Js. Brown et al., THE EFFECT OF TEMPERATURE ON THE DEVELOPMENT OF EPIDEMICS OF COFFEE LEAF RUST IN PAPUA-NEW-GUINEA, Crop protection, 14(8), 1995, pp. 671-676
Epidemics of coffee leaf rust (CLR) were monitored to establish the se
asonal pattern of epidemic development in various coffee growing regio
ns of Papua New Guinea (PNG) and to determine the effect of temperatur
e on those epidemics. There is a seasonal pattern to the epidemics of
CLR in PNG. Rust incidence (% infected leaves) is lowest during the Oc
tober-November to January-February period. Thereafter rust incidence i
ncreases and reaches a peak in May-June-July, after which the disease
incidence declines. The average maximum disease incidence (MDI) was le
ss than 20% leaves infected. MDI was positively correlated with the me
an minimum monthly temperature five months before the MDT. This associ
ation indicated that if the average minimum temperature is less than 1
5 degrees C in January, epidemic development 5 months later will not r
each levels which require chemical control. The minimum temperatures r
ecorded in PNG suggest that conditions are sub-optimal for the develop
ment of epidemics of coffee leaf rust in the main coffee growing areas
of the country. The possibility that CLR became established in the ma
in coffee growing regions of Papua New Guinea before 1986 and remained
undetected for a number of years is discussed.