Effects of IGR treatment against insect pests of stored rice in Malaysia
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Date
1980-09
Authors
T. Abdullah, T. Azemah
Journal Title
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Abstract
Four insect growth regulators (IGRl, ZR 512, ZR 515, ZR 7/7
(all 3 possess juvenile hormone (JH) activity) and dimilin (a chitin
inhibitor) were tested against several common insect pests of stored
rice in Malaysia. The lepidopterans, Ephestia cautella (W.) and
Corcyra cephalonica (Staint), and the coleopteram;, Tr-ll>olfum (Kwlalti'IIJII
(Herbst), O:ryzaephiZus szwinamensia(L.), C!'yptoZestes ferrugineus (Staph. J
I
and SitophiZus sp.were exposed 'to IGR-diet admixture. Reduction in the
number of the first generation (F1J adults after initial exposure of
parental adults to treated diet was the basis for the evaluation of the
test compounds. At 10 ppm, ZR 512 and ZR 515 effectively reduced the
F1 adult population by at least 80% in all the species except Sitophilus.
Dimilin was less effective than the IGR with Jll ncl;:lv1ty and f'nllud tc•
supprees the F1 adult progeny in lepidoptera, but was effective against
the coleopterans particularly T. castaneum and C. ferrugineus by
inducing ec~ysial failure. At 10 ppm, ZR 512 and ZR 515 completely
inhibited pupation in E. cautezza~ T. castaneum and c. feY'Y'Uflineus. At
lower concentrations IGR induce~ incomplete eclosion, the formation of
non-viable larval-pupal intermediates and deformed adults in most
species. Particularly in E. cauteZLa and C. cephatonica IGR treatment
induced a ma~ked prolongation of larval stage. Superlarvae were produced
in E. oauteZLa at 10 ppm of ZR 512 and ZR 515. Response appeared to be
dose dependent as no euparlarva was produced at lower concentrations.
Among the species tested, the most and least susceptible species were
T. castaneum and Sitophi~ue sp. respectively. All 4 IGR at 10 ppm reduced
the F1 adult population by more than 99% in T. caataneum1 while in
SitophiZus the reduction was less than 60%.
Adult emergence was also inhibited when last instar larvae of
E. cautella and C. cephalonica were exposed to IGR-treated 'corrugated
cardboard pupation site' or when topically applied with IGR. In both
treatments, IGR induced incomplete eclosion, the formnt:inn nl' lril.tll'H~uli.tl.tJ!i
and deformed adults with poorly developed wings. However, no superlarva
was produced. C. cephaZonica was less susceptible to IGR than E. cautelta.
Similarly topical treatment of newly formed pupae of T. castaneum with
IGR led to the formation of non-viable pupa-adult intermediates and
short-lived deformed adults. Oimilin was ineffective in preventing
adult·emergence in these treatments.
cauteZZa and C •. oephaZonioa reduced egg hatch. ZR 512 and ZR 515, at o. 9
~g/cm2 inhibited egg hatch by more than 75% and 70% in E. oauteZZa and .
C. cephaZonica respectively. Both IGR produced higher ovicidal effect
than either ZR 777 or dimilin.
Disc electrophoresis separation of proteins revealed 11 and 15
distinct bands in the haemolymph of last instar larvae of E. cautella
and C. cephalonioa respectively. 7 esterase bands were detected in both
species. In E. cautella 3 arylesterase, 3 cholinesterase and 1 carboxylesterase
bands were obtained, while in C. cephalonica 4 arylesterase, 2
carboxylesterase and 1 cholinesterase were identified. There was no
marked difference between the haemolymph protein/estrase band patterns of
control and IGR-treated larvae of E. cautella. However, in C. aephalonica
an extra carboxylesterase band was found in the haemolymph of ZR 512- and
ZR 515-treated larvae but not found in control.
The significance of the above observations is discussed in the
light of the insecticidal potential of IGR as pest control agent of
stored commodities.
Description
Keywords
IGR treatment against insect pests , Stored rice in Malaysia