Phytomyza rufipes Meigen, 1830
On cabbage the main host plants of Phytomyza rufipes, another fly, called cabbage root fly (Anthomyiidae: Delia radicum), occurs. As the common name suggests, this fly infests the root but instead of the leaves. This species does not belong to the Agromyzidae and is therefore not a subject for this CD-ROM. The adults are larger than agromyzids and are most similar to house flies.
IMPORTANT CHARACTERS
Adults
Wing length: 2.1 - 3.5 mm. Rather light species with small eyes and a broad frons. Usually four large frontorbital setulae present, of these the anterior two are inwards directed. Sometimes a fifth smaller one may be found. Only a part of the frontorbital setulae proclinate, the other setulae are erect or even reclinate. Eyes remarkably small.
Male terminalia
The aedeagus is highly characteristic.
Immature stages
The larva is rather elongated, up to 6 mm long, posterior spiracles each with 25-30 minute bulbs. The puparium is somewhat elongate, mat yellowish, 3 mm long.
BIONOMICS
Oviposition takes place in the leaf-blade, usually near a vein at the margin of the leaf. The young larva produces a mine towards the nearest vein and then feeds inside this downwards towards the midrib and petiole where the main feeding takes placePhy rufipes mines.pct. At the end of the petiole, if it is not by now fully grown, it can either turn and continue feeding in the reverse direction or, particularly in young plants, it may enter the stem. The feeding occurs mainly within the stem pith, vascular tissue is hardly affected. Therefore leaves can often survive even high abundance of miners. Sometimes, larvae have been observed to eat their way out of one stalk and bore into another (Berg, 1956). This is a very unusual skill among Agromyzidae. The females were observed to lay up to 81 eggs in their life (Frey, 1951). Pupation and hibernation occurs in the soil.
In Central Europe the flies usually emerge in May and after an unknown number of generations they are still found in November.
HOST PLANTS
Wide host range among Brassicaceae, known from various cultivated Brassica species and cultivars: Brassica oleracea (cabbage, kale, cauliflower, broccoli, ..), B. juncea Coss. (Leaf mustard), B. napus L. (rape), B. rapa L. (Turnip).
Other genera include Alliaria, Armoracia, Conringia, Diplotaxis, Moricandia, Peltaria, Raphanus, Rorippa and Sinapis (Hering, 1957).
DISTRIBUTION
Spencer, 1973: Widespread in Central Europe, also known from Italy, Russia (St. Petersburg), Egypt, Canary Islands and Madeira, USA and Canada. Recently the species was also reported form Turkey (Civilek in prep.).
Damage is known from Europe only.
ECONOMIC IMPORTANCE
Although Phytomyza rufipes is widespread among brassicean plants, damage is usually restricted to cabbage, especially cauliflower. On rape, for example the yield loss appears to be negligible (Berg, 1956). The larvae can be found mainly in the petioles of lower leaves of the plant, which are usually removed before further processing or consumption of the vegetable. These kind of damage is sometimes regarded as tolerable but more dangerous are the effects of heavy infestation of seedlings, whose growth can be stunted by heavy infestation (Berg, 1956). On the other hand, Hattesen, 1956 added that also heavy infestation of mature plants can reduce their commercial value considerably.
Spencer, 1973 thoroughly discussed the literature on damage and economic importance published before 1973. Since several obviously severe outbreaks were recorded in the literature he concluded that Phytomyza rufipes must be considered as a serious pest. However, although the species seems to be abundant, after 1973 only a few cases of real damage were reported (e.g. Coaker, 1973, Zuranska, 1985). The small numbers of records may have two reasons: Either the populations do not very often experience outbreaks to economic levels or the inconspicuous miner are often not recognized as cause of damage.