Biology and Control of the Fall Webworm ( Hyphantria cunea Drury) in the Middle‐ and East European Countries

The fall webworm was first discovered in Hungary in 1940 and severe outbreaks occurred in 1945. This insect which goes through 7 larval instars usually has two annual generations under the conditions prevailing in the infested areas of this country. The optimal conditions are met most often in Central and South Hungary (1,950 ‐ 2,050 sunshine‐hours yearly, 17°C average temperature during the vegetation period, a humidity of 65–70% and 300–350 mm. of precipitation). Three categories of host‐plants are distinguished: first‐grade host‐plants for which the pest has a clear preference and on which it develops best; second‐grade host‐plants on which the larvae feed mostly during the outbreak years and third‐grade host‐plants on which the larvae only feed when their original host‐plants are almost completely defoliated. Special attention is paid to the natural enemies of Hyphantria cunea Drury comprising predators and parasites. From larvae and pupae 8 Tachinids, 5 Ichneumonids, 13 Chalcidids and 3 Braconids were reared. The importance of natural enemies in controlling the pest seems to be greater in North America than in Europe. Despite drastic control measures, there has been a marked increase in the dissemination of the fall webworm in Hungary in 1969 and 1970 but is was possible to reduce the crop losses. A network of survey and forecasting posts facilitates the carrying out of mechanical and chemical methods. Strict quarantine regulations are in force to keep the pest under control.