Egg parasitoids of the corn leafhopper, Dalbulus maidis (Delong and Wolcott) (Homoptera: Cicadellidae) in Nicaraguan maize

4 Pages·1994·1.1 MB·

PROC. ENTOMOL. SOC. WASH.
96(1). 1994. pp. 143-146
EGG PARASITOIDS OF THE CORN LEAFHOPPER,
DALBULUS MAIDIS (BELONG AND WOLCOTT)
(HOMOPTERA: CICADELLIDAE) IN NICARAGUAN MAIZE
Sarah M. Gladstone, Alba de la Llana, Raquel Rios,
AND Lissette Lopez
Escuela de Sanidad Vegetal, Universidad Nacional Agraria, Managua, Nicaragua.
Abstract.—Jv^o species of parasitoids were reared from eggs of the com leafhopper,
Dalbithis luaidis (DeLong and Wolcott), collected in experimental maize plots in the
Department of Managua, Nicaragua. Anagnis sp. (Hymenoptera: Mymaridae) and Par-
acentrobia sp. (Hymenoptera: Trichogrammatidae)were identified from individually reared
eggs in approximatelyequal numbers. Peak emergence ofAnagnissp. occurred seven days
afterpeakemergence ofParacentrobia sp. The combined rate ofparasitism was 77%when
host egg density reached its maximum at 22 days after plant emergence (DAE) and 93%
by 36 DAE when egg densities had declined.
Key Words: Egg parasitoids, com leafhopper, Dalbiiliis maidus, Cicadellidae, Anagrus,
Paracentrobia. Trichogrammatidae
As a plant pathogen vector, Dalbulns nymphs ofD. maidis as reviewed by Vega
maidis (DeLongand Wolcott) (Homoptera: and Barbosa (1990) include predators such
Cicadellidae) causes severe yield losses in asspiders, coccinellidsandants, twospecies
maize (Zea mays L.) grown in some eco- ofentomopathogenic fungi and two species
logical zones of Central America, Mexico ofparasitoids. Todate, themortality factors
and the Caribbean. Populations ofD. mai- ofthe egg stage ofthis important pest have
dis can reach densities ofup to 30 individ- not been studied.
uals per maize plant in the latter part ofthe A search for egg parasitoids ofD. maidis
rainy season between September and No- was conducted in the Centro Nacional de
vember (personal observation). Investigacion de Granos Basicos "Hum-
Because maize is grown chiefly by re- bertoTapia Barquero," Department ofMa-
source-poor farmers, research efforts on the nagua,Nicaraguainmaizegrownintherainy
management of D. tnaidis and the patho- season of 1989. The study site is at 60 me-
gens it vectors have focused on inexpensive ters above sea level, a seasonal deciduous
methods such as resistant maize varieties forestzonenowconvertedtotheproduction
(Urbina 1982), cultural methods including ofbasicgrainsand cattleranching. The area
varietalmixtures(Power 1987)andplanting has a five to six month dry season and an
densities and weed management (Power average of 1200 mm of rainfall from May
1989,Sediles 1989), microbialcontrol(Qui- through November.
roz 1991), rationalization ofinsecticide use
Materials and Methods
(Gomez 1989) and parasitoids and preda-
tors(Perfecto 1989, Vegaand Barbosa 1990, Weexaminedeggscollectedfrom fourex-
Vega et al. 1991, Quezada 1979). The nat- perimental plots ofeach ofthree maize va-
ural enemies known to affect adults and rieties (NB-6, NB-12, and H-5). A total of
—
N-4 PROCEEDINGS Ol IIIL LN lOMOLOGKAL SOC ILn 0\ WASIUNUION
—
70 -° Anaarus sp.
-^ Paracentrobia sp.
60 -
Q
CO
•H 50
u
-rH
a>
<0 40
u
re)
Ck4
30 -
dP
20 -
10 ~i
1 2 3 4 5
Days after plant emergence
Fig. 1. Emci'gtMKc o( AHii\;nis sp. and Panwenlrobia sp. tVoni Piilhiiliis maidis eggs collected in niai/c,
IX-partnionl ol'Managua, Nicaragua, 1"^S^>.
