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The fungal genus Myrothecium was once polyphyletic but a recent reconsideration of the family Stachybotryaceae spilt it into several genera. The ex-neotype specimen of the species Myrothecium verrucaria is now recognized as Albifimbria verrucaria. The well-studied plant pathogen and candidate bioherbicide CABI-IMI 368023, previously identified as M. verrucaria, was analyzed morphologically and genetically and found to be most consistently aligned with the other representatives of A. verrucaria.

Spore formulations of the bioherbicidal fungus Colletotrichum gloeosporioides f. sp. aeschynomene (ATCC No. 20358) (CGA) were evaluated for control of three weed species: northern jointvetch (Aesch...

A simple method, 'Stabileze', is described for granulating fungi with water-absorbent starch, sucrose, corn oil and silica. The potential biological control fungi, Colletotrichum gloeosporioides and Fusarium oxysporum , were stabilized using this protocol. Bioassays were performed on C. gloeosporioides and showed retention of pathogenicity. Sucrose and oil were tested for their effects on the viability of F. oxysporum over time, and sucrose appears to be the most beneficial factor.

Maintaining adequate viability of microorganisms in products for biocontrol is critically important for commercial reasons. Microsclerotia (MS) of the mycoherbicide agent, Colletotrichum truncatum, are its hardy, over-wintering fungal structures. Microsclerotial inoculum at 2, 7, and 23 MS/granule were matrix-encapsulated in wheat flour–kaolin granules (‘Pesta’), in which the flour provided gluten for the matrix and a food base for the fungus. Pesta granules were dried to a water activity of 0.18–0.29. After storage for 52 weeks at 25°C, granules containing 7 and 23 MS were 100% viable and granules with 2 MS were 95% viable. Granules with 7 MS were 50% viable after 36 weeks at 35°C. Pesta granules (440 granules/g) with conidial inoculum at 3.3×105 c.f.u./g were less storage-stable than granules at the 2 MS/granule level. At all MS inoculum levels, granules stored for up to 2years produced 108 c.f.u./g in vitro when incubated on water agar. High water activity was detrimental to long-term viability. In the greenhouse, 7 MS/granule samples controlled 94% of hemp sesbania when incorporated into the soil pre-planting. The strategy of encapsulation of the naturally stable C. truncatum MS and drying to a favourable water activity led to excellent shelf-life for a live biocontrol agent.

Natural products of an isolate of Fusarium solani App. & Wr. NRRL 18883 grown on rice medium were discovered to be phytotoxic to morningglory. This isolate was evaluated for biocontrol potential on morningglory species including ivyleaf [Ipomoea hederacea (L.) Jacq.], multicoloured (I. tricolor Cav.), paimleaf (I. wrightii Gray), pitted (I. lacunosa L.), purple moonflower (I. turbinata Lag.), red (I. coccinea L.), sharppod (I. cordatotriloba Dennstedt), smallflower (Jacquemontia tamnifolia (L.) Griseb], and tall [I. purpurea (L.) Roth] morningglory. When sprayed at a concentration of 10 g fungus‐infested rice per 50 ml of water, this isolate caused phytotoxic damage including necrosis, chlorosis, growth inhibition, and mortality. Deleterious effects were recorded in all species, ranging from necrotic spots to death, depending on the species. Mortality ranged from 0% at 3 weeks for purple moonflower to 89% for smallflower morningglory. Soil‐drench application (10–20 ml fungal material per 150 g so...

AAL-toxin, produced byAlternaria alternata, was investigated for its phytotoxic effects on 86 crop and weed species. On susceptible tomato leaf discs, AAL-toxin caused electrolyte leakage and chlorosis at 0.01 μM in 24 h. Plants tested exhibited a range of response. AAL-toxin damaged sensitive plants at 5 μM while other plants showed minimal damage at > 1000 μM. Cotton and the important weeds, Canada thistle, field bindweed, and velvetleaf were largely unaffected. Monocots tested were largely immune.

