THE SWEDE MIDGE SITUATION IN ONTARIO, CANADA

摘要

The Swede midge was first correctly identified in York county in 2000, which was the first report of this pest in North America. The Swede midge is of European origin and is widespread in European Union countries. The midge is a poor flyer and thus the rate of natural spread is thought to be relatively slow. The pest can spread with crucifer crop transplants and related swede midge host species including ornamentals, and soil associated with plant material or equipment. Swede midge infestations are often misdiagnosed. Damage occurs when the larvae feed on newly developing vegetative material. Damage symptoms can be confused with molybdenum deficiency, hormonal herbicide injury, genetic variability of seed, and heat stress or frost damage of crucifercrops. Young shoots and leaf stalks may be swollen, distorted and twisted, resulting in the death of the main shoot or growing point, forming a blind head. Heart leaves become crinkled and crumpled. Flower buds remain closed and become swollen. Brown scarring may also be observed, particularly along petioles and stems. Where the main stem has been destroyed, the development of secondary stems may be enhanced, resulting in a multi-stemmed plant. Severity of damage is directly related to crop development at the time of attack. If the plant is attacked at the seedling stage, there will be no marketable yield.