INSECT ENEMIES OF EASTERN FORESTS 29 
Fill the holes with soil and pack it in firmly immediately after the 
chemical has been applied. If possible, the holes should be placed 
between the seed drills in order to keep the chemical as far away from 
the plants as possible. ‘The chemical may be injected with a hypo- 
dermic syringe with the needle removed or with an automatic injector. 
Flooding the infested areas with 50-percent miscible carbon disul- 
fide, consisting of equal parts of carbon disulfide and soap solution, 
may be used w vith some success on seedbeds of even topography. This 
method, however, is not practical on rolling seedbeds since puddles will 
result im uneven distribution of the chemical and severe plant injury. 
The treatment is made by diluting the 50-percent stock emulsion in 
the proportions of 1 quart to 50 gallons of water and applying it at the 
rate of 3 pints per 100 square feet of soil surface. Six or eight holes 
(made with a broomstick) per square yard, will aid in the penetration 
of the chemical into the soil. 
Recent work with DDT for soil-inhabiting insects suggests that it 
will be effective on white grubs in nurseries and plantings. 
Numerous cultural pr actices have been tried as control measures. In 
the Lake States, making the furrows of various depths and widths 
has not prevented grub injury and has been generally unsatisfactory 
from the standpoint of control. Seedbed screens made of 14-inch 
hardware cloth have been recommended for nursery use, but these are 
expensive and inconvenient, and do not prevent the migration of grubs 
except when placed around the seedbeds below the gr ound level. The 
mechanical destruction of larvae by piercing the soil with many- 
{ined wire brushes has likewise proved unsatisfactory. Large nurser- 
ies are using a tractor-drawn rotary tiller for general nursery cultiva- 
tion, and this machine is proving an effective means of mechanical 
control. It may not, however, be successful in all localities or under all 
cultural conditions. Its use is restricted to soil relatively free from 
rocks, roots, and heavy debris, but it can be used in mulch and litter. 
In long-established nurseries damage results through oviposition by 
adult beetles attracted into the nursery for feeding on the foliage of 
certain trees, and these preferred trees should be removed from near 
the nursery. New ground should not be planted to tree seed until it 
has been clean-cultivated for at least 2 years. 
Little control of grubs may be expected from parasites, predators, 
or diseases. Parasites may become an important control factor of the 
Japanese beetle, however, owing to the importation and establishment 
of Asiatic parasites. The native parasites of grubs appear to be inef- 
fective against white grubs. 
The possibilities of control, based on a knowledge of the food pref- 
erences and other ecological relationships of the various species of 
white grubs, is beginning to be recognized. Since female beetles gen- 
erally Ooviposit m He vicinity of their food plants, and as the larvae 
are probably not capable of long migrations, it is obvious that the 
density of infestation is in direct pr oportion to the proximity of adult 
food. An illustrative instance showed an average of 0.1 grub per 
square foot at about 200 feet and 1.562 grubs at 25 feet from an oak- 
aspen-maple stand on the Huron National Forest, Mich. A similar 
distribution has been found to hold in numerous instances on the 
Huron Forest and elsewhere. 
