THE SYMPTOMS OF ATTACK BY SWEDE MIDGE (CONTARINIA NASTURTII) AND EFFECTS ON THE YIELD OF SWEDES

Abstract

Four experiments in S.E. England (1960–1963) and one in N.E. England (1963) used different methods to expose selectively plants to swede midge infestations in the field. The two methods which were satisfactory in assessing yield losses were 1) marking naturally infested plants and 2) marking artificially infested plants with small temporary cages to confine the ovipositing midges over the plants and comparing the yields with those of nearby clean uninfested plants. The symptoms of attack were recorded and classified as either primary or secondary. The primary symptoms “swollen petiole” and “crumple leaf” were commoner and more reliable indicators of swede midge attack than the secondary symptoms “many neck” and “cabbage top” which could be caused in other ways. Yields of infested and uninfested plants were compared and it was found that the sowing date and tolerance to attack were related. Early sown plants yielded more and were more tolerant to midge attack than late sown plants even when heavily attacked. It seems that only in unfavourable growing seasons this pest would seriously affect yields of swedes. Résumé LES SYMPTÔMES DE L'ATTAQUE PAR LA CECIDOMYIE DU NAVET (CONTARINIA NASTURTII) ET L'EFFET SUR LA RÉCOLTE DES NAVETS Des expérimentations conduites en Angleterre, quatre dans le Sud‐Est (1960–1963) et une dans le Nord‐Est du pays (1963), ont utilisé différentes méthodes en vue d'exposer sélectivement des plantes de plein champ aux attaques de la Cecidomyie du navet. Les deux méthodes qui ont donné satisfaction pour l'évaluation des pertes dues à ces attaques furent: 1° — soit de marquer les plantes naturellement infestées 2° — soit d'utiliser des plantes artificiellement infestées, en les maintenant dans de petites cages temporaires avec des Cecidomyies afin de limiter la ponte à ces plantes, et de comparer ultérieurement les récoltes de ces plantes marquées avec celles de plantes à peu près saines. Les symptômes de l'attaque ont été classés en primaires ou secondaires. Les symptômes primaires «pétiole renflé» et «feuille frippée» étaient plus fréquents et représentent des indicateurs plus valables de l'attaque par la Cecidomyie que les symptômes secondaires: «many neck» et «cabbage top» qui pourraient avoir une autre origine. Les récoltes de plantes infestées et non‐infestées ont été comparées et il a été montré que ces récoltes dépendaient de la date du semis et de la tolérance aux attaques. Les plantes issues de semis précoces produisaient davantage et étaient plus tolérantes à l'égard des attaques de la Cecidomyie, même quand elles étaient fortement attaquées, que celles semées plus tard. Il semble que cet insecte ne puisse affecter de façon sérieuse les récoltes de navet que dans les années défavorables à la croissance de cette culture.

Potential distribution and relative abundance of swede midge, Contarinia nasturtii, an invasive pest in Canada

“…Initial parameter values were based on published data that resulted from laboratory and field studies (Stokes, 1953; Readshaw, 1961, 1966; Bardner et al., 1971; Rygg & Braekke, 1980; Bouma, 1996) and are defined in Table 1. Climatic requirements were inferred from known distributions of swede midge in Europe.…”

“…Plant hosts include cruciferous weeds and most cultivated crucifers such as broccoli, canola, cauliflower, cabbage, and Brussels sprouts (Stokes, 1953; Darvas et al., 2000). Plant damage is caused by larval feeding; symptoms include misshapen plants and the formation of galls on leaves and flowers (Bardner et al., 1971). The larval stage overwinters in the soil, adults emerge in May and females lay eggs, in clusters of 2–50, on the surface of actively growing plants.…”

Patterns of diapause frequency and emergence in swede midges of southern Ontario

“…Pesticide applications that target adult emergence from diapause (i.e. before late July depending on climatic conditions) should provide the most efficient means of population control for two reasons: eliminating the majority of adults emerging from diapause will (i) diminish the potential for population expansion later in the season and (ii) prevent damage to early, often more susceptible, plant stages by first larval generation feeding (Rogerson, ; Bardner et al , ). We encourage additional multi‐year field studies of swede midge population dynamics and factors controlling diapause entry and emergence to enable the development of appropriate pest management programmes for this invasive pest.…”

Potential Biological Control Agents for Management of Cogongrass (Cyperales: Poaceae) in the Southeastern USA

“…No adults were reared, but larvae were identified as a Contarinia sp. Plant deformity in response to feeding by members of the genus Contarinia has been reported (Bardner et al 1971;Brewer et al 1994), and in sunflowers is thought to be associated with elevated levels of auxin (Brewer et al 1994). As many cecidomyiid midges have narrow host ranges (gagné 1989; Yukawa 2000; gagné 2004), the midge found in cogongrass may warrant further investigation as a potential biological control agent.…”