518 



ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 



and the acid arsenates. In those of the 

 first group the ratio of lead oxide to ar- 

 senic oxide is approximately 3 to 1. In 

 those of the second group the ratio is as 2 

 to 1. The neutral or ortho-arsenates are 

 made by combining lead acetate and so- 

 dium arsenate; the acid arsenates by us- 

 ing lead nitrate in place of lead acetates. 

 The insecticidal value of the various 

 brands depends upon the actual amount of 

 lead arsenate which is present. 



Concerning the relative value of neutral 

 and acid arsenates no reliable experiments 

 have demonstrated the superiority of 

 either. It is commonly believed that the 

 acid arsenates are more likely to burn 

 foliage and we have received reports of 

 injury from the use of Swift's which 

 would seem to support the inference. 

 Manufacturers advise using 3 pounds ar- 

 senate of lead to 50 gallons of water. We 

 usually recommend 2 pounds, and Me- 

 lander, of Washington, recommends to 

 drench the trees with a weak solution of 

 1 pound to 50 gallons. Recently there 

 has been placed upon the market a prod- 

 uct known as zinc arsenite, which is said 

 to be cheaper and better than arsenate of 

 lead. Several growers have reported in- 

 jury from this spray and it does not ap- 

 pear favorable. We have experimented 

 with this spray during the past season 

 and found it quite satisfactory. 



fotfony Maple Scale 



Pulvinaria vitis Linn. 

 Pulvinaria innumerahilis Rathv. 



General Appearance 



This species can be easily recognized 

 in early summer by the large white cot- 

 tony egg-sacs which are posterior to the 

 brown female bodies. 



Life History 



The eggs are very small, oval, and 

 white to yellow in color. They are de- 

 posited in the large, loose, cottony sacs, 

 which are secreted by the females. The 

 young first settle on the leaves and later 

 move to the limbs. The males appear 

 late in the fall to mate and die. In the 

 spring the females increase very rapidly 

 and after egg-laying shrivel and die. 

 There is but one generation a year. 



Distribution 



Maine to California. 



Food Plants 



Maple, pear, apple, plum, peach, grape, 

 sumach, linden, sycamore, locust, beech, 

 elm, oak, orange, box-elder, spindle-tree, 

 mulberry, alder, hawthorn, lilac, black- 

 berry, willow. 



Control 



Kerosene and carbolic acid emulsions, 

 or resin wash, applied when the young 

 are hatching will aid in reducing the 

 coming broods. 



Natural Enemies 



There are many natural enemies, in- 

 cluding Rhizohius ventralis, Coccophagus 

 lecanii and Encyrtus flavus, which prey 

 upon this coccid. 



E. O. EssiG 

 Curculio 

 Anthonomus guadrigibbus Say 

 C onotrachehis nenuphar Herbst. 



Two species attack the apple. The 

 plum curculio and the apple curculio. 

 ConotracUeliis nenuphar, Herbst. and 

 Anthonomus guadrigibbus. Say. Doubt- 

 less the curculio does more injury to the 

 apple crop in some of the Central states 

 than any other insect except the codling 

 moth. It is a snout beetle about one- 

 fourth inch long and of a dark grayish 

 color. The snout is long and slender and 

 may be folded under the body. The beetle 

 winters under rubbish or in the soil and 

 in early spring begins feeding on the 

 opening leaves. After fruit sets it may 

 gnaw little holes in the fruit, but it does 

 most damage by laying its eggs in the 

 fruit, cutting a crescent flap at the place 

 where the egg is laid. 



This insect infests the plum, cherry, 

 and peach, as well as the apple. Com- 

 paratively few of its larvae develop in the 

 apple but they develop freely in the plum 

 and sweet cherry. They develoi) less 

 readily in the sour cherry and peach. 

 Since damage to peach, cherry and plum 

 often results from the fruit rot fungus 

 entering through the wounds made by 

 the curculio. Orchards well cared for 



