Studies on the soybean agromyzid fly in Shantung Province.
Melanagromyza sojae (Zhnt.) is one of the most important pests of soyabean in Shantung Province, China. Its food-plants include more than 9 cultivated and wild legumes. Larvae bore into stems and interrupt the passage of water and nutrients, resulting in seedlings being killed, the growth of older plants retarded and crop yields greatly reduced. The agromyzid has 5 generations a year. Pupae overwinter in the stems of soyabean plants, and adults emerge in the following June. Larvae and adults of the first generation are present in July and those of the second in August. Third-generation larvae reach peak numbers in late August, and thereafter the fourth and fifth generations may overlap. Adults are most active from 06.00 h to 08.00 h, and eggs are laid singly, mostly on the undersides (near the midrib bases) of leaves on the upper portions of plants. The incubation period lasts 2-3 days. Larvae of the first generation infest the spring crop, those of the second and third generations both the spring and summer crops, and those of the third and fourth generations the late crop. Control measures include the removal of field debris and plants harbouring overwintering pupae, increasing the use of fertilisers, early sowing and the thinning out of seedlings, and the application of sprays of fenitrothion (Sumithion), phoxim, malathion and dimethoate when adult populations reach peak numbers.