Both larvae and adults of the onion thrips (Thvips tubucz Lindeman) showed a preference for particular parts of leek (Allium porrum L.) plants. In the vertical plane most thrips were located in the transition zone where the leaves in the shaft were still white but gradually changed through yellow to pale green. At high population densities mixed groups of adults and larvae could be found along the entire leaf. In the horizontal plane larvae and adults showed a normal distribution pattern preferring certain leaves. Chemical treatments did not influence the within-plant distribution pattern of larvae and adult rhrips in the horizontal plane when compared to distribution patterns in untreated plants. Reinfestation of treated pIants by immigrating adults took place swiftly and developed into the characteristic pattern within a few days.

The onion thrips, Thrips rabaci Lindeman is a major est of leek (Allium porrurn L.) in Europe. To develop supervised control methods for pests and &eases in vegetable crops such as leek more information is needed on the within-field distribution and opulation levels of pests. For the onion thrips various methods of assessing population levels in l ee! have been tested and compared during one cropping season. The distribution of larvae in the field is more clustered than that of the adults. The effects of control treatments usin parathion and cypermethrin are reflected in the population levels as estimated by dissection of infividual plants. The variabilit of thrips populations per plant causes problems with regard to the attainable accuracy of the popultion estimates.

A specimen of a flea beetle collected by plant sweeping from an experimental plot of oregano in Warsaw showed characteristics of the invasive species Luperomorpha xanthodera. This beetle, originating from Far East, appeared in Europe at the beginning of this century and seems to extend its range continuously. So far, it has been noted from England, Italy, France, The Netherlands, Germany, Austria and Hungary but not from Poland. Being polyphagous, adult flea beetles of this species may appear in numbers on flowers of various ornamental plants causing considerable damage.