38 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



(mildew of the rose bush) ; SphaerotJieca Castagnei, Lev. (mildew of 

 the hop). 



Hot water has found numerous applications against insects very 

 'sensitive to heat. Galernca of the elm ; Formica, ants ; Picrides of 

 the cabbage ; Cochylis Pyralis of the vine ; Cabbage lice ; Diaspines, 

 Cochineals, red spider. 



Galernca Calmariensis {Galernca of the elm). — To destroy this 

 insect, Robert sprays the stock and the lower part of the trees with 

 boiling water. The time for doing so is selected when the larvae are 

 being transformed into grubs around the stock, i.e. about the end of 

 July or beginning of August. 



Formica (ants). — Boiling water destroys ants. It may be used 

 each time that there is no risk of touching the roots, which do not 

 stand hot water at that temperature. 



Pier is {Pier ides of the cabbage). — "When they are not destroyed 

 when they are small, the grubs of Pierides (white butterflies) so ravage 

 cabbage as to render them unsaleable. Eiley has observed that the 

 grubs die when they are sprayed with water at 55° C. (131° F.), whilst 

 cabbage leaves do not suffer at that temperature. 



Conchylis AmbigncUa, Hubn {Cochylis of vine) ; Tortryx vitana 

 {Pyralis of vine). — Scalding is the best method of destroying these in- 

 sects. It consists in spraying the stocks with boiling water when vege- 

 tation is arrested, and when the insects have chosen the fissures in the 

 bark as a common refuge. This process, discovered in 1828 by Benoit- 

 Raclet, vine grower at Romaneche (Saone et Loire), was not known 

 until 1838. Raclet experimented on the same vines for ten years, 

 and after having found all the advantages of scalding, he advised its 

 use, preferably in March or April. According to the researches 

 published in 1868 by Terrel des Chenes, it has been definitely de- 

 cided : (1) That scalding, even when applied ten years running, did no 

 harm. (2) That it not only destroys Pyralis, but also many other 

 insects of the vine. (3) That it also destroys the vegetable parasites 

 of the vine, mosses, lichens, etc. (4) That it stops the growth of ad- 

 ventitious buds along the old wood which is a loss of sap for the 

 stock and thus saves pruning. However, in spite of the excellent re- 

 sults, this method is practised very little, and that because it requires 

 a litre of boiling water per stock, and it is not easy to use such large 

 quantities in the middle of a field. For some years scalding of vines 

 has become common by an improvement in the apparatus. The 

 water is now heated in a portable boiler (fig. 1) fitted with two lugs by 

 which it can easily be carried. It costs 30-50 francs (24s. -40s.). When 

 the water boils the workman is warned by a whistle on the safety valve. 

 He then fills a sort of tinned-iron coffee-pot (fig. 2', holding a litre, 

 and covered with cloth, or better still with a double jacket, so as to 

 prevent cooling. The water must be at 80° C. (176° F.) at the time 

 it touches the stock for the de-truction of Pyralis, and 90°-100° C. 

 (194°-212° F.) for Cocliylis, so that it may penetrate the silky cocoons 

 which protect the small grubs. To increase the temperature of the 

 water carbonate of soda may be added ; 5° or 6° C. (9^-10-8° F.) extra 

 are t nis obtained which makes up for the exterior cooling. In 

 emptying the coffee-pot entirely on each stock the workman must 



