Tildenia inconspicuella Murtfeldt Lepidoptera Gelechiidae

Natural History

Distribution. Eggplant leafminer is present in the southeastern and midwestern United States north to about New Jersey and Iowa, and west to Nebraska and Texas. This species has a rather confused history, but records from most western states appear to be due to related species. Eggplant leafminer is a native insect.

Host Plants. Eggplant leafminer apparently limits its attacks to eggplant and horsenettle, Solanum carolinense. Horsenettle is the natural host.

Natural Enemies. Several parasitoids are known, and apparently effective in keeping this insect from becoming very numerous. Among the common species are Apanteles epinotiae Viereck, Bracon gelechiae Ashmead, Cardiochiles sp., Macrocentrus delicatus Cresson, Orgilus mellipes Say, Agathis gibbosa (Say) (all Hymenoptera: Braconidae); and Chrysonotomyia sp. and Miotropis sp. (both Hymenoptera: Eulophidae). Cirrospiloides bicoloriceps (Girault) and Campoplex phtho-rimaeae (Cushman) also parasitize this leafminer. A eumenid, Parancistrocercus fulvipes (Saussure) (Hyme-noptera: Eumenidae), has been observed to prey upon larvae by digging them from their tunnels. Gross and Price (1988) observed mean parasitism rates of about 33% in Illinois, and equivalent levels of parasitism on larvae developing in both eggplant and horsenettle.

Life Cycle and Description. Eggplant leafminer can complete its development, from the egg to the adult stage, in about 25 days when cultured at 27°C. In Illinois, eggplant leafminer was active from JuneSeptember, and underwent three generations.

  1. The eggs are deposited singly on the leaf surface, with deposition occurring on both the upper and lower surfaces, but the lower surface is heavily favored. They are somewhat cylindrical, but with rounded ends. Mean egg length (range) is 0.34 mm (0.30-0.38 mm); mean width (range) is 0.19 mm (0.160.21 mm). Egg color is yellow. Duration of the egg stage is about seven days.
  2. Larvae burrow within the leaf along the edge of the leaf blade. If the larvae do not hatch at the leaf edge, they may construct a small linear mine near the egg, but soon relocate to the leaf margin. Other than to move to the leaf edge, larvae do not leave the mine and do not web together foliage. Larvae form a blotch-shaped mine and deposit feces and silk within the mine. There are five instars, with mean head capsule widths of 0.17, 0.27, 0.38, 0.57, and 0.76 mm for instars 1-5, respectively. The larva initially is white or pale yellow except for the head and thoracic shield, which are brown. By the third instar the larva acquires a brownish or greenish color, and in the fourth or fifth instar becomes dark green, turquoise, or dark blue. The thoracic legs are light in

Eggplant leafminer larva.

Eggplant leafminer larva.

  1. Mature larvae attain a length of 7-8 mm and are slightly flattened in form.
  2. When ready to pupate, mature larvae spin down to the soil on a strand of silk. Pupation normally occurs within a silken cocoon in the soil, and usually quite close to the soil surface. The pupa is dark blue when first formed, but becomes dark brown with maturity. Eggplant leafminer pupae have no distinctive features, resembling most moth pupae. They measure 3.4-5.2 mm long and 1.0-1.7 mm wide.
  3. The adult is a small grayish brown moth that is marked with yellowish brown. The forewings, but especially the hind wings, bear a long fringe of hairs. The wingspan measures 10-14 mm. Adults are nocturnal.

Eggplant leafminer is quite similar in appearance to potato tuberworm, Phthorimaea operculella (Zeller), and they share common hosts. However, eggplant leafmi-ner tends to mine leaf margins, whereas potato tuber-worm attacks the central areas, particularly the area of the main veins. Also, eggplant leafminer does not leave the mine to web leaves. Poos and Peters (1927) gave the morphological characters useful in distinguishing the species, but accurate determination is best accomplished by an authority.

The biology of eggplant leafminer was given by Jones (1923) and Gross (1986). A key that included eggplant leafminer larvae (as Keferia glochinella Zeller) is provided by Capps (1946).

Damage

Though commonly found mining eggplant in southern states, eggplant leafminer is not considered to be a serious pest. The leaf edge is preferentially mined, acquiring a dry, sometimes swollen, blotch.

Tildenia Inconspicuella
Adult eggplant leafminer.

Management

This insect is not known to be a serious pest and its presence should not normally be cause for concern. However, insecticides applied to the foliage should be effective if suppression is warranted.

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