Field experiments were conducted to determine the effect of selected rice pesticides on the mycoherbicide Colletotrichum gloeosporioides (Penz.) Sacc. f. sp. aeschynomene (designated as C.g.a.) for northern jointvetch control in dry-seeded rice. Sequential treatments of pencycuron at 0.56 kg ai/ha, SN-84364 at 0.40 kg ai/ha applied 7 and 14 days after C.g.a., or pencycuron sprayed sequentially after a tank mixture of C.g.a. plus actifluorfen did not reduce infectivity of C.g.a. Also, propiconazol at 0.60 kg ai/ha or pencycuron applied 7 days before and after C.g.a. did not reduce fungus development on northern jointvetch. Sequential treatments of benomyl at 0.56 kg ai/ha or propiconazol applied 7 and 14 days after C.g.a. reduced pathogen activity on northern jointvetch.

Paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) was evaluated as a pretreatment for eastern redcedar (Juniperus virginiana L. # IUPVI) before spring burning in tallgrass prairie. Wetting sprays of paraquat at 0.3 g ai/L or 0.6 g/L were applied to crowns of small (0.8 to 1.5 m), medium (1.5 to 2.5 m), and large (2.5 to 5.0 m) eastern redcedar trees in August 1983 and 1984 before prescribed burns in the springs of 1984 and 1985. Paraquat alone at the 0.6 g/L concentration killed about 90% of the crown of small trees but as little as 30% of the crown of large trees. Paraquat pretreatments increased post-fire damage to small- and medium-size trees and partially compensated for light fine fuel loading.

Multiflora roses showing symptoms of rose rosette were found in nine counties in southern Indiana and two counties in northern Kentucky. The eriophyid mite, Phyllocoptes fructiphilus Kiefer (Acari: Eriophyidae), implicated as the vector of the rose rosette agent, occurred on most symptomatic material. Another eriophyid mite, P. rosarum Liro, was found on symptomatic material collected in Kentucky. Transmission of the causal agent into multiflora rose by shield budding and by P. fructiphilus was successful. The rose rosette agent appears to be spreading east and is established on multiflora rose in the Ohio Valley.

Six postemergence herbicides were applied two consecutive years in single and split applications to compare johnsongrass [Sorghum halepense (L.) Pers. # SORHA] control in soybeans [Glycine max (L.) Merr.] planted in 25- and 76-cm inter-row spacings. Significantly less johnsongrass existed at harvest in the 25-cm spacings than in the 76-cm spacings with split applications of fenoxaprop {(±)-2-[4-[(6-chloro-2-benzoxazolyl)oxy] phenoxy] propanoic acid} at 100 g ae/ha, fluazifop {(±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} at 100 g ae/ha, sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} at 200 g ai/ha, and SC-1084 {3-hydroxy-4-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] pentanoic acid} at 250 g ae/ha. Quizalofop {(±)-2-[4-[(6-chloro-2-quinoxalinyl)oxy] phenoxy] propanoic acid} at 70 g ae/ha and haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} at 100 g ae/ha controlled johnsongrass so well that differences between the two row spacings were not significant.

Desmedipham applied at 0.5 kg ai/ha at the 4-leaf stage of common buckwheat controlled wild mustard over 90%. Desmedipham at 1.0 kg/ha at the 2- and 6-leaf stages also controlled wild mustard approximately 90%, at least in 1985, but significantly injured the crop. Fluorochloridone controlled wild mustard over 90% when applied preplant incorporated at 1.0 kg ai/ha or preemergence at 0.28 to 0.56 kg/ha. Fluorochloridone applied postemergence at 0.10 to 0.20 kg/ha also controlled wild mustard over 90% but injured common buckwheat by 41 to 57%.

In field experiments in 1981, 36 g ai/ha of chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] carbonyl] benzenesulfonamide} applied to winter wheat (Triticum aestivum L. ‘Arthur’) in early spring reduced seed yield in conventional and no-till plantings of double-cropped soybeans [Glycine max (L.) ‘Essex’]. From 1982 to 1984, three rates of chlorsulfuron (9, 18, and 36 g/ha) were applied at three different times (preemergence, early winter, and early spring) to study their residual effects on double-cropped soybeans. Chlorsulfuron at 36 g/ha applied preemergence or early spring reduced soybean seed yields when averaged over the 3-yr period. Metsulfuron {2-[[[[(4-methoxy-6-methyl-1,3,5-triazine-2-yl)amino] carbonyl] amino] sulfonyl] benzoic acid} was tested at three rates (4.5, 9, and 18 g/ha) applied at three times (same as chlorsulfuron) in field studies in 1983 and 1984. Metsulfuron did not injure subsequently planted no-till soybeans.

