SPRAYING FOR THE ALFALFA WEEVIL. 
Geo. I. Reeves, Hntomological Assistant, T. R. CHAMBERLIN, Scientific Assistant, 
and K. M. Pack Field Assistant, Cereal and Forage Insect Investigations. 
CONTENTS. 
Page. Page. 
The turning point in weeyil injury AU AVe 4 Gps t0y ol) ae SOP de oe ee i183 
determines the time to spray__-~ a), Lhe pressure ‘gauges = -—- = = ue 14 
-The time of the turning point is TPhersirainer a= ase ae ee le rere 14 
governed by weather conditions__ Dini Le enone ee anaes bet SS ee 15 
Second-crop protection _~__________ all On ey Con eee eens Se ates Lee ee ee 16 
Stubble spraying not reeommended__ 8 || he mozzlesue ee S22 2 See ee eee, re 
Preparation of machinery______---- Sri (POOLS 2 a en ee a 18 
Necessary equipment______________ SlleThe poisones= == = se ee ae 18 
Gapacity, of the outht=2- > —2—=___ 9); Applicationvof the sprays—— 2 19 
Pe PAVehiClets see 2 owes Soe we 12 | Danger of poisoning stock_________ 20 
CAG TENT ge Se a ee ee Dye) CON CHILO Mae ene aU Bee te eg Su 20 
THE TURNING POINT IN WEEVIL INJURY DETERMINES 
THE TIME TO SPRAY. 
| ian BEST TIME TO SPRAY for the alfalfa weevil is de- 
termined by the progress of weevil injury in the alfalfa field. 
The ‘seasonal activity of the weevil is as follows: The adult 
beetles or weevils, after hibernating in the fields, come out in early 
spring, feed sparingly upon the leaves and stems, and deposit eggs, 
at first in the softer dead stems on the ground and later in the green 
stems. The eggs develop slowly at first and faster as the temperature 
rises, until in May and June they hatch within two weeks after they 
are laid. 
The feeding of the larve begins early in the spring and increases 
steadily until after the height of the hatching season in May, but the 
plants outgrow the injury until shortly before cutting time, when 
the young larve become so numerous that they completely destroy 
the growing tips and thus stop the growth of the plants (fig. 1). 
This is the turning point in injury, and after it is passed the ap- 
- pearance of the field changes rapidly; the leaves are consumed until 
nothing is left but woody fibers, and the tops of the plants are as 
white as if they had been frostbitten. This condition is shown in 
3 
