Research
Epidemic Roller Coaster: Maize Stunt Disease in Nicaragua
J. Hruska,
Allan
Sarah M. Gladstone, and Rafael Obando
ABSTRACT The incidence of maize stunt diseases, orachaparramiento, rose in Nicaragua from an insignificant level to national crisis
proportions, then declined to insignificant levels again, all in the space of 10 yr. The 3 pathogens that cause achaparramiento, corn stunt
spiroplasma, maize bushy stunt phytoplasma, and maize ray ado fino virus are transmitted by the corn leafhopper, Dalbulus maidis (DeLong & Wolcott). Vector populations did not change sufficiently over time to explain the epidemic pattern. Nor did changes in the varieties
of maize that farmers used cause the differential expression of disease symptoms during this period. The most likely explanation of the
epidemic pattern is an abrupt 3- to 4-yr increase in irrigated maize production during the dry season, when maize was not grown traditionally. Irrigated maize provided a temporal bridge for the pathogens, which then were transmitted to rainy season plantings and caused
epidemic disease incidence throughout the country. This explanation demonstrates the powerful impact that governmental agricultural
policies, in this case to strongly promote dry-season maize production, can have on crop pest and pathogen problems.
M
AIZE GROWN IN NEW WORLD TROPICAL DRY LOWLANDS IS A1TACKED
by several insect pests but is remarkably free from plant
diseases. A complex of pathogens causing maize stunt disease, or achaparramiento, is, however, endemic and causes variable
losses wherever the vector, the corn leafhopper, Dalbu/us maidis
(DeLong & Wolcott)(Homoptera: Cicadellidae) is present.
During the mid-1980s, Nicaragua underwent one of the most
severe outbreaks of achaparramiento recorded in the Americas. The
ecological bottlenecks of the vector/pathogen/plant system that normally keep the disease at low levels were eliminated and the consequences were severe. The result was a dramatic reduction in maize
yield. In the early 1990s, the disease subsided just as quickly to endemic levels.
The 1980s outbreak of achaparramiento provides an opportunity to examine what changes in agricultural practices might have
fueled the epidemic roller coaster. While working to develop rational
pest management strategies for maize in Nicaragua during this time,
we formed several hypotheses to explain the phenomenon. In this
article, we integrate evidence from various sources, including farmer
opinion surveys, acreage records from the Ministry of Agriculture
and Livestock, and results of field experiments, to evaluate these
hypotheses.
PathogenNector/Host
Plant Ecology
Pathogen. Throughout much of Central America, Mexico, and the
Caribbean, maize is infected by 3 pathogens, the corn stunt spiroplasrna (CSS), Spirop/asma kunkelii (Whitcomb et al.); the maize bushy
stunt phytoplasma (MBSP); and the maize rayado fino virus (MRFV),
which cause similar symptoms in the maize plant. They occur often in
mixed infections (Larsen et al. 1992) and are difficult to distinguish by
the symptoms in the field (Sveinhaug and Jorgensen 1988). The
shared symptom is plant stunting or achaparramiento, which is the
term used by Latin American farmers for the effect of 1 or more of the
diseases. The pathogens also cause extensive reddening or yellowing
of leaves, chlorotic spots or short lines, and proliferation of ears
(Shurtleff 1980). Most importantly, infected plants produce small and
noncommercial ears. Complete yield losses have been reported in the
fields of some farmers (Anaya 1975, Urbina 1982).
Vector. The corn leafhopper is the sole vector of the 3 pathogens in
Nicaragua and is a specialist herbivore, reproducing only on Zea species including maize, Zea mays L., and teosinte species (Nault 1985).
248
All 3 pathogens are transmitted persistently by D. maidis adults and
nymphs. Hence, they require an incubation period in the insect vector
before they can be transmitted to a new plant, and they are retained for
long periods by the vector (Na u1t 1980). Pathogen transmission by D.
maidis is highly efficient. A1ivizatos (1983) reported that some D.
maidis can acquire CSSby feeding on an infected plant for as little as 2
min, and that all D. maidis tested acquired CSS after an acquisition
access period of 7 d. Anaya (1975) found a 40-90% transmission
rate of achaparramiento pathogens when infected D. maidis fed on
healthy maize for 30 min.
