Show ALFALFA WEEVIL CONTROL AN individual PROBLEM by W W owens U S A C extension service Edl Edi dors flors note this is the second of a series of seven articles prepared I 1 by mr air owens for or this paper on weevil control alfalfa weevils which damage a crop of hay are hatched from eggs laid by adult weevils which were raised in that same field the year before it if a farmer permits a large number of weevils to mature in his field this year he Is certain to suffer damage next year it he prevents most ot of the weevils from maturing this year he will have little or no weevil damage next year in other words the offending weevils are home grown the old idea that weevils take to flight in the late summer and fall and are equally distributed over a wide area the next spring Is wrong there Is a gradual widening of weevil territory each year but not a sufficient migration to endanger the farmer who keeps the numbers down on his own farm the weevil problem may be compared to that of wild oats by planting clean seed and preventing volunteer wild oats from seeding one farmer may rid his land of this pest even though all his neighbors still produce wild oats so too with alfalfa weevil ono one farm may be tree free from damage or even one field of a farm when surrounding fields suffer gutter severe damage the writer saw a field which was white with weevil injury while a field across the road showed no signs of damage the difference was caused by methods of the previous year which allowed a large number ot of weevils to be produced and live over in one field while most of them in the other field were destroyed alfalfa weevil control Is an all individual problem it may be held in check on one farm or on one field while surrounding fields are literally eaten up EFFECT OP OF STAND OP OF ALFALFA ON WEEVIL DAMAGE article 3 it if one wanted to produce large numbers of alfalfa weevils he would choose a thin stand of alfalfa as the ideal breeding ground the weevil multiplies much taster faster in a field where the alfalfa plants aro are some distance apart with bare spots in between than it does where the alfalfa Is so 0 thick that it completely covers and shades the ground female weevils seem to ie be endowed n by nature to lay large numbers of eggs heat la Is the factor which determines when they lay and how many eggs they lay warm weather promotes egg laying while cold weather retards regards it assume that the temperature of the air over an alfalfa field la is 76 75 degrees fahrenheit the temperature on moist ground which Is shaded by a heavy stand of alfalfa will be 65 degrees F the temperature on tho the ground next to a bare spot in a thin stand of alfalfa will be 87 degrees F the adult female weevil lives on the ground and lays her eggs in dry stems on the ground and at the base of growing alfalfa stems in the field of heavy hay where the temperature Is 65 degrees F the weevil will be slow in starting to lay eggs she will perhaps lay a total of eggs only during the season the time required tor for eggs to hatch la Is also dependent upon heat the eggs in this field will take five weeks to hatch into the worms which do the damage in the field where there to la a stand of alfalfa with a temperature pera ture of 87 F down where the adult weevil lives egg laying will be hastened each female weevil will lay about eggs twice as many as she would in the heavy hay where it Is colder the eggs will hatch in two and one halt half to three weeks not much more than half the time required in the other field A little arithmetic applied to the above figures will show that the weevil damage in a thin stand of alfalfa where there are only halt half as many plants as in a heavy stand la Is not just twice as much but is actually more than four times as much the damage occurs earlier in the thin stand of at alfalfa because the weevils hatch earlier the plants are less 1698 able to withstand injury than they would bo be later for protection from weevil injury as well as tor for higher yields of hay bay per acre plow up the old thin alfalfa fields and replace them with young heavy stands |