390 



In many areas improved drainage would help the maize to grow- 

 steadily and assist the growers to destroy the food-plants of the billbug. 

 It is an advantage to break up the land the year before the first crop 

 is planted, as if the food-plants are completely destroyed before the 

 winter, any surviving billbugs will leave and maize can safely be planted 

 the following spring. When the food-plants have only been partly 

 destroyed, it would be advisable to plant such crops as pumpkins, 

 turnips, melons, flax, cotton or beets, that are not susceptible to billbug 

 injury. Usually, injury by billbugs ceases to be serious after the second 

 crop has been produced on new land where the wild food-plants have 

 been abundant, but it may extend over several years, according 

 to the time taken in completely destroying them. 



Sherman (F.). The Green Clover Worm {Plathypena scabra, F.) as a 

 Pest on Soy Beans. — Jl. Econ. Entom., Concord, N.H., xiii, no. 3, 

 June 1920, pp. 295-303. 



An account is given of a bad infestation of soy beans by the larvae 

 of the Noctuid, Plathypena scabra, ¥., tha,t occurred in the- east of 

 North Carolina in July 1919. Witliin a week from the first report of 

 the outbreak, a preliminary survey had been made and two temporary 

 field stations were in operation. Life- history studies were made from 

 1st August to 10th September. Eggs were found in late August on 

 either surface of the leaves of soy beans, and hatched in about 5 days. 

 The larvae are very active, and when small often hang suspended 

 from a thread. They begin feeding on the utider-side of the leaf, but 

 within a few days have eaten a hole through to the upper surface and 

 are found equally frequently there. Even when present in great numbers 

 the damage is not conspicuous for the first 15 days of larval life, but 

 after that it is very pronounced. In the outbreak described, the beans 

 were so defoliated that the lace- work of dried leaf -veins gave a cobweb- 

 like appearance to whole fields. In the majority of cases, however, 

 the growing bud and the older, lower leaves were left, and enabled the 

 plants to make a quick recovery when the caterpillars were killed or had 

 matured. The larvae become mature after 25 days, and then drop 

 from the plant and seek shelter for pupation in crevices in the soil, 

 under rubbish, etc. They remain 2 days in their silkeu cocoon before 

 pupating, the latter stage lasting 11 days ; emergence, mating and 

 oviposition require another 8 days. Winter is passed in the adult and 

 perhaps also in the pupal stage. 



When the present investigations were begun, the larval infestation 

 was nearing its height and immediate remedial measures were necessary, 

 and it was obvious that nothing less than a prompt appHcation of 

 arsenicaLs would save the situation. Dusting was therefore advocated 

 with 1 lb. dry powdered lead arsenate to 8 lb. lime dust, or spraying 

 with 1 lb. to 25 U.S. gals, water. This remedy was found effective, 

 and neither prohibitive in cost nor in labour of apjilication, but prompt 

 treatment was essential to success. Collection of larvae and of 

 adults with nets,* attraction to lanterns and bonfires, and bait-traps, 

 were all tried with very poor results. Apparently no injury attached 

 to the hay crop by the use of arsenicals ; the dust quickly disappears 

 from the plants and no bad results were recorded. It was found that 



