INSECTICIDES AND GENERAL REMEDIES. 411 



remedy against insects is to trench the ground. Not only do the 

 trees grow ever so much faster as compared with pitting, but the more 

 rapid landscape effect and the greater increment amply compensate for 

 the initial outlay in trenching. 



(4) In replanting, it may be noted that careless or indifferent man- 

 agement of the woodland, in the period intervening between the cut- 

 ting of the old crop and the replanting, not only gives every advantage 

 to the dissemination of insects, but the essential conditions of soil are 

 often so much placed out of order that the next crop is weakened and 

 more liable to be injured by insects. All branches should either be 

 carted off the ground or burned on the spot, which of course destroys 

 the breeding-ground for many species of beetles. Then in many cases, 

 UK^re especially pure Scots pine woods, the ground should be well 

 stocked with cattle or sheep three or four years prior to replanting. 

 The effect of this is that the soil is so much trodden away from the 

 old stools that the bark falls off, and the stools are more unfit for 

 breeding-places. Scrub bushes are prevented from getting up, which 

 also often serve for the propagation of many species. 



As regards the advantage of " stocking " with cattle or sheep, it 

 should be noted that, as a result of pasturing, the " spongy " layer 

 underlying the rough turf disappears. This is a great improvement 

 to the soil, inasmuch as the spongy layer is acid in reaction, and con- 

 tains nitrogenous matter derived from the decayed plant residues of 

 which it is composed. In the rough state the nitrogenous matter, 

 however, is not directly available as a plant food, but must be con- 

 verted into a soluble and available form by the action of the nitrify- 

 ing organisms always present in the soil. It will therefore be obvious 

 that the ground can be more cheaply and successfully replanted ; and 

 as the plants will not only do better and give a more regular crop, as 

 compared with planting on rough unprepared ground, the young trees 

 get better over the most critical period against the attacks of insects. 



With regard to the prevention of insects in young woods, it may 

 be said that again it is essential to adopt sound sylvicultural prin- 

 ciples, and as a rule the insects will not be troublesome. One notable 

 exception is the Retinia or pine-shoot moth, which does not disappear 

 under good management as many others do. In young plantations 

 it is well to see that they are planted " thick " and kept so. Secure 

 a rapid canopy, get all grass l-illed off as quicAiy as possihle, and keep 

 the soil conditions right bv having a covering of leaves from the 



