EXPERIMENT STATION BULLETINS. 



659 



Table III. Effect of Time of Planting on Hopperburn, 

 U. P. Exp. Sta., Chatham, Mich., 1921 



Hopperburn is not severe on late planted potatoes because the plants 

 are either very small or have not come through the soil at the time 

 the spring migration takes place, and remain practically free from leaf- 

 hoppers until the flight of the first generation adults. This summer-mi- 

 gration occurs during the latter part of July and is obviously too late 

 to cause extensive injury. Conditions for the Lower Peninsula were 

 not worked out with respect to this migration. 



These time of planting observations suggest a feasible method of 

 combatting the leaf hopper where danger from early fall frosts does not 

 preclude late planting of potatoes. 



WEATHER RELATIONS 



Natural phenomena, such as the time of blossoming of fruit trees, 

 date of emergence, and length of life cycle of insects, etc., are governed 

 by weather conditions. It is well known that apple trees do not blossom 

 on the same date every year. Likewise the time of emergence of insects 

 from their winter quarters varies with the season. 



It is intresting to note the weather relations of hopperburn during 

 the three years covered by the present investigations. The departures 

 from the normal temperature, precipitation, and sunshine during the 

 months of April to August inclusive for these years are given in the 

 table following. 



