THE EFFECT OF AZADIRACHTIN ON THE MIDGUT HISTOLOGY OF THE LOCUSTS, SCHISTOCERCA-GREGARIA AND LOCUSTA-MIGRATORIA

The effects of azadirachtin on midgut cells of adult Schistocerca greg aria and Locusta migratoria were investigated by both light and electr on microscopy. Pathological effects were seen in both species which co uld be related to dose and time after treatment. The midgut cells show ed a slow necrosis, a rounding up of the cell and swelling of organell es; the nidi were reduced in size and number, the connective tissue be neath the epidermal layer became enlarged with many invading cells/nuc lei and the circular and longitudinal muscles become rounded and swoll en. The pathological effects were closely linked to a loss of feeding, with injections of 5, 10 and 15 mu g/g azadirachtin causing an increa singly rapid onset of the effects associated with an increasingly redu ced food intake. At the highest dose, full histopathological effects w ere seen at 8 hr and death occurred after 3 days. At 1 mu g/g, however , the insects showed midgut disruption and reduced feeding by day 3 po st-treatment but both feeding and gut pathology had recovered by day 7 . At all times, histopathological effects were different from those in starved insects.