NURSERY PRACTICE FOR PRAIRIE-PLAINS PLANTING 133 



minor damage. Soil poisons or fumigants offer the best possibilities 

 for control, but they must be used with certain precautions to prevent 

 injuring the seedlings. 



WHITE GRUBS 



White grubs are the larvae of the large, well-known May beetles 

 or "June bugs" (Phyllophaga sp.). These larvae are white, fleshy 

 grubs with a brown head and three pairs of prominent legs. The 

 body is held in a curved position. They are general feeders on the 

 roots of plants and, although more common in grassland, at times are 

 serious nursery pests. Soon after the roots of forest tree seedlings 

 are eaten off, the foliage wilts, and the seedlings can be pulled with 

 ease. When only part of the roots are destroyed, the trees may be 

 dwarfed. 



In South Dakota, Nebraska, and possibly in Kansas, the more 

 injurious species require 3 years to complete their life cycle. The 

 smaller first-year grubs, from eggs deposited in the soil late in the 

 spring of the current year, generally cause little damage unless they 

 are very numerous. Most of the damage occurs during the second 

 year of development when the grubs are feeding heavily through the 

 entire season. Feeding the third year continues only until midsummer 

 when the grubs transform to pupae and adults in the soil, emerging 

 the following spring. Adults are emerging each year, and conse- 

 quently grubs in all stages may be found at any time. In the region 

 where the 3-year life cycle prevails, the brood which emerged in 

 1932, 193.5, and 1938 was by far the most numerous. Consequently 

 there is more danger of white grub damage the year following these 

 Mights, if the nurseries are infested. In North Dakota it is likely 

 that 4 years are required for some species to develop, while in the 

 south the life cycle may be completed in 2 years. 



Fumigation by flooding the infested soil with carbon disulfide 

 emulsion has given some success in control on small areas, but the 

 results vary in different soils and under different temperature and 

 moisture conditions. Since the grubs go deep for the winter, this 

 method can be used only during w^arm summer weather when they are 

 feeding within a few inches of the surface. As the surface dries the 

 grubs go down; consequently, fumigation while the upper soil is moist, 

 or a day or two after irrigation, would probably be most effective. 

 Half-grown stock apparently will not be damaged by the chemical, 

 but young seedlings are more susceptible to injury. 



A 50-percent emulsion, consisting of equal parts of carbon disulfide 

 and a special commercial soap solution, may be used for this purpose. 

 Treatment consists of diluting this 50-percent stock emulsion in the 

 proportion of 1% quarts to 50 gallons of water and applying at the 

 rate of 3 pints per square foot of soil surface. An emulsion may also 

 be prepared by using 1 part of rosin fish-oil soap, 3 parts of water, and 

 10 parts of carbon disulfide, by volume. Place the soap and water in 

 a closed container and agitate until the mixture is uniform. Then 

 add the carbon disulfide and agitate until the mixture becomes 

 creamlike. This stock emulsion is diluted in the proportion of 1 

 quart to 50 gallons of water, and is applied at the rate of 3 pints per 

 square foot as above. Late in the afternoon while the ground is still 

 warm is the best time for application. The making of six or eight 

 holes per square yard will also aid in the penetration of the gas. 



