Invasive Stink Bugs and Related Species (Pentatomoidea)

476 Invasive Stink Bugs and Related Species (Pentatomoidea)

10.3.5 Population Dynamics on Coffee

10.3.5.1 Seasonal Variation

A study of seasonal variation in population size of Antestiopsis intricata was conducted for ≈10 years in
southwestern Ethiopia. It showed that the pest populations increased from February to March, peaked in
May to June, and declined thereafter (Abebe 1987). Similar trends were reported by Chichaybelu (2008)
for seasonal variations of the same species in the same area.
Another study conducted in Cameroon at two different elevations revealed different trends (Mbondji
Mbondji 2001); at 1100 m asl, Antestiopsis intricata population density remained at ≈2 bugs per tree
between January and May, then decreased between June and October, and then increased quickly to
reach a peak in December, with ≈9 bugs per tree (Figure 10.3A). In this study, pest infestations at 1100 m
asl reached or were above the economic threshold of 2 bugs per tree for half of the year, which was used
to trigger control measures. By contrast in this study, A. intricata populations never reached the density
of 1 bug per tree at 1800 m asl (Figure 10.3B) but showed similar seasonal variation as populations in
southwestern Ethiopia.
In Rwanda, a study conducted in the middle of 1950s described seasonal variations in populations of
Antestiopsis thunbergii ghesquierei (Foucart and Brion 1959). Densities were assessed using the “pyre-
thrum test,” a knock-down technique based on pyrethrum spraying. Population densities were high with
not less than 5 bugs per coffee tree during the period, and the peak density was 45 bugs per tree in
February (Figure 10.4). Populations were between 10 and 18 bugs per tree from July to September, with
a small peak in August, then quickly increased from November to reach a peak in February and steadily

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FIGURE 10.3 Seasonal variation of two Antestiopsis intricata populations at 1100 m asl (A) and 1800 m asl (B) in
Western Cameroon (from Mbondji Mbondji 2001). Densities were obtained using the “knock-down” technique by spraying
100 coffee trees sampled in four plantations with insecticide every month during 2 years.