THE HUISACHE GIKDLER. y 



On January 13, 1913, four prunings of huisache were stripped of 

 bark, and the following table made : 



Table II. — Infestation of the huisache girdler ty parasites, based on examinations 



made January IS, 1913. 



Number of branch. 



Diameter 



of branch 



(mlUi- 



meters). 



Number of 

 eggs. 



Number of 

 living 

 larvae. 



Number of 

 larvae par- 

 asitized. 



I 



36 

 30 

 25 

 38 





 

 



59 



363 

 104 

 79 

 135 



11 



n 



5 



in 



6 



rv 











These tables give the degree of infestation to a single branch and 

 the mortality of the larvae at a very early date. The parasites of the 

 larvae are more numerous a little later in the season, although the 

 egg parasite appears even as early as December 1. This parasite is 

 more effective against the larvae before they approach a size more 

 than two-fifths of an inch in length; although it attacks the larvae 

 throughout the season it does not appear in as large number then 

 as it does early in the season. 



METHOD OF CONTROL. 



Since this insect spends at least 10 months in the severed branch 

 during the egg, larval, and pupal stages, its control is only a matter 

 of collecting the pruned branches and destroying them by burning. 

 This would not be a laborious task, as the girdled branches are so 

 large that it is not difficult to locate them, and as the species does not 

 appear to migrate very rapidly to new territory, this method would 

 nearly eradicate the species in isolated localities, at least, in one or 

 two seasons' time, taking it for granted that a few branches might go 

 unnoticed. (See PL III, fig. 2.) The work of burning the branches 

 could best be done from the first week of January to the first of Au- 

 gust, as the writer has not observed the laying of any eggs as late as 

 January 1. As the huisache wood burns readily, it should be com- 

 paratively easy to collect and destroy primed branches from a large 

 number of trees in a comparatively short time. In addition to this 

 measure, the beetles might be collected by hand where one has only a 

 .small number of trees to guard against this girdler, and in this way 

 the trees could be protected before any damage had been done. 



WASaiNOTON ; aOVKIlNMBNT PIlINTINa OPFICB ! 1010 



