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English :
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New approaches to control whiteflies to minimize the use of insecticides and environmental pollution.
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Arabic :
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الاتجاهات الحديثة لمكافحة الذباب الأبيض للحد من استخدام المبيدات وتلوث البيئة.
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| Abstract |
The first part of the present work was to record, by a general survey, the most abundant whitefly (Homoptera: Aleyrodiae) species from different host plants in several localities in Egypt. Furthermore, a documentation of any associated parasites was carried out. The whitefly species and their parasites were taxonomically identified. Also, their monthly abundance was followed up and recorded in certain cultivated fields not exposed to any chemical control. ,
The second part of this investigation involved the control of the most prevalent whitefly species, namely Bemisia tabaci (Genn.) by means of:
(i) A parasite namely Eretmocerus mundus (Mercet) (Hymenoptera: Aphelinidae).
(ii) Relatively ecologically safe chemicals which included an insect growth regulator, buprofezin and a botanical extract from the neem tree, neem azal (azadirachtin).
From the conducted survey 12 whitefly species were collected and taxonomically verified from specimens at Agricultural Research Center, Plant Protection Research Institute, Cairo.
Only five parasitoids were found concerned with the collected whitefly species. The whitefly species were:
1. Bemisia tabaci (Genn.), the most widespread species on many host plants. Insects were generally found all year round but with a peak in population in August and October. Two parasites were associated with species, Encarsia lutea (Masi) and Eretmocerus mundus (Mercet).
2. Dialeurodes citri (Ashmead), infesting mainly citrus trees. High insect density was observed from June to September: During the course of this study no parasites were detected for this species.
3. Parabemisia myricae (Kuwana), also infesting Citrus sinensis. Insect population was relatively high from August to the beginning
of November. Encarsia lutea (Masi) was the only parasite concerned with this species.
4.Siphonimu.s phillyreae (Hal.), mainly found in Assiut governorate where its major host plant pomegranate is cultivated. The parasite Encarsia inaron (Walker) was the only species detected.
5. Trialeurodes vaporatiorum (Westwood), although not found in great numbers, this species was found to infest other host plants than those recorded in the reviewed literature. Encarsia inaron (Walker) was its only detected parasite.
6. Al.eyrodes proletella (Linnaeus), insects were found in great numbers from February to April on Solamum nigrum. Two parasites were associated with this whitefly species, Encarsia inaron (Mercet).
7. Aleurolobus niloticus (Priesner and Hosny), mainly abundant in Assiut governorate with a peak in population in February Encarsia elegans Masi and Encarsia lutea (Masi) were found on this species.
8. Aleurolobus olivinus (Silvestri). It was collected from olive trees in Fayoum governorate. Highest insect density occurred in April. Encarsia elegans Masi and Eretmocerus mundus (Mercet) were its two parasitoids, although their rate of parasitism was relatively low.
9. Acaudaleyrodes CitYt (Priesner and Hosny) which was mainly detected on citrus trees. This whitefly population density. reached a peak in October to November. Its parasites were Encarsia mineoi (Viggiani) and Eretmocerus mundus (Mercet).
10.Aleurocanthus ziziphi (Priesner and Hosny), insects were found mainly Ziziphus jujuba. Generally, their population was in high numbers from August to December. During the course of this study no parasites for this species were found.
11 Aleyrotuberculatus porosus (Priesner and Hosny), the insects were relativelv abundant in Julv. No parasites were collected for this species.
12. Bemisia qfer (Priesner and Hosuy), this species infested Ziziphus spinachristi. Insects were in slightly higher density in May. At no time parasites were detected.
The efficiency of the parasite Eretmocerus mundus was calculated in suppressing the population of Bemisia tabaci (Genn.). The parasitoid reduced the number of whiteflies and a correlation was found between the host density and percentage of parasitism.
From the study conducted to control the whitefly, Bemisia tabaci (Genn.), different developmental stages by the insect growth regulator, buprofezin and botanical neem extract used either as direct spray or their vapour action the following results were found:
1. Of the immature stages, the last nymphal iustar also known as "pupae" was found to be the most tolerant. The early instars were more sensitive specially second and third instars. The egg stage showed moderate sensitivity. This fact applies to both chemicals tested. When the vapour action was considered, the LC50's for buprofezin were relatively high, which reached 13, 42, 32 and 17 folds more than spray action for egg stage, 1, 2, 3 and last i.nstars, respectively. Similarly, the increase in LC50's for neem seed extract vapour was found to be 35, 33, .31 and 51 folds more than spray action, for the respectively mentioned developmental stages.
2. Experiments conducted in a greenhouse showed that 2 and I m1/L of buprofezin in vapour form caused 29.59 and 21.70%, respectively. Meanwhile, if used as direct spray in the two mentioned respective concentrations, it caused 63.24 and 50.58% reduction in population. Neem at 4 and 2 m1/L. vapour action caused a reduction in B. tabaci population by 24.36 and 19.80%, respectively. This reduction increased to 53.23 and 40.90% when used as a spray in the same respective mentioned concentrations. The vapour action of the two exposed chemicals could be considered together with spray action in a control program. This might be useful in minimizing the use of chemicals. However, the building up of insect resistance has to be considered.
3. When the efficiency of the two tested chemicals, buprofezine and neem seed extract were considered on the parasitoid E. mundus, they showed a remarkable species specific activity. The selective factor for buprofezin was 11.4 and 1.51 folds for the parasitoid pupae when associated with the host B. tabaci 2nd or last nymphal stage, respectively. Meanwhile, when neem azal was tested, it was 5.88 and 3.32 fold for the respective mentioned instars.
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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:
كليه الزراعة-عين شمس
Place:
القاهره-مصر
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| Author(s) from ARC |
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| Agris Categories |
Protection of plants - General aspects
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AGROVOC
TERMS |
Aleyrodes.
Bemisia tabaci.
Citrus sinensis.
Dialeurodes.
Encarsia.
Eretmocerus.
Parabemisia.
Pesticides.
Rationalization.
Trialeurodes vaporariorum.
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| Publication Type |
Master Thesis
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