“Did I tell you about the Caddis worm attack on water-cresses? So much harm was being done that the unlucky grower was in much trouble, and on running the matter up it appeared that formerly there were numbers of trout in the water, but lately the landlord’s wife had a fancy to encourage herons, and so came the curious sequence. The herons cleared off the insect-loving trout, so the vegetable-eating insects got ahead, and the watercress grower could not pay the rent of his half acre of cresses. I suggested that as the herons were encouraged by the lady, perhaps she, if applied to, might to some degree make good the damages!”]
March 5, 1897.
Dear Mr. Wise,—You asked my views about moles at Strawberry roots. I should say it would be quite worth while to spare them as you are doing, and see what comes of it. If they take the Otiorhynchus grub (of Orchard and Hop weevils) this would meet a difficulty which we hardly know how to fight at present, and if the moles took these grubs one might hope that they would take other underground kinds, which are kitchen garden pests, almost unconquerable by other remedial means. I should doubt, however, whether they would be of much service against Winter moth chrysalides (fig. [30]). Very likely I am not right, but the mole seems to me to prefer more open ground and a larger scope of operations.
April 8, 1897.
So far as I know the only treatment for Black Currant Gall mite, Phytoptus ribis (fig. [65]), which has been in a measure successful, is that reported by Mr. J. Biggs, of Laxton, East Yorkshire, in my seventeenth Annual Report, p. 93. There, if you will turn to it, you will see we have treatment to clear the pest from all localities, whether straying on the twigs or on the ground; or in the buds, this by breaking them off. Mr. Biggs observed, writing on the 20th of April, 1892: “You will, I am sure, be interested in knowing that I have, to a certain extent, prevented the Phytoptus utterly ruining my black currant trees. As you suggested in a letter of last March, we syringed the bushes twice with the solution of Paris-green, which I procured from Messrs. Blundell, and gave the soil all under the bushes a good coating of caustic lime; I also gave the bushes another dressing of the Paris-green. Just when the buds appeared this spring I had a boy gathering all the little knobs off the trees. The result has proved as satisfactory as I could expect, considering the condition of the trees last year, and I have every prospect of securing a good half crop. Our neighbour’s trees in this village are utterly ruined, scarcely a leaf to be seen, and the trees completely covered with the affected knobs.”
But with regard to the life history of the pest, I believe it breeds entirely in the infested buds, and I believe also breeds, i.e., lays eggs, there at any time during the winter. I know that the nearly allied nut-Phytoptus does, for I have seen them. Outside the buds, so far as I know, the life is wholly spent in sheltering in crannies or straying about, on the stems, or on the ground. What we want, appears to me to be, to clear the mite by syringings from the stems when the buds (of which we have now the galled growth) are first beginning to form. But I do not see how we could do this, for we should ruin the fruit. My only hope for real prevention where black-currants are grown on this large scale, is in an alteration of the method of cultivation. As it stands now, the mites can convey themselves, or be carried by wind-borne leaves, or may creep from one bush to another on the ground, but if there could be a mixing of some field crop in strips with the black-currants, I believe it would do a deal preventively. If the ground between the rows were occupied by some crop that the Phytopti would not pass, it could not fail to lessen their presence. Even strips of strawberries or of gooseberries would be beneficial. I wonder whether kainite would be a good remedial application? It might kill all the mites that are about, but it is quite plain to me that, as nothing that has been tried for so many years answers thoroughly, we are on the wrong lines and need a new plan. I wish you would, at your leisure, tell me what you think of mixing crops, and if you could let me have just a few little bits of galled twigs for figuring, I should be very much obliged. I wish I could help better about the matter, but so far the attack appears to have fairly baffled us all.
April 13, 1897.
I am very much obliged for these remarkably fine specimens of Currant galls, which reached me safely this morning. About the life history of the Phytopti, I do not think that anything more is recorded than what both you and I know. But as we know well that the mites are in the galls (such as you send me), it seems to me that what we have got to act upon is their condition (or locality, rather) in the time between their leaving these galls and when they are starting new attack in the embryo buds. I wish I could tell you more, but I do not see how to get at the point of locality, excepting by watching shoots with a hand magnifier. I really am quite at a loss as to what can be done.
April 19, 1897.
I wrote out to Vienna to Professor Dr. A. Nalepa, who is the great authority on the Phytoptidæ, and he is much interested in hearing about this great spread of attack, but is not able to give us better advice, as to practical remedies, than what we are already trying. (See also p. 248.)