- 3 - 
Conditions Affecting Injury 
The larvae (white grubs) of May beetles feed on the roots of grasses 
hej an. usually more abundant in uncultivated soils 
devoted to the production of grasses than in cultivated soils. Conditions 
under which pecan trees were severely injured or completely defoliated by 
eetles in Louisiai a rare as follows: (1) Young pecan trees in both 
cultivated and uncultivated orchards, 10 to 40 acres in area, located near 
sod land; 2) old growing in the outer rows of well-cultivated 
- n i en: or more sides ky extensive areas of 
sod land, 3 pec; Lng in yards near homes; and (4) old pecan 
trees in uncultivated plantings, varying from a few trees to large orchard 
trao a j e sod land (fig. 1). Practically no damage 
aed s on j can trees in well-cultivated commercial orchards 
eurrouicd. M large trai oi cultivated farm lane's. 
Some oui infestations in cultivated pecan orchards 
irera mee. s, pastures, cut-over ..codlands, levees, road sides, and fence 
Control 3/ 
rhorjv. : i cultivation whenever possible of all areas in or near pecan 
orchards, in which ruks, or beetle larvae, may develop is of 
great .alue i.i control. Since this is not always feasible, other control 
_ a., n :o \ - nt injury to pecan trees by the beetles. 
Experiments were conducted near Shreveport, La., in 1935 and 1937, 
to study the effect of arsenical sprays in preventing damage by May beetles 
on i oung pecan trees. One application of lead arsenate failed to produce 
conclusive results in 1935 on a light infestation of the beetles. A single 
application of lead arsenate, 3 to 4 pounds in 100 gallons of water, caused 
no injury to pecan foliage that year. 
In 1937 lead arsenate was used at the rate of 3 pounds to 100 gallons 
of water in combination with 3 pounds of hydrated lime. Twenty-nine pecan 
trees in an orchard containing 114 trees were sprayed with this material at 
weekly intervals for 5 weeks. The first spray application was made on April 
20, and the last on May 19, 1937. Differences in the extent of beetle injury 
on spraved and unspra: . ss first became apparent 4 to 6 days after the 
date of the first spray application. 
Sprayed trees retained their foliage and continued growth, while the 
amount of foliage on unspra; ed trees decreased with each night of beetle 
feeding until all unsprayed trees were completely defoliated. Photographs 
of sprayed and unspra s (figs. 2 and 3) were taken on May 14 and 
3/ For more detailed in Terr: at ion on May beetle control, particularly v/ith 
reference to the grufc stage, see Farmers' Bulletin No. 1798, U. S. Department 
of Agriculture, Control of Common White Grubs in Cereal and Forage Crops. 
