النشر العلمي

  • morphological and molecular identification of some indigenous fruit fly species in Sennar State, Sudan

Fruit flies (Diptera:Tephritidae) are among the major constrains in commercial horticultural production in many African countries. DNA barcoding was used in this study to obtain quick and precise identification and to confirm the morphological identification of fruit fly specimens. Yellow sticky and Dome traps were used to collect some specimens from Sennar State whereas other specimens were reared under laboratory conditions at University of Gezira, from infested fruits. DNA from different specimens was extracted using the NucleoSpin® Tissue method. Three DNA fragments with sizes of 340, 220 and 280 bp. (base pairs) were recognized using specific primers and amplified from the 5’ region of the cox1 gene from the mitochondrial DNA to give a full barcode of 660 bp. Then, purified PCR products were subjected to sequencing reactions using the BigDye Cycle Sequencing Kit. The nucleotide sequences were aligned using the cluster W algorithm included in the Bioedit 7.0 software package. Sequence divergences were determined using similarity index (P-distance model). Morphologically, six fruit fly species, namely B. invadens, B. cucurbitae, C. cosyra, C. quinaria, D. ciliatus and D. longistylus were identified. The molecular phylo-genetic tree of the Sudanese fruit flies was established by sequencing of 12 specimens representing five fruit fly species at the mitochondrial cytochrome oxidase cox1 gene fragments. The  morphological identification of the fruit fly specimens was confirmed by molecular identification. Although B. invadens is a highly variable species, specimens of the same species collected using yellow sticky traps, methyl eugenol and those reared from magad fruits (wild plant belonging  to the family Cucurbitaceae) appeared to have the same or with a little variation (0.7%) in the DNA sequences cox1 fragments. D. ciliatus and B. cucurbitae appeared in separate clusters, with no variation among sequences of their specimens. The three common fruit fly genera: Bactrocera, Ceratitis and Dacus exhibited low intra-specific variation compared with that between inter-species in the amplified sequences.

published in Gezira Journal of Agricultural Science, Volume 10 (1): 91-104.

  • Evaluation of Various Insecticides on the Cotton Whitefly, Bemisia tabaci (Genn); Population Control and Development of Resistance in Sudan Gezira

The effects of endosulfan (chlorinated hydrocarbon), deltamethrin (pyrethroid) and chlorpyrifos (organophosphate) on the control of the cotton whitefly, Bemisia tabaci (Genn), were investigated during the 1989\1990 season with five applications in the field. The results indicate that endosulfan was a more effective insecticide than chlorpyrifos. However, the three pesticides did not perform well, as they did not decrease the pest population below the Economic Threshold Level (ETL) (i.e. 200 adults/100 leaves). The decreasing efficacy of the three insecticides, with increasing application, suggest the presence of multiple resistance in the Sudanese cotton whitefly B. tabaci in the Sudan Gezira. The result showed that the rate of resistance development increased with the increased intensity of selection i.e. the magnitude of the population exposed to insecticide and the population killed. The results show that pesticide application did not significantly enhance the grade quality of the cotton.

published in Resistant Pest Management Newsletter Vol. 15, No. 2 (Spring 2006)

  • Insecticide resistance status in Anopheles spp in Blue Nile State (December 2012 – May 2013)

During 2012-2013, a network for the monitoring of insecticide resistance was set up in the Blue Nile state to assess the insecticide resistance status of the major malaria vectors in Damazin - Rosaries - Geissan. Bioassays were performed on adult mosquitoes using the standard WHO susceptibility test with diagnostic concentrations of permethrin 0.75%, deltamethrin 0.05%, bendiocarb 1% and DDT 4% to determine if pesticide resistance had been developing in local mosquito populations. After using procedures developed by WHO, the results collected from areas serviced by our adulticide program were presented. After three months of intense insecticide resistance monitoring a clear picture of insecticide resistance status of malaria vectors was achieved. In Geissan, Damazin and Rosaries insecticide resistance in the malaria vectors An. arabiensis was almost present. According to the WHO criteria for characterizing insecticide susceptibility; in the present study the An. arabiensis was found to be resistant to DDT 4% in two areas, Damazin 78.4% and Rosaries 81.6%, and found to be tolerant in Geissan 94.4%. The status of pyrethroid (deltamethrin and permethrin) tested, the exposed An. arabiensis from two study area (Damazin and Rosaries) show tolerance, while in Geissan it found to be susceptible the mortality rate is 98%. A unique baseline data on insecticide resistance is now available in the Blue Nile State in three localities, which enable to follow trends in susceptibility status in the whole state and which will serve as basis for further resistance management .

