The Insecticidal Effects of Different Neem Formulations and Bacillus thuringiensis sub-sp. aizawai on the Immature Stages of the Greater Wax Moth Galleria mellonella L. (Lepidoptera: Pyralidae)

Abstract

Three experiments were carried out at Shambat in the entomology laboratory of the Department of Crop Protection, Faculty of Agriculture, University of Khartoum in the period from March to August 2003. The main objective of the experiment was to investigate the contact and systemic effect of local neem water extract and two commercial formulations i.e. Celaflor® and NeemAzal-T/S® on the greater wax moth. The effect of the bacterium Bta applied separately and in combination with NSWE was also studied. The first experiment dealt with dipping the fifth larval instar for 30 seconds in three different NSWE concentrations i.e. 25, 50 and 75 g/Litre water, Celaflor® 1,4 and 7 ml/litre water and NeemAzal-T/S® 2,5 and 8 ml/Litre water. This method was followed to study the contact effect on the developing stages (Larva, pupa and adult). In the second experiment, the bee wax was treated with three different concentrations of Bta suspension i.e. 1.1 x 108, 1.1 x 107 and 1.1 x 106 cfu/g. The 2nd and 3rd larval instars were then fed on these treated bee wax. The third experiment investigated the effect NSWE (50 g/L) and Bta (1.1 x 108 cfu/g and 5.7 x 107 cfu/g), applied separately and in combination on the 2nd and 3rd larval instars. The bee wax was dipped for 30 seconds in the different formulations. The results showed that the highest mortality (60%) was obtained in larval stage treated with NSWE. Celaflor® and NeemAzal-T/S® resulted in the highest mortality in pupal stage (66.6%). The results also revealed that treatment of Celaflor® resulted in the lowest emergence percentage of adults (30%) while NeemAzal-T/S® showed little effect. The NeemAzal-T/S® has the highest effect on the longevity of the different developmental stage of the greater wax moth. The longevity of the larval stage was 11 days compared to 5.25 days in the control. The longevity of the pupal stage was 11 days compared to 6.25 days in the control. Adult longevity was 11 days compared to 5.5 days for the control. Celaflor® and NSWE resulted in the lowest duration of the developmental stage. The efficacy of Bta suspension increased with the increase in concentration. The highest mortality (88.8%) was obtained with the concentration 1.1 x 108 cfu/g). The efficacy of NSWE and Bta applied in combination were 21.5% and 37.5% in the first and second experiment respectively. An antagonistic effect was obtained when NSWE 50 g/L and Bta (1.1 x 108 cfu/g) were applied together. However, an additive reaction was gained when Bta (5.7 x 107 cfu/g) was applied in combination with NSWE (50 g/L). The neem seed water extract (50 g/L) and the combined treatment of (NSWE 50 g/L + Bta 5.7 x 107 cfu/g) gave the highest effect (reduction) on the consumption of the treated bee wax. Bta treatment alone resulted in the lowest effect. The different treatments resulted in significant decrease in the weight of larvae compared to the control.