RESUMEN
Hybrid bermudagrass (Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy) is widely used on golf course putting greens in the southern United States. In March and April 1998, circular patches of dead grass 2 to 10 cm in diameter were observed on a bermudagrass putting green in College Station, TX, that had been overseeded with rough bluegrass (Poa trivialis L.) the previous October. Rapid death and deterioration of the rough bluegrass within the spot revealed extensive foliar and crown necrosis and root decay of the remaining bermudagrass. Diseased bermudagrass leaves in the patch were reddish brown to tan. Dark ectotrophic hyphae were not found on the roots or stolons, but dark hyphae were observed within the affected root tissues. Numerous pseudothecia were embedded in necrotic leaf and stolon tissues. The characteristics of the pseudothecia and ascospores coincide with the description of Ophiosphaerella agrostis Dernoeden, Camara, O'Neil, van Berkum, and Palm (1,2). This fungus was consistently isolated from stolons and roots, and single-ascospore isolates were obtained from pseudothecia. Inoculum was prepared by transferring fungal mycelium from a single-spore isolate grown in potato dextrose agar (PDA) to a moistened, autoclaved mixture of rice hulls (Oryza sativa L.) and milled rice (2:1, vol/vol) for 28 days at 24°C. 'FloraDwarf' bermudagrass was grown from stolons in 15-cm-diameter pots containing a mixture of sand, peat moss, and perlite (8:3:1, vol/vol). The bermudagrass was maintained at a height of 1 to 1.5 cm for ≈ 1 month. Plants were inoculated by forming a hole that was 0.8 cm in diameter and 7 cm deep in the center of the pot, using a rod and filling the hole with inoculum. Control pots received the same treatment, except uninoculated rice hull-milled rice mixture was used. The treatments were replicated three times, and the experiment was performed twice. The pots were maintained in a greenhouse for 6 weeks. In all inoculated pots, patches of dead bermudagrass 6 to 10 cm in diameter developed. Roots, stolons, and leaves were necrotic, and pseudothecia were abundant in stolon and leaf sheath tissues. O. agrostis was consistently reisolated from infected root and stolon tissues. All isolates produced colonies identical in appearance to the culture used for inoculation. To our knowledge, this is the first report that O. agrostis is pathogenic to hybrid bermudagrass. References: (1) M. P. S. Camara et al. Mycologia 92:317, 2000. (2) P. H. Dernoeden et al. Plant Dis. 83:397, 1999.
RESUMEN
A blight on buffelgrass, Cenchrus ciliaris L., has been observed for several years in south Texas and Mexico. The disease did not reach epidemic proportions until 1996. The causal agent, identified as Pyricularia grisea (Cooke) Sacc., is a common pathogen of grasses and other cultivated crops. Several Pennisetum spp. have been reported as hosts of Pyricularia spp.; this is the first report of buffelgrass as a host of this pathogen (1,2). Pathogenicity of P. grisea on buffelgrass was confirmed by greenhouse inoculations of 2-month-old buffelgrass plants with conidia washed with distilled water from monoconidial isolations of the pathogen, grown on potato dextrose agar, from infected leaves collected in several locations in south Texas and Mexico. Plants were placed for 8 h every night inside a plastic enclosure with a humidifier, simulating the high relative humidity conditions prevalent during the epidemic. Typical lesions developed after 7 days. The pathogen was re-isolated from the lesions after 10 days, fulfilling Koch's postulates. Conidia harvested from the sporulating samples were hyaline, transversely septate, with one to three septa, most of them having two. Conidia were obpyriform, with hylum often protuberant, measuring 20.6 to 26.3 µm in length and 8.5 to 10.1 µm wide. These measurements are consistent with those given for Pyricularia spp. by Ellis (1). Conidiophores were hyaline, single, slender, and unbranched. Initial symptoms were dark, discolored spots on the leaf that developed into tan, round to elliptical, necrotic lesions with a dark red border and a yellow, chlorotic halo. With increasing severity, lesions can coalesce, killing the entire leaf blade. Under heat and moisture stress, leaves with few lesions and yellow discoloration will wilt completely. Except for the presence of distinct lesions, wilted plants appear to be suffering from severe drought stress or herbicide injury. Losses vary from a few lesions to wilted whole plants and entire pastures. The pathogen also reduces the quantity and quality of seed by infecting involucres of the head. In the absence of the disease, even under severe moisture or drought stress, buffelgrass is able to thrive. Common T-4464 buffelgrass, which is highly susceptible to P. grisea, was introduced into south Texas in the late 1940s and is currently grown on 8 to 10 million acres in south Texas and Mexico. Buffelgrass reproduces by obligate apomixis, in which seeds are formed without sexual fertilization. Consequently, the progeny are genetically identical to the maternal parent. The monoculture of this grass with its unique type of reproduction encompasses millions of acres with genetically identical plants. Interaction of inoculum with weather conditions (nights with 8 to 10 h of more than 75% relative humidity) in 1996, 1997, and the late summer of 1998 produced epidemics of buffelgrass blight throughout south Texas and northern Mexico. P. grisea was also isolated from lesions on grassburr Cenchrus incertus M. A. Curtis collected throughout the area. References: (1) M. B. Ellis 1971. Dematiaceous hyphomycetes. Commonwealth Mycological Institute, Kew, Surrey, England. (2) D. F. Farr et al. 1989. Fungi of Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN.
