weed control and crop response in transplanted ‘Keystone RG3’ bell pepper. Clomazone did not injure bell pepper. Common lambsquarters and jimsonweed control was 77 to 95% by clomazone treatments but was variable by rimsulfuron treatments at 41 to 93% common lambsquarters control and 42 to 68% jimsonweed control; common ragweed control by both herbicides was unacceptable. Injury by rimsulfuron to bell pepper in the field was 19 to 47% at 21 DAT. In the greenhouse, injury to Keystone RG3 and three additional bell pepper varieties, ‘Camelot,’ ‘Jupiter,’ and ‘Memphis’ was similar at 44 to 62% by rimsulfuron at 17 to 35 g/ha POST, and bell pepper had lower height and dry weight than untreated controls. In the greenhouse, jimsonweed control was below 49% and black nightshade control was below 23% by 17 to 35 g/ha rimsulfuron. In these studies, clomazone controlled common lambsquarters and jimsonweed without injury to bell pepper. The solanaceous weeds treated in this study were not well controlled by rimsulfuron, and bell pepper was not sufficiently tolerant to rimsulfuron to permit its use in this crop.

The experimental sulfonylurea herbicide ASC-67040 was evaluated preemergence (PRE) and postemergence (POST) at 25 to 100 g ai/ha and PRE at 50 g/ha followed by ASC-67040 POST at 50 g/ha for broadleaf weed control in potato and tomato. In Virginia, ASC-67040 POST at 50 and 100 g/ha gave 70 to 98% control of common lambsquarters, common ragweed, and jimsonweed with slight (0 to 6%) ‘Superior’ potato and moderate (0 to 23%) ‘Agriset’ tomato injury. This crop injury was present primarily as chlorosis in terminal growth and disappeared by 3 wk after treatment (WAT). Potato tuber and tomato fruit yields were high in ASC-67040-treated plots. In North Carolina, ASC-67040 PRE and POST at 50 and 100 g/ha controlled 10 species of annual broadleaf weeds and grasses, and at 25 g/ha ASC-67040 gave greater than 90% control of most species. ASC-67040 injured ‘Fontenot’ potato more than Superior and caused 10 to 13% injury to ‘Mountain Spring’ tomato but did not injure ‘Mountain Pride’ tomato. Mountain Spring tomato recovered rapidly and produced high yields. In the greenhouse, yellow nutsedge control by ASC-67040 POST at 25 to 100 g/ha was 59 to 86% 3 WAT and yellow nutsedge height, dry weight, and regrowth dry weight were reduced by all rates. Lower rates of ASC-67040 might control weeds and cause less injury to potato and tomato.