September, 1909 



THE GARDEN MAGAZINE 



Peculiar fruit-like Swellings occur on the sumac. 

 These are full of the aphids 



spiny, green bud gall some three-fourths to 

 an inch long on witch-hazel. This species 

 also occurs upon the birch, causing irregular 

 corrugations in the leaves and exhibits 

 some very interesting modifications in struc- 

 ture. Some of the generations differ so 

 markedly that they might easily be mistaken 

 for scale insects or bark lice. 



The conspicuous alder blight, so common 

 on alder in midsummer, is a plant louse 

 decked out with long, white tresses and, 

 strange to say, this plant louse also occurs 

 upon maple leaves, and for a time was 

 regarded as a distinct species. 



SOME PRETTY GALLS 



The cockscomb elm gall, easily recognized 

 by the long, irregular, frequently red-tipped, 

 cockscomb-like swelling running parallel 

 with the veins, is very common, and is 

 sometimes so abundant as to seriously 

 deform the leaves. The green or reddish, 

 cone-like galls some three-fourths of an 

 inch long on spruce are produced by another 

 plant louse which is occasionally quite 

 injurious to this tree. The globular aphid 

 galls on hickory with a geode-like interior 

 due to the hosts of plant lice on the inner 

 surface, are very common and are caused 

 by close allies of the destructive grape 

 phylloxera. 



The hickory leaf stem gall, an irregular 

 green or black swelling half an inch in 

 diameter, is abundant and destroys many 

 leaves. Both the sumac and the slippery 

 elm are the host plants of gall-making lice, 

 noteworthy because they produce a very 

 large, irregularly pear-shaped, bladder-like 

 retreat, thickly populated with aphids in 

 various stages of development. It is remark- 

 able that certain plants find themselves 

 literally compelled to produce extra tissue 

 in the form of galls, and thus provide shelter 

 for their enemies. 



Plant lice may be destroyed in large num- 

 bers by pelting rains and other adverse 



climatic conditions. They are also subject 

 to attack by insect enemies. The familiar 

 red, black-spotted lady beetles and their 

 ugly, black grubs are among the most com- 

 mon and beneficial of the natural enemies. 



NATURAL CHECKS 



Many an outbreak has been arrested in its 

 incipiency by the activities of those little 

 creatures. The handsome flower flies 

 deposit delicately sculptured eggs in colonies 

 of plant lice and the greenish or yellowish 

 varicolored maggots devour hosts of aphids 

 before they attain maturity. The small, four- 

 winged parasites are most efficient checks. 

 Many a colony has been depopulated by 

 these little insects, as is evidenced by the 

 clusters of greatly swollen, brown corpses, 

 each presenting indisputable evidence of hav- 

 ing once been the home of a parasite. These 

 beneficial forms, as explained above, usually 

 become abundant with the advent of warm 

 weather and check these enemies of plant 

 life. 



NOT OFTEN SERIOUS 



Trees and shrubs are rarely very seriously 

 injured by the abundance of plant lice, 



Young condition of the alder blight, due to a louse 

 which may also be found on maple leaves 



The white tresses of the alder blight are conspicuous 

 in midsummer, making a very striking effect 



Sometimes the ■whole leaf may be changed in ap- 

 pearance. Ash leaf deformed by a jumping louse 



though growth is frequently checked and 

 the size and quality of the crop materially 

 reduced. Only very occasionally, when 

 the attack is exceedingly severe and pro- 

 longed, is the tree severely injured. Ordi- 

 narily a well cultivated, vigorous tree or shrub 

 will quickly recover from such attacks. 

 It is unwise to cultivate and fertilize trees 

 and shrubs freely after July, in an attempt 

 to overcome the effects of a plant louse out- 

 break, since a succulent growth late in the 

 fall is liable to be followed by winter injury. 



PREVENTION VS. CURE 



It is impossible to control plant lice satis- 

 factorily by the application of contact 

 insecticides after the foliage has become 

 badly curled, unless is it feasible to dip the 

 tips, a process specially adapted to young 

 trees. The most practical way to handle 

 these insects is to closely watch their 

 development. 



A rapid increase of the pests with an 

 absence of parasites and an undue pro- 

 longation of cool weather should be followed 

 by thorough spraying before the leaves curl 

 to any extent. Even an ordinary ivory 

 soap solution, a five cent cake to eight 

 gallons of water is very effective in checking 

 many plant lice and not harmful to leaf 

 tissues. A whale oil soap solution, used 

 at the rate of one pound to six or seven 

 gallons of water, or the standard kerosene 

 emulsion diluted with nine to fifteen or more 

 parts of water is frequently employed. The 

 latter is made by dissolving a half pound of 

 soap in a gallon of water, adding two gallons 

 of kerosene and then agitating thoroughly 

 until a milky, homogeneous mixture is pro- 

 duced; then dilute to the required amount. 

 Ready made oil emulsions requiring dilutions 

 only before application are on the market 

 and are much more convenient for the small 

 grower. 



