YELLOW-STKIPE IN DAFFODILS. 



165 



to push its leaves through the soil in early spring, and is consequently 

 one of those most likely to suffer injury from frost and easterly winds. 

 1 Mrs. C. Bowley,' and some others in which I have noticed yellow-stripe 

 are, it is true, later, but I have not seen a bad attack except in the early 

 varieties. 



After some hesitation I have come to the conclusion that Mr. Jacob's 

 theory of cold being the cause of yellow-stripe may be a probable explana- 

 tion of its occurrence in the particular cases I have mentioned. I was 

 at first of opinion, as my treatment indicated, that poverty of soil and 

 drought might be the cause of the attack. It was a possible explanation in 

 the case of the group of ' M. J. Berkeley,' one group of ' C. J. Backhouse,' 

 and two rather large groups of ' Sir Watkin,' but on further investigation 

 I found a bed of ' Sir Watkin ' badly attacked in 190G, growing in a soil 

 particularly rich and deep, and a small group of ' C. J. Backhouse ' in 

 almost pure peat, where drought was very unlikely to have occurred, also 

 suffering in that year. It is quite clear that in varieties not particularly 

 prone to the disease poverty and drought will not cause it. I have been 

 observing with considerable interest a bed of ' Stella ' planted under a 

 cedar tree. The plants have been gradually starving for years. They have 

 long since ceased to flower and the leaf growth is getting more and more 

 restricted each year, but I have never detected in any of them the least 

 trace of yellow-stripe. 



But to come back to the group of ' M. J. Berkeley ' I referred to as 

 having, in 1906, the worst attack I have seen. I have already mentioned 

 that manure is not in this case a possible explanation of the attack. It 

 is equally impossible that it can have arisen from over- division of the 

 bulbs, for at the time they suffered from it they had not been lifted for 

 over three years, and had twice (in 1903 and 1904) flowered fairly satis- 

 factorily since their planting. Moreover, their complete and unexpected 

 recovery in 1907, without being moved, shows that, other conditions being 

 satisfactory, change of soil and " maiden loam " are not necessarily 

 essential to apparently complete recovery. 



Again, the occurrence of yellow-stripe may nearly always be observed 

 in the neighbourhood of bulbs that have been attacked by the caterpillar 

 of the Swift Moth. Now the method of attack of the caterpillar is this. 

 The eggs of the moth are laid either in a colony on one bulb or on several 

 bulbs close together. The caterpillars hatch in late summer or autumn 

 and commence to feed on the fleshy roots emitted by the bulb, and when 

 they have eaten all the roots off the bulb, and perhaps bored into the bulb 

 itself (but not usually very far in), they find their way through the soil 

 and attack the roots of other bulbs growing near. The bulbs are thus 

 destroyed in a patch, but those on the outside of the patch will have their 

 roots only partially destroyed, and among these yellow-stripe will almost 

 always be found. 



In these circumstances I have found yellow-stripe in the leaves of 

 ' Mrs. Langtry,' a variety not as a rule subject to it. When bulbs attacked 

 in this way develop yellow-stripe, it seems reasonable to attribute the 

 disease to the physical injury caused by the caterpillars. 



If the caterpillar has eaten all the roots it may sometimes attack the 

 shoots as well, but it seems to care less for the shoots than the roots. 