RESUMEN
Isolates of Gaeumannomyces graminis var. graminis were obtained from St. Augustinegrass, bermudagrass, and rice in Florida, and rice and St. Augustinegrass in Texas. In Florida, all seven isolates evaluated were cross pathogenic on each of the three grass hosts. Rice isolate FL-173 caused significantly greater disease of the lower leaf sheath and root disease severity of rice compared with other isolates, whether from rice or both turfgrass species. The rice and both turfgrass isolates generally suppressed heights and shoot and root weights compared with the control. All isolates from either rice or both turfgrass species generally had root disease ratings significantly different from the control for either bermudagrass or St. Augustinegrass. However, rice isolate FL-173 and St. Augustinegrass isolate FL-104 were significantly more aggressive on St. Augustinegrass; whereas the maximum root disease rating of bermudagrass was only associated with bermudagrass isolate FL-19 and St. Augustinegrass isolate FL-104. In Texas, both the rice isolate TX-91-1 and the St. Augustinegrass isolate TX-10466-2 of G. graminis var. graminis were pathogenic on St. Augustinegrass, common bermudagrass, and rice. Both isolates caused similar disease severity on common bermudagrass and St. Augustinegrass, but isolate TX 10466-2 caused less severe disease symptoms on rice than did isolate TX-91-1. Overall, G. graminis var. graminis was most aggressive on the host from which it was originally isolated, such as rice or St. Augustine, but differences in host-plant reactions were not always statistically significant, especially with bermudagrass.
RESUMEN
A 23-year-old white woman was admitted because of cardiac failure (functional class II), palpable purpura and hypereosinophilia. A month before, she had been operated due to right femoral embolus. In this occasion, enhanced cardiac size on X-ray film of the chest and 12,300 eosinophils/mm3 were observed. She was asthmatic from her childhood. The laboratory data did not detect an etiology of hypereosinophilia. Serologic test for collagenous diseases, Chagas, hydatidosis, toxocariasis, Coxsackie B 1-6 and cytomegalovirus were not considered reactive. Three parasitologic stool examinations were negative. Duodenal sounding was negative. Myocardial dilatation was confirmed by mode M and B echocardiogram (60 mm left ventricular diastolic diameter), and by 99Tc radiocardiogram (left ventricular ejection fraction -LVEF-: 29% and right VEF: 15%). On the 25th day of treatment with 16-beta-methyl-prednisone (1 mg/K/d), eosinophil count was reduced to 300/mm3. On the 45th day, clinical improvement, dilatation reduction on echocardiogram and a 32% LVEF were observed. On the 10th month, the patient has no signs or symptoms of cardiac failure under treatment. Although endomyocardial biopsy was not performed but considering the low prevalence of myocardial dilatation at such an age, it is possible to postulate that the patient has undergone the initial necrotic stage (dilated cardiomyopathy) and the intermedial thrombotic stage (femoral embolus) of the eosinophilic endomyocardial disease.
Asunto(s)
Cardiomiopatía Dilatada/complicaciones , Eosinofilia/complicaciones , Adulto , Cardiomiopatía Dilatada/sangre , Eosinofilia/sangre , Eosinofilia/diagnóstico , Femenino , Humanos , Recuento de LeucocitosRESUMEN
The incidence of Meloidogyne incognita and Rotylenchulus reniformis on cotton was determined in 1989-92 from 1,089 soil samples collected from 31 counties that account for nearly 60% of the 2.2 million hectares planted to cotton in Texas. Meloidogyne incognita was commonly found in the Southern High Plains and Brazos River Valley regions of Texas (57% and 34%, respectively, of samples) but was found in less than 8% of samples from the Central Blacklands, Coastal Bend, Low Plains, or the Upper Gulf Coast regions. Rotylenchulus reniformis was widely distributed in the Brazos River Valley (24% of samples) and found occasionally in the Upper Gulf Coast (8% of samples). Meloidogyne incognita was found only rarely in soils with greater than 40% clay content, whereas Rotylenchulus reniformis was frequently found in finely textured soils but was less common in soils with greater than 40% sand content. In samples infested with M. incognita or R. reniformis, population densities of these species were at least 10-fold greater than population densities of other plant-parasitic species present in the sample. Root-knot and reniform nematodes were not found together in high population densities (>100 individuals/500 cm(3)) in the same sample.
RESUMEN
A 23-year-old white woman was admitted because of cardiac failure (functional class II), palpable purpura and hypereosinophilia. A month before, she had been operated due to right femoral embolus. In this occasion, enhanced cardiac size on X-ray film of the chest and 12,300 eosinophils/mm3 were observed. She was asthmatic from her childhood. The laboratory data did not detect an etiology of hypereosinophilia. Serologic test for collagenous diseases, Chagas, hydatidosis, toxocariasis, Coxsackie B 1-6 and cytomegalovirus were not considered reactive. Three parasitologic stool examinations were negative. Duodenal sounding was negative. Myocardial dilatation was confirmed by mode M and B echocardiogram (60 mm left ventricular diastolic diameter), and by 99Tc radiocardiogram (left ventricular ejection fraction -LVEF-: 29
and right VEF: 15
). On the 25th day of treatment with 16-beta-methyl-prednisone (1 mg/K/d), eosinophil count was reduced to 300/mm3. On the 45th day, clinical improvement, dilatation reduction on echocardiogram and a 32
LVEF were observed. On the 10th month, the patient has no signs or symptoms of cardiac failure under treatment. Although endomyocardial biopsy was not performed but considering the low prevalence of myocardial dilatation at such an age, it is possible to postulate that the patient has undergone the initial necrotic stage (dilated cardiomyopathy) and the intermedial thrombotic stage (femoral embolus) of the eosinophilic endomyocardial disease.