Identification and Control of the Orchid Pest, the Spiny Whitefly

The spiny whitefly, Aleurocanthus spiniferus Quaint, belongs to the order Homoptera, family Aleyrodidae. It is distributed throughout southern China, where its larvae damage Chinese rose,orchids, roses, lilac, osmanthus, camellia, white orchid (Michelia alba), and others. Its larvae gather on the undersides of leaves, piercing their mouthparts into the plant tissue to suck sap. The damaged areas develop yellow spots; in severe cases, the leaves and branches turn black and the leaves drop off, eventually killing the entire plant. In addition to direct damage, the pest excretes large amounts of honeydew, which drips down as transparent droplets onto the lower leaf surfaces, inducing sooty mold, inhibiting growth, and causing death and defoliation, which ruins the plant's appearance. Morphological characteristics: Adult: Males and females are similar, with a body length of 1.0-1.3 mm, orange-yellow in color and covered with a waxy white powder. The forewings are purplish-brown with 7 irregular white markings; the hindwings are small and light purple; the legs are yellow. Males are smaller in size. Egg: About 0.25 mm long, milky yellow when first laid, turning deep yellow before hatching, banana-shaped, with a pointed tip and a small stalk at the base. Nymph: Newly hatched nymphs are oval, flat and pale yellow, about 0.2 mm long, with serrated margins around the body edge, four tail hairs at the posterior end, and a glossy surface. The body is surrounded by a secreted white waxy layer, and the dorsal surface bears 14 pairs of bristles. The body length is about 0.7 mm. Pupa: Black, glossy, 0.7-11 mm long, with a raised dorsal surface. The thorax bears 9 pairs of waxy setae, the abdomen bears 10 pairs of setae, and the lateral margins bear 10-11 pairs of setae. Occurrence pattern: The spiny whitefly produces 4-5 generations per year, and 4 generations per year in the Jiangsu-Zhejiang region. It overwinters as mature nymphs on the undersides of host leaves, pupates in March of the following year, and adults emerge in early to mid-April. The peak periods of nymph occurrence are respectively mid-to-late May, mid-to-late July, mid-to-late August, and late September to early October. In greenhouses there is no overwintering phenomenon; it continues to reproduce and cause damage, with overlapping generations. Adults mostly emerge in the morning, breaking out from the dorsal surface of the pupal shell through a "T"-shaped split, and mate and lay eggs soon after emergence. Offspring from parthenogenesis are all male. The adult stage lasts 1-6 days. Eggs are laid singly on the undersides of leaves, with more eggs on old leaves than on young leaves. Each female lays 20-30 eggs, and the egg stage lasts 10-15 days. Shortly after hatching, the larvae insert their mouthparts into the leaves to suck sap, while secreting honeydew that contaminates the leaves. The nymph has a total of three instars, with the later stage lasting 20-36 days. After the nymph matures, it pupates in place, and the pupal stage lasts 7-34 days. Control methods: 1. Maintain environmental hygiene around the orchid nursery, remove weeds and dead branches and fallen leaves, and ensure proper ventilation and light penetration. 2. Biological control: Protect natural enemies. When pest density is low and natural enemy numbers are high, stop or reduce the use of broad-spectrum chemical pesticides. 3. Chemical control: Refer to the control of the greenhouse whitefly. Liu Zhongjian