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English :
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A screening of occluded viruses of certain lepidopterous cotton pests in Egypt, with a special reference to cutworms
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Arabic :
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تتبع لفيروسات مغلفة على آفات القطن من حرشفية الأجنحة فى مصر مع إشارة خاصة للديدان القارضة
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| Abstract |
Summary
A screening of occluded viruses of certain lepidopterous cotton pests in Egypt, with a special reference to cutworms
The present investigation is an attempt to follow up the mortalities among natural population of cutworms (Agrotis spp) and bollworms (Pectinophora gossypiella_(Saund.) and Earias insulana) in Egypt. The screening was aimed to isolate pathogenic occluded viruses. The cutworms (A. ipsilon and A. segetum) were subjected to susceptibility tests using 5 isolates of nuclear polyhedrosis virus namely: A. segetum NPV (England), A. segetum NPV (Poland), A. californica NPV, H.armigera NPV and S. littoralis NPV.
The obtained results can be summarized in the following: 6.1. Cutworms and Their Natural Mortalities
A total number of 1047 Agrotis spp. were collected during 1985/1985-1986. The dominant species A. ipsilon comprises 1000 individuals, of which 46.3% were larvae. Collected larvae were reared in the laboratory until population and adult emergence, where mortalities amongst larvae and pupae were recorded and inspected to determine the cause of death. The occurrence of larval and pupal mortalities recorded 29.1% and 33.1%, respectively. Among larval mortality, 39.5% did not express any signs of pathological disorder, while 60.5%, resembled different signs ranging from soft bodies to dried or momified. The smear tests indicated that, bacterial cells and spores were found in the cadvers of 45.4% of dead larvae and did not reveal any detectable occluded viruses. The infection tests, using suspect larvae, were carried out on the 2"d - 3`d instar test larvae. The present study recorded the presence of non¬occluded virus particles in A. segetum of size 30 nm. The screening of
pathogenic occluded virus did not lead to virus isolation, but does not rule out the possibility of virus presence at a vary low level.
6.2. Bollworms And Their Natural Mortalities
A total of 307 Earias insulana larvae were collected, during 1984/1986. Collected larvae were reared in the laboratory until pupation and adult emergence, where emortalities amongst larvae and pupae were recorded to determine the cause of death. Larval and pupal percentage of mortality was 37.5% and 11.7%,.respectively. Bacterial cells observed in diseased larvae were found in 75.7% of dead larvae, while 2.6% contained microsporidia. The smear tests of resulted dead larvae, had not revealed any occluded virus. The infection tests, using suspect larvae, were carried out on the 3 rd instar test larvae.
P. gossypiella was represented by 3087 collected larvae, of which the rate of natural mortality was 31.1%. A wide range of symptoms was observed; 9.4% explosed larvae, 2.9% v-shaped, 5.1 % swollen bodied, 76.6% soft bodied and 3.6% dried larvae. Bacterial cells were frequently observed in 66.7 of dead larvae. The smear test of resulted dead larvae, had not revealed any occluded virus. The infection tests, using suspect larvae, were carried out on the 3`d instar test larvae, and, again, no virus had been recovered. The present negative results has been discussed in conjunction with previous reports in Egypt.
6.3. Susceptibility of Agrotis spp., to certain nuclear polyhedroses viruses
6.3.1. Present investigation developed a modified bio-assay technique which proved reliability and simplicity, when compared to other techniques. Detailed description of the modified technique as well as its efficiency are presented.
6.3.2. Agrotis ipsilon:
Among the tested NPVs, A. ipsilon 2"d instar larvae (5 -day old) proved susceptible to infection induced by AsNPVE, HaNPV and AcNPV. The calculated LDS0 values, are 4.4 X 104, 105 and 6.7 X 105 PIB's/larva for AsNPVE, HaNPV and AcNPV. The difference in LD between the three virus candidates is probably insignificant. The susceptibility of A. ipsilon larvae to AsNPVE is reported, for the first time, in present study. A conelusion has been made that AsNPVE may be as efficient as AcNPV in field application.
6.3.3. Agrotis segetum:
Among the tested NPVs, A. segetum 2"d instar larvae (5-6 day¬old) proved susceptible to infection induced by AsNPVE, HaNPV and AsNPVP. The calculated LDso values, were 6.2, 2.7 X 103 and 3.4 X 105 PIB's/Larva for AsNPVE, HaNPV and AsNPVp, respectively. Thus, A. segetum expressed a reasonable rate of susceptibility towards HaNPV. The bioassay test also showed that the AsNPVE achieved a relatively high rate of mortality at a very low dose (1.7 X 102 and 1.7 PIB's/larva induced 66.6% and 44% mortality, respectively). Therefore, AsNPVE, seems also a very efficient disease agent against A. segetum while, AsNPVP was significantly less infective on 2"d instar larvae than AsNPVE . The considerable high rate of A. segetum susceptibility to AsNPVE, suggests the importance of this particular isolate as a biocontrol agent.
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| Publication year |
1988
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| Availability location |
معهد بحوث وقاية النباتات - ش نادى الصيد - الدقى
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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:
كلية الزراعة -جامعة القاهرة
Place:
كلية الزراعة -جامعة القاهرة
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| Author(s) from ARC |
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| Agris Categories |
Pests of plants
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AGROVOC
TERMS |
Agrotis.
Agrotis ipsilon.
Agrotis segetum.
Earias insulana.
Pectinophora gossypiella.
Viruses.
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| Publication Type |
Master Thesis
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