EXPERIMENT STATION BULLETINS. 



351 



ground. At this time the adults fly to the potato fields and the females lay 

 great numbers of eggs on the young potato vines. Thousands of eggs are 

 kno-^^i to have been laid on a single hill. If weather conditions are favora- 

 ble — dry and warm — these eggs will hatch in approximately fifteen days. 

 A longer period will be requirecl if the weather is cold. The growing nymphs 

 are voracious feeders and by sucking from the veins and veinlets near the 

 edges of the leaflets cause the characteristic burning of the leaves. Very 

 httle burning is apparent before the nymphs begin to appear, the adults 

 causing a very small percentage of the injury. A period of fifteen days of 

 favorable weather conditions are required for the nymphs to reach maturity. 

 Approximately a month or thirtj^-five days is estimated as the length of 

 time required for a leaf hopper egg to hatch and the nymph to reach the 

 adult stage and lay eggs for the next generation. It is probable therefore 

 that in favorable seasons there are two generations of the potato leaf hopper 

 under Upper Peninsula conditions, the first generations reaching the adult 

 stage during the latter part of July and the second generation the last of 

 August and first of September. Njnmphs of the third generation are no 

 doubt killed by frosts before reaching maturity. 



BORDEAUX MIXTURE AIDS IX CONTROLLING HOPPERBURN, 



Ever since bordeaux mixture* began to be used as a spray for potatoes it 

 has been repeatedly noted that the percentage of Tipburn in sprayed fields 

 was considerably less than in fields which had not been sprayed. The fact 



Fig. No. 22. Potato leaves showing burned areas (Hopperburn) at tips and margins caused by potato 



leaf hoppers. 



•Directions relating to the manufacture and use of bordeaux mixture may be obtained from your 

 County Agricultural Agent or by writing the Michigan Experiment Station, East Lansing, Mich., 

 for Special Bulletin No. 85 — Michigan Potato Diseases. 



