Observations on the effects of γ-radiation on eggs of the desert locust, Schistocerca gregaria (Forsk.)

Abstract

It has been suggested that nuclear radiation might be used for locust control, but insufficient knowledge has hitherto been available to decide whether such a measure is feasible. In this paper, the results of some laboratory experiments on the effect of γ-radiation on eggs of the desert locust, Schistocerca gregaria (Forsk.), are described.After a single dose of γ-radiation, the resulting mortality among the eggs was correlated with the size of the dose received and the age of the egg at the time of irradiation. The dose of radiation required to kill the older eggs was 40 times greater than that required to kill young eggs; thus, a dose of 144 rads caused almost complete inviability among eggs deposited one or two days before irradiation, but a dose in excess of 5,500 rads was required to kill eggs deposited eleven days earlier. For comparison, the lethal dose of γ-radiation for humans is estimated to be 400–700 rad.When the irradiation dose was applied in three small fractions, with intervals between them, the percentage of eggs killed was less than when the same total dose was given in one exposure. This difference was presumably due to tissue recovery during the inter-radiation periods. The temperature to which the eggs were exposed during the inter-radiation periods also affected survival, recovery being greater at higher temperatures.The possibility of using γ-radiation to control locust egg-fields, the cost of the equipment needed and the hazards involved are discussed. It is concluded that control by this method not only offers no advantage in terms of cost, effectiveness or convenience as compared with conventional insecticide treatment but would be very impractical and dangerous to operators and the inhabitants, human and domestic animal, of the treated area. It is possible that other control techniques utilising radiation, such as sterile-male release or attractant traps treated with a sterilant, may be useful against certain species of locusts after further work on the development of chemical attractants has been carried out.