Etiology and control of stem rot of sunflower (helianthus animus l.)

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Sokoine University Of Agriculture


Surveys were curried out on the distribution in Tanzania of a new sunflower disease first observed in Morogoro Region. Experiments were conducted at the Tropical Pesticides Research Institute (T.P.R.I.) ana Sokoine University of Agriculture (SUA) to identify the causal agents, assess their pathogenicity to sunflower varieties commonly grown in Tanzania and other crops normally grown in association with sunt lower, and to determine biological activity of some selected fungicides to the disease causing organisms. Out of all eight surveyed regions, sunflower stem rot was confirmed only in Morogoro region. Fusarium moni liforme She Id and F. graminearum Schwabe were identified as the causal organisms inciting the new sunflower disease which was later named "sunflower stem rot". Sunflower- varieties namely Record, Jupiter, Gor 104 and Dwarf comet were found less affected by both Fusarium spp. while Giant 549, IS 894, IS 894 amd 6F5 were more susceptible. Groundnuts, simsim. cowpeas and greengram did not show symptoms upon artificial inoculations with the two Fusarium spp. while maize, sorghum, beans and garden peas showed necrotic symptoms in the areas inoculated. The fungicides Sisthane (fenapanil) and Ridomil (metalaxyl) were not effective against both fungi in laboratory culture tests while Benlate (benomyl) was effective. But Benlate proved inffective in controlling the disease in the field during field tests.iv Severity of sunflower stem rot was more apparent in fields planted a t ve ry close spacing whether it was a monoculture or interplanted with other crops resulting in more plant deaths. It is recommended that sunflower varieties which were found resistant be distributed to peasants in Morogoro Region and that only resistant ij Ten r. .1 be used in crops like groundnuts, simsim, cowpeas intercrop u- f lower and all other Wherever stem rot is endt intercrops should be planted at w’^nr tpacin which favour disease development. . *“het particularly on breeding for more ■e •’void overcrowding ”C se.i <_«> is being suggested t« nt van The suitability of fungicide «_or.- : -I cf .> s. in peasant grown sunflower appears remote an<" .‘:urrLe«r ;.r /e i.^vxuns on this aspect sl.nould be on large farms



Sunflower plant, Etiology, Helianthus annuus L, New sunflower disease