The Pamphlet Collection of Sir Robert Stout: Volume 14
When wireworms have once become settled in a hop plantation it is a most difficult matter to dislodge them. They have a stronghold in and around the plant-centres, in which they ensconce themselves, and they cannot easily be got at. Nitrate of soda, guano, lime, soot, and other manures of a caustic nature have been put as near the plants as it would be safe to put them, and in most cases without much success. The wireworms work upon and in the young shoots, to which it would be most injurious to apply substances that would affect the insects.
It is almost impossible to move them from their position by cultivation. They are frequently moved, at all events temporarily from wheat, oat, and turnip plants by heavy rolling and harrowing, but it will be seen that such remedies cannot be applied in hop plantations. Digging or prong-hoeing round the plants might be advantageous, though the grubs actually upon them could not be directly reached.
In young hop plantations of the first year it has been found practicable and efficacious to make a ring very close round the plants with the little short hoe used for covering in after dressing, and to sprinkle earth, ashes, or sawdust saturated with paraffin oil in these, taking care not to put too much oil, so as to kill the shoots. Planters will see that this cannot be so easily done in the first year of poling and afterwards, still with care and contrivance it might be managed, even when the full complement of poles is set up. But the best and most sure means of deal- page 18 ing with wireworms when at work upon hop plants is to put baits near them, two or three inches below the ground, in the shape of pieces of mangel wurzel, turnip, carrot, potato, or rape cake. These should be taken up once a week at least, and wireworms attracted by the more pleasant food from the hop plants, will be found imbedded in them, and may be taken out and destroyed. As many as 150 wireworms have been caught in this way near one plant-centre. Continental and American entomologists and planters highly commend this method.
Dressings of rape dust dug in round infested plants will also draw the wireworms, relieving them for a time, but also tending to collect the wireworms round or near the plant-centres. Rape dust is employed as a manure for hop plants in enormous quantities, and this without doubt has caused the increase of wireworms in hop plantations, as they are particularly fond of it. The common notion that rape dust is a remedy against wireworms, because they eat so greedily of it that they burst their skins, is without any foundation at all.