The preliminary toxicity screening of 13 plant extracts against Musca domestica
L. adult at 300 and 1000 ppm, revealed excluding both Opuntia vulgaris and
Saccharum spp. which showed very low toxicity even at the higher concentration.
Based on the obtained LD50 values for the eleven ethanolic extracts applied topically
to the house fly adult, the extract of Piper nigrum showed the highest toxicity (LD50
= 0.115 ug/insect), while Punica granatum induced the lowest toxicity (LD50 = 0.278
ug/insect). Toxicity values of the other tested extracts ranged between the above
mentioned values. For the tested insecticides, the LD50 values ranged between
0.00026 ug/insect for methomyl and 0.0013 ug/insect for flufenoxuron. Combining of
11 botanical extracts with 4 insecticides has resulted in 44 binary mixtures; all of
them showed potentiating effects with different degrees. Moreover, mixing the
insecticides at LC0 (a concentration level causing no observed mortality) with the
LC50 of each of the plant extracts have resulted in 44 paired combinations of high
synergistic factor (S.F.). Based on the obtained RC50 values (repellent concentration
for 50% of the tested house flies), the bioassayed extracts could be arranged with
respect to their efficacy as follows: Salix safsaf (0.24 mg/cm2)> Conyza aegyptiaca
(0.25 mg/cm2) > Azadirachta indica (0.28 mg/cm2); followed by 5 extracts of the
same RC50 value; 0.29 mg/cm2 (Cichorium intybus, Citrus aurantifolia, Piper nigrum,
Sonchus oleracues and Zea mays). The results of toxicity against adult stage of
house fly by sugar bait method revealed that the most potent plant extract was C.
aegyptiaca which showed LC50 value of 4.8 ppm, and the lowest one was P. granatum
(LC50 = 10.4 ppm). Compared to the plant extracts, the tested insecticides showed
very high toxicity; where the obtained LC50s equaled to 0.60, 0.64, 0.66 and 0.74
ppm, respectively for deltamethrin, chlorpyrifos, methomyl, and flufenoxuron. The
residual toxicity of the tested plant extracts and insecticides against the adult stage of
M. domestica indicated that C. aegyptiaca possessed the highest t50 and t20 values
(10.6 and 24.8 days, respectively). Dissipation of residual toxicity for the tested
insecticides followed the following descending order: chlorpyrifos > deltamethrin >
methomyl > flufenoxuron. The overall results of the present investigation reveal the
broad-spectrum toxic properties of the tested plant extracts against Musca domestica
adult; findings which may encourage further research on house fly control in tropics
using indigenous plants.