Effects of repeated late-fall applications of the isopropylamine salt of glyphosate at 1.7 kg ae/ha plus 0.5% (v/v) surfactant on adventitious root buds, thickened propagative roots (> 1.3 mm diam), and shoot density of Canada thistle were studied in continuous hard red spring wheat over a 4-yr period. Glyphosate suppressed Canada thistle shoot density more quickly and to a greater extent than thickened root fresh weight or root bud number. A single fall application of glyphosate drastically decreased Canada thistle shoot density for 1 yr after treatment. However, shoot density was the same as the untreated control by 2 yr after a single fall treatment. Two consecutive late-fall applications of glyphosate in 2 yr decreased Canada thistle shoot density 94% in the fall 1 yr after the last treatment. Glyphosate reduced Canada thistle thickened root fresh weight 70% in the first fall 1 yr after a single fall treatment. However, 2 yr after a single fall application of glyphosate, root fresh weight equalled the controls. Two consecutive fall applications of glyphosate reduced thickened root fresh weight 77% 1 yr after the second treatment.

The tolerance of several field pea cultivars to glyphosate was compared in the laboratory and greenhouse, using root, foliar, and tissue culture exposure techniques. Pea cultivar response among glyphosate exposure techniques did not always agree. However, the cultivar ‘Alaska’ was consistently one of the most susceptible cultivars regardless of exposure technique. ‘Melrose’ was one of the most tolerant cultivars, especially when its roots and cells were exposed to glyphosate. The response of ‘Frogel’, ‘Glacier’, and other cultivars varied among glyphosate-exposure techniques.

Field studies were conducted in 1985 and 1986 to determine the influence of herbicide rate, carrier, and carrier volume on off-site movement of clomazone {2-[2-chlorophenyl)methyl]-4,4-dimethyl-3-isoxalidinone} using sunflower (Helianthus annuus L. ‘HY-894’) and wheat (Triticum aestivum L. ‘Caldwell’) as indicator plants. Clomazone applied at the lowest rate (0.56 kg ai/ha) had less off-site movement than higher rates. Off-site movement was similar among water carrier volumes applied at each clomazone rate but was less when clomazone was impregnated onto dry fertilizer.

Vegetative growth of ‘Tifway’ African bermudagrass (Cynodon transvaalensis Burtt-Davy # CYNTR) x bermudagrass [C. dactylon (L.) Pers. # CYNDA] treated with flurprimidol {α-(1-methylethyl)-α-[4-trifluoromethoxy)phenyl]-5-pyrimidinemethanol} at 0.2 kg/ha and repeated at 3-week intervals for a total rate of 0.8 kg/ha was suppressed for 6 weeks compared to growth of nontreated grass. A single application of flurprimidol at 0.8 kg/ha in late May suppressed growth for 4 weeks. When the single 0.8 kg/ha application was delayed until mid-July, bermudagrass growth was suppressed for only 2 weeks. Applications of nitrogen (N) at 25 and 50 kg/ha did not influence flurprimidol's suppression of bermudagrass growth. Turf quality in some instances was lower when treated with 50 kg N/ha or the turfgrass required a longer recovery period than when treated with 25 kg N/ha following flurprimidol treatment. Although single or multiple applications of flurprimidol, each totaling 0.8 kg/ha, injured bermudagrass in some instances, the injury was not severe and the turfgrass fully recovered.

Greenhouse experiments were conducted to determine effects of AC 94,377, seed depth, and commercially applied seed protectants on emergence and early growth of grain sorghum. Mean height of grain sorghum was increased by 500 to 2000 ppmw AC 94,377 but not by 250 ppmw. Emergence and fresh weight of grain sorghum was not affected. Plants arising from seeds without protectants were taller and heavier than those with protectants intact. Soybean sown in soil containing AC 94,377 at 0.6 to 2.5 kg ai/ha was injured; however, soybean grew normally if seeds were not sown until at least 1 week after applying AC 94,377. Cotton was not injured by AC 94,377.

A modified nutrient solution, used to study lettuce cultivar response to thiobencarb, provided an excellent medium for lettuce growth and is an alternative to other nutrient solutions. Leaf dry weight was inhibited 50% by 3- and 5-μM thiobencarb in ‘Dark Green Boston’ and ‘Great Lakes 366’, respectively, while ‘Bibb’, ‘Slobolt’ and ‘Valmaine’ responded intermediately. Growth inhibitions and herbicide injury symptoms, which included abnormal growth and stunted secondary leaves, were similar in both nutrient solution and soil assays. Due to its ease of preparation and elimination of the variability associated with soil assays, the nutrient solution may be considered a superior alternative to soil assays.

Diuron, fluorochloridone, hexazinone, metribuzin, norflurazon, oryzalin, prodiamine, simazine, and terbacil controlled seedling asparagus planted in sprinkler-irrigated plots similarly (>89%). In furrow-irrigated plots, cinmethylin, diuron, fluorochloridone, hexazinone, napropamide, oryzalin, and prodiamine provided similar control (>86%) of planted seedling asparagus. Herbicides with high water solubilities that depended upon root uptake for maximum activity tended to control seedling asparagus better in sprinkler-irrigated tests than in furrow-irrigated tests. Fluorochloridone, norflurazon, and prodiamine provided partial control of volunteer asparagus (48 to 84%) in an established stand of furrow-irrigated asparagus.

