One or more of the features that are needed to show you the maps functionality are not available in the web browser that you are using.
Please consider upgrading your browser to the latest version or installing a new browser.
More information about modern web browsers can be found at http://browsehappy.com/
Systemic symptoms may be observed in the first true leaf stage as chlorotic
stripes or a pale yellow colour throughout the entire leaf. Local symptoms
(long, chlorotic streaks with a downy growth of conidia and conidiophores) may
be present from the two-leaf stage until the appearance of tassels and silks.
Sporulation of the fungus was observed on both upper and lower leaf surfaces,
but was more abundant on the lower.
Tassels may be malformed and produce less pollen, and ears may be aborted. Early-infected plants become stunted and many die.
There are no external symptoms on seeds. The fungus becomes established in the pericarp layer in the form of mycelium. The fungus is also present in the embryo and endosperm. There are no reports on the effect of P. philippinensis on seed quality.
There are no external symptoms on stems but early-infected plants may be stunted. The fungus invades the stem, moving upward and downward, becoming established in the shoot apex.
The fungus invades the shoot apex and may be found there throughout the life of the infected plant. Invasion of the shoot apex produced chlorotic areas which were at first confined to the base of the lower leaf. These chlorotic areas later increased in size in succeeding leaves. The youngest leaf emerging from the whorl became completely chlorotic (Exconde, 1976).
Cultural Control and Sanitary Methods
High levels of nitrogen increase the susceptibility of susceptible cultivars, but have less effect on the resistance of resistant cultivars (Yamada and Aday, 1977).
Resistant varieties of maize have been developed (Exconde, 1976; Raymundo and Exconde, 1976; Schmitt and Freytag, 1977). Studies of the inheritance of resistance indicate that resistance is under polygenic control and is governed mainly by additive gene effects (Leon et al., 1993; Carpuno and Carpena, 1982). Quantitative resistance was expressed in a study in which resistant inbred lines showed extended duration of local infection, delayed onset of systemic infection, and slow rate of downy mildew development with the area under the disease progress curve remaining low. Patterns of systemic symptoms varied among lines. These resistance components were correlated with one another (Ebron and Raymundo, 1987).
Fentin hydroxide and maneb provide effective control (Exconde, 1975; Exconde, 1976; Raymundo and Exconde, 1976). Metalaxyl was also effective, when applied as a foliar spray (Cordero and Tangonan, 1988).
Philippine downy mildew is confined to parts of Asia. It is a major problem in
the Philippines where losses in maize were estimated at 8% nationally in
1974-75 (Exconde, 1976). One yield loss study showed losses of 100% (Exconde
and Raymundo, 1974). The disease is generally less severe in India, but losses
of up to 60% have been reported (Bonde, 1982; Payak, 1975).
An experimental plot study with sugarcane Clone Phil.6723 showed yield losses of 36% associated with P. philippinensis (Husmillo, 1982).