314 



THE AGllICCLTURAL NEWS 



October 1, 1910