Studies on the Role of the Coleopteran Species Callosobrochus Maculatus Fab., Sitophilus Zeamais Mots. And Tribolium Castaneum Herbst. In The Dispersal of Fungi among Stored Grains of Maize (Zea Mays L.) And Rice (Oryza Sativa L.) And Seeds Of Cowpea (Vigna Unguiculata Walp.) And Bambara Groundnut (Vigna Subterranea L.) Verdc]
Date
1995-12
Authors
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Publisher
University of Ghana
Abstract
Seven Aspergillus species, A . clavatus, A . flavus,
A.fumigatus, A. niger, A . ochraceus, A. sulpl1ureus and A. ustus
have been used to investigate the role of three Coleopteran insect
pests, namely, Callosobrochus maculatus, sitopl1ilus zeamais and
Tribolium castaneum in the persistance and spread of contaminant
fungi among grains of maize (Zea mays) and rice (oryza sativa) and
seeds of bambara groundnut (vigna subterranea) and cowpea (Vigna
unguiculata) . The Aspergillus species were among fungi isolated
from the grains and seeds.
Bambara groundnut seeds on saIe at Kaneshie , La, Madina,
Makola and Mallam Atta markets in Accra district contained species
of Absidia, Aspergillus, Cladosporium, Fusarium, Neurospora,
Paecilomyces, Penicillium and PIll lularia. The dominant genera were
Aspergillus and Penicillium represented by five and [our species,
respectively, and the dominant species were Aspergillus flavus and
Aspergillus niger .
The predominant apecles of rowpea seeds from the same markets
were Aspergillus £lnvus <lnu l'ner:Jlomyces puntonii among 19 species,
and, the dominant genera were Aspergillus, Paecilomyces and
Penicillium . The rest of the genera were Cladosporium, Drecl1s1era,
Epicoccum, Fusarium, Mucor, Neocosmospora, Neurospora, Phoma,
pullularia, Rl1izopus and verticillium.
Aspergillus flavus and Penicillium citrinum were the
predominant spec i es on maize grains from the five markets among 16
contaminant fungal species belonging to the genera Aspergillus,
Fusarium, Mucor, Neocosmospora, Neurospora, Penicillium, Pullularia
and Rl1izopus.
Rice grains had the shortest list of genera. The fungi
belonged to only four genera, Aspergillus, Cladosporium, Mucor and
Penicillium and there were 14 species in all. The most frequently
occurring species >Jere Aspergillus oryzae, Cladosporium herbarum,
Penicillium cl1rysogenum and Penicillium expansum.
Although all the . seven As pergillus species could grow on
insect body leachate agar prepared >J i th leacha te of the three
insect pests, the conidia of some of them could germinate in the
leacha te of only some of the insects. only A. flavus and A.
ocl1raceus condidia germinated in all the three leachates.
Germination of the conidia of all the species occurred , anY>Jay, in
leachates containing extracts of various tissues of seeds (axis of
the embryo , cotyledon and testa) and extracts of grains. Conidia
of all the species germinated in solution of dissolved faecal
pellets of Callosobrochus maculatus, while conidia of 11.. clavatus,
A. ocl1raceus and A . sulplJureus only germinated in the solution of
dissolved faecal pellets of Sitophilus zeamais and conidia of also
three species, 11. . clavatus, A . flavus and A. ochraceus germinated
in the solution of faecal pellets of Tribolium castaneum.
Aspergillus flavus conidia adhering to the bodies of
sitoplJilus zeamais and Tribolium castaneum were transported through
maize grains packed in wide glass tubes. The amount of the conidia
detached as the insects moved depended on the size of the spaces
among the grains and the frequency of contact between the insects
and the grains. s. zeamais lost 87.8, 8~.7 and 76.7 percent of the
original load of conidia as the insects travelled over 100cm
through grains measuring 5.3-8.3 x 4.04-7.3mm, 8.1-10.2 x 6.0-8.2mm
and 9.5-12 . 2 x 7.5-9.5mm, respectively. The corresponding figures
for conidia on T. castaneulll 'vere, 88.5, 87.9 and 82.8 per cent
respectively.
Dead insect bodies were invaded by many fungi despite the
presence of large populations of sur face bacter ia. The colonyforming-
units of bacteria recorded for C. lIlaculatus, S. zeamais and
T. castaneum per ml of suspending medium immediately after death
were 27 . 5 x 10', 281 x 10' and 104.5 x 10' respectively i and six days
later they were 37.8 x 1~, 5.0 x 1~ and zero, respectively. On
the sixth day, Aspergillus flavus was isolated from the bodies of
all the three insect pests. In addition, Aspergillus niger, Mucor
sp., Rhizopus sp. and Trichoderma Viride were isolatC2.cI ·: c_,: from
C. lIlaculatus . , Aspergillus niger and Curvularia sp. from S. zeam~
is and Clasdosporiulll sp. from T. castaneulll.
The mycelium growing in the bodies after death might have
arisen from inoculum either on the surface of the body or in the
gut . For, the gut of the insects had extensive mycoflora.
Fourteen, thirteen and sixteen fungal species were isolated from
the gut of C. maculatus, S. aeolllois and T. castaneum, respectively.
The predominant genera were Aspergillus and Penicillium and five
species, namely Aspergillus £lavus, Aspergillus fumigatus,
Cladosporium herbarum, PellicilliJ.J.m citinum and Penicillium
purpurogenum were isolated from the guts of all the three insect
pests.
Three Aspergillus species red experimentally to the insects
persisted for different lengths of time in the guts. A. flavus was
isolated 6,8, and 5 days respectively, after feeding the insects,
from the guts of C. maculatus, s. zeamais and T. castaneum. The
corresponding survival periods for A . fumigatus were 4,6 and 5 days
respecti vely, and for A. oC/lraceus, 6,4 and 3 days respectively.
It was concluded that products and dead bodies of the insects
would contribute to the persistence of the contaminant fungi and
living insects would be responsible for both persistence and
dispersal of the fungi in stored grains and seeds. Persistence and
dispersal of the fungi could be reduced by measures which control
the insect pest popUlation, by periodic removal of dead insect
bodies especially in comparatively smaller stocks kept i.n the
markets and by exposure of the products to light to drive the
insects to the dark base and discourage the frequent migration.
Description
MPhil. Botany
Keywords
Aspergillus, Coleopteran, Callosobrochus Maculatus