infestations of adults can "burn" entire pastures,
stunting growth and lowering nutritive value and
palatability (Pagan and Picado 1971, Valerio and
Nakano 1988). Infestations may also reduce the per-
sistence of improved pastures by promoting the in-
vasion of undesirable weeds and grasses (Taliafero
et al. 1967, Valerio and Nakano 1987). In Monteverde,
conversion to a more pest-tolerant pasture species
(Star Grass) was an adequate short-term control. How-
ever, in recent years, Star Grass pastures have later
suffered high pest densities and increased froghopper
burn. Declining soil fertility and drier wet seasons
may reduce pest tolerance of this grass.
Dairy farmers in Monteverde rely largely on cul-
tural controls to reduce the incidence of outbreaks.
The dairy plant and the Ministry of Agriculture and
Ranching (Ministerio de Agricultura y Ganaderia,
MAG) promote heavy grazing and regular use of fer-
tilizer to reduce habitat favorability to spittlebugs and
to promote vigorous regrowth of the sward. The min-
istry also promotes biological control with Fusarium,
a fungus that attacks adult Prosapia. Poor insect scout-
ing and application techniques, however, limit the
fungus's effectiveness. If these preventive measures
fail, farmers can opt to do nothing and absorb the
damage or to use remedial measures such as Mala-
thion (an organophosphate) and Vidate (a systemic
nematocide). Pesticide use is heaviest in pastures
where farmers persist in managing Kikuyu Grass.
The persistence of outbreaks in Monteverde is
partly due to the lack of information on this pest's
ecology. I studied the agroecology of spittlebugs and
froghoppers in Monteverde during the wet seasons
of 1991-94, focusing on factors that influence their
abundance and distribution, including their be-
havior, population dynamics, and natural enemies.
Four species are pests in local pastures: Aeneolamia
postica, Prosapia simulans, P. plagiata, and a unde-
termined species related to P. bicincta. The most
abundant species, P. nr. bicincta, feeds on all the
local forage grasses, including East African Star
Grass, Kikuyu Grass, Pitilla (Sporobolus spp.), and
King Grass (Pennisetum purpureum). The nymphs
construct masses of protective spittle at their feed-
ing sites on host grasses low in the pasture sward.
The adult froghoppers are black and crimson with
three transverse red stripes across the back. They are
approximately 10.7 mm long and 4.8 mm wide. At
peak times, more than 250 nymphs/m^2 and 500
adults per 100 sweeps of an insect net can be cap-
tured (Peck 1996).
Adult P. nr. bicincta lay eggs in the top layer of the
soil at the base of the host plants. Eggs hatch at the
beginning of the wet season (April-May). Nymphs
pass through five instars before they molt to adults;
they require six weeks to mature. Eggs enter a period
of diapause that lasts throughout the dry season. Un-
like other grassland cercopids, this species achieves
only one relatively synchronous generation per year
(Peck 1996).
A key step for cercopid management is prediction
of outbreaks. Early season rainfall may determine the
timing and synchrony of the egg hatch, which may
allow prediction of when nymphs and adults will
appear and when pressure on pastures will peak.
Scouting fine-tunes those predictions and identi-
fies problem areas, which guides the timing and loca-
tion of chemical application. If the time of hatching
can be accurately predicted, the feeding of first-
instar nymphs on roots can be predicted, and heavy
grazing of pastures at that point may reduce pest
populations.
Local population surveys revealed that frog-
hoppers migrate; colonists arrive in Monteverde
from areas where nymphs have already matured
(Peck 1996). Thus, pest management must be consid-
ered on a regional scale. A paddock treated on one day
may be swamped with new colonists the following
day. Research should address how cercopids damage
their hosts to predict how colonizing adults affect
grasses that are already stressed by local nymph popu-
lations. Nymphs and adults are attacked by natural
enemies. Maggots of the syrphid fly Salpingogaster
nigra (Diptera: Syrphidae) crawl into spittle masses
to feed on the nymphs. Two entomopathogens,
Fusarium and Baktoa, also attack adults in the zone.
Further research is needed on the factors that influ-
ence the abundance of these enemies and their po-
tential as agents of biological control. An expanded
knowledge base will equip farmers to consider pest
management alongside pasture management. Effec-
tive management requires an integrated approach that
addresses (1) vulnerable windows in the pest's life
cycle, (2) pest life span and capacity for reproduction,
(3) the impact of local natural enemies, and (4) the role
of grazing and forage management.410 Agriculture in Monteverde: Moving Toward Sustainability