Liriomyza brassicae Riley Diptera Agromyzidae

Natural History

Distribution. The cabbage leafminer is common throughout tropical areas of North and South America, Africa, Australia, and Asia, but it also occurs in some temperate regions. In North America, cabbage leafminer has been reported from most regions of the United States, and is found as far north as Manitoba, Canada. However, it occurs as a pest principally in southern states. It likely is not native to North America.

Host Plants. Cabbage leafminer attacks many plants in the family Cruciferae, including broccoli, cabbage, cauliflower, radish, turnip, watercress, and various mustards (Stegmaier, 1967). It is also known from peas (Leguminosae), and nasturtium (Tropaeola-ceae). Although it is the most common leafminer attacking crucifers, other species are sometimes found on these crops.

Natural Enemies. Stegmaier (1967) reported three species of eulophid wasps parasitizing cabbage leaf-miner in Florida: Diaulinopsis callichroma Crawford, Chrysocharis sp., and Pnigalio sp. (all Hymenoptera: Eulophidae). Oatman and Painter (1969) found seven species of Eulophidae, as well as one species each of Pteromalidae, Cynipidae, and Braconidae attacking this leafminer in California. In the latter study, the proportion of flies parasitized was lowest in January (26%) and highest in October (84%). The eulophid Diglyphus begini (Ashmead) was the predominant parasitoid, and attacked the larval stage.

Life Cycle and Description. Cabbage leafminers breed continuously in tropical climates. In more temperate climates such as California, L. brassicae occurs throughout the year, but it is much more abundant during the summer months (Oatman and Platner, 1969).

  1. Most feeding and egg deposition occurs beneath, and along the margins, of leaves. The shiny white egg measures 0.16 mm wide and 0.28 mm long, and hatches in about three days.
  2. The small larva tunnels through the mesophyll tissue, initially forming an elongate mine on the lower surface of the leaf. Accumulations of fecal material are usually evident along the center of the leaf mine, though this is more evident as the larva matures and produces a wider mine. Duration of the three active instars is about 6-7 days, with their duration averaging about two, two, and three days, respectively. The mouthpart (cephalopharyngeal skeleton) length of these instars measures about 0.09, 0.18, and 0.28 mm, respectively. About half-way through the third instar the feeding behavior changes, with the larva moving from the lower leaf surface to the upper leaf surface to feed. As the larva approaches maturity it cuts a slit in the surface of the leaf and drops to the ground to form a puparium. A fourth larval instar occurs between puparium formation and pupation, but no feeding occurs so this instar is generally overlooked (Parrella, 1987).
  3. The yellow-brown puparium measures about 1.75 mm long and 0.8 mm wide. The time spent in the puparium is about 8-10 days. The adult emerges from a slit in the anterior region of the puparium, usually during the afternoon or evening hours. Mating occurs in the morning following adult emergence.
  4. These small black and yellow flies are easily confused with vegetable leafminer, L. sativae Blanchard, but can be distinguished by using the male genitalia (Spencer, 1981). As in vegetable leafminer, the hind margin of the eyes is black, but cabbage leafminer differs in that it has less yellow color on the mesono-tum. Vegetable leafminer generally has yellow on more than 25% of the mesonotum surface, whereas cabbage
Cabbage Leaf Miner
Adult cabbage leafminer.

leafminer has less than 25% yellow. The female deposits the egg singly by puncturing the lower surface of leaves with her ovipositor. Such punctures always serve as feeding sites, but sometimes also serve as egg receptacles.

The biology of this insect is not well known. Beri (1974) presented the most detailed life history information.

Damage

The principal form of plant damage is caused by larvae mining the leaf tissue. An elongate, irregular mine that widens as the larva matures is typical of this insect's feeding pattern. Feeding and oviposition punctures may damage young tissue, but this is usually insignificant. The large numbers of mines evident on many plants do not always result in serious damage. Oatman and Platner (1969), for example, reported that though mine numbers reached 178 per plant, most of the mining was confined to the old, outer leaves that drop off or are removed at harvest.

Management

Management of this insect is poorly studied. The techniques discussed under American serpentine leaf-miner, L. trifolii (Burgess), and vegetable leafminer, L. sativae, are probably appropriate for this insect as well.

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    How to kill liriomyza au?
    5 years ago

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