Web blotch, caused by Phorna arachidicola, has varied in severity from year to year in Texas, depending on survival of inoculum on peanut crop residue, presence of susceptible peanut cultivars and suitable environmental conditions, especially favorable temperature and high relative humidity. The web and blotch symptoms may develop in sequence on the same leaflet or independently on different leaflets. At relative humidities below 80% within the plant canopy, the fungal hyphae grew under the leaf cuticle causing a web-type symptom. At relative humidities above 908, hyphal strands grew more repidly and branched extensively in the l e d resulting in the blotch-type symptom. P. arachidicola isolates from South Africa, Argentina, and the USA were ail pathogenic and caused similar symptoms. Of 32 legumes, peanut, sweetclover, hairy vetch and alfalfa were the most susceptible. Symptoms on hosts other than peanuts consisted of small necrotic spots. A hypersensitive reaction developed on eight legumes. Typical web blotch symptoms were observed only on peanuts in the field.

A foliar disease of peanuts, previously unreported in the USA, was found in Texas in 1972. The pathogen was identified as a species of Ascochyia. Further cultural studies have revealed this fungus to be Phoma arachidicola Marasas, Pauer, and Boerema. Pycnidia form profusely at 20 C and 25 C. Pycnidiospores are borne on short pycnidiosphores and are predominantly one-celled in culture. Spores produced in pycnidia on infected leaflets become 1 septate. Large l-septate spores, as well as an occasional 2-septate spore, may form in culture. Optimum temperature for mycelial growth in 20 C; little or no growth occurs at 5 C or above 30 C. The teleomorphic state develops in the field on fallen leaflets and can be induced to form in the laboratory on sterilized peanut leaflets between 15 and 20 C. Cultures derived from single ascospores form pseudothecia. Pycnidiospores, ascospores, and chlamydospores are all infective units. Because this fungus produces hyaline ascospores and pseudoparaphyses, it has been transferred to the genus Didymella as Didymella arachidicola (Choch.) comb. nov. Comparisons with 15 isolates causing web blotch of peanut in the USA, Argentina, and South Africa indicate that web blotch symptoms are produced by the same fungal species.

Poor stand establishment, failure to recover after grazing, and premature plant death have reduced the utilization of arrowleaf clover (Trifolium vesiculosum Savi) as a forage crop in the southeastern United States in recent years. Clover plants collected from poor stands in east Texas pastures during the 1995 to 1996 and 1996 to 1997 seasons first exhibited root disease symptoms as young seedlings in the fall. Symptoms consisted of one or more of the following: tan discoloration of lateral roots and taproot; root pruning; and small, tan, sunken lesions on the taproot and crown. Many Rhizobium nodules were brown and dead. Toward spring, symptoms increased in severity. Root lesions became larger and darker, and internal crown discoloration was observed. Disease incidence reached 100% in both growing seasons. Premature death of plants also was observed, especially in pastures where plants had been grazed. Most of the fungi isolated from diseased roots were Pythium, multi- and binucleate Rhizoctonia, and Fusarium spp. Many plants were infected with two or three pathogens simultaneously. Two Rhizoctonia isolates (AR96-17 and -26) were identified as R. solani anastomosis group 4 (AG4; D. R. Sumner, University of Georgia). AR96-8 was identified as Fusarium proliferatum (T. Matsushima) Nirenberg (Fusarium Research Center, Penn State University; deposited as isolate M-8382). Three Pythium isolates (AR96-7, -11 and -39) were identified as P. irregulare Buisman, based on oogonial and sporangial characteristics. Eight other Pythium isolates were not identified. Pythium isolate AR97-1, found in 1997, was identified as P. ultimum Trow. Greenhouse studies to confirm pathogenicity of these isolates were conducted by sowing cv. Yuchi arrowleaf clover seed into artificially infested soilless medium. In pathogenicity tests for P. ultimum, seedling emergence for controls was 69% after 8 days, but no seedlings emerged from P. ultimum-infested media. Several seeds showed imbibition and emerging radicles but were symptomatic. The pathogen was reisolated from necrotic radicles. After 19 weeks, survival and root disease symptoms were recorded for plants infected by the other isolates. Pathogens were reisolated from diseased plants. Disease symptoms were similar to those observed on plants collected in the field, and differed among pathogens. The Pythium isolates and P. irregulare caused tan discoloration and pruning of the entire root system, sometimes leaving only stubs along the taproot. Survival of clover plants infected by Pythium spp. and P. irregulare isolates averaged 79 and 83%, respectively. R. solani AG4 isolates caused internal crown discoloration, root lesions, and severe root rot, and plant survival was only 31%. F. proliferatum caused hyperelongation of the hypocotyl and stem, mild chlorosis, tan discoloration of roots, and 94% plant survival. Survival was 86% for control plants. P. ultimum, P. irregulare, R. solani AG4, and F. proliferatum are part of a larger disease complex occurring on arrowleaf clover in east Texas that also includes bean yellow mosaic virus (1) and possibly other root and crown rot diseases. This report is the first to identify some of the components of this disease complex impacting arrowleaf clover in Texas, and to demonstrate pathogenicity of each fungal pathogen individually. There are no arrowleaf clover cultivars currently known to have resistance to any of these pathogens. Reference: (1) I. J. Pemberton et al. Phytopathology 81:1001, 1991.

Plants of Rosa `Mr. Lincoln' and `Peace' were established in March 1992. Using a RCB design, fungicide treatments were initiated on 15 May and terminated on 22 Oct. 1992. Foliar applications were made with a Birchmeier® Closed System Unit equipped with a ConeJet® #5500 adjustable spray tip at 50-65 psi. Treatments were cyproconazole at 0.1, 0.2, and 0.4 kg·ha-1 applied at either 14 or 28 day intervals, mancozeb at 2.250 g·1-1 applied every 7 days, and an untreated control. Cyproconazole treatments were applied in 946 1·ha-1 water and mancozeb was sprayed to runoff. Disease pressure and plant defoliation ratings were taken on 29 June and 26 August. The disease rating was based on a scale of 1-10, where 1 = no infection and 10 = severe infection and defoliation. The defoliation rating was based on a scale of 1=10, where 1=0-10% and 10=91-100% defoliation of canopy. A full season control rating was determined on 17 Nov. 1992, based on a scale of 1-3, where 1=excellent, 2=acceptable, and 3=unacceptable control of blackspot. Blackspot control with mancozeb was unacceptable on either cultivar. Cyproconazole at 0.1 kg·ha-1 every 28 days did not control blackspot by mid-November with `Peace' and was marginally acceptable on `Mr. Lincoln'. Season long disease control was near excellent for both cultivars with 0.2 kg·ha-1 cyproconazole every 28 days. All other cyproconazole treatments proved to be excellent.

To determine the efficacy of cyproconazole for control of black spot [Marssonina rosae (Lib.) Lind] when applied as a drench, treatments of 0, 32.5, 65, 97.5 and 130 g a.i./ha were initiated 9 May 1994 on individual Rosa `Peace' plants in a randomized complete-block design. Treatments were applied once per month until 18 Oct. 1994. Data were taken in July, Sept., and Nov. 1994 when separate disease and defoliation ratings were assigned. By July, the controls were heavily infected; the higher treatment rates resulted in significant control. By September, the disease and defoliation ratings exhibited a linear response with cyproconazole rate, with the highest treatment rate giving the best control. The relationship between disease and defoliation ratings and treatment rate remained the same in November, although there was increased disease incidence overall. No phytotoxicity was observed. These results indicate that soil applied treatments of cyproconazole can control black spot effectively on roses.