Biology of Trioza apicalis - a review

The morphology and biology of immature stages and the distinguishing characters of generations in summer are briefly reviewed. The time of migration of the overwintered generation and the use of the median flight time are given. The longevity of overwintered adults, and the start and course of oviposition by overwintered females were observed mainly during June and July. The interval between adult emergence and flights from carrots appears to be very short, 2-3 days. Departure from developmental summer host plants culminates at the beginning of September. The sex ratio of the overwintered generation is not persistent, since it is usually female-biased. In emerged adults in summer the ratio is 50:50, with weak protandry. The systemic action of sucking for the curling of leaves was found by Láska already in 1964. Inliterature records, both subspecies of Daucus carota dominate as developmental hosts, more recently Coriandrum sativum was shown to be more suitable than Petroselinum hortense. Norway spruce, and to a lesser extent other conifers, are predominantly mentioned as overwintering shelter plants. It is not clear how overwintering occurs in regions without coniferous forests, and only undefined shrubs or trees are given in the literature. The first damage was reported inDenmark about in 1896, spreading from about 1918 over just a few years to the other Fennoscandian countries, and later in some other European countries. The spring migration is discussed, which occurs in central and northern Europe on the same date, perhaps explicable by the orientation of this pest or its particular populations to long days, despite the climate and phenology of each region. It is hypothesised that a particularly aggressive race evolved inSjaelland (Denmark) at the turn of the nineteenth and twentieth century, which later spread to other regions of northern and centralEurope.