ROUNDHEADED APPLE-TREE BORER. 35 



A series of tests were made with applications of casein and glue 

 in varying combinations with gypsum, paris white, china clay, sylex, 

 barytes, zinc white, and other pigments, but none of the materials had 

 sufficient lasting qualities to recommend them. 



WHITE-LEAD PAINT. 



Nothing in the foregoing line of protectors gave better results 

 from every standpoint than white-lead paint. As is shown in Table 

 XI, three forms of this paint were used, one in which the lead was 

 mixed with boiled linseed oil, one with raw linseed oil, and one 

 ready-mixed paint purchased on the market. The first two mixtures 

 were applied annually to 31 trees each for six years and the last to 

 31 trees for four years. At the end of the periods none of the trees 

 showed any injury, growth being normal and comparable in every 

 way with that of check trees growing in adjacent rows. The total 

 number of borers found during the entire periods of treatment in the 

 trees painted with white lead was 67, the number found in an equal 

 number^of check trees during the same period being 258. This shows 

 for the paint a control efficiency of 74.3 per cent. 



In one test of paints a large wire-screen cage was built over a 

 clump of 15 4-year-old apple trees in a neglected nursery row. 

 Three of the average-size trees were painted at the base with white- 

 lead paint, 3 with a proprietary tree paint, and 9 were left untreated. 

 As soon as the paint was dry, 7 male and 7 female beetles that had 

 just issued from apple wood were confined in the cage. At the end 

 of the season an examination showed that 193 eggs had been laid by 

 the 7 females, every egg being in the 9 untreated trees, the paints 

 showing 100 per cent efficiency in control. The same season a 

 female beetle that was ready to oviposit was removed from a cage 

 and placed on the trunk of an apple tree in the orchard that had 

 been treated with white-lead paint in the same way as those in the 

 cage. When liberated the female at once crawled up the trunk to a 

 point above the paint', made a slit in the bark, and deposited an egg. 

 She then moved down near to the ground, and, with no apparent 

 difficulty, bit a hole through the paint, made the oviposition slit in 

 the usual way, and placed an egg in the opening. These and other 

 observations showed that the beetles can very easily oviposit through 

 the paint but prefer to place their eggs in the natural bark. 



It was very noticeable that some of the borers hatching from eggs 

 deposited beneath a coat of white-lead paint were at first affected 

 deleteriously by the oil which penetrated into the bark. They were 

 slow in getting a start, fed but little, and, in a few cases observed, died 

 within a few weeks after hatching without having made any per- 

 ceptible growth. Others that were able to burrow deeper into the 

 tissues, beyond the effect of the oil, grew and developed normally. 