6^)0 eggs were collootcd in weekly samples Eggswerelocatedwith alight box,excised
for si\ weeks in .-Kiigust and September of from the leaf with a sharp pin, sterilized
I'-^S'^. Colleetions were made from 10 seed- with 3"o sodium hypochlorite for two min-
lings in eaeh of the 12 plots at 10 and 15 utes, rinsed with sterile water and placed
da>s after plant emergence (D.AE). At 22, individually in small glass vials. The vials
2^, 36 and 43 D.-\E collections were made were capped with rubber stoppers or corks
from thethird unfurled leafbelow thewhorl and a small filter pack wick under the stop-
on 10 plants in each of the 12 plots. The per was used to introduce sterile water to
density ofD. niaidts eggs per m- ofleafwas the Nial to prevent the egg from desiccating.
calculated using a leafarea meter. The eggs were maintained in an air-condi-
On examination with a microscope, mi- tioned laboratory at approximately 24-25
crofilaments were seen on man\ ofthe eggs C. with natural day-length. Slightly more
which later yielded parasitoids. .All species than 50'\) ofthe eggs reared in this manner
o(DliIIhiIus have microfilaments extending eclosed or produced parasitoids. Mortality
from the egg (.Heady and Nault h)84) but ofthe rest was caused principal!) b> fungal
no other species in this genus ha\e been contamination or by desiccation, both con-
recorded from Nicaragua (Power N87). sidered to be a function ofthe rearing con-
Other leatliopper genera also produce mi- ditions.
crohlaments (Heady and Nault h)84) but Samplesofthe parasitoidswere identified
an extensive study of leathoppers in Nica- at the Systematic Entomolog> Laboratory,
raguan maize (Saenz 1971) showed that Plant Sciences Institute, I'SD.X. U.S..-\. and
100"o were D. nuiidls. Given these studies at the Bee Research Laborator\, Plant Sci-
and the fact that only Cicadellid n>mphs ences Institute, USD.A. l'.S..A. Represen-
emerged from the unparasiiized eggs, we tati\e specimens were deposited in the
conclude that the eegs studied were D. niui- United States National Collection and
dis. voucher specimens were placed in the Co-
VOLUME 96, NUMBER 1 145
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300
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PROCEEDINGS OFTHE ENTOMOLOGICALSOCIETY OF WASHINGTON
146
USDA foridenUfyingAnagrussp.Thiswork blaciones de Dalbulus maidis DeLong and Wol-
was supported by a grant from the Nor- cNoatcl.ionAgarlicAuglrtaurriaal. MEangniangeuear.TNhiecsairsa.guUan.iv1e9r9s1i,da3d2
wegian Agency for Development Corpora-
pp.
tion to the Universidad Nacional Agraria, Saenz,L. 1971. ElachaparramientodelmaizenNica-
Managua, Nicaragua. ragua,yunaposiblesolucion: Variedadestoleran-
tes. AgriculturalEngineerThesis. EscuelaNacion-
Literature Cited al de Agricultura y Ganaderia. Managua,
Nicaragua. 1971, 69 pp.
Gomet?'e,stMac.ion1p9o8r9.chEitcehcalmotdaedeplermiaoid/o,sDcariltlincdoussdemmin-- Sedilmesa.lcAz.as1s9o8b9r.e eElfencitvoeldepodbleancsiiodnaadlddeelsiDeamlbbrualuys
dis(DeL.andW.)(Homoptcra:Cicaddlidae)sobre maidis (DeLong and Wolcott) en dos variedades
elrendimienloy la incidcnciadelachaparramien- demaizenNicaragua. AgriculturalEngineerThe-
toenmaiz. AgriculturalEngineerThesis.InsliUUo sis. Universidad Nacional Agraria. Managua, Ni-
Superior de Cicncias Agropecuarias. Managua, caragua. 1989. 39 pp.
Nicaragua. 1989. 38 pp. Urbina. R. 1982. Evaluacion de vanedades experi-
Heady. S. E. and L. R. NauU. 1984. Leafhopperegg mentales de maiz resistentes al achaparramiento
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