28 MISC. PUBLICATION 273, U.S. DEPT. OF AGRICULTURE 



to transplants. Leaf-feeding insects usually are easily controlled 

 by the use of sprays. 



Key to Diagnosis of Insect Injury to Forest Nursery Trees 



A. Roots of seedlings completely bitten off or the bark badly chewed, 1 



injured, or dying. Look for soil-inhabiting insects appearing 

 as — 



1. Curled, white grubs, with three pairs of prominent legs and 



with brown heads 2 White grubs, p. 28 



2. Small, curled, white grubs with small, brown heads but 



without legs 2 Root weevils, p. 29 



3. Long, slender, hard-shelled, yellow or brown "worms" with 



feebly developed legs 2 Wireworms, p. 30 



4. Nearly hairless, soft, sluggish, dark-colored caterpillars 



working below surface of ground 2 Cutworms, p. 30 



5. Soft, white, slim, legless maggots burrowing within stem 



below ground Seed-corn maggot, p. 31 



6. Small, white, centipede-like animals found in moist soil 



Symphylids, p. 31 



B. Stems of young seedlings bitten off, badly chewed, or injured. 3 



1. Nearly hairless, sluggish caterpillars working at night 



Cutworms, p. 30 



2. Grasshoppers Grasshoppers, p. 74 



C. Leaves of seedlings either chewed, skeletonized, mined, discolored, 



or attacked by leaf-sucking insects Defoliators, p. 75 



1 Damage meeting this description is done also by root-feeding mammals 

 such as gophers, and squirrels. 



2 These characters are not specific and sometimes noninjurious larvae of 

 similar appearance may be confused with these forms. 



3 Similar damage is often done by small animals, such as mice, squirrels, 

 and porcupines. 



WHITE GRUBS 



White grubs (41, 85, 105) (fig. 10), the larvae of June beetles 

 (Phyllophaga spp., Pohjphijlla spp., and other related genera), may 

 be encountered in forest nurseries, particularly where the land has 

 previously been covered with weeds and grass. The white grubs 

 feed on the roots of a great variety of plants and the adult beetles 

 are voracious feeders on the leaves. A large number of species are 

 widely distributed throughout the United States. 



The large, shining, brown June bugs usually lay their eggs in 

 the spring of the year in grassy places or where the ground vege- 

 tation is heavy. The grubs hatch 3 or 4 weeks later. In the North, 

 where the life cycle usually requires 3 years, the small white grubs 

 feed during the first summer on organic material and on small 

 rootlets near the surface of the soil. As cold weather approaches 

 they burrow more deeply into the soil and hibernate. The second 

 season the grubs are larger and do their greatest damage to the 

 roots of seedlings and small trees. They again hibernate deeply in 

 the soil over the second winter, and again feed near the surface 

 the following spring. The full-grown grubs are white, thick-bodied, 

 with dark-brown heads and three pairs of well-developed legs. 

 They always lie in a tightly curled position and are familiar ob- 

 jects to everyone who has dug for fish bait. Usually in midsummer 

 of the third season they reach full growth, and then transform 



