Observations on the biology of carrot tiy (Psila rosae{F.)) were made ifl the important carrot-growing areas of eastern England in the period 1948-72.

Population assessment methods for Heterodera schachtü were compared in two tests. In the first there were no consistent differences between numbers of H. schachrü extracted by Fenwick cans (at two laboratories), a flotation column and an automatic cyst extraction apparatus, from dried soils from three sites containing no other cyst nematodes. The second, made on 54 commercial sugar beet fields, compared numbers of H. schachtü extracted from dried soil samples by Fenwick cans (at two laboratories) with results of a bioassay of soil samples and a subsequent examination of roots in the field. Most samples were placed into the same broad groups by the cyst extraction and bioassay methods and the two techniques were equally good at predicting field infestations.

Brassica cyst eelworm {Heterodera cruciferae Franklin) was found in 74 out of 99 fields in a random survey of 11 parishes in Bedfordshire. Population densities of up to 25 eggs/g of soil occurred in 70 fields, and denser populations in only four fields. Population densities were greater, and more fields were infested, on farms of less than 50 acres than on larger farms.

SUMMARY At sites in Norfolk in 1970, 1971 and 1972, growing carrots were covered in situ with soil or straw for varying periods in attempts to prevent egg laying and subsequent late‐season damage by larvae of the carrot fly (Psila rosae) (F.))‐ Neither soil nor straw was sufficiently effective in this respect. Carrots chemically defoliated and/or covered during the main egg‐laying period in August and September were adversely affected in size and quality.