﻿6 BUIZiETIN" 1357, U. S. DEPARTMENT OF AGRICULTURE 



During the winter of 1919-20 Primm and Trimble, of the Pennsyl- 

 vania Bureau of Plant Industry, found infestations in 15 different 

 establishments in the vicinity of Philadelphia. According to two 

 florists in this locality, the beetles, known to them as " chocolate 

 bugs," had been encountered in their houses for 12 and 18 years, 

 respectively. 



A careful survey by means of a circular letter sent to all the State 

 entomologists and the subsequent publicity accorded this insect and 

 its injury in florists' trade journals (i, 17^ 19^ and ^^) have brought 

 to attention infestations in the States of Michigan, Missouri, Lou- 

 isiana, Rhode Island, and Massachusetts. These reports emphasize 

 the fact that the insect is now of prime importance in practically 

 all of the commercial rose districts of the United States east of the 

 Rocky Mountains. The severity of injury found in houses or beds 

 where the plants were 3 or more years old indicated that they were 

 the sources of infestation, and that the insect had been brought in 

 either with the soil or the plants in those sections. 



DISTRIBUTION 



The strawberry leaf beetle, or adult of the rootworm, which is a 

 native insect, has been frequently recorded as occurring out of doors 

 generally throughout the United States and Canada (i^, p. £6). 

 The records available at the present time show that it is injurious 

 to roses under glass in the District of Columbia, Illinois, Indiana, 

 Louisiana, Maryland, Massachusetts, Michigan, Missouri, New Jer- 

 sey, Pennsylvania, Rhode Island, and Virginia. 



NATURE OF INJURY. AND ECONOMIC IMPORTANCE 



Two stages of the strawberry rootworm are involved in the injury 

 to the plants, (1) the adult and (2) the larva. The casual observer 

 immediately notices the ravages of the beetles on almost every part 

 of the plant above ground. The leaves become perforated so exten- 

 sively that one easily imagines charges of small shot being fired at 

 the plants. This shot-hole appearance (fig. 1) is very characteristic 

 and completely destroys the ornamental value of the foliage. The 

 beetles also eat the green succulent bark of the forced plants, par- 

 ticularly in crotches, scarring and often girdling the stems. 



The most serious injury to the plants occurs when the tops are 

 " cut back," because little foliage remains for the beetle to feed upon. 

 A.t this time the beetles severely scar the stems and eat into the 

 '' eyes," as the developing buds are termed by the florists. The im- 

 portance of this particular type of injury is very evident when it is 

 considered that the future crop of flowers depends on these buds, 

 which require from six to eight weeks to develop, and that any set- 

 back naturally results in a decreased production and financial re- 

 turn. The succulent nature of this growth, as compared with the 

 woody stems, causes the beetles to center their attention upon it, and 

 in a single night they may eat the heart out of almost every eye. 

 In one infestation observed in March, after the buds of Ophelia 

 plants had been destroyed during September and October of the 

 previous year, the first growth produced from these nodes was only 



