Induced resistance for plant disease control - Disease Control in Crops - page 66

against wound inoculation with B. cinerea (Iriti et al., 2007). Konstantinidou-Doltsinis
et al. (2006) reported that Milsana induced resistance to powdery mildew ( Leveillula
taurica (Lev) Arn.) on 'Manthos' tomato and reduced foliar infection by 4264% in
glasshouse trials. The level of control was equivalent to that obtained using sulphur, but
was not as effective as conventional fungicides. Foliar applications of Milsana and chito-
san (Chitoplant ® , ChiProGmbH-Germany) reduced powdery mildew severity on 'Bison'
and 'Elpida' greenhouse tomatoes (Dafermos et al., 2007). Disease severity was further
reduced if plants were grown in soil amended with chitin. The authors suggested that the
integrated use of these treatments, particularly on cultivars with low susceptibility, could
be an alternative to sulphur for the management of powdery mildew in organic tomato
production.
Bourbos & Barbopoulou (2006) reported that harpin (Messenger) provided over 98%
control of late blight ( Phytophthora infestans ) in glasshouse 'Bella Dona' tomato and also
increased fruit yield by over 47%. In contrast, twice-weekly foliar applications of harpin
did not control late blight on 'Sunrise' glasshouse tomatoes as effectively as fungicide
(Becktell et al., 2005). Immersion of tomato seeds (Santa Cruz 'Kada') in a Bacillus
cereus suspension before sowing signifi cantly enhanced fi eld resistance to late blight and
also to foliar infections caused by Alternaria solani (early blight) and Septoria lycoper-
sici (septoria leaf spot) (Silva et al., 2004). Disease severity was further reduced by foliar
application of chlorothalonil fungicide. The combination of these treatments enabled
a reduction in the number of fungicide applications without loss of disease control or
crop yield. More recently, chitosan and mustard seed extract (Tillekur ® , Biofa, Germany)
demonstrated potential to protect tomato seed against infection by the fungus Didymella
lycopersici Kleb. (Kasselaki et al., 2007). This is one of the most important seedborne
diseases of tomato and causes serious reductions in germination and seedling survival.

4.2.1.2 Pepper

The effi cacy of ASM as a potential management tool for Phytophthora root and crown rot
( Phytophthora capsici ) was demonstrated in glasshouse studies (Matheron & Porchas,
2002). In highly favourable disease conditions, ASM was less effective than the fungicide
mefenoxam (Ridomil Gold ® 44WP). However, in more moderate conditions, plants that
received three ASM applications plus a soil treatment of mefenoxam survived signifi -
cantly longer in naturally infested soil, and produced greater shoot growth, than those
treated only with ASM or mefenoxam. Resistance to mefenoxam in P. capsici has been
detected in North Carolina and it was suggested that the use of ASM may prolong the
effectiveness of this fungicide for disease control. The effi cacy of copper-based sprays
to control bacterial spot in pepper, caused by Xanthomonas axonopodis [ campestris ] pv .
vesicatoria , can be disappointing because of the occurrence of copper-resistant bacterial
strains. Integrated use of ASM with copper hydroxide has shown potential as a manage-
ment option to control bacterial spot in pepper (Romero et al ., 2001; Buonaurio et al.,
2002). In fi eld studies, a tank mix containing ASM plus copper hydroxide had higher effi -
cacy against leaf (69%) and fruit (67%) infection than either products alone (Buonaurio
et al., 2002). Seven or more applications of ASM signifi cantly reduced bacterial spot in
bell pepper but resulted in lower yields compared with copper plus mancozeb treated
plots (Romero et al ., 2001). However, when ASM was applied in rotation with copper