Induction of New Isolates ofTrichoderma harzianumTolerant to Fungicides and Their Experimental Use for Control of White Rot of Onion

Integrated control of Allium white rot with Trichoderma viride, tebuconazole and composted onion waste

“…When T. viride L4 or S17A was combined with a tebuconazole‐based seed treatment in glasshouse onion seedling bioassays at two different application times, AWR control was always improved compared with using either T. viride or tebuconazole alone, and this effect was significant for a number of treatments. This additive effect of Trichoderma and fungicide confirms the results of Abd‐El‐Moity et al (1982), where T. harzianum and iprodione were more effective against AWR in combination than alone. The reduced effect of T. viride S17A in the field in 2004, however, meant that, although the same combination treatments were effective, they were comparable with using tebuconazole alone, and AWR control was enhanced only compared with using T. viride S17A alone.…”

“…Similarly, C. minitans was demonstrated to be compatible with iprodione for control of Sclerotinia sclerotiorum in glasshouse soil despite its sensitivity to the fungicide in agar tests (Budge & Whipps, 2001). In some cases, therefore, the soil can act as an effective buffer between BCAs and fungicides, so the selection of fungicide‐resistant antagonists of S. cepivorum , either by spontaneous mutation on selective media (Abd‐El‐Moity et al , 1982) or UV mutation (Kay & Stewart, 1994b), is not necessarily required for successful integration of the two control methods.…”

“…The continuing reliance on tebuconazole for the control of AWR in the UK and elsewhere, and the increasing demand for reduced fungicide inputs, has also led to a search for biological control agents (BCAs) of S. cepivorum . Successful AWR control has been demonstrated both in pot trials and in the field using Trichoderma spp., Coniothyrium minitans and Sporidesmium sclerotivorum (Adams & Ayers, 1981; Abd‐El‐Moity et al , 1982; Kay & Stewart, 1994a; Gerlagh et al , 1996; Clarkson et al , 2002, 2004). However, as so often observed with biological control, results in the field with AWR can be variable (Entwistle, 1988).…”

“…DADS and tebuconazole reduced AWR incidence from 76% (untreated) to 44 and 37%, respectively, whereas the combined treatment reduced disease further to just 11%. In the second study, an iprodione‐tolerant strain of T. harzianum was combined with the fungicide, which was applied in‐furrow (Abd‐El‐Moity et al , 1982). Trichoderma harzianum and iprodione reduced AWR incidence from 86% (untreated) to 13 and 51%, respectively, while the combined treatment resulted in 6% disease.…”

Selection of fungal biological control agents of Sclerotium cepivorum for control of white rot by sclerotial degradation in a UK soil

“…Disease control in the field experiments might also have been improved if additional BCA treatments had been made preseeding (perhaps as a different formulation), and also if the fluid‐drill configuration had allowed more BCA to be delivered, thereby potentially destroying more sclerotia and affording further plant protection. Indeed, the BCA biomass application rate used in the field trials (68 kg ha −1 ) was considerably lower than that used for white rot control in other studies using T. harzianum (240 kg ha −1 ; Abd‐El‐Moity et al ., 1983) or C. minitans (600–1500 kg ha −1 ; Ahmed & Tribe, 1977).…”