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TWENTY-EIGHTH FRUIT-GROWERS' CONVENTION. 



THRIPS. 



By PROF. A. J. COOK, of Claremont. 



When a new insect pest comes upon us, or when an old well-known 

 insect appears in a new role of mischief, either of which threatens the 

 pocketbook of our people, it becomes a matter of great concern with us 

 all. In all such cases every detail of history is very important. 



History. — Late last January I received from an orchardist in Fer- 

 nando lemons which were seriously marred by brown spotting, that 

 looked greatly like rust, and not a little like the work of the silver 

 mite, yet quite distinct from the latter. Within a few days after that I 

 received from our own county — Los Angeles— from three different per- 

 sons at San Dimas, both oranges and lemons similarly marked. In 

 every case it was reported that the fruit was fair and perfect when 

 gathered, but became disfigured in about three weeks after the picking. 

 I made careful examination with a microscope, using both high and 

 low powers; and though I discovered no signs of fungus, I did note 

 injury of the superficial cells — the very surface or epidermal cells of the 

 fruit. I reported this through the press. On Monday, February 2d, 

 Mr. H. H. Garstin, of Redlands, came to me with many samples of 

 oranges — some just picked, others picked some days before. The first 

 showed a very indistinct injury, to discover which required very close 

 observation; the other was really the same trouble that had interested 

 me in the cases just reported. I said to Mr. Garstin, " This is plainly 

 the work of some insect, and I know of no insect common enough in 

 our orchard to do it except the thrips; and besides, the thrips is capable 

 of just such mischief." He replied that Professor Eaton, of Redlands, 

 claimed actually to have seen the thrips doing the mischief. I learned 

 later from Mr. Williams, one of our students, who had visited his home 

 in Redlands a few days before, that the orange-growers of Redlands 

 were seriously anxious about the work of the thrips. They also 

 suggested to Mr. Williams that he study up the history of the thrips, 

 which he did, giving an illustrated article in our college paper, "The 

 Student Life." Thus the suggestion of thrips was first made by growers 

 at Redlands. The first mention of thrips in print, so far as I know, 

 was in the Los Angeles "Times" of February 4th, in a report of our 

 Claremont Pomological Club, at which meeting I first called public 

 attention to the injury and the probable agency of the thrips as the 

 cause. Mr. Garstin also stated to me at the same time, February 2d, 

 that fruit left on the tree must recover, as early picked fruit was 

 spotted, while that picked later was free from blemish. This important 

 truth seems now fully established. We are not surprised that this is 

 so. The insect is very minute and the injury is very slight and very 

 superficial. If the fruit is picked it fails to receive more sap and the 



