16 DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 



In the conidiophore stage on the tree the fungus hj-j^hse break forth 

 in groups from between the body segments and extend out as h)ng 

 slender thi-eads, which in turn branch and form numerous fruiting 

 organs. This stage of the fungus has been taken only from adult 

 thrips on the tree and not from the larvae, and it has been foimd 

 present almost everywhere that the pear thrips has been collected. 



There is no doubt that the fungus spends a part of its life on the tree 

 and a pait in the ground, the rapidly fruiting stage among the active 

 thrips and the heaA"3'-w ailed dormant stage within the hibernating 

 individiuds in the ground; but we can onl}' surmise how it is carried 

 from one to the other. The bodies of the larval thrips within the 

 ground are all absorbed by the fungus and naturalh', therefore, the 

 spores must be carried to a new host before the}- can germinate to 

 any great extent. We have found adult thrips in the ground A\liose 

 dead bodies contained only a few spores and others which developed 

 some of the external mycelial grow^ th -w-ithin their cells. If this were 

 often the case, and these individuals in the ground produced fruiting 

 spores as they do on the trees, it would be an easy matter for healthy 

 individuals in coming from the ground to become accidentally infested 

 and to carry the parasite up to the tree where, because of the gre- 

 garious habits of the insect, it would spread rapidly. 



The fungus grows readily in the nutrient agar under ordinary con- 

 (Utions and seems to retain its virulence and can be transferred from 

 cultures to the living thrips. The fimgus ma}^ prove to be a check 

 for the pear thrips, but its effectiveness is uncertain because it is so 

 sul)ject to climatic conditions. 



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