Influence of sunflower (Helianthus annuus L.) crop management on Phoma black stem (Phoma macdonaldii Boerema)
2003
Debaeke, Philippe | Pérès, A.
Collaborative work was done by INRA and Cetiom from 1994 to 2001 to characterize and evaluate the effects of individual cultural techniques and crop management systems applied on sunflower (Helianthus annuus L.) on the frequency and severity of fungal attacks by Phoma macdonaldii Boerema at stem and collar levels. The proportion of stems infected by Phoma black stem always increased with additional nitrogen and water supply. In conditions of excessive nitrogen nutrition, the most severe attacks were observed for the lowest plant densities. In conditions of limiting water and nitrogen, the heaviest attacks were observed for the highest densities. With limited water, the water holding capacity of the petiole groove might be responsible for the success of infection whereas when nitrogen was limiting, the more favourable microclimate of dense stands could explain the higher level of infection. When these cultural factors (irrigation, nitrogen and plant density) were expressed via their effects on the plant canopy using leaf area index or fraction of photosynthetically active radiation intercepted (fPARi) at anthesis, it was possible to rank the proportion of infected stems and the number of lesions per stem according to the increasing level of crop intensification.
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