BIOLOGY, ECOLOGY AND CONTROL OF THE PLUM SEED WASP [EURYTOMA SCHREINERI SCHREINER (HYMENOPTERA: EURYTOMIDAE)]
The plum seed wasp, Eurytoma schreineri Schr. is a new pest on plum trees in Bulgaria. It is a serious pest for plums in northeastern Bulgaria. This wasp attacks the fruits of various plum cultivars. Damage by E. schreineri on plums ranges from 26-92%. The damage percent depends upon bioecological conditions and on the susceptibility of the plum varieties. Late-flowering cultivars are the most sensitive, where the attack can reach up to 90-92% of Stanley cultivar. This is univoltine and overwinters as a fully developed larva within stones of the fallow fruit under the plum trees. During the spring, usually in early May, the adults go out of the fallen mummified fruits and after mating the females oviposit inside the newly formed plum fruit. The egg is inserted into the endosperm of the fruit before the formation of the stone. Incubation lasts about 20-22 days, and hatch begins about the time that the plum seed embryo becomes visible. Larva development is completed by the end of June or early July, then the larvae enter diapause and remain in this state for 1-3 winters. Locally penetrating insecticides, applied when the larvae begin to hatch, provide a significant degree of larval control.