THE PEAE THEIPS IN CALIFOENIA. 11 



loss to the county attributable to the work of the pear thrips amounted 

 to at least $750,000. 



The damage in Sacramento County was noticeable only in a com- 

 paratively limited area in 1909, increasing considerably both in area 

 and destructiveness during 1910 and 1911, and the total loss to that 

 county probably amounted to at least $250,000. 



No accurate figures are available for the damage caused in Alameda 

 County, but a considerable area has been infested for several years 

 and many conservative estimates put the total loss to, but not includ- 

 ing, 1912, as more than $150,000. 



The pear thrips has more recently been found in slightly injurious 

 numbers in Yolo and Napa Counties, in the eastern part of Sonoma 

 County, in the northwestern part of San Joaquin County, and in 

 some parts of San Benito County. 



Including the infested areas in Santa Clara, Contra Costa, Solano, 

 Sacramento, Alameda, Yolo, Napa, and Sonoma Counties, it is safe 

 to say that the thrips, in absence of treatment, would cause an average 

 yearly loss of over $2,000,000. With each additional year an addi- 

 tional loss of several hundred thousand dollars, due to the increase of 

 the area infested and the increased losses in the areas previously 

 infested, is to be expected. The total damage to the fruit industry 

 of the State of California since the first appearance of the insect 

 aggregates, it is believed, at least $6,630,000 up to but not including 

 1912. 



FOOD PLANTS. 



While the pear thrips is distinctly a deciduous-fruit insect and 

 practically all of its damage is confined to this class of plants, it has 

 been found upon a great variety of plants the list of which is increas- 

 ing each year. The fact of its wide range of food plants makes 

 extermination practically impossible, whereas control can be readily 

 practiced. It has been taken upon the following plants and could 

 probably subsist upon a number of them long enough to make it a 

 constant menance to the fruit industry of California: Apricots, 

 apples, almonds, cherries, figs, grapes, pears, plums, prunes, wahiuts, 

 madrona (Arbutus menziesii), wild California lilac (Ceanothus thyrsi- 

 florus), poison oak (Rhus diversiloba) , dogwood (Cornus sp.), acacia, 

 willow (Salix sp.), laurel (Umbellularia calif ornica) , mustard (Bras- 

 sica nigra), live oak (Quercus wislizeni), miner's lettuce (Montia 

 perfoliata) , and various grasses and weeds. 



CHARACTER OF INJURY. 



MANNER OF FEEDING AND TYPE OF MOUTHPARTS. 



Injury to plants by the pear thrips is caused directly by the feeding 

 of the adults and larva? upon the various portions of the fruit, buds, 

 flowers, and leaves, and also by the deposition of eggs in the leaf 

 surfaces, fruit stems, and newly formed fruit. 