Host Plant. Maize is grown traditionally on "'200,000 ha in Nicaragua in small holdings (1-3 hal during the rainy season (May to
December). There are typically 2 consecutive planting cycles on the
flat Pacific Plain, a region of fertile volcanic soils, hot temperatures,
and a marked dry season of 4 mo (December to April), during which
time virtually no rain falls. Maize is planted in Mayor June and
again in September or October. A small planting ("'200 hal of irrigated maize is grown in the dry months for seed and for sale as a
fresh vegetable.
Maize is the only host for D. maidis in Nicaragua (A.J.H., unpublished data) and is generally dry and unsuitable by December.
Traditionally, therefore, the system is simple, consisting of an essentially monophagous insect vector transmitting 3 pathogens over
large amounts of acreage during 8 mo of the year but restricted to a
much reduced refuge of irrigated maize during 4 dry months.
History of D. maidis and Achaparramiento
Background Levels of Achaparramiento. Although native to
Mexico, D. maidis first was reported as occurring in Nicaragua in
1956 (Salazar 1964). Achaparramiento first was reported from
Nicaragua in 1956 (Litzenberger and Stevenson 1957), and first
reported in commercial plantings in 1961 (Saenz 1971). In 1968,
several maize fields in La Paz Centro, in the Department of Leon,
were affected severely by achaparramiento, and symptoms of reddening and stunting were reported (Urbina 1987).
Throughout the 1970s, achaparramiento was reported but its distribution was limited to the Pacific Plain. The disease was noted especially in maize planted in September or October during the postrera,
the 2nd maize season. During the late 1970s, reports of the disease
extended to dry interior valleys, especially the Valle de Sebaco, Dario,
Terrabona, and Pueblo Nuevo.
AMERICAN ENTOMOLOGIST
•
Winter 1996
In 1978 maize farmers (192) in 4 major maize-producing regions
of Nicaragua were asked to identify D. maidis, whether they considered the insect a pest, and if they used pesticides to control the insect
(Van Huis et a!. 1982). Although almost half of the farmers on the
Pacific Plain (49%) could identify the pest, only 12% considered it a
pest and only 5% applied insecticides for its control.
Changes During the 1980s. The following account of the changes in the importance of achaparramiento is pieced together from our
own experience in Nicaragua from 1986 to the present, from a few
documented accounts, and from scientist and farmer opinions. As is
often the case in a sudden crisis, documentation lags significantly
behind the developing situation.
In 1985, achaparramiento was reported on a large scale for the
first time from the interior of the country, not only in the dry valleys
but also from the northern interior (Matagalpa and Jinotega), a
mountainous region with greater rainfall (800-2,000 mm/yr) and a
shorter dry season (1-3 mol (Urbina 1987) than the Pacific Plain.
During 1986, achaparramiento produced the greatest losses up
to that time. The areas affected included virtually all the maize-growing regions of Nicaragua, from the dry Pacific zones to the humid
northern interior. Also, in 1986, for the first time, great losses were
reported during the primera, the 1st growing season (May to September). Because of the severity of the problem, the Ministry of Agriculture carried out its 1st and only quantification of achaparramiento
damage to maize (Urbina 1987). Yield losses of 100% on 18,900 ha
of maize were reported, as were partial losses on an additional 8,78 3
ha. The total production lost was 26,768,000 kg of maize, an 11 %
reduction in national output (Table 1). Yield losses to achaparramiento were severe again in 1987 and 1988 but were not documented.
By 1989, the opinions of farmers on achaparramiento and D.
maidis had changed considerably. In a survey of 373 farmers carried
out in northwestern Nicaragua (Departments of Leon and Chinandega), 82% of maize farmers said that D. maidis was a pest of
maize; 27% said it was the most important maize pest and 47% said
it was the 2nd most important maize pest, after the fall armyworm
Spodoptera frugiperda (1. E. Smith). Thirty-one percent of the farmers applied insecticides most often against D. maidis. Seventy-four
percent of the farmers considered :;lchaparramiento to be the most
important disease of maize (A.J.H'1 unpublished data).
In 1990, yield losses were greatly reduced. By 1991, there were
few reports of achaparramiento and no reports of significant yield
loss. Furthermore, the percentage of farmers who considered D.
maidis to be the worst problem in maize dropped from 27% at the
height of the epidemic to 10% in 1992 (Fig. 1). By 1993, farmers
who during the achaparramiento epidemic years had abandoned
higher-yielding but highly susceptible hybrid varieties of maize, began to plant them again on the Pacific Plain.
