Modelos de pontos críticos para relacionar o rendimento de grãos de aveia branca com a intensidade de doença no patossistema múltiplo ferrugem da folha: helmintosporiose

Abstract

A ferrugem da folha e a helmintosporiose são as principais doenças fúngicas foliares de aveia branca. Em cultivares suscetíveis, o controle químico não considera o limiar de dano econômico (LDE). O objetivo deste trabalho foi obter funções de dano, por modelos de ponto crítico, ao relacionar o dano pela ocorrência simultânea da ferrugem da folha e a helmintosporiose com o rendimento de grãos nas safras de 2006 e 2007, em Lages, Santa Catarina (SC). O gradiente da intensidade das doenças foi gerado por número de aplicações e doses de fungicidas nas cultivares 'UPFA 20' e 'UPFA 22'. Os ensaios consistiram de 10 tratamentos, distribuídos em blocos casualizados, com quatro repetições. As doenças foram avaliadas nos estádios de alongamento, emborrachamento e florescimento. Os modelos de ponto crítico foram obtidos por regressão linear entre rendimento de grãos e incidência (I) e severidade (S). Em 2006, funções significativas foram obtidas para 'UPFA 20' no emborrachamento (R=6.345-22,07I), enquanto para a 'UPFA 22' foi obtida no alongamento (R=5.726-17,96I; R=5.160-541,5S), emborrachamento (R=5.961-21,85I; R=5.433-966,8S) e florescimento (R=6.217-36,41I; R=5.539-1.185S). Em 2007, para 'UPFA 20', no alongamento (R=6.369-55,61I; R=4.965-2.911S), emborrachamento (R=6.620-40,91I; R=5.181-1.702S) e florescimento (R=6.129-32,34I; R=5.252-638,6S), e para 'UPFA 22', no alongamento (R=5.201-41,96I; R=4.977-657,8S), emborrachamento (R=5.329-60,51I; R=4.238-798,1S) e florescimento (R=5.604-32,83I; R=4.680-588,5S). A produção na cultivar 'UPFA 22' foi mais afetada pela ocorrência das doenças, e a intensidade das doenças no estádio de florescimento apresentou maior relação com o rendimento de grãos. As funções geradas permitem obter o coeficiente de dano para uso no cálculo do LDE em patossistema múltiplo ferrugem da folha e helmintosporiose.

Critical-point models to relate yield and disease intensity of the multiple pathosystem in rice leaf spots disease

“…Considering the coefficients of determination, the variables incidence and severity showed good relationship with the data, while NERBASS JUNIOR et al (2010), had better relationship with the variable incidence in damage function equations for the culture of oats and AGOSTINETTO et al (2012) for variable severity in barley crop.…”

“…The equations were adjusted to a ton of rice grains, in order to facilitate its use in the calculation of EDT, according to simple pathossystem (REIS & CASA, 2007) and multiple pathossystem (BOHATCHUK et al, 2008) in wheat; simple pathossystem (REIS et al, 2008) and multiple in oat (NERBASS JUNIOR et al, 2010), and simple pathossystem (REIS et al, 2002) and multiple pathossystem in barley (AGOSTINETO et al, 2012).…”

“…According to REIS & CASA (2009), the complexity that involves the decision of apply fungicides, and the doubts about the probable damages of production leads to decisions that can be precipitated, resulting in unnecessary spending or delayed decisions resulting in unrecoverable losses. The EDT is characterized as scientific criteria for the use of fungicide on crops such as: some pathosystems in wheat (REIS & CASA, 2007;BOHATCHUCK et al, 2008) mildew and brown spot on barley (Reis et al, 2002;AGOSTINETO et al, 2012) and leaf rust in oat (NERBASS JUNIOR et al, 2010). Through EDT by using the critical point model is possible to identify a certain stage of development, in which the intensity of this disease is correlated with future damage (BERGAMIN FILHO & AMORIM, 1996).…”

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).…”

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

“…Therefore, the high percentage of caryopsis, the high weight of hectoliter and the grain size have been increasingly required [6]- [8]. These characteristics are not always obtained due to climatic factors and the prevalence of fungal diseases [9] [10]. Among the diseases, leaf rust (Puccinia coronata C da.…”