American Serpentine Leafminer – Chrysanthemum Leafminer – Liriomyza trifolii
American Serpentine Leafminer: Appearance, Territory, Damage and Life Cycle
Adult flies of the American serpentine leafminer are 1-2mm in size, grey-black in colour, and have a noticeable yellow patch at the base of the wings. The larvae are a white-yellow colour. Despite the fact that female adults are larger and more robust than males, their diminutive size makes field identification difficult.
Liriomyza trifolii is primarily recognized as a chrysanthemum and celery pest, but it has a wide range of hosts. Stegmaier (1966), for example, identified 55 Florida hosts, including bean, beet, carrot, celery, cucumber, eggplant, lettuce, melon, onion, pea, pepper, potato, squash, and tomato. Chrysanthemum, gerbera, gypsophila, and marigold are among the flower crops that are easily affected and known to aid in the spread of this pest.
The eastern United States and Canada, northern South America, and the Caribbean have long been home to this native leafminer. However, it has recently been brought to California, Europe, and other parts of the world.
Females can cause stippling on foliage by puncturing it during the feeding and oviposition processes, especially at the leaf tip and along the leaf edges (Parrella et al. 1985). The main source of damage is larvae mining leaves, which results in the breakdown of leaf mesophyll. Three to four days after oviposition, the mine becomes visible and grows in size as the larva matures.
Life Cycle and Habits
The life cycle of leafminers is relatively short. In warm climates like Florida, a whole life cycle might take anywhere from 21 to 28 days, implying that many generations can occur annually. Temperatures up to roughly 30°C boost development rates; temperatures beyond 30°C are usually unfavourable, and larvae die quickly. The three active larval instars took 1.4, 1.4, and 1.8 days to complete, respectively, and the puparium took 9.3 days. A preovipostion period of 1.3 days was also seen in adults. Except for egg laying, which requires roughly 12°C, the temperature threshold for development of the other phases is 6 to 10°C. Egg: Eggs are usually laid in the centre of the plant, with the adult avoiding juvenile leaves. The eggs are laid on the lower surface of the leaf by the female, however they are implanted just beneath the epidermis. The larva is a legless creature. The larva is colourless at first, but as it matures, it turns yellowish. Unlike many other flies, this insect’s larva does not taper sharply toward the head end. It also has a pair of spiracles on the back end.