Efficacy of rue extract, sodium bicarbonate and fungicides at ... - Inea

Lahoz et al. Efficacia dell’estratto di ruta, bicarbonato e....... 61Figure 4 – Leaves of untreated control plants at theend of the trial showing severe powdery mildewsymptoms.Fig. 4.Foglie del controllo non trattato alla fine dellaprova con gravi sintomi di oidio.ResultsThe colonization of the untreated tobacco leaveswas complete 30 days after the inoculation, lateron spots became necrotic and basal leaves died.Inoculation methods using 10 5 conidia /mlsuspended in 0.1% SWA showed constant andreproducible results.Greenhouse testing of active ingredients. Nophytotoxicity was observed on plants for anycompound tested in the trials (Table 2).Rue extract was very effective forcontrolling powdery mildew in both trials.Sodium bicarbonate at 500 g/hl reduced diseaseover control, even if, in trial A, more than 9spots/leaf were observed, 8 days after the lastapplication. Penconazole, tebuconazole andbenomyl completely controlled diseasedevelopment (Table 2). On untreated controlplants were counted over 24 and 20 coloniesper leaf respectively in trial A and B,equivalent of about 60% damaged leaf surface(Fig.4), indicating that the disease pressure washigh.An increased disease severity was observedafter repeated applications of sodiumbicarbonate at 500 g/hl, while its efficacy washigher at 1000 g/hl, and a most satisfactorycontrol was reached after three applications.On benomyl treated plants, less than 1sporulating spot per leaf was observed, startingfrom the second applications. Bupirimatereduced disease severity to a level equivalentto that attained with rue extract, requiring twoapplications to obtain its maximumeffectiveness. A trend similar to sodiumbicarbonate at 1000 g/hl was observed fordinocap application (Fig. 5).Both trials gave similar results on percentof disease control. In trial B sodiumbicarbonate at 1000 g/hl, dinocap, bupirimateand rue extract showed statistically equivalentresults. In both trials the efficacy of sodiumbicarbonate at 500 g/hl was below 70%. Rueextract application reduced disease to a levelstatistically not different from bupirimate (Fig. 6).Table 3 – Disease severity as CORESTA index in thefield trials.Tab. 3. Gravità della malattia secondo gli indiciCORESTA per le prove in campo.ActiveingredientsratesDisease severityg/hl19971998Penconazole3.750 0Tebuconazole100 0Benomyl250 0Bupirimate37.5 0 0Rueextract 1000 0NaHCO10000 03Dinocap17.5 1 1NaHCO5000.5 0. 53C ontrol/ 2 2ue22ing.p65 6125/03/2005, 17.22