Table 1. Area of partial and complete maize yield loss, and
production lost because of achaparramiento in Nicaragua in 1986 (data
from Urbina 1987)
Region
Partial losses,
ha
100% losses,
ha
Lost production
thousands of kg
Pacific North
Pacific Central
Interior North
Interior South
Total rainy season
Irrigated maize
3,513
703
703
2,811
7,729
1,054
3,724
0
7,096
7,377
18,197
703
6,127
273
10,250
5,959
22,609
4,159
Total for year
8,783
18,900
26,768
AMERICAN ENTOMOLOGIST
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Winter 1996
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(f)
a:
w
:z:
a:
20
c:(
u.
u.
o
10
o
1989
1990
1991
1992
YEAR
Fig. 1. Percentage of maize farmers on the Pacific Plain of Nicaragua
who considered D. maidis to be the most important pest of maize. Data
are from farmer surveys (A.J.H., unpublished data).
As we write this article in 1995, few farmers feel that achaparramiento in an important problem, and few are applying pesticides
for D. maidis. Also, achaparramiento is no longer given high priority by government policy makers, researchers, or extension specialists.
Explanations for the Epidemic
What happened in Nicaragua to make achaparramiento the
greatest biological constraint to maize production during the mid1980s and then cause it to decline to insignificant levels even more
quickly? We asked a series of 3 questions in an attempt to disentangle possible changes in the ecological interactions between pathogen, vector, and host plant populations. First, did farmers switch to
different maize varieties, thereby effecting a change in the pathogen
transmission rate or in the expression of symptoms of achaparramiento? Second, was the achaparramiento epidemic caused by an
increase in the number of D. maidis vectors? Did D. maidis populations suddenly increase and then decline? Or, third, was the epidemic the result of increased incidence of the pathogens in the system,
especially during bottleneck dry months?
Maize Varieties. Researchers in the government-financed National Basic Grains Program worked throughout the early 1980s to
develop open-pollinated, locally adapted varieties of maize tolerant
to achaparramiento. The work intensified in the early 1980s, and
the 1st tolerant varieties were available for sale in 1985. The basis of
the tolerance is not understood clearly and numerous studies indicate that all varieties attract and maintain similar numbers of vectors (Obando 1986, Turley 1989).
In 1978, 65% of small maize farmers in Nicaragua always planted seed saved from previous planting cycles (Van Huis et a!. 1982),
and these traditional varieties demonstrated high susceptibility to
achaparramiento. One percent of the farmers always used improved open-pollinated varieties and 5% always used hybrids (Van
Huis et a!. 1982). Despite the introduction of tolerant varieties in
1985, the greatest expression of achaparramiento symptoms occurred the following year.
By 1989, 79% of small maize farmers who were organized in
cooperatives in northwestern Nicaragua bought achaparramientotolerant seed. Only 13% continued to use their traditional, susceptible varieties (A.J.H., unpublished data). The rapid adoption rate,
after 1 yr of introduction, was facilitated by the vertical integration
249
of the government research program with its extension program
and rural credit bank and by the organization of farmers in cooperatives; it was further motivated by high losses to achaparramiento.
The decline of achaparramiento
in the late 1980s was correlated
with the adoption of tolerant varieties. However, after being widely
used for 3 yr, the achaparramiento-tolerant
varieties are no longer
planted except in limited areas. New government policies beginning
in 1990 removed subsidies to purchase seed and privatized the state
seed company, which opted to produce low quantities of tolerant
varieties. The tolerant varieties were now difficult to locate and more
expensive and, as a result, most small maize farmers began saving
their own seed again. Although much of this seed was at first tolerant, experience with the acha parramiento-tolerant
varieties revealed
that they quickly lost tolerance when outcrossed (R.O., unpublished data). Larger scale farmers switched to hybrid varieties.
Despite the resurgence of susceptible varieties, the incidence of
achaparramiento
has remained economically insignificant through
1994. We conclude, therefore, that the changes in varietal use that
occurred in the 1980s may partially explain the initial decline in the
incidence of achaparramiento
but cannot explain why it has stayed
low nor why the mid-1980s surge occurred in the first place.
Dalbulus maidis Populations Levels. Was the achaparramiento
epidemic caused by a rapid increase in vector numbers? Although
no systematic measurements
of D. maidis population
levels over
time have been made in Nicaragua, a series of unrelated studies with
similar sampling methodologies
were conducted on D. maidis between 1980 and 1991. We examined those studies conducted within
a 2 km radius of Managua and the Sebaco Valley to determine
whether vector population
levels rose or remained constant during
the decade. These 2 areas reported high achaparramiento
incidence
and maize yield loss during the epidemic.
