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English :
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Combined effects of certain insecticides and I.G.I's on some stored grain beetles
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Arabic :
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التأثيرات المشتركةلبعض المبيدات الحشرية ومثبطات النمو على بعض خنافس الحبوب المخزونة
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| Abstract |
The Khapra beetle, Trogoderma granarium Everts. and the rice weevil, Sitophilus oryzae (L.) are considered among the most destructive insects to stored grain and grain products. Several methods of insect control have been used for combating them and protecting stored grain and seeds from their infestation. In search for safe & effective pest control agents, much attention has been focused on compounds which disrupt the normal processes of development; as the insect growth regulators, insect growth inhibitors and their combination with certain insecticides.
The present study, therefore, deals with the effect of Pyriproxyfen
(insect growth regulator), Fenpropathrin (pyrethroid insecticide) and Prempt (combination of both toxicants) on certain biological and biochemical aspects of the aforementioned pests. It covered the following points:
1 - Susceptibility tests.
2 - Effect on productivity and biotic potential.
3 - Persistence of toxicants in storage.
4 - Effect on grain germination.
5 - Effect on total haemolymph protein and fractions.
6 - Effect on haemocyte counts and viability.
Following is a summary of the obtained results:
(1) The susceptibility of both insects to the tested toxicants was concentration dependent, i.e. mortality increased by increasing concentration. Based on their LC50 values, in case of khapra beetle larvae (25 days old), Fenpropathrin was the most toxic (6.0 ppm) followed by Prempt (11.5 ppm); while Pyriproxyfen was much less effective (75 ppm). Differences were highly 'significant (P< 0.01). In case of the rice weevil, Fenpropathrin was still more effective than Prempt, but the differences was not statistically significant (P >0.05); their LC50 values were 24 and 29 ppm, respectively. Pyriproxyfen, on the other hand, appeared not toxic to the rice weevil (LC50 > 100 ppm).
(2) Pupation and adult emergence of Khapra beetle larvae fed on toxicant treated wheat kernels were adversely affected. The effect was also concentration dependent. moreover, Pyriproxyfen caused some malformations in treated larvae as well as in pupae and adults emerged therefrom, These included:
a) Decrease in the larval size, particularly at high concentra¬tion. Such larvae lived much longer and failed to pupate.
b) Undifferentiated larval external features; and their failure to free themselves from their skin.
c) Uncleared pupal appearance; and failure to free themselves from larval skin.
d) Production of intermediate pupal - adult stages that also failed to free themselves from the pupal skin.
(3) Treatment of Khapra beetle larvae with LC50's of the tested toxicants increased both larval and pupal durations, but decreased the longevity of produced adults. Fenpropathrin was the most effective, followed by Prempt and then Pyriproxyfen.
(4) The progeny of the rice weevil fed on wheat kernels treated with Pyriproxyfen decreased with increasing concentrations. Adults of the produced F1 generation, however, gave rise to an almost normal F2 progeny when transferred to untreated wheat kernels.
(5) Data on the response of the rice weevil (adults) and the Khapra beetle (25-day old larvae) to wheat kernels treated with the three toxicants and stored for different periods before infestation should that:
a) Pyriproxyfen was the least effective and the least persistent
even at the high concentration.
b) Fenpropathrin and Prempt were much more effective and
persistent even at low concentration, but Fenpropathrin was
somewhat more toxic than Prempt. Their toxic effect
remained high for more than four months.
c) Mortality of both insects was toxicant concentration
dependent during the different exposure periods and after
the different storage periods.
d) Mortality of both insects increased with increased exposure
periods to any of the tested toxicants; but steadily
decreased with increased storage periods of treated kernels.
(6) The three tested toxicants at different concentrations did not show
any significant effect on the germination of treated wheat kernels
even after four months of storage.
(7) Pyriproxyfen and Prempt (at LC50 levels) adversely affected protein
synthesis in Khapra beetle larvae (25 days old), as the total
haemolymph protein considerably decreased than in the untreated
larvae. The former toxicant was much more effective than the later.
Fenpropathrin on the other hand, did not show any significant effect.
(8) Polyacrylamide gel electrophoresis of haemolymph protein of
normal (control) and treated Khapra beetle larvae (25 days old) at
LC50 levels indicated that:
a) Ten different protein bands (1 - 10) were detected in normal
and toxicants treated larvae.
b) Eight protein bands (1, 2, 3, 5, 6, 7, 9 and 10) were recorded in normal larvae.
c) Six protein bands (1, 2, 2, 5, 9, 10) were detected in larvae treated with pyriproxyfen; bands 6 and 7 disappeared.
d) Eight protein bands (1, 2, 4, 5, 7, 8, 9, 10) were detected in larvae treated with either Fenpropathrin or Prempt; bands 3 and 6 disappeared, while bands 4 and 8 appeared. These last two bands were not detected in normal larvae.
(9) Five types of haemocytes could be recognized in the haemolymph of Khapra beetle larvae. They were differentiated on the bases of certain cytological characteristics such as size, shape, nuclear/cytoplasmic ratio, cytoplasmic constituents and staining affinity. These are prohaemocytes, plasmatocytes, granulocytes, spherule cells and oenocytoids.
(10) The three tested toxicants differently affected the differential and total haemocyte counts in treated larvae. Haemocytes viability, however, significantly increased in all treatments (P<0.01).
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| Publication year |
1997
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| Availability location |
معهد بحوث وقاية النباتات
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| Availability number |
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| Organization Name |
Plant Protection Research Institute (PPRI)
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| Country |
Egypt
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| Publisher |
Name:
قسم علم الحشرات -كلية العلوم - جامعة عين شمس
Place:
كلية العلوم - جامعة عين شمس
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| Author(s) from ARC |
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| Agris Categories |
Pests of plants
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AGROVOC
TERMS |
Fenpropathrin.
Insect growth regulators.
Insecticides.
Sitophilus oryzae.
Stored products pests.
Trogoderma granarium.
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| Publication Type |
Master Thesis
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