EFFECT OF INTERCROPPING ON THE POPULATION DENSITY OF PESTS IN SOME VEGETABLES

Abstract

The vegetables take a major place in the structure of the crops in Bulgaria. The climatic conditions in the country favour not only their growth and development, but also the mass spread series of diseases and pests. The effect of the contemporary plant protection systems for pest control is determined by the rational use of the potentialities of particular crops. In regard to this, the aim of this research was to study the influence of intercropping of some vegetables on the population density of their economically important pests. The scheme of the vegetable field included the following vegetables: onion-carrot; potato-beans; peas and caster-oil plant. The density of the major economically important pests related to the relevant crop was followed during the vegetative period: Onion - Onion fly (Helemiya antiqua Meig.) Carrot - Carot fly (Psyla rosae F.) Potato - Colorado potato beetle (Leptinotarsa decemlineata Say) Bean - Peas weevil (Acanthoscelides obtectus Say) Peas - The green pea aphid (Acyrthosiphon pisi Har.) The samples were collected by entomological sweepnet and by bush counting. On the basis of conducted study, it was determined, that some of the plant species act repellently on the density of economically important pests. With best qualities in this respect are: Onion - Carrot fly (Psyla rosae F.) Carrot - Onion fly (Helemiya antiqua Meig.) Peas - Colorado potato beetle (Leptinotarsa decemlineata Say) Caster-oil plant - The green pea aphid (Acyrthosiphon pisi Har.) The study of repellent behaviour of some plant species to different pest insects reveals new opportunities for decrease of chemical use, especially in vegetable-growing.