IK SECTS INJURIOUS TO AGRICULTURE IN" JAPAN 65 



en masse on the underside of the foliage and hatch in about one week. 

 The early-stage larvae are gregarious and feed both day and night, 

 whereas the more mature ones are solitary and feed at night only, 

 passing the clay in the soil. Control measures are the hand picking 

 of the egg masses, the digging of ditches along the field borders as 

 traps, and spraying with soap and pyrethrum powder when the 

 larvae are in the early stages. In other sections of the world, 

 particularly in the Tropics, this species is an important crop pest. 



Agrotis (Rhyacia) c-nigrum (78) occurs in Japan, Chosen, and 

 China as a pest of sugar beet, but is of most importance in Hokkaido. 

 In that island there are two broods each year, the adults appearing 

 in late June and July, and from the latter part of August, respec- 

 tively. The winter is passed in the mature larval stage in the soil 

 or among dead leaves on the surface. The eggs are laid singly dur- 

 ing the night upon the exposed portions of the root or on the lower 

 sides of the leaves. The larvae as well as adults are nocturnal in 

 habit. The egg stage of the first generation is from 7 to 10 clays 

 and that of the second 5 or 6 days, while the larval and pupal stages 

 of the first cover periods of 1 month and 2 weeks, respectively. 



Polia illoba (78) occasionally becomes abundant on sugar beet in 

 Hokkaido, though it is not so common as the above species. Nor- 

 mally two broods are produced each year, though occasionally 

 there is only one. The life history is similar to that of A. c-nigrum 

 except that the eggs are laid in groups of from 50 to 60 on the 

 foliage and hatch in two weeks, and the winter is passed in the 

 pupal stage in the soil. The larvae feed during the day as well 

 as at night. 



The black cutworm, Agrotis ypsilon, and A. tohionis (7), the first 

 of which is distributed through practically all oriental countries, 

 are common pests in Chosen and Manchuria. Both occur in Japan, 

 and A. ypsilon in Taiwan also. Though they are found attacking 

 many crops, the sugar beet is most seriously affected. The leafstalks 

 are cut away, thus causing a considerable loss of foliage during 

 periods of cutworm abundance. 



The Hawaiian beet webworm, Zinchenia fascialis (7), is of general 

 distribution and is an important pest of sugar beet in Chosen and 

 Hokkaido. According to Eguchi (13) there are three or four broods 

 per year in Chosen, and the winter is passed in the pupal stage in 

 the soil. The duration of the egg, larval and pupal stages in the 

 summer generations is from 2 to 7, 7 to 20, and 7 to 15 days, respec- 

 tively. The adults are nocturnal in habit, and the females deposit 

 their eggs on the lower leaf surface near the veins. The larvae feed 

 upon the lower surfaces of the leaves only. In addition to sugar 

 beet a variety of other Chenopodiaceae and Amarantaceae are 

 attacked. 



The method of control is fall cultivation to kill the larvae in the 

 soil and spraying with soap and pyrethrum powder for the larvae 

 in the earlier stages. 



Among the Coleoptera probably the most important sugar-beet 

 pests are the Scarabaeiclae, both in the larval and adult form. 

 Among these may be mentioned particularly Serica saiebrosa, Malci)- 

 dera (Aserica) orientalis, Holotrichia diomphalia, and Ligyrus rugi- 

 ceps (Taiwan only). The grubs, particularly those of Holotrichia. 



55059—31 5 