For each study, we recorded the date of planting the date of peak
infestation, the peak D. maidis population (individuals per plant),
and the range of D. maidis numbers per plant recorded during sampling done between 10 and 30 d after planting. All studies used similar sampling procedures: visual examination
of individual maize
plants during early morning hours when D. maidis is sedentary
(Power 1987).
Dalbulus maidis numbers did not increase noticeably in 19861987, when the incidence of achaparramiento
increased dramatically (Table 2). In fact, the 4 studies carried out in Managua during
those years had lower maximum and range of D. maidis individuals
per plant than did studies conducted before and after the epidemic.
We conclude that D. maidis populations did not increase in the mid1980s and, therefore, a vector population explosion could not have
been the primary cause for the achaparramiento
epidemic.
During the achaparramiento
epidemic, there were massive information campaigns carried out in the mass media and by extension
agents and pesticide companies. The campaign taught farmers that
D. maidis is the vector of the pathogens of achaparramiento.
The
campaigns were successful; within a few years, most farmers understood the essential biology, could identify and name D. maidis, and
applied pesticides against it.
Increased Pathogen Incidence in a Dry Season Reservoir. What
changed abruptly in the mid-1980s was host plant availability for
D. maidis during the dry months. A host-plant bottleneck (Larsen et
aI1992, Ebbert and Nault 1994) that reduced the pathogen population every year in the dry season from December to April was widened and rainy season maize crops apparently were exposed to a
higher percentage of pathogen-carrying
insects entering the fields.
Beginning in 1983, the Nicaraguan
government
undertook
a
policy of promoting maize production during the dry season on the
Pacific Plain. This policy, part of a formal contingency plan, was
aimed at assuring the country adequate supplies of basic grains for
urban centers at a time when war in the interior of the country made
production and transportation
of grains difficult.
The contingency plan subsidized seed, fertilizers, machinery, and
pesticides for basic grain farmers on the Pacific Plain and installed
center-pivot irrigation systems and subsidized the energy to run
them. The government also guaranteed a purchase price for all basic
grains produced. Irrigation permitted a 3rd growing season in this
region of Nicaragua, during the dry season of December to April.
For the first time in Nicaragua, maize was grown during the dry
season on the Pacific Plain on a large scale. From a few hundred
hectares grown in 1983, maize production under irrigation grew to
10,276 ha by 1986, representing
14% of the maize production in
the area (Fig. 2). Irrigated maize planting was staggered throughout
the dry season and, therefore, maize plants of all ages were available
continuously for D. maidis to colonize.
But beginning in 1989, and accelerating after the elections of
1990, government policies changed dramatically. Subsidies to energy, pesticides, fertilizers, seed, and credit were eliminated, as were
Table 2. D. maidis infestation levels in maize from 1982 to 1991 extracted from 9 experiments done in Managua and the Sebaco Valley,
Nicaragua.
Location
Study
Planting date
DAP max
infestation
reached
Max D. maidis
per plant
Range D. maidis
per plant (10-30 DAP)
Managua
5-10
1-3.5
0.5-3.5
21
15
30
10
3.5
3.5
2
5
23
7.6
Sept. 1982
23
3.5
1-3.5
June 1988
Sept. 1987
20
Power 1987
Turley 1989
Perfecto and Sediles 1992
Perfecto 1990
Sediles 1989
Rios 1991
Valle 1992
Sept. 1982
July 1986
Aug. 1986
Sept. 1986
Nov. 1987
Aug. 1989
July 1991
20
30
25
Power 1987
Sveinhaug and
Jorgensen 1988
Hruska 1995
2
2-5
12-23
1-7.6
Sebaco
2
9
3-9
DAP, days after planting
250
AMERICAN ENTOMOLOGIST
•
Winter 1996
12000
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manuscript. The work was financed, in part, by the Norwegian Ministry
of Development Cooperation.
10000
References Cited
l'll
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.......
-•..
8000
"0
Q)
Ul
Q)
>
6000
l'll
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4000
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•..
