578 



LuGiNBTLL (P.) & AiNSLiE (G. G.). The Lesser Corn Stalk-Borer. — 

 U. S. Dept. Agric, Washington, D.C, Bull. no. 539, 8th September 

 1917, 27 pp., 3 plates, 6 figs. 



Elasmopalpus lignosellus, Z. (lesser corn stalk-borer) has hitherto 

 appeared abundantly only in sporadic outbreaks, but has lately become 

 an important pest in the southern United States, where crops grown 

 in poor and sandy soils are readily affected. 



This paper is a compilation of the results of observations and 

 experiments made during the years 1913-1915. Injuries due to this 

 moth were first recorded in 1881, but it was twenty years later before 

 it became the subject of entomological study. The species occurs 

 practically throughout South America and almost over the entire 

 southern half of the United States. Gramineae are the favourite 

 food-plants and would probably be exclusively attacked, if always 

 obtainable. Beans, maize, cow-peas, Japanese cane, Johnson grass, 

 peanuts, sorghum, sugar-cane, turnips and wheat are among the crops 

 attacked. Descriptions of all stages of the insect are given. Egg'^ 

 have not been found in the field, but judging from the results obtained 

 from rearing, they are probably deposited on the stems of plants, in 

 the axils of the leaves or on the ground at the bases of the stalks, 

 which the larvae ascend in order to feed. The eggs are generally 

 deposited singly, 190 being about the average number for each female. 

 Oviposition has not been known to occur at a temperature of much 

 less than 80° F. The larvae hatch in three to six days according to 

 temperature and pass through four to seven instars according to the 

 season, the average length of the larval period being 17 days, or 

 considerably longer at low temperatures. The larvae bore into the 

 stems of young plants and make tunnels, near the surface of the 

 ground, where they feed, the injury closely resembling that of the 

 southern corn rootworm, Diabrotica duodecimputictata, Oliv. In 

 older plants the stems are frequently girdled at or slightly below the 

 ground surface. The larvae are seldom found in the tunnels of the 

 plants, but more often in specially constructed tubes which lead away 

 from the entrance to the tunnel, lying even with or slightly beneath 

 the surface of the ground, or sometimes curved round the stems. 

 These tubes are composed of particles of sand and dried excrement 

 spun together with silk by the larvae, which apparently use them as a 

 means of retreat if disturbed while feeding. The pupal stage varies 

 according to temperature from 7 to 21 days, and the adults live from 

 5 to 18 days. There are probably four generations in a year, the 

 summer broods averaging 38 days for the total life-cycle and the 

 autumn broods 64 days. The winter is apparently passed in the 

 larval and pupal stages. 



Natural enemies exercise very little control on the borer, owing to 

 the protection afforded to the larvae at all times. An Ichneumonid, 

 NeopristomerKS sp. , was reared from this species in the laboratory and 

 the Braconid, Orgilus laevireniris, Cress., has been obtained in Florida. 



Cultivation is the best method of combating the borer. Infested 

 fields should be j^loughed in late autumn or early winter after all 

 remains of the old crop have been removed and the borders of the 

 field should be harrowed to stir up the ground and break up the winter 

 quarters of the pupae. Any sandy areas in the field should be treated 



