204 



p:ests of garden and field crops 



The Onion Thrips {Thrips tabaci Lind.) 



A great variety of truck crops and some flowering plants under 

 glass are subject to injury by this minute form of insect life. 

 The juices are sucked from the leaves, causing numerous tiny 

 white spots. The insect itself is so small 

 as almost to escape notice. It is yellowish, 

 slender, and one twenty-fifth of an inch long. 

 Eggs are laid within, the leaf tissue. Several 

 generations may be developed in a season. 



Crop remnants and neighboring weeds should 

 be burned in the fall. Attack may be checked 

 by spraying with tobacco extract, being careful 

 to get the material into the axils of leaves, 

 since such places are favored by the pest. The 

 insects are more active on the outer parts of 

 the plant in the early morning, and thus are 

 more easily reached at that time. 



The Tobacco Thrips {Euthrips nicotianceHinds) 



The work of this minute insect may be rec- 

 ognized by a whitening of the leaves, especially 

 along the veins. The adult winters in tobacco 

 fields, and breeds rapidly in the warmer 

 months. Before tobacco plants are up and 

 after they are gathered it lives on weeds, or 

 often on oats. 

 Spray with kerosene emulsion, diluting the stock emulsion with 

 10 parts of water. 



Fig. 253.— White spots 

 on onion leaf caused 

 by the Onion Thrips. 

 Enlarged to twice nat- 

 ural size. Original. 



The Grass Thrips {Anaphothrips striata Osborn) 



Usually the work of this insect is observed rather than the pest 



itself. Various grasses, including oats, turn white, the appearance 



being known as " silver top." More closely examined, the leaves will 



be found covered with white dots where the juices have been sucked out, 



