Identification and Control Methods for the Orchid Pest Green Peach Aphid

Green peach aphid Myzus persicae (Sulzer), also known as the peach aphid or tobacco aphid, belongs to the order Homoptera, family Aphididae. Its damage range is broad, found in most parts of the world, and it is distributed throughout China, with more than 300 species of host plants. It mainly harms:orchids, cherry blossoms, hollyhocks, plum blossoms, peaches, Chinese roses, pomegranates, crabapples, etc. Adult aphids and nymphs pierce and suck plant sap on the undersides of leaves, causing leaves to curl, turn yellow, and even dry up. Their excrement often induces sooty mold, affecting plant growth. In addition, they can transmit viruses, causing viral diseases inorchidsand other plants. Morphological characteristics: Winged viviparous female aphid: body length about 2mm, head and thorax black, abdomen highly variable in color, green, yellow-green, brown or reddish-brown, with light brown markings on the dorsal surface. Antennae 6-segmented, cornicles slender, cylindrical, cauda slightly concave in the center, bearing three pairs of curved lateral hairs. Wingless viviparous female aphid: body length about 2mm, body stout, with two body colors, yellow-brown and red-brown. Compound eyes red, legs dark brown except for the pale green base, frontal tubercles and ocular tubercles both prominent, antennae 6-segmented, longer than the body, cornicles pale black, slender, cauda conical, equal in length to the cornicles. Nymph: similar to the wingless viviparous female, but smaller in body size and pale red in body color. Egg: elongated oval, 1-1.2mm long, yellow-green when first laid, later jet black and glossy. Occurrence pattern: The number of generations of the green peach aphid per year varies by region. In the north, generally more than 10 generations occur, while in the south 30-40 generations can occur. The life cycle is complex; some green peach aphids are of the full-cycle type (migratory type), while others are of the half-cycle type (resident type). Full-cycle green peach aphids overwinter as eggs in winter on the branches, bud axils, cracks and other places of peach and other stone fruit trees. From mid-March to April of the following year, they hatch into fundatrices, which reproduce parthenogenetically on flowering plants, multiplying for 2-3 generations. As the flowering plants bud, they first gather on the buds to cause damage, then suck sap on the undersides of leaves. In April and May, winged aphids are produced and migrate and disperse, reproducing in large numbers and causing severe damage. By October, sexuparae are first produced; winged aphids produce female sexuparae that migrate back to the winter host and produce only wingless female aphids, while wingless aphids produce male sexuparae that produce winged male aphids on the summer host. The winged male aphids migrate back to the winter host, mate, and lay eggs to overwinter. Half-cycle green peach aphids complete their annual life cycle entirely by parthenogenesis. In dry spring years, outbreaks and damage are often very severe. Control methods: 1. Carry out sanitation management in the orchid nursery, eradicate weeds, prune away dead branches and fallen leaves, with special attention to pruning or thinning out infested leaves and infested seedlings to prevent the spread of the pest. 2. After most overwintering eggs have hatched, around March, spray 50% phoxim emulsifiable concentrate at 2000 times dilution or 80% di chlorvos emulsifiable concentrate at 1000 times dilution. 3. During the period of green peach aphid damage, 40% dimethoate emulsifiable concentrate at 1000 times dilution or 50% malathion emulsifiable concentrate at 800 times dilution may be sprayed. Alternatively, 25% deltamethrin emulsifiable concentrate at 2000-3000 times dilution or 20% fenvalerate emulsifiable concentrate at 2000 times dilution may be sprayed, and 50% pirimicarb wettable powder at 2000 times dilution also has a good effect. (Liu Zhongjian)