THE AGRICULTURAL NEWS. 



.1 i\i \i:y If,, 1915. 



INSECT NOTES. 



CYANIDE OF POTASSIUM IN TREES. 



In two recent numbers ol Science, short articles have 

 ippeared on the use oi potassium cyanide for the destruction 

 of scale insects on leaves and branches of trees, by placing 

 the poison in a hole bored in the stem of the tree. 



In the first "i these articles a correspondent wrote to 

 s . giving his experience in treating ;t few tires which 

 were attacked bj scale insects, and generally lacking in 



vigour. In this case it was believed that tl peration was 



tccessful in reducing the numbers of the scales, and in 

 improving the general condition of the trees. The later 

 irticle i- a communication from Professor II. A. Surface, 

 Department of Agriculture, Pennsylvania, 

 ■who is verj strong in his condemnation oi this method. 

 After the appearance of the first of these articles i Science, 

 October 9) trials were made at the Office of the imperial 

 Department of Agriculture in order to see whether certain 

 plants would sho\i any result from the use of the cyanide. 

 Three trees were chosen: a small mulberrj (Aforus alba), 



a king of flower- i J.ifi, rstrn mm iii'liea), and a led gum 

 { Bursera gummifera). 



The cyanide was applied as follows: a hole |-inch in 

 diameter was bored into the stem of the tree to a depth of 



tbout 1 \ to 1 , : inches, then nearly filled with finely crushed 

 cyanide of potassium, and plugged with paraffin wax. 

 This was done on October 21, 1914. A tew days later 

 the mulberry tree showed signs of some injury, as the bark 

 in the vicinity of the hole was discoloured; the Lagerstrcemia 

 and the Burseragave the same indication in a short time also. 

 On January 7, 1915, an examination was made of the 

 three trees. The mulberry was badly infested at the 

 time the trial was started by a white scale, Anlacatpit 

 pentagona. This tree is now very nearly dead, but it may 

 be said that in this respect it is not very different from 



tdjacenl trees of the same kind suffering from the same scale 

 insect attack. What is very noticeable however, is the 

 large area of dead and blackened hark ill the immediate 

 neighbourhood of the hole which contained the cyanide. 



In the case of the Lagerstrcemia, the injury to the plant 

 is indicated in the same way by an area of dead and discolour 



ed hark. 



The Bursera tree gives a very much clearer idea of what 

 has happened, because of its larger size, and of the greater 

 length ot trunk. The hole for the cyanide was bored at 

 i height of about ■">', feet from the ground, at which point 

 the trunk of the tree is about 2 feet in diameter. 



The injury resulting from the application of the cyanide 

 was easily to he mtii in the dead and blackened hark to 



a distance of about .'!.', feet upwards, and 8 or !) inches down 



wa ds, i i the hole. When the hark was removed it was 



found that the cambium and hark had been injured sufficient 

 l\ for the injury to be easily followed to a distance of nearly 

 5 feet upward- and 18 inches downwards. 



This indicates that the .\ oiide was taken up bj lie 

 ii omi i .tent, I that when ipplied in that manner and in 



that quantity, it is capable ol causing severe injury to the 

 tissues of the plant. 



This test does not prove anything with regard to the 

 effect of cyanide applied in this manner on insects on. or in 

 the tree, hut it is obviously a dangerous method to emploj 

 one which is liable to result in serious injury to the plant- so 

 . tted. 



The following extract is from Professor Surface's commu- 

 nication in Science, already mentioned, in which he states 

 that cyanide of potassium i- the chief basis of treatment 

 bj a firm located in a town in Pennsylvania which does an 

 extensive business, claiming to render trees immune from 

 attacks by all insects and diseases, and also to fertilize 



them: 



•Their theory is that a tree can be given medicine, is 



well as f 1, by placing the same in capsules and fastening 



these iii incisions under the bark. While the chief insect 



poison i- cyanide of potassium, yet they use chlorate of 

 potash and sulphate of iron "to give the trees chlorine, 

 sulphur, iron and potash". They make wonderful claims 

 for de-: rue! ion of the -call-, and invigoration of trees, and 

 commenced by charging 50c. per tie, ■ for the so-called 

 "vaccination". The price is now reduced to 15c, but tl 

 are taking thousands of dollars from the confiding public. 



'The important scientific poinl i- that I have examined 



hundreds of tree- treated by them, and have ii some instances 

 found no evidences that scale insects were ever present, while 

 in other- 1 have found the San Jose scale alive on the trees 

 some time after treatment. What is much worse, is that 

 I have found, it i- true, that some one or more of these 

 chemicals is evidently taken up in the sap of the tree, and 



that to a considerable extent. While the material was 



placed under the hark about 3 feet from the ground, it 

 blackened the cambium layer as high as I could reach 



and remove the hark, and started blight or death of 

 tissue at the place where inserted. 1 have the names 

 Of scores of persons whose trees Or orchard- were filially 

 killed by this treatment. One man, whose name and 

 address 1 can give, thought that it benefited his trees, 

 and had it applied the second year, and the trees then died 

 quickly.' 



BEAN CATERPILLARS IN FLORIDA. 



The Florida Agricultural Experiment station has for 

 several years past been carrying out extensive experiments 

 in the cultivation of velvet and other related beans, and in 

 the production of useful hybrids. 



According to the Annual Report of that station for 

 1913, which has just been received, the velvet beans under 

 cultivation there were, in 1912, seriously attacked by the 

 larvae of the corn ear worm (Laphyyma jrugiperd>i), of which 

 the local name in Florida is the grass worm: and also 

 by the velvet bean caterpillar (Anticania [Thermesia] 

 gemniatilis), which is known in the West Indie- as the 

 woolly pyrol moth. 



The latter of these was often found to be heavily 

 parasitized bj an entomogenous fungus, which in many 

 instances exercised a fairly complete control over it. At 

 other times, however, especially in the drj weather, the 

 Anticarsia larvae nearly destroyed the crop. It was n© 

 sary to experiment with insecticide- for the control of these 



caterpillars, hut as velvet beans, like many other leguminous 

 plants, are very -eusitive to the effect of poison-, the 

 problem was rather difficult. 



It was found by repeated trial- that a fairly satisfactory 

 control could he maintained over these caterpillars by the 



USe of arsenate of lead applied as a -pia\.aud of zinc 



arsenite. The caterpillars were not all killed by any one 



application, and there was always some burning of the leaves. 



- These results are of importance to planters in the West 



Indies, and should lead them to experiment with these substan 



, Ces in order to find out at what Strengths, and at w hat stages 

 , ill the growth of the plant they may lie applied to combine 



j the greatest degree of efficiency with the least injury to the 



have- of leguminous plants. 



