Possible Synergistic Effect Against The Desert Locust Of A Mixture Of Decis With Water Extracts Of Mucuna Pruriens (Fabacae)

• Abdalla M. Abdalla ¹, Michel Lecoq², M. H. Luong-Skovmand² and S. El Bashir³.
  ⁽¹⁾University of Kordofan, PO Box 160 El-Obeid, Sudan;
  ⁽²⁾Centre de coopération internationale en recherche agronomique pour le développement, Prifas, TA 40/D, 34398 Montpellier Cedex 5, France, France
  E-mail: lecoq@cirad.frý
  ⁽³⁾ Department of Plant Protection, Faculty of Agriculture, University of Khartoum, Shambat, Sudan.

  Abstract

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  A series of concentrations of Decis (3.125, 1.56, 0.78, 0.39 and 0.195g/l) were tested in the lab on the Desert Locust, Schistocerca gregaria, alone and with a fixed concentration (25g/l) of water extracts of roots of Mucuna pruriens. A set of ten 2^nd instar nymphs were treated with each respective concentration using hand sprayer (400 ml). Nymphs sprayed only with water served as control. The treatments were replicated 4-8 times. Knockdown effect was recorded one hour after treatment, while mortality was recorded on hourly basis for the first six hours after treatment and then on subsequent days until complete mortality or transformation into 3^rd instars. At the end, the total mortality was calculated for each treatment. Data was analyzed using Mstat c statistical package applying one way variance analysis. Results revealed significant differences between treatments with Decis, Mucuna and Mucuna/Decis when compared with the untreated control. There were also significant differences between treatments with Mucuna/Decis mixtures and Decis alone. Results show a dramatic increase in the effect of Decis when mixed with Mucuna water extracts (both knockdown and mortality were enhanced). The resulting effect of the two toxic components exceeded the total sum of the effect of the two components used separately, indicating a possible synergistic effect. Thus a low dose of Decis may cause pronounced kill of locust when mixed with an extract of Mucuna. This is beneficial to the environment especially since at such low doses of Decis a less harmful effect would be expected to occur.