240 THE MONTHLY BULLETIN. 



CITRUS FRUIT INSECTS. 



The Citrus Thrips. 



The citrus thrips are minute, active brownish or yellowish insects. 

 Four species have been recorded an injurious to citrus fruits in the 

 United States. One species, the green-house thrips, causes the surface of 

 the fruit to turn a pale silvery color. Occasionally scarring of the fruit 

 may result. The species known as the citrus thrips proper causes 

 the characteristic crinkling and thickening of the new tender foliage, 

 as well as the marking of the fruit in the form of a ring around the 

 stem-end or down in streaks. Thrip attacked oranges are often forced 

 back into the second and third grades. The insects feed in both the 

 young and adult stages. Their attack is practically limited to the 

 exterior portion of the tree. A. W. Morrill, in the report of the Arizona 

 Entomologist for 1911, mentions the fact that he obtained as good results 

 with lime-sulphur solution, 36 degrees Baume, diluted at the rate of 

 1 part to 85 parts of water, as with the lime-sulphur solution, 1 

 to 85, combined with tobacco extract 40 percent nicotine, 1 to 

 ],800. The number of applications will depend upon the abundance 

 of the thrips, and the citrus fruit growers should be able to determine 

 whether or not the thrips are sufficiently abundant to warrant spray- 

 ing. Use an angle nozzle so as to reach both sides of the leaves and 

 maintain a pressure, if possible, of from 175 to 200 pounds. 

 Thoroughly drench the trees, especially the outer portions. 



Diabrotica soror. 



DiahroUca soror is a plant-feeding beetle which eats the foliage of 

 a large variety of plants, including the citrus. It is recognized by its 

 greenish color and the twelve black spots on the wing cover. Num- 

 bers may be killed by jarring the beetles from the trees into tar or 

 receptacle containing oil in the early morning, at which time they are 

 sluggish, or by poisoning them by spraying the foliage with arsenate 

 of lead, two pounds to 50 gallons of water. 



The Citrus Red Spider. 



The adult citrus red spiders are tiny reddish mites with eight legs. 

 They are generally found on the under sides of the leaves and are 

 much more common in the interior portions of the trees than in the 

 outer. The leaves infested have a spotted appearance. Mr. J. A. 

 Frizer, entomologist of the San Diego Fruit Company, has found that 

 under certain weather conditions— a night when dew is plentiful, 

 followed by hot days— dry sulphur mil produce fine results. Lime- 

 sulphur solution 2 per cent to 2i per cent strength applied at a 

 pressure of from 150 to 200 pounds is generally used if unfavorable 

 conditions for the dry sulphur exist. Atomic sulphur 6 to 7^ pounds 

 to 100 gallons of water may also be used and is less likely to 

 burn the foliasre than the lime-sulphur solution. Spray when the 

 mites become numerous enough to produce injury. In very hot 

 weather it is not advisable to spray unless the seriousness of the situa- 

 tion demands it. 



