10 



FA'RMERS' BULLETIN 831. 



A peculiar sort of red-spider infestation arises from pokeweed, 

 ^vhich occurs comnionl}' on terraces and along field borders. Owing 

 to its long growing period it rarely becomes heavily infested until 

 midsummer, so that infestation from this weed to cotton usually is 

 noticed later than from violets or spring weeds. 



It has been found that adidt females are able to travel over smooth 

 surfaces at the rate of about 5 inches per mmute, or 600 feet in 24 

 hours. "When forced to migrate because of the scarcity of proper 

 food, they commonly take to the gromid and travel to other plants. 

 During heavy rains man}" red spiders are dashed to the groimd and 

 carried considerable distances in the surface water, whereupon those 

 not kiUed estabhsh themselves on the 

 plants that are near by. Heavy winds 

 also at times blow them from place to 

 place. When the uijury becomes severe 

 hi a portion of a field it is common for 

 the red spider to travel directly from 

 plant to plant by means of the inter- 

 weaving branches, 



PLANTS ATTACKED. 



The red spider ha?, been found breed- 

 ing on 183 kinds of plants, ot which 55 

 per cent are cultivated and 45 per cent 

 are native wild species. Weeds, orna- 

 mental plants, and garden and field 

 crops are included. The following hst 

 -of food plants, arranged in the order of 

 their susceptibility to red-spider attack in the cotton belt, includes 

 those most conmionly infested : Cotton, cultivated violet, sow thistle, 

 hollyhock, dahha, garden beans, corn, tomato, onion, carnation, 

 sweet pea, hedge nettle, nastm'tiimi, morning-glory, clover, wild 

 vetch, ironweed, Jerusalem oak, wild geraniimi, evening primrose, 

 pokeweed, and strawbeny. 



NATURAL ENEMIES. 



The red spider on cotton is known to be attac]%ed by 31 predacious 

 enemies, which render valuable assistance m its control. Of these, 

 5 are mites, 3 are thrips, 4 are bugs, 4 are lacewing fhes^ 2 are midges, 

 4 are syrphid flies, 8 are lady-beetles, and 1 is a caterpillar. These 

 predatory enemies, in turn, are }vno^^^l to be attackcnl by 75 species 

 of predatory enemies and parasites. 



REMEDIES FOR THE RED SPIDER. 



Fig. 7.— Diagram showing how viol; 1 ! 

 growing in dooryard give rise to rcJ- 

 spidcr infestation in adjoining cotton 

 field. The infestation is most severe 

 near the yard. This diagram is typical 

 of manv ia,ses. 



PREVENTIVE ME.\SURES. 



The red-spider problem must be solved tlirough preventive efforts 

 rather than curative if it is to be done with economy. The location 

 of the mites through the winter and spring, their rapid development 



