Effects of farming system, chemical control, fertilizer and sowing density on sharp eyespot and Rhizoctonia spp. in winter wheat

Abstract

Effects of agronomic practices on the occurrence of sharp eyespot and Rhizoctonia spp. in winter wheat were determined in two field experiments. In Experiment 1, in the village of Osiny, a comparison was made of disease in different farming systems. The farming systems were: organic, integrated, conventional, and monoculture. In Experiment 2, in the village of Mochełek, the effects of different chemical controls (no treatment, herbicide, herbicide + fungicide), mineral fertilizer doses (147 and 221 kg/ha NPK) and sowing densities (400 and 600 grains/m2) on the occurrence of sharp eyespot were compared in wheat grown in short-term monoculture. There was considerably more sharp eyespot in 2007 (disease index 1.63-29.5%) than in other years. Significant effects of the treatments were mostly noted at the milk ripe growth stage. The fewest sharp eyespot symptoms were seen in the integrated farming system. The most sharp eyespot symptoms were seen in the conventional and organic systems. There was a tendency for an increased intensity of symptoms in successive wheat-growing years of short-term monoculture. The application of pesticides showed no clear effect on the occurrence of sharp eyespot. The herbicide resulted in increased or decreased disease intensity depending on the cultivation year and the date of observation. Fungicide application did not decrease infection. Without chemical control, more symptoms were observed at the lower NPK rate. There were more symptoms at the higher sowing density. Stems with sharp eyespot symptoms were mostly infected by Rhizoctonia cerealis, and less frequently by R. solani. Binucleate Rhizoctonia spp., which could not be identified to species using polymerase chain reaction (PCR) techniques, were also recorded. Two R. zeae isolates were also obtained from stems with disease symptoms in Mochełek. R. solani was more often isolated from roots or stems with symptoms of true eyespot or fusarium foot rot. Most isolates of Rhizoctonia spp. were obtained at the milk ripe stage. A wheat-growing system and chemical control did not greatly affect the frequency of Rhizoctonia spp.

Ancient Wheat Species (Triticum sphaerococcum Perc. and T. persicum Vav.) in Organic Farming: Influence of Sowing Density on Agronomic Traits, Pests and Diseases Occurrence, and Weed Infestation

“…In addition, Eken et al [63] found no effect of sowing density on the occurrence of root and crown rot diseases. On the other hand, other authors noted an increase in the severity of root and stem base diseases in winter wheat crops at higher sowing densities [28,64], which was particularly evident at the early developmental stages of the analyzed plants. In the case of take-all diseases, increased plant density means a shorter distance between the inoculum and host, which significantly increases the likelihood of the pathogen reaching, through developing mycelium or spores, the next plant and infecting it.…”

“…In properly cultivated wheat crops, especially spring forms, take-all diseases usually do not pose the greatest threat, however, during the growing season the symptoms of take-all (Gaeumannomyces graminis), Fusarium foot rot (Fusarium spp.) and eyespot (Oculimacula acuformis, Oculimacula yallundae) can be observed, and less often, of sharp eyespot (Rhizoctonia cerealis, Rhizoctonia solani) [26][27][28]. The occurrence of diseases on wheat depends largely on weather conditions.…”

Susceptibility of winter Triticale Cultivars to Rhizoctonia Cerealis (sharp eyespot) and R. Solani

“…Geographical differences in the occurrence of sharp eyespot on winter triticale grown commercially were also previously noticed (Lemańczyk 2010a). This can result from the type of rotation, which seems to affect significantly the occurrence and intensity of disease (Colbach et al 1997;Żółtańska 2005;Bockus et al 2010;Lemańczyk 2012b). The lower incidence and severity of disease at Dębina, Kończewice, and Minikowo may have resulted from the use of winter oilseed rape as the preceding crop.…”

“…This may be because of the late application of the fungicide. Azoxystrobin applied after inflorescence emergence has little effect on infection by R. cerealis (Lemańczyk 2012b). Neither the type of fungicide nor time of its application affected the intensity of sharp eyespot in commercially grown winter triticale (Lemańczyk 2010a).…”

“…The disease usually occurs on winter wheat (Żółtańska 2005;Kurowski and Adamiak 2007;Lemańczyk 2012b). R. cerealis attacks numerous Poaceae species, including rye, barley and oats, although wheat appears most susceptible.…”