Identification and Control Methods for the Black Locust Aphid

The black locust aphid damages many leguminous plants such as black locust, Chinese scholar tree, and false indigo. Adults and nymphs gather on new black locust shoots to suck sap, causing new shoots to bend, young leaves to curl, and branches to stop growing, while their secretions often cause sooty mold. The wingless aphid is about 2 mm long, oval, pitch-black and glossy, with distinct hexagonal reticulation on the dorsum of the head, thorax, and abdominal segments 1-6; abdominal segments 7 and 8 have transverse striae; the winged aphid is long-oval, black and smooth, with grayish-white, transparent wings.

The black locust aphid has more than 20 generations per year. It mainly overwinters as wingless parthenogenetic aphids and nymphs in the heart leaves and at the junction of roots and stems of plants such as Asian plantain, wild alfalfa, and wild vetch in wind-sheltered, sunny sites. In March of the following year, it reproduces in large numbers on the overwintering hosts; by mid-to-late April, winged parthenogenetic aphids are produced and migrate to leguminous plants such as spring peas and black locust, forming the first migration and dispersal peak; at the end of May and beginning of June, a second migration peak appears; in early June, the population density on black locust gradually increases, and in mid-to-late June, reproduction accelerates, forming the third migration peak; in mid-to-late July, during the rainy season and hot weather, except for black locust in shady places and the second migration peak; on false indigo, where aphids continue to reproduce and cause damage, the population density declines markedly. In October, they again reproduce and cause damage on new tender shoots of harvested hyacinth bean, common bean, and false indigo, after which winged aphids are gradually produced and migrate to the overwintering hosts to reproduce, cause damage, and overwinter.

Control methods. During the period when aphids occur and cause damage, spray 40% dimethoate emulsifiable concentrate, 25% parathion emulsifiable concentrate, or 50% malathion emulsifiable concentrate at 1000-2000 times dilution; alternatively, drill holes at the base of the trunk and inject 50% monocrotophos emulsifiable concentrate or 40% omethoate emulsifiable concentrate at 5-10 times dilution, or scrape away old bark around the trunk and apply the same concentration of the pesticide solution in a 5-10 cm wide ring.