Greenhouse studies were conducted to determine host status of weed species for Rhizoctonia solani AG-1, which causes Rhizoctonia foliar blight of soybean. Weed species were barnyardgrass, broadleaf signalgrass, common cocklebur, entireleaf morningglory, hemp sesbania, itchgrass, johnsongrass, large crabgrass, northern jointvetch, prickly sida, purple nutsedge, redweed, sicklepod, and smooth pigweed. Seedling weeds were inoculated with suspensions containing intraspecific group IA and IB isolates of the fungus. In the first study, sclerotia of IA were recovered from tissue of all weeds except smooth pigweed, and mycelia of IA were recovered from all except smooth pigweed and redweed. In that study, neither microsclerotia nor mycelia of IB were recovered from sicklepod, barnyardgrass, or large crabgrass, and only microsclerotia were recovered from itchgrass and purple nutsedge. In the second study, sclerotia of IA, microsclerotia of IB, and mycelia of each isolate were recovered from all weed species. In other studies, R. solani spread from at least six of seven weed species to a noninfected soybean plant growing in close proximity. These studies emphasize the importance of weed control, not only for reducing plant competition and increasing yield, but also for the potential impact on development of RFB.

Field experiments were conducted in 1986, 1987, and 1988 to evaluate imazethapyr rate and time of application on postemergence control of 24 weed species. Contour graphs were developed that predicted imazethapyr rates required for various levels of weed control based upon weed leaf number at application. Rates below the labeled rate (70 g ha−1) provided 90% or greater control of common cocklebur, smallflower morningglory, and smooth pigweed if applied to 3 true-leaf or smaller weeds and of barnyardgrass, seedling johnsongrass, and Palmer amaranth if applied while weeds were in the cotyledon or 1 true-leaf stage. A rate of 70 g ha−1 provided 90% control of large crabgrass in the 1 true-leaf stage. Entireleaf morningglory, red rice, pitted morningglory, and velvetleaf are not susceptible enough to imazethapyr for 90% or greater control to be obtained with rates lower than 70 g ha−1 at the 1 true-leaf growth stage. These data demonstrate how control data can be used for developing effective reduced-rate herbicide recommendations based on weed leaf number.

The potential of several common weed species to produce adventitious shoots when the plants were excised approximately 1.0 cm below the cotyledonary node at the cotyledon growth stage and at the four true-leaf stage is reported. Indian jointvetch (Aeschynomene indica L. ♯3 AESIN), northern jointvetch [Aeschynomene virginica (L.) B.S.P. ♯ AESVI], and wild poinsettia (Euphorbia heterophylla L. ♯ EPHHL) produced adventitious shoots at both growth stages after shoot excision. Adventitious and vegetative regeneration of wild poinsettia damaged by herbicides was similar to that from decapitation.

A low-volume (21.5 L/ha) spinning disc (controlled droplet applicator) and a high-volume (187 L/ha) boom-nozzle applicator were compared in applying tank mixtures of the weed pathogen Colletotrichum gloeosporioides (Penz.) Sacc. f. sp.] aeschynomene (henceforth designated C.G.A.) and acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} for control of northern jointvetch [Aeschynomene virginica (L.) B.S.P. # AESVI] and hemp sesbania [Sesbania exaltata (Raf.) Rydb. ex A.W. Hill # SEBEX] in soybean [Glycine max (L.) Merr. ‘Tracy M’]. Application with a spinning disc did not increase control of either weed species over the boom-nozzle applicator. C.G.A. controlled northern jointvetch in 2 of 3 yr. Northern jointvetch control with the spinning-disc was poorer at lower rates in years of unfavorable environment. Acifluorfen at 0.56 kg ai/ha and applied with either applicator controlled hemp sesbania satisfactorily.

Field research was conducted in Arkansas to determine the effect of selected rice pesticides on the microbial herbicide Colletotrichum gloeosporioides (Penz.) Sacc. f. sp. aeschynomene (henceforth designated C.g.a.) and to integrate C.g.a. into control programs for northern jointvetch [Aeschynomene virginica (L.) B.S.P. # AESVI] in rice (Oryza sativa L.). Water suspensions of dry-formulated spores of C.g.a. at 1.9 × 1011 spores/ha were applied midseason in sequence with normal use rates of other pesticides. Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methyl-carbamate) at 0.56 kg ai/ha, propanil (3’4’-dichloropropio-anilide) at 2.2 kg ai/ha, acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} at 0.14 kg ai/ha, or fentin hydroxide (triphenyltin hydroxide) at 0.56 kg ai/ha did not reduce disease development of C.g.a. on northern jointvetch. Sequential applications of benomyl [methyl 1-(butylcarbamoyl)-2-benzimidazolecarbamate] at 0.56 kg ai/ha reduced activity of the fungus on northern jointvetch when fungicide applications began 1 week after C.g.a. application but had no effect on mycoherbicide activity when applications began 2 weeks after C.g.a.

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.

Field studies were conducted to evaluate weed control with combinations of glyphosate at 750 g ae/ha and the insecticides acephate (370 g ai/ha), dicrotophos (370 g ai/ha), dimethoate (220 g ai/ha), fipronil (56 g ai/ha), imidacloprid (53 g ai/ha), lambda-cyhalothrin (37 g ai/ha), oxamyl (280 g ai/ha), or endosulfan (420 g ai/ha) and insect control with coapplication of the herbicide with insecticides acephate, dicrotophos, dimethoate, and imidacloprid. Applying lambda-cyhalothrin or fipronil with glyphosate reduced control of hemp sesbania by 19 and 9 percentage points, respectively, compared with glyphosate alone. Acephate, dicrotophos, dimethoate, imidacloprid, lambda-cyhalothrin, oxamyl, and endosulfan did not affect hemp sesbania, pitted morningglory, prickly sida, and redweed control by glyphosate. Lambda-cyhalothrin and fipronil did not affect glyphosate control of weeds other than hemp sesbania. Addition of glyphosate to dicrotophos improved cotton aphid control 4 d after treatment compared with dicrotophos alone. Thrips control was improved with addition of glyphosate to imidacloprid. Insect control was not reduced by glyphosate regardless of insecticide.