Control Methods for the Giant African Snail on Impatiens

The giant African snail on impatiens, scientific name Achattna fulica Ferussac, synonyms A. couroupa Lesson, A. fulica Tiyon, order Stylommatophora, family Achatinidae, also known as the African snail. Native to the coastal regions of East Africa, it was introduced to Guangdong, Guangxi, Yunnan, Fujian, Hainan, Taiwan, China and other places in China in the 1830s. Its hosts include impatiens and many other flowers, as well as vegetables and fruit trees.

Damage characteristics: it is an omnivorous pest; young snails are mostly saprophagous and damage the leaves of host plants. In severe cases they cut off tender stems and tender buds, ultimately causing gaps in the rows of seedlings or plant death.

Morphological characteristics

The body is long ovoid or elliptical. The shell is right-coiled, with a somewhat thick calcareous outer shell. Shell height 130 mm, width 54 mm. It is the largest snail in China, with 6.6-8 whorls. Each whorl grows slowly. The spire is conical, and the body whorl is swollen, with its height about 3/4 of the shell height; the apex is pointed and the suture is deep; the shell surface is yellow with scorched-brown mist-like patterns, the protoconch is jade white, and the remaining whorls have intermittent brown stripes. The growth lines are thick and obvious. The inside of the shell is blue-white or light purple. The spiral lines on the body whorl are not obvious, and the spiral lines of the middle whorls interlace with the growth lines; the aperture is ovoid, the peristome is complete and simple, the outer lip is thin and sharp and easily broken; the inner lip adheres to the body whorl, forming an "S"-shaped blue-white callus; the columellar margin is folded outward; there is no umbilicus. The foot is muscular, with the dorsum dark brown-black, and the mucus is colorless. The egg is round-oval and white.

Occurrence pattern: in the south it generally emerges and becomes active in early March. It prefers warm environments, but can survive in low-temperature places or under unfavorable conditions through dormancy. Its lifespan is 5-6 years, and it can reach 9 years. It is frequently active around Qingming and until early October. When the external environment is cold or dry, it secretes a milky-white opaque mucus membrane of the same size and shape as the aperture to seal the aperture. It lays eggs in shallow soil. It is phototactic, crawling out at night to move and feed, and during the day it prefers to rest in shady, moist environments with lush weeds and trees, or in loose soil rich in humus, or hidden on the underside of leaves. After rain, on clear days it can be active all day. A temperature of 17-24 °C is suitable for its life. It is dioecious. It hatches after 30 days. When encountering unfavorable living conditions, it quickly enters dormancy and can remain dormant for several years. During drought it can burrow 150 mm deep into the soil, and during winter dormancy it burrows 150 mm deep into the soil.

Control methods

(1) Strict quarantine: when transferring vegetable seedlings, flowers, nursery stock and other plants as well as packing boxes from epidemic areas to the north, careful quarantine must be carried out, and once found they must be subjected to disinfestation treatment.

(2) Because of its phototaxis, black light traps can be used to trap and kill it.

(3) During the young snail stage, 1 part calcium arsenate and 1 part lime powder can be spread.