702 



PARKS 



APHIDS 



Some years, and very often in the spring, aphids or plant lice are 

 abundant on trees. These are sucking insects, small, soft bodied, somewhat 



pear-shaped and colored from pale yel- 

 low or green to pink or blackish. They 

 are usually found on the undersides of 

 leaves or on the tender new growth. 

 Maple, beech, birch, linden and tulip 

 poplar are among the most frequently 

 infested trees. The feeding of the aphids 

 is usually not a serious menace to the 

 life of the trees attacked. They may, 

 however, cause paling and early falling of 

 the foliage. Sometimes they are very 

 annoying because of their honeydew 

 the sweet liquid they excrete which 

 falls, wetting the upper surfaces of the 

 leaves and the ground beneath the tree 

 and soiling everything with which it 

 comes in contact. Aphids are usually nat- 

 urally controlled by weather conditions 

 and various insects that feed on them, 

 such as the ladybird beetles, but some- 

 times it is advisable to combat them 

 artificially. For this purpose a spray com- 

 posed of the following is very effective: 

 Nicotine sulphate, I pint; soap, 12 pounds; water, 100 gallons. This spray 

 should be applied at least twice, with an interval of one week or ten days 

 between treatments. It should be applied in such a way that the material 

 will come in contact with the bodies of the lice; it usually works best on 

 warm, bright days. 



SCALE INSECTS 



Under park and shade tree conditions scale insects are of great impor- 

 tance. These insects weaken and kill trees, limbs and branches. The pine 

 leaf scale found on pine and spruce needles and the juniper scale are impor- 

 tant scale enemies of ornamental conifers. The San Jose scale, the oyster 

 shell scale, the gloomy scale, the cottony maple scale, the obscure scale, 

 the golden or pit-making oak scale, the tulip tree soft scale and many others 

 are all important enemies of the various hardwood trees. 



The presence of scale on hardwood or deciduous trees is best deter- 



PLATE No. 260 



THE WOOLLY MAPLE AND ALDER 

 BLIGHT APHID ON MAPLE LEAVES 



Photograph by United States Bureau of 

 Entomology. 