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«
2000
o
1983 1985 1986 1987 1988 1990 1991 1992
YEAR
Fig. 2. Area of irrigated maize (hectares) harvested on Pacific Plain of
Nicaragua 1983, 1985-1988, 1990-1992.
guaranteed prices for maize (Hruska 1990). Irrigated maize production declined to 655 ha in 1990. The rise and decline of irrigated dryseason maize correlates
well with the rise and decline of
achaparramiento
as a problem in Nicaragua.
Interestingly, 10,276 ha of dry-season maize apparently were not
enough to significantly alter the number of D. maidis that dispersed
into rainy season maize nationwide.
However, the percentage of
pathogen carriers within the D. maidis population must have been
high enough to cause a major increase in pathogen transmission to
rainy season crops. The results of this study suggest that the numbers of D. maidis entering a field at the beginning of the crop cycle are
not as important as the percentage of carriers in determining the levels of achaparramiento
the farmer will experience. This conclusion is
supported by Power's (1988) studies in which she found no significant correlation between the numbers of D. maidis present in a crop
and the incidence of achaparramiento.
During the 1980s, the national maize research program dedicated most of its resources to developing and distributing locally improved open-pollinated
maize varieties that were tolerant
of
achaparramiento.
The cost of devoting scarce human, material, and
financial resources to trying to solve a created problem can be extremely high in undeveloped countries such as Nicaragua. Unfortunately, the root causes of a sudden phytosanitary
problem usually
are not obvious immediately, nor are they avoidable, and, as in the
case of the achaparramiento
epidemic, resources often are spent on
remedial solutions.
In conclusion, roller-coaster levels of achaparramiento
in Nicaragua apparently was caused ultimately by political and economic decisions. In the 1980s, the Nicaraguan government faced a complex
set of political problems, including a rapidly declining economy and
civil war. It responded by trying to boost maize production
and
availability to the urban population on the Pacific Plain by promoting planting during a normally maize-free time of year. Consequently, the government
implemented
policies that reduced ecological
constraints on a pest/pathogen/plant
system and, ironically, served
to threaten maize production entirely.
Acknowledgments
We thank L. R. Nault (Ohio State University, Wooster), F. Gould, G.
G. Kennedy, J. R. Bradley, Jr., and T. Riggin Bucci (all of North Carolina
State University, Raleigh) for their helpful comments on drafts of the
AMERICAN ENTOMOLOGIST
•
Winter 1996
Alivizatos, A. S. 1983. Acquisition in vitro of corn stunt spiroplasma by
the leafhopper Dalbulus maidis Ann. Inst. Phytopath. Benaki 14:
101-109.
Anaya Garcia, M. A. 1975. Determinacion del periodo minimo y optimo
de inoculacion necesaria para que el vector Dalbulus maidis transmita
el patogeno causante del achaparramiento del maiz. SIADES (El Salvador) 4: 9-14.
Ebbert, M. A., and L. R. Nault. 1994. Improved overwintering ability in
Da/bu/us maidis (Homoptera: Cicadellidae) vector infected with
Spirop/asma kunkeli (Mycoplasma tales: Sprioplasmataceae). Environ. Entomol. 23: 634-644.
Hruska, A. J. 1990. Government pesticide policy in Nicaragua: 19851989. Global Pestic. Monitor 1: 3-5.
1995. Reducing insecticide use among resource-poor maize farmers in
Nicaragua. Ph.D. dissertation, North Carolina State University, Raleigh.
larsen, K. J., L. R. Nault, and G. Moya-Raygoza. 1992. Overwintering
biology of Da/bu/us leafhoppers (Homoptera: Cicadellidae): adult
populations and drought hardiness. Environ. Entomol. 21: 566-577
Litzenberger, S. c., and J. A. Stevenson. 1957. A preliminary list of Nicaraguan plant diseases. U.S. Dep. Agric. Plant Dis. Rep. 243: 19.
Nault, L. R. 1980. Maize bushy stunt and corn stunt: a comparison of
disease symptoms, pathogen host ranges, and vectors. Phytopathology 70: 659-662.
1985. Evolutionary relationships between maize leafhoppers and their
host plants, pp. 309-330. In L. R. Nault and J. G. Rodriguez [eds.],
The leafhoppers and planthoppers. Wiley, New York.
Obando S. R. 1986. Dimlmica poblacional de Da/bu/us maidis (DeL. &
W.) en siembras de maiz con riego, febrero-junio de 1985. XXXII
Reunion Anual del Programa Cooperativo Centroamericano para el
Mejoramiento de Cultivos Alimenticios, San Salvador, EI Salvador.
