15 



Hosts 



By all odds the cultivated apple is the chief host of the apple flea- 

 weevil in Ohio and Illinois. That this is fortunate is evident, since any 

 insect pest which thrives equally well on one or more uncultivated hosts 

 renders its control on cultivated species more difficult. However, the 

 apple flea-weevil is known to feed in the larval or the adult stage on a 

 number of other hosts. What were presumably larvae of this species 

 were seen mining the leaves of the winged elm (Ulmus alata), American 

 elm (Ulmus americana), and elder (Alnus sp.) at Falls Church, Va., 

 and hazelnut (Corylus americana) , at Wooster, Ohio. Larvae were 

 found mining the leaves of quince in Illinois and Ohio, choke cherry 

 (Primus virginiana) and hawthorn (Crataegus mollis) in Ohio and 

 adults were reared from the infested leaves. Lastly, the beetles were seen 

 feeding on the leaves of the wild crab (Pyrus coronaria) in Ohio and 

 Illinois, and are reported by others as feeding on the leaves of willow 

 and on the flowers of service berry (Amelanchier). 



In no instance has a wild or unusual host been found severely in- 

 fested by either the mining larvae or the feeding beetles, even when 

 growing in the immediate vicinity of severely infested apple trees. 



Natural Checks on Multiplication 



Probably the most effective factor in natural control is the white 

 muscardine fungus (Sporotriclium globulifernm Speg.), a well-known 

 fungus parasite of insects, the spores of which germinate on the surface 

 of the beetle, sending their threadlike mycelium into and throughout its 

 tissues and causing its death. It continues to thrive on the carcass and 

 in time its white growth entirely envelops it. During the extremely wet 

 summer of 1915, weevils covered with this fungus could be found liter- 

 ally in thousands under the loose scales of bark on the trunks of apple 

 trees and in the cover around the bases of the trees in Illinois orchards 

 (see Figure 12). The dampness caused by repeated rain had been very 

 favorable to the development of this fungus in orchards that had been 

 heavily infested for several seasons previous, and in some of them the 

 flea-weevil was almost entirely exterminatd. In an orchard at Plain- 

 view, Illinois, where at least :«() per cent, of the leaf surface was de- 

 stroyed in 1!»14, a careful search of nearly two hours was required to 

 find a single weevil in 1!)16. No appreciable damage has been done in 

 this orchard during the past five years, although the weevils are now 

 becoming more abundant and were present in considerable numbers 

 during the summer of 192L It is, however, only during prolonged 

 periods of wet weather that this fungus has ever been an important 

 factor in the control of the flea-weevil. Such general prevalence of this 

 disease has never been ol)servcd in Ohio orchards, although beetles dead 

 with it are very commonly encountered there. 



