Possibility of Reducing Chemical Treatments Aimed at Control of Plum Insect Pests

During the last two years the main insect pests on plum trees in the region of Plovdiv (Central-South Bulgaria) were black and yellow plum sawflies (Hoplocampa minuta and H. flava) that destroyed 68-84% of fruitlets after bloom. Red plum maggot (Grapholitha funebrana) damaged more than 24-32% of fruits. Other important pests were two aphids (Hyalopterus pruni and Brachycaudus helichrysi), infesting 86-95,3% of shoots and brown scale (Parthenolecanium corni). Leaf sawfly (Neurotoma nemoralis), fall webworm (Hyphantria cunea), and plum ermine moth (Yponomeuta padellus) caused significant damage on leaves too. Some secondary pests, such as weevils, Rhynchites sp. and Phyllobius sp. as well as pear lace-bug (Stephanitis pyri) and others, damaged buds, fruits and leaves. Plant protection systems recommended for control of plum pests commonly include 10-12 chemical treatments. The experiments carried out in the orchards of the Agricultural University -Plovdiv have shown that the number of treatments may be significantly reduced without any negative effect on the trees or on the crop quantity and quality. This can be done by optimisation of the date of treatments, selection of proper insecticides and use of pheromones for mating disruption.