388 PEAR GROWING IN CALIFORNIA. 



form and it is a common practice to dust trees or other plants with 

 flowers of sulphur. 



The important consideration with all summer treatments is the 

 making of the application early before the trees have been damaged. 

 Frequently it happens that some injury is done before the orchardist 

 is aware that the pests are present. Hot dry weather is favorable to 

 their increase, and unirrigated orchards suffer much more heavily than 

 irrigated, which are more vigoroiLS and the conditions of which are more 

 unfavorable for mite breeding. 



EELWORM (Heterodera radicicola). 



Frequently the roots of pear and other nursery trees contain small 

 knots or swellings as a result of the attack of the eel worm. This condi- 

 tion is known as root knot and should not be confused with crown gall, 

 which is described in the chapter on Bacterial and Fungous Diseases of 

 the Pear. The so-called eelworm is one of the nematodes or flat-worms 

 of which there are a great many species. Their damage is always worst 

 in light, sandy soils and in the heavier soils there is little danger from 

 them. At times this pest is quite serious, causing the death of fibrous 

 roots, and in severe cases roots of considerable size may be injured or 

 killed. It is a verj^ general feeder, attacking many garden vegetables 

 as well as fruit trees, berries and shrubbery, therefore its introduction 

 into an orchard may be the means of its getting started on other things 

 in the vicinity. 



Control. 



Control measures are preventive and consist in a careful inspection 

 of nursery trees. When found to be infested they should be discarded 

 unless for planting in heavy soil where it is thought that the pest can 

 not thrive. 



RABBITS. 



In many parts of California the rabbit pest must not be overlooked 

 when the orchard is set. Without any warning, and before one is 

 aware that any damage is beina- done, rabbits frequently play havoc 

 in the newly-set orchard. If the expense of a rabbit-tight fence, the 

 best method of prevention, is considered to be prohibitive, young trees 

 may be protected by placing a cylinder of a small-mesh woven wire 

 about the trunks. If trees are low headed and jackrabbits are present, 

 protection of portions of lower limbs may also be necessary, as these 

 rabbits can reach a considerable height above the ground, "instead of 

 woven wire the ordinary tree protectors of heavy paper or yucca may 

 be used. Whitewash containing aloes (see Formula No. 20) acts as a 

 repellant against rabbits. Without the aloes whitewa.sh is of little value. 

 Salt, which is sometimes used as an adhesive with whitewash, should 

 never be used in orchards where the rabbits can get in as it attracts 

 them, rendering the use of the wash extremely dangerous. 



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