Canada thistle [Cirsium arvense [L.] Scop. # CIRAR] is a major weed problem in birdsfoot trefoil (Lotus corniculatus L. ‘Norcen’) seed production in northern Minnesota. Several systemic herbicides applied with selective applicators (roller and ropewick) were evaluated for Canada thistle control in birdsfoot trefoil. Picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid), clopyralid (3,6-dichloro-2-pyridinecarboxylic acid), and glyphosate [N-(phosphonomethyl)glycine] controlled Canada thistle better than MCPA [(4-chloro-2-methylphenoxy)acetic acid] and dicamba (3,6-dichloro-2-methoxybenzoic acid). Glyphosate and MCPA did not injure birdsfoot trefoil foliage or bloom, whereas, picloram, clopyralid, and dicamba injured both. Although selective applications of glyphosate controlled Canada thistle for a short term with the least birdsfoot trefoil injury, long-term Canada thistle control in birdsfoot trefoil does not appear feasible with selective herbicide applications.

Locoweed poisoning of livestock is the most widespread poisonous plant problem in the western United States. This paper presents a historical review of control methods to reduce locoweed plant density. Hand grubbing, the most common method of control before phenoxy herbicides, was practical in small pastures considering the number of livestock saved. Trials in the 1950s indicated that 2,4-D and 2,4,5-T generally controlled locoweeds effectively if applied when plants were actively growing and soil moisture was not limiting plant growth. Picloram, dicamba, clopyralid, and triclopyr provide more consistent control than 2,4-D and 2,4,5-T when applied at less than optimum environmental conditions.

A simple, labor-efficient screening procedure was developed for identifying metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] tolerant southernpea [Vigna unguiculata (L.) Walp.] germplasm in the greenhouse. Of 1241 southernpea plant introduction (PI) accessions screened, two (PI 293569 and PI 427221) tolerated metribuzin. In additional greenhouse experiments, the two selected southernpea accessions were slightly more tolerant than the susceptible cultivar ‘Lady’ or the moderately tolerant cultivar ‘Big Boy’. However, several accessions from related Vigna species tolerated 1.5 ppmw metribuzin, twice the concentration that killed the southernpea selections.

The productivity of herbicides used in corn and soybeans was calculated from field data collected in Ontario from 1967 to 1985. Combinations of preplant incorporated and preemergence treatments were selected and were evaluated to determine their effect on crop yield. Corn and soybean yields increased from herbicide use, thereby resulting in a positive net benefit to growers. Benefit/cost ratios for herbicide use in corn and soybeans were calculated to be 2.8/1 and 2.6/1, respectively, at an average price of $132/1000 kg for corn and $275/1000 kg for soybeans. The benefit/cost ratios varied with test location, method of herbicide application, and prevailing market price.

Puccinia canaliculata (Schw.) Lagerh. from Salisbury, MD, identified in greenhouse tests as specific to yellow nutsedge, was field evaluated for biological control of yellow nutsedge over a 2-yr period. Treatments included all combinations of P. canaliculata and 0.3 or 0.6 kg ai/ha benzaton. Disease development was reduced 50% by treatment with bentazon, compared with P. canaliculata alone. P. canaliculata reduced tuber recovery by 44%. Phytotoxicity was significantly higher from the rust treatments than controls. Treatment with P. canaliculata did not affect the number of shoots/m2.

Sicklepod control with one or two cultivations or postemergence (POE) directed-spray applications of linuron or metribuzin plus 2,4-DB was less than 50% in August evaluations when no soil-applied herbicide had been used. However, sicklepod control greater than 75% was noted through August when two cultivations or metribuzin plus 2,4-DB applied POE followed either metribuzin applied preplant incorporated (PPI) and preemergence (PRE) or metribuzin plus alachlor applied as a PRE treatment. One cultivation after these soil-applied herbicide treatments did not reduce sicklepod populations compared to the chemical treatments alone. Soybean yields more than doubled over yields in untreated plots when a combination of soil-applied herbicides and two cultivations or metribuzin plus 2,4-DB applied POE were used.

Crop-herbicide systems for johnsongrass [Sorghum halepense (L.) Pers. # SORHA] control were compared in a 5-yr study at two locations in central Ohio. Monocultures of corn (Zea mays L.) and soybeans [Glycine max (L.) Merr.] were compared with a 3-yr rotation of corn, soybeans, and winter wheat (Triticum aestivum L.). Johnsongrass was controlled most effectively (over 95%) when glyphosate [N-(phosphonomethyl) glycine] was applied to emerged johnsongrass, followed by moldboard plowing, preplant incorporated (PPI) application of trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine], then soybean planting (MS-G-T). The second best control was in corn (over 90%) treated PPI with EPTC (S-ethyl dipropylcarbamothioate) in the rotation (RC-E). Johnsongrass control was least in monocultured corn treated PPI with EPTC (MC-E) and in monocultured soybeans treated PPI with trifluralin (MS-T).