Modelo de ponto crítico para estimar danos de doenças foliares do trigo em patossistema múltiplo

Abstract

A Região Sul do Brasil responde pela maior parte da produção nacional de trigo. O estado de Santa Catarina apresenta a menor área cultivada entre os estados do sul do Brasil (Conab, 2007), no entanto, alguns produtores têm obtido produtividades superiores a 3.600 kg.ha -1 . O país tem condições de solo, de clima, de material genético e de tecnologia disponíveis para incrementar a produtividade do trigo (Bisotto, 2005). Porém, as doenças foliares, que incidem sobre o trigo, constituem uma das principais causas que levam a reduções na produtividade. As condições climáticas da Região Sul do Brasil favorecem tanto a ocorrência como o aumento da intensidade das doenças, principalmente pelo excesso de chuva durante o ciclo da cultura (Reis & Casa, 2005a ABSTRACT A critical-point model to estimate damage caused by wheat leaf diseases in a multiple pathosystemWheat leaf diseases cause damage by reducing photosynthetic activity in leaves. The objective was to obtain damage model equations for a wheat multiple pathosystem, by examining the relation between grain yield and the incidence of leaf diseases at different plant growth stages. The experiments were carried in Lages and São José do Cerrito, SC, during the 2005/06 and 2006/07 crop seasons with cultivars Ônix and BRS Louro. The gradient of disease incidence was obtained by the number of fungicide applications (one, two, and three) and three different fungicide rates: azoxystrobin+cyproconazol (40+16, 60+24 and 80+32 g of a.i. ha -1 ), trifloxystrobin+tebuconazol (25+50, 50+100 and 75+150 g of a.i. ha -1 ) and pyraclostrobin+epoxyconazol (33.25+12.5, 66.5+25 e 99.75+37.5 g of a.i. ha -1 ). Each experiment consisted of ten treatments distributed according to the random block scheme with four repetitions. The leaf disease incidence was evaluated at the growth stages EC 31, 34, 40, 52 and 60 according to Zadok's scale. There was significant correlation between two places and harvests for BRS Louro cultivar in the 40 and 50 plant growth stages. However, this was only significant for the Ônix cultivar in São José do Cerrito in both harvests. The variation between the damage model equations indicates the necessity to continue this research in different places and years, using cultivars with similar leaf disease reactions to those tested in this work.

Adaptability and Stability of Yield and Industrial Grain Quality with and without Fungicide in Brazilian Oat Cultivars

“…Furthermore, similar to the thousand grains weight, the weight of hectoliter in oats also shows the further damage by foliar diseases [9]. These damages are awarded by the reduction of area photosynthetic active and interference in translocation of photoassimilates from the leaves to the grains, consequently, lower deposition of reserves and reducing the commercial value of the final product [31].…”

Critical yield-point model to estimate damage caused by brown spot and powdery mildew in barley

“…Each plot had an experimental unit area of 5.0x2.5m. To generate the disease gradients, strobilurin and triazol fungicide rates (one half and full recommended rates) and numbers of fungicides sprays (once, twice, third and fourth) were applied, according to REIS et al, (2000REIS et al, ( , 2002REIS et al, ( , 2008, BOHATCHUK et al (2008) andNERBASS et al (2010). The fungicide applications were performed at the plant GS 22 (Main shoot and 2 tillers), GS 31 (Swelling 1st node detectable), GS 39 (Flag leaf ligule just visible), GS 45 (Full-boot, boot above ligule of 2nd last leaf) and GS 56 (50% of spikes visible), according to the diagrammatic scale of ZADOKS et al (1974).…”

EFEITO RESIDUAL DE FONTES FOSFATADAS, CALCÁRIO E SILICATO E NO DESENVOLVIMENTO DE Avena strigosa

“…No Sul do Brasil, as principais doenças foliares em trigo são oídio (Blumeria graminis), ferrugem da folha (Puccinia tritici), e as manchas amarela (Drechslera tritici-repentis) e marrom (Bipolaris sorokiniana) (BOHATCHUK et al, 2008), as quais podem reduzir até 80% da produtividade dos grãos (NAVARINI;. Além disso, giberela (Fusarium graminearum) e brusone (Pyricularia grisea) são doenças tipicamente florais, e têm sido diagnosticadas como de difícil controle, até mesmo por fungicidas de alta fungitoxicidade, devido aos baixos níveis de cobertura das espigas (REIS et al, 2013).…”