Insect Pksts of Interkst to Cotton Growers 201 



plants are shown in Fig. 28. The insects work on the under sur- 

 faces of the primary leaves and on young leaves of later growth 

 which are soon crinkled by their attacks. It is probable that this 

 insect infests certain weeds and other vegetation in and near cotton 

 fields and that clean culture will act as a preventive of injurious 

 attacks. When the young plants are seriously infested spraying is 

 the only available remedy. For this purpose nicotine sulfate — soap 

 solution is probably the best insecticide. This should be used at 

 the rate of six ounces of nicotine sulfate (Black leaf 40) and two 

 and one-quarter pounds of whale oil or fish oil soap in fifty gallons 

 of water. The spray should be applied with as strong pressure as 

 can be used without injury to the plants. A right angle nozzle or 

 a combination of angle nozzle and elbow joint giving a ninety 

 degree spray is needed in order to reach the under surfaces of the 

 leaves and to drive the spray into the crinkled leaves from all sides. 

 Fortunately the cotton thrips, so far as observed, is destructive 

 only when the plants are small, and the early injury is usually out- 

 grown by otherwise thrifty plants. 



THE RED SPIDER 



During the past few years the two-spotted red spider (Tetrany- 

 chiis himaculatiis Harvey) has become quite prominent among the 

 cotton pests of the Southeastern United States. This same species 

 is of common occurrence in the Salt River Valley where it attacks 

 violets, climbing roses (Dorothy Perkins), strawberries, blackber- 

 ries, and beans. So far, how-ever, it has not been observed on cot- 

 ton plants in Arizona. It seems very likely that sooner or later 

 this insect will be found doing damage to cotton in the fields, al- 

 tho, apparently, conditions for the infestation of cotton are not 

 as favorable here in Arizona as they are in the Southeastern states. 



The red spider is a true mite rather than an insect, having eight 

 legs instead of six in the adult stage, lacking antennae and other- 

 wise differing from true insects. The adult female is only one- 

 fiftieth of an inch in length and the adult male is only about half as 

 large as the female. Infested cotton leaves turn deep red on the 

 upper surface, producing a condition sometimes called "rust". An 

 examination of the under surfaces of the leaves, however, reveals 

 the presence of the minute red mites. Badly infested leaves become 

 distorted and finally drop. The pest develops very rapidly, produc- 

 ing in a single season as many as seventeen generations. It is of 

 special interest in the arid Southwest on account of belonging to a 