Perfecto, I. 1990. Indirect and direct effects in a tropical agroecosystem:
the maize-pest-ant-system in Nicaragua. Ecology 71: 2125-2134.
Perfecto, I., and A. Sediles. 1992. Vegetational diversity, ants (Hymenoptera: Formicidae), and herbivorous pests in a neotropical agroecosystem. Environ. Entomol. 21: 61-67.
Power, A. G. 1987. Plant community diversity, herbivore movement, and
an insect-transmitted disease of maize. Ecology 68: 1658-1669.
1988. leafhopper response to genetically diverse maize stands. Entomol. Exp. Appl. 49: 213-219.
Rios Gonzalez, R. 1991. Parasitoides de huevos de Dalbu/us maidis (Delong & Wolcott) (Homoptera: Cicadellidae) en el cultivo del maiz
(Zea mays) en eI departamento de Managua, Nicaragua. Agricultural Engineer Thesis, Universidad Nacional Agraria, Managua, Nicaragua.
Saenz, L. 1971. Dimimica poblacional de Da/bu/us maidis (Del & W.), el
achaparramiento del maiz en Nicaragua y una posible solucion: variedades tolerantes. Agricultural Engineer Thesis. Escuela Nacional de
Agricultura y Ganaderia, Managua, Nicaragua.
Salazar, A. 1964. EI cultivo del maiz en Nicaragua. Estacion experimental "la Calera", Ministerio de Agricultura y Ganaderia, Managua,
Nicaragua.
Sediles, A. J. 1989. Efecto de densidad de siembra y malezas sobre el nivel
poblacional de Dalbu/us maidis (Del & W.) en dos variedades de
maiz en Nicaragua. Agricultural Engineer Thesis, Instituto Superior
de Ciencias Agropecuarias, Managua, Nicaragua.
Shurtleff, M. C. [ed.]. 1980. Compendium of corn diseases, 2nd ed. American Phytopathological Society.
Sveinhaug, T., and M. Jorgensen. 1988. Corn stunt and maize bushy stunt
disease: population levels of the vector Da/bu/us maidis (Homoptcra:
Cicadellidae), and incidence of the diseases in six maize varieties at
four locations in Nicaragua. M.S. thesis, Agricultural University of
Norway.
Turley, F. 1989. Biologia y control de la chicharrita del maiz Da/bu/us
maidis (DeL. & W.) (Homoptera: Cicadellidae) el vector del achapar251
ramiento de maiz. Final Report, Ministerio de Desarrollo y Reforma
Agraria/Centro Nacional de Proteccion Vegetal.
Urbina Algabas, R. 1982. Evaluacion de variedades experimentales de
maiz resistentes al achaparramiemo, en tres epocas de siembra en dos
localidades de Nicaragua. Memoria de la 28 Reunion Anual del Program a Cooperativo Centroamericano para eI Mejoramiento de Cultivos Alimenticios. San Jose, Costa Rica.
1987. Incidencia y efectos del achaparramiento en la produccion del
maiz en Nicaragua. Program a Nacional de Investigacion de Maiz,
Centro Nacional de Granos Basicos-Ministerio de Desarrollo y Reforma Agraria.
Valle Gomez, N. A. 1992. Effect of tillage system and presence of weeds
on the abundance of Dalbulus maidis DeLong & Wolcott (Homoptera: Cicadellidae) and the incidence of stunt disease in maize.
M.S. thesis, Swedish University of Agricultural Sciences. Uppala.
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Wageningen. 82-6.
Allan J. Hruska is head of the Department of Crop Protection,
and Sarah M. Gladstone is associate professor of applied ecology,
both at the Pan american Agriculture College, Zamorano, Honduras. Allan's research interests include sustainable pest management practices among resource-poor farmers, including yield loss,
extension methods, program implementation,
monitoring, and
evaluation, and the effects of policy environment on farmers' decisions. Sarah's research interests include the biological and microbial control of agricultural and forest pests in tropical America. She
worked for 10 years on teams developing IMP programs for maize,
cotton, cucurbits, and sugar cane in Nicaragua. Her new interests
include involving neighboring producers in new pest management
ideas for coffee, bananas, and vegetables on her farm in Nicaragua. Rafael Obando is an entomologist with the Basic Grains Division of the Instituto Nicaragiiense de Tecnologia Agropecuaria. He
has over 20 years experience in maize pests in Nicaragua.
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