300 THE CITRUS FRUITS 



Thrip. — Besides the scale insects several others are injur- 

 ious. The orange thrip is often troublesome and is found 

 principally in the flowers of the citrus fruit. The presence 

 of the thrip is usually first detected by the distorted and 

 irregular growth of young leaves. 



The thrip injures the fruit by producing irregular scars 

 around the stem and at other places over the surface. The 

 damage done to the fruit does not injure the edible qualities, 

 but it reduces the sale and places it in an inferior grade. 



The most effective remedy for the thrip recommended 

 by the United States Department of Agriculture is 2J quarts 

 of commercial lime sulphur at 22° B. plus 3f fluidounces of 

 a 40 per cent. Black Leaf extract to 30 gallons of water. 

 This material should be sprayed on the trees with a force 

 of 175 or 200 pounds, pressure. 



Red Spider. — There are two species of red spider injurious 

 to the citrus fruit. They are found throughout the citrus 

 regions both in Florida and in California. 



The red spider is a small red insect which often becomes 

 so abundant on a leaf as to give a reddish color to it. The 

 best remedy for the red spider is sulphur. It is used in 

 either the dry form or in the form of lime sulphui solution. 

 When it is used dry the sulphur is dusted on the plant, 

 usually when the foliage is a little damp. When lime 

 sulphur is used the commercial product is diluted 1 gallon 

 to 35 gallons of water. The lime sulphur is becoming more 

 popular and its cost is much less than fumigation. 



Control of Insects. — The control measures for the citrus 

 insects are different than the control measures for most 

 other insects. This is made necessary because the trees 

 have their leaves the entire season, and since most of the 

 serious insects are scale insects it is impossible to spray 

 the trees with a solution strong enough to kill the insects 

 and not kill all of the foliage. Because of this combination 

 some other way for the control of insects is necessary. 



About 1886 California first seriously considered fumiga- 

 tion as a means of destroying injurious insects. As time 

 passed the methods of fumigation were greatly improved 

 but the fundamental principles remain the same. 



