תפריט נגישות
ניגודיות עדינהניגודיות גבוהה
מונוכרום
הדגשת קישורים
חסימת אנימציה
פונט קריא
סגור
איפוס הגדרות נגישות
להורדת מודול נגישות חינם תפריט נגישותניגודיות עדינהניגודיות גבוההמונוכרוםהדגשת קישוריםחסימת אנימציהפונט קריאסגוראיפוס הגדרות נגישותלהורדת מודול נגישות חינםPotatoes are grown in Israel in two main seasons. For the autumn crop, potatoes are planted in late August to early September and harvested during December and January. For the spring crop, potatoes are planted in late January to February and harvested during May to July. Two Alternaria species infect potato plants in Israel: A. solani, the causal agent of early blight and A. alternata, the causal agent of necrotic lesions. Nevertheless, the most destructive pathogen is Phytophthora infestans, the causal agent of late blight. Analysis of disease progress curves revealed that early blight is more important in the autumn than in the spring season. Results of field experiments suggested that A. solani intensifies towards the end of the season, in mature plants and that the yield was reduced and application of fungicides was profitable in the autumn but not in the spring seasons. Based on these experiments we developed an integrated strategy for management of both early and late blights. The strategy was evaluated in field experiments, under natural infections, and found accurate. In observations carried out in commercial fields it was found that necrotic lesions appear suddenly in large areas, often after heavy rain events and that the phenomenon was more common in crops growing in sandy soils. Alternaria alternata was isolated from necrotic lesions and the Koch postulates were completed and proved the pathogenicity of that fungus. Based on these observations it was hypothesized that heavy rains wash the nitrogen fertilizer from the root zone and that necrotic lesions appear in plants suffering from stress imposed by sudden reduction in nitrogen content in the foliage. These hypotheses were tested and it was found that necrotic lesions develop primarily in nitrogen-deficient plants and that applying supplemental N fertilization reduces necrotic lesion severity. Accordingly, it was decided not to recommend fungicide spraying for suppression of necrotic lesions.
Potatoes are grown in Israel in two main seasons. For the autumn crop, potatoes are planted in late August to early September and harvested during December and January. For the spring crop, potatoes are planted in late January to February and harvested during May to July. Two Alternaria species infect potato plants in Israel: A. solani, the causal agent of early blight and A. alternata, the causal agent of necrotic lesions. Nevertheless, the most destructive pathogen is Phytophthora infestans, the causal agent of late blight. Analysis of disease progress curves revealed that early blight is more important in the autumn than in the spring season. Results of field experiments suggested that A. solani intensifies towards the end of the season, in mature plants and that the yield was reduced and application of fungicides was profitable in the autumn but not in the spring seasons. Based on these experiments we developed an integrated strategy for management of both early and late blights. The strategy was evaluated in field experiments, under natural infections, and found accurate. In observations carried out in commercial fields it was found that necrotic lesions appear suddenly in large areas, often after heavy rain events and that the phenomenon was more common in crops growing in sandy soils. Alternaria alternata was isolated from necrotic lesions and the Koch postulates were completed and proved the pathogenicity of that fungus. Based on these observations it was hypothesized that heavy rains wash the nitrogen fertilizer from the root zone and that necrotic lesions appear in plants suffering from stress imposed by sudden reduction in nitrogen content in the foliage. These hypotheses were tested and it was found that necrotic lesions develop primarily in nitrogen-deficient plants and that applying supplemental N fertilization reduces necrotic lesion severity. Accordingly, it was decided not to recommend fungicide spraying for suppression of necrotic lesions.