In greenhouse tests, the host specificity of Alternaria crassa (Sacc.) Rands, a mycoherbicide for jimsonweed was altered by the addition of water-soluble filtrates of jimsonweed and hemp sesbania or fruit pectin to fungal conidia suspensions. Several crop and weed species that were resistant to the fungus alone exhibited various degrees of susceptibility following these amendments, with 100% mortality occurring to the weeds hemp sesbania, showy crotalaria, and eastern black nightshade when treated with the fungus/pectin mixture. Nonhost plants that were inoculated with conidial mixtures amended with sucrose or cellulose were not affected. Modification of host specificity of this pathogen could have an influence on its bioherbicidal potential. Nomenclature: Jimsonweed, Datura stramonium L. #3 DATST; hemp sesbania, Sesbania exaltata Rydb. ex A. W. Hill # SEBEX; eastern black nightshade, Solanum ptycanthum Dun. # SOLPT; showy crotalaria, Crotalaria spectabiis Roth, # CVTSP. Additional index words: Biological control, mycoherbicide, host selectivity alteration, DATST, SEBEX, SOLPT, CVTSP.

Nine isolates of Alternaria alternata were obtained from infected tomato (cv. Beefsteak) plants. Each isolate was grown on autoclaved rice medium and corn meal agar medium and evaluated for pathogenesis and phytotoxicity to jimsonweed plants. Only A. alternata SWSL 1 (NRRL 18822) caused lodging on 1-week-old jimsonweed plants when sprayed at a rate of 20 g of fungus-infested rice per 100 mL distilled water. The symptoms began within 24 to 48 h following inoculation, and all plants were dead after 96 h. Treatment of 2-week-old jimsonweed plants in the same manner affected growth only. No symptoms occurred when SWSL 1 spores from corn meal agar were applied to jimsonweed at a rate of 2 × 107 spores/mL, with or without dew. The filtrates of fungus-infested rice of the SWSL 1 isolate were found to contain the following phytotoxins: AAL-toxin (100 μg/g), tenuazonic acid (10 μg/g), and alternariol monomethyl ether (580 μg/g). Crude and cell-free filtrates and AAL-toxin (concentration 200 μg/mL) caused similar damage on excised leaves, characterized by soft rot diffusing from the point of inoculation along the veins, adaxially or abaxially to leaves. Alternariol monomethyl ether (concentration 800 μg/mL) and tenuazonic acid (concentration 420 μg/mL) applied to excised jimsonweed leaves caused no visible damage. In intact plants, symptoms resulting from the crude filtrate, cell-free filtrate, and the AAL-toxin were identical. A dose–response study of AAL-toxin on excised jimsonweed and black nightshade (Solanum nigrum L.) leaves showed effects at concentrations of 1.56 μg/mL and 0.01 μg/mL, respectively. This is the first report of phytotoxicity of AAL-toxin to these two weeds and it may have potential as a weed control agent. Key words: weed, natural products, solid media, fungi.

Eight Fusarium spp. were isolated from greenhouse-grown jimsonweed (Datura stramonium L.) in Mississippi in 1990. Four isolates of Fusarium moniliforme were obtained and when grown on autoclaved rice, produced 115 to 3,200 mg/kg fumonisin B1, (FB1). Other fumonisin-related compounds, such as FB2, FB3 and FB4 were also produced at levels of 240, 210 and 160 mg/kg, respectively. F. semitectum (1 isolates) was negative for production of fumonisin and other phyto-toxins. F. oxysporutn (1 isolate) produced only 3.5 g/kg moniliformin. This is the first report of production of fumonisins by F. moniliforme isolated from weeds such as jimsonweed.

An indigenous, host-specific, pathogenic fungus that parasitizes winged waterprimrose [Jussiaea decurrens(Walt.) DC.] is endemic in the rice growing region of Arkansas. The fungus was isolated and identified asColletotrichum gloeosporioides(Penz.) Sacc. f.sp. jussiaeae(CGJ). It is highly specific for parasitism of winged waterprimrose and not parasitic on creeping waterprimrose (J. repensL. var.glabrescensKtze.), rice (Oryza sativaL.), soybeans [Glycine max(L.) Merr.], cotton (Gossypium hirsutumL.), or 4 other crops and 13 other weeds. The fungus was physiologically distinct from C.gloeosporioides(Penz.) Sacc. f. sp.aeschynomene(CGA), an endemic anthracnose pathogen of northern jointvetch[Aeschynomene virginica(L.) B.S.P.], as indicated by cross inoculations of both weeds. Culture in the laboratory and inoculation of winged waterprimrose in greenhouse, growth chamber and field experiments indicated that the pathogen was stable, specific, and virulent in a wide range of environments. The pathogen yielded large quantities of spores in liquid culture. It is suitable for control of winged waterprimrose. Winged waterprimrose and northern jointvetch were controlled in greenhouse and field tests by application of spore mixtures of CGJ and CGA at concentrations of 1 to 2 million spores/ml of each fungus in 94 L/ha of water; the fungi did not damage rice or nontarget crops.