A two-year investigation was carried out in 1997 and 1998 in the province of Maputo (Mozambique) to determine the effect of environmental factors, planting date, plant growth stage and variety on the occurrence and incidence of four sunflower pathogens (Puccinia helianthi, Alternaria helianthi, A.alternata and Sclerotium bataticola). In 1997 rainfalls during the latter half of the year were abundant whereas 1998 was a hot and dry year. The incidence of P.helianthi was low, less than 10% of the leaf area affected during 1997 and rust incidence was slightly higher (about 20%) in 1998. On the contrary, A.helianthi incidence was about 30% during the seedings of 1997 and it was lower during the same periods of 1998. Generally, rust and A.helianthi infections started at budding and at vegetative stage and budding respectively and usually they became severe at growth stages of anthesis and seed development. The incidence of A.alternata was very low in both years and usually the occurrence of this fungus appeared about one/two months later of A.helianthi infections. In 1997 the percentage of S.bataticola infected plants was generally low, with the exception of the September seeding, and this may be attributed to the high and frequent rains recorded in the latter half of 1997 until to March 1998 when sunflower plants were at flowering time. In contrast the low incidence of charcoal stem rot observed during 1998, a dry and hot year until harvesting may be attributed to the seedings in an experimental field never previously planted with sunflower and therefore to the insufficient presence of inoculum in the soil. In both years, significant differences occurred among planting dates whereas all varieties were susceptible to all pathogens. Field evaluations were highly influenced by environmental conditions in both years, so these experimental results are not sufficient to provide final informations on the development and progress of these diseases.
Effect of planting date, plant growth stage and environmental factors on some sunflower diseases progress in Mozambique
ZAZZERINI, Antonio;TOSI, Laura;
1999
Abstract
A two-year investigation was carried out in 1997 and 1998 in the province of Maputo (Mozambique) to determine the effect of environmental factors, planting date, plant growth stage and variety on the occurrence and incidence of four sunflower pathogens (Puccinia helianthi, Alternaria helianthi, A.alternata and Sclerotium bataticola). In 1997 rainfalls during the latter half of the year were abundant whereas 1998 was a hot and dry year. The incidence of P.helianthi was low, less than 10% of the leaf area affected during 1997 and rust incidence was slightly higher (about 20%) in 1998. On the contrary, A.helianthi incidence was about 30% during the seedings of 1997 and it was lower during the same periods of 1998. Generally, rust and A.helianthi infections started at budding and at vegetative stage and budding respectively and usually they became severe at growth stages of anthesis and seed development. The incidence of A.alternata was very low in both years and usually the occurrence of this fungus appeared about one/two months later of A.helianthi infections. In 1997 the percentage of S.bataticola infected plants was generally low, with the exception of the September seeding, and this may be attributed to the high and frequent rains recorded in the latter half of 1997 until to March 1998 when sunflower plants were at flowering time. In contrast the low incidence of charcoal stem rot observed during 1998, a dry and hot year until harvesting may be attributed to the seedings in an experimental field never previously planted with sunflower and therefore to the insufficient presence of inoculum in the soil. In both years, significant differences occurred among planting dates whereas all varieties were susceptible to all pathogens. Field evaluations were highly influenced by environmental conditions in both years, so these experimental results are not sufficient to provide final informations on the development and progress of these diseases.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
