Fungicides, seed dresser adjuvants and storage time in the control of Drechslera teres in barley seeds

Abstract

In the 2010 growing season in Brazil, barley crop was cultivated in an area of 80,000 ha, yielding a final production of 248,000 t. In that season, 200,000 sacks of seeds (40kg/sack) were sown (4).The main fungi associated with barley seeds are those causing leaf spots such as net-blotch (Drechslera teres (Sacc.)Schoem), heminthosporiosis [Bipolaris sorokiniana (Sacc.) Shoem.], stripeblotch [D. graminea (Rabe.) Schoem], and scab [Gibberella zeae (Schw.) Petch]. The major inoculum sources of these pathogens are seeds and host crop residues (6).The damage caused by barley net-blotch can be assessed by using the linear equation y = 1,000 -13.9 I (where y = barley normalized grain yield kg/ha), I = leaf incidence (%) (10).Net-blotch control measures are focused on the development of cultivars especially resistant to D. teres and B. sorokiniana, crop rotation with plant species non-susceptible to target pathogens and, fungicide applied in seeds and sprayed on above-ground plant parts (12).Little attention has been given to barley seeds as a source of inoculum for the necrotrophic fungi that cause leaf blotches and common root-rot. Currently, only three fungicides, or mixtures, are recommended for barley seed treatment (carboxin + thiram, difenoconazole and triadimenol) (12).Nevertheless, their efficiency does not eradicate the pathogenic fungi infecting the barley seed. Moreover, the incidence in harvested seeds is high, further compromising the treatment effectiveness. As a result, everywhere barley is cultivated, there are always leaf blotches causing damage to the crop, even under crop rotation with nonsusceptible crops such as oats, rape, canola and hairy vetch (1).The aims of this study were to (i) improve the performance of RESUMO Palavras-chave adicionais: Hordeum vulgare, mancha-em-rede, patologia de sementes.Em experimentos conduzidos em laboratório quantificou-se o efeito de fungicidas, de veículos de cobertura e do tempo de armazenamento no controle de Drechslera teres em sementes de cevada cultivar BRS Elis com incidência natural de 58%. Foram testados os fungicidas nas doses indicadas pela pesquisa de cevada (carboxina + tiram, difenoconazol e triadimenol) comparados com a mistura carbendazim + iprodiona. Como veículos testou-se a água (500 mL/ 100 kg) e um polímero (150 mL/100 kg). As sementes após o Reis, E.M.; Danelli, A.L.D.; Casa, R.T. Fungicidas veículos de cobertura e tempo de armazenamento no controle de Drechslera teres em sementes de cevada. Summa Phytopathologica, v.38, n.3, p.187-191, 2012. tratamento foram armazenadas em sacos de papel e mantidas em refrigerador a 5 o C. A intervalos de 30 dias, até completar três meses, as sementes foram plaqueadas em meio semi-seletivo de Reis (1983). O melhor controle foi obtido pelas misturas carboxina + tiram e carbendazim + iprodiona, com o veículo polímero. A eficiência do controle foi melhorada pelo tempo de armazenamento sem afetar negativamente a germinação das sementes. Devido à eficiência de transmissão a erradicação do fungo em sementes deve ...

Pyrenophora teres: Taxonomy, Morphology, Interaction With Barley, and Mode of Control

“…Seed treatment effectiveness depends on fungal sensitivity, chemical fungitoxicity, and seed coverage quality. Iprodione is the fungicide providing the best control of dematiaceous fungi ( Bipolaris and Drechslera ) on seeds ( Reis et al, 2012 ). Another study demonstrates the efficiency of one application of propiconazole at spike emergence for the management of net blotch ( Sutton and Steele, 1983 ).…”

Viability of seed-borne fungi Alternaria alternata, Bipolaris sorokiniana and Drechslera teres in barley seeds in the south of Brazil

“…were completely eliminated from cucumber seeds after eight months. Reis et al (23) showed that storage of wheat seeds for long periods (19 and 22 months) reduced the viability of Pyricularia oryzae to 0%.…”

“…Nevertheless, seed health testing has revealed that a large number of treated seeds are infected by A. alternata, B. sorokiniana and D. teres (4). Moreover, incidence of seed-borne fungi in harvested seeds is high, further compromising the treatment effectiveness (6, 13,23). Incorrect or inefficient fungicide treatment may allow the survival of necrotrophic fungi and the spread of diseases to other uninfested sites (6, 7).…”

Fungicide baseline for mycelial sensitivity of Exserohilum turcicum, causal agent of northern corn leaf blight

“…and D. teres (Sacc.) Shoem, used in wheat and barley seed treatment (13). The following fungicides [technical name, trade name, active ingredient (g/L) and chemical group] were used in the tests: i) captan (Captan 500) phthalimide; ii) carbendazim (Derosal 500), benzimidazole, iii) iprodione (Rovral 500), dicarboximide, iv) fludioxonil (Maxim 25), phenylpyrrole, v) metalaxyl-m (Apron XL 33), acetylalaninate, vi) thiram (Rhodiauram 65.9), dimethyldithiocarbamate (1).…”