Sodium alginate was used to prepare pelletized formulations for each of five fungi. Aqueous mixtures of 1.0% (w/v) sodium alginate and homogenized mycelia of Alternaria cassiae Jurair & Khan, Alternaria macrospora Zimm., Fusarium lateritium Nees ex Fr., Colletotrichum malvarum (A. Braun & Casp.) Southworth, or a Phyllosticta sp. were pelletized by dropwise additions of each mycelial-alginate mixture into 0.25 M CaCl2. Abundant conidia were produced on the pellets 24 to 48 h after the pellets were spread into trays and exposed 10 min/12 h to 275-W sunlamps. These conidia germinated readily (90 to 100%) and readily infected the respective host plants. Each liter of mycelium plus growth medium from submerged liquid cultures produced 4 L of the mycelial-alginate mixture. Each liter of the mycelial-alginate mixture produced approximately 18 g of air-dried formulation. When 10% (w/v) clay was incorporated into the pellets, each liter of the mycelial-alginate mixture produced approximately 118 g of air-dried formulation. The pelletized fungi sporulated readily following storage at 4 or 25 C for 6 to 8 months. This method of pelletization is potentially useful for the formulation of inoculum of fungi used as mycoherbicides, for the mass production of pycnidium-forming fungi, and for the production of inoculum for host-plant resistance studies.

In greenhouse experiments, conidia of Colletotrichum truncatum applied in an invert emulsion formulation controlled hemp sesbania 100% in the absence of a dew treatment. In field experiments, hemp sesbania control averaged 95 and 97% in 1989 and 1990, respectively, when this formulation was applied to hemp sesbania seedlings using tractor-mounted, air-assist nozzles. This level of weed control was comparable to that achieved from the herbicide acifluorfen. These results indicate that C. truncatum has excellent potential as a mycoherbicide for controlling hemp sesbania and that this potential can be augmented by formulating the pathogen as an invert emulsion.

A method is described for the large-scale production of a granular formulation of Alternaria macrospora Zimm. The granular preparation consisted of spores, mycelia, and vermiculite. This formulation of A. macrospora, applied preemergence or postemergence, controlled spurred anoda (Anoda cristata Schlecht.) plants in greenhouse and field tests. The pathogen did not significantly affect emergence or dry weight production of cotton (Gossypium hirsutum L. ‘Stoneville 213’) seedlings. The fungicides PCNB (pentachloronitrobenzene) and ETMT [5-ethoxy-3-(trichloromethyl)-1,2,4-thiadiazole] did not significantly affect spurred anoda control with A. macrospora. The method for production and formulation of A. macrospora was modified to produce spores and granular formulations of other Fungi Imperfecti: Drechslera sp. and Fusarium spp. (Moniliales), Colletotrichum spp. (Melanconiales), and Phyllosticta sp. (Sphaeropsidales).

A strain of Fusarium oxysporum was isolated from infected sicklepod stems in Stoneville, MS, in 1989. When formulated as granules either in a fungus-infested rice preparation or encapsulated in a wheat-gluten matrix called ‘Pesta’, biocontrol of sicklepod, coffee senna, and hemp sesbania was achieved with preemergence or preplant-incorporated treatments. Liquid conidial applications were less effective. Plants were killed by a preemergence damping-off. Applications made postemergence were significantly less effective. Results of these tests suggest that this fungus has potential as a mycoherbicide for controlling sicklepod, coffee senna, and hemp sesbania.

An isolate of Fusarium lateritium (Nees) emend. Snyder and Hansen was associated with naturally occurring disease of spurred anoda [Anoda cristata (L.) Schlecht.] and prickly sida (Sida spinosa L.) plants. In greenhouse inoculation studies, the Fusarium isolate was pathogenic to healthy spurred anoda and prickly sida plants. The disease symptoms were characterized by leaf, stem, and root lesions. The stem lesions enlarged with time and formed cankers that often girdled the stems and killed inoculated plants. In host-range studies, velvetleaf (Abutilon theophrasti Medic.), Venice mallow (Hibiscus trionum L.), okra [Abelmoschus esculentus (L.) Moench], and hollyhock [Althaea rosea (L.) Cav.] were also susceptible to the pathogen. This is the first report of these six species as hosts for this pathogen. Corn (Zea mays L.), cotton (Gossypium hirsutum L. and G. barbadense L.), soybean [Glycine max (L.) Merr.], and 18 other representative crop and weed species in eight families were resistant to the pathogen. F. lateritium may be a useful biological herbicide for susceptible malvaceous weeds.

In greenhouse and controlled-environment tests, velvetleaf (Abutilon theophrasti Medic. ♯ ABUTH) and prickly sida (Sida spinosa L. ♯ SIDSP) control with Fusarium lateritium Nees ex Fr. was affected by inoculum concentration and plant growth stage at the time of inoculation, by postinoculative air temperature, and by dew period duration and temperature. A higher level of control of both weeds was obtained with inoculum concentrations of 7.5 × 105 and 1.5 × 106 macroconidia/ml when the weeds had fewer than seven true leaves. Postinoculative air temperatures above 25 C significantly reduced control of both weeds. Mortality of both species was higher at dew temperatures of 25 C than at temperatures of either 15 or 35 C. At least 12 h of dew at 25 C was required to achieve satisfactory control of prickly sida, while a dew period of 16 h was required to achieve a comparable level of control of velvetleaf.