218 OHIO EXPERIMENT STATION: BULLETIN 332 



scourges, since this insect, like others of our native harmful species, 

 has its periods of prevalence and scarcity. During the last few 

 years the amount of bag- worm injury has been increasing gradually, 

 and at present considerable harm is being done in some sections. 



Control. Two methods of control are generally recognized. 

 The safest, cheapest and most generally effective control measure 

 in combating general outbreaks is spraying with poisons, but the 

 bag worm larvae are somewhat resistant to the action of arsenicals, 

 and hence the materials should be used in slightly stronger doses 

 than are usually employed. Four pounds of arsenate of lead paste, 

 however, is sufficiently powerful, particularly if applied when the 

 caterpillars are small. When the over- wintering bags are plentiful 

 and upon examination the eggs within are observed to be healthy, 

 spraying plans should be made and the work should be done as soon 

 as all the eggs have hatched. As indicated in the discussion of the 

 life history, this will be in early June. 



The second control measure, one which is practicable only in 

 case the trees are small, consists in hand-picking the over-wintering 

 bags. The work may be done any time after the foliage drops in 

 the fall and before it starts the following spring. Light pole- 

 pruners are useful for clipping the infested twigs. Like all hand 

 operations and particularly where labor is costly, this control 

 method has a limited field of usefulness and is practicable only under 

 most favorable conditions. The collected bags should in no case be 

 destroyed but should be placed in open containers, semiprotected 

 from rain and distant from any food supply so that the parasites 

 may have an opportunity to emerge during the following summer. 



THE ELM LEAF BEETLE 

 (Galerucetta luteola Muller) 



Description. The adult elm leaf beetle (See Plate XXfV) in 

 shape, size and color more closely resembles the striped cucumber 

 beetle than any of our other common forms. The color, however, 

 is somewhat variable according to the season. The newly-emerged 

 beetle is about one-fourth of an inch long, the general color being 

 reddish yellow. Several black spots occur on the head and thorax 

 and a black area extends down each wing cover, near and parallel 

 to the outer margin. With the older and particularly the over- 

 wintered beetles as they are observed in the spring, the reddish- 

 yellow areas of the body become dark yellowish-green. The eggs 

 are bright yellow, pointed and deposited large end down in double 

 rows on the underside of the leaves. (Plate XXIV, Fig. 1, illus- 

 trates a characteristic cluster.) Usually several and rarely more 

 than 25 eggs are placed together. 