published in Resistant Pest Management Newsletter Vol. 22, No. 2 (Spring/Fall 2013)

  • SUSCEPTIBILITY OF PERIPLANETA AMERICANA L. (ORTHOPTERA: BLATTIDAE) POPULATION FROM WAD MEDANI (SUDAN GEZIRA) TO THREE PUBLIC HEALTH INSECTICIDES

This American cockroach, Periplaneta Americana (L.) (Orthoptera: Blattidae), as a public health pest, did not receive the attention it deserves by the Sudanese researchers. The study was initiated to investigate the susceptibility of this pest to three recommended public health insecticides in Wad Medani town as a representative of the Gezira State cockroach population.
Adults were collected from the sewage at night, topically treated with different concentrations of each insecticide, viz. lamdacyhalothrin, deltamethrin, and pirimiphos-methyl. Results were taken after 24 hr in terms of LC50, LC90, LD50, LD90, the slope of the log -dose probability line (Ldp-line), and the prime resistance (RR'=LC90/LC50).
The results revealed that the adult American cockroach exhibited acceptable levels of susceptibility to all the tested insecticides (LC50
ranged between 0.02 and 11 μg/roach). The prime resistance ratio, i.e. RR' that shows the performance of the LC90 or LD90 compared to that of the LC50 or LD50 revealed that this ratio was as follows: Pirimiphos methyl 1.4x, deltamethrin 1.4x, lambda cyhalothrin 3.2x.
All populations proved to be homogeneous to pirimiphos-methyl (slope=7.93) and deltamethrin (10.62), and heterogeneous to lamda-cyhalothrin (2.45).
Generally, the American cockroach was more sensitive to lamda-cyhalothrin (LC50 = 0.022 μg/roach), and less sensitive to pirimiphos-methyl (LC50 =11 μg/roach); the cockroach tolerated double the dose required from lambda-cyhalothrin when treated with deltamethrin (LC50 =0.04 μg/roach).

published in Resistant Pest Management Newsletter Vol. 19, No. 2 (Spring 2010)

  • Susceptibility of Anopheles species populations collected from four localities in Juba County to DDT and deltamethrin, Central Equatoria State, Southern Sudan

The study aimed to evaluate the susceptibility of Anopheles species to DDT 4% and deltamethrin 0.05%. Mosquitoes were tested for their susceptibility to both insecticides following WHO standards and using test kit provided by WHO. The study indicated that Anopheles mosquito was found tolerant to DDT 4% and deltamethrin 0.05% in Juba County in all mosquitoes collected from the sentinel sites. However, the mosquito species was found tolerant according to WHO criteria where the mortality rate during 24 hrs is less than 98%. The results of the present study showed that the DDT 4% KDT50 to Anopheles species exposure for 1 hr was found 6.7, 1.6, 1.4 and 0.9 minute in Northern Bari payam, Katour payam, Juba payam and Munuki payam respectively. The results of the study showed that the mortality rate after 24 hrs in the sentinel sites selected in Northern Bari payam, Munuki payam, Katour payam and Juba payam was found 98%, 96%, 96% and 97.6% for DDT 4% and 74.7%, 90.4%, 88% and 88.8 respectively, therefore according to
 the WHO criteria all the Anopheline mosquito species found in Juba County seemingly tolerant to DDT 4% and deltamethrin 0.05%.
Keywords: Anopheles species, DDT, deltamethrin, knockdown time, Resistance, Juba County, Southern Sudan

published in Resistant Pest Management Newsletter Vol. 19, No. 2 (Spring 2010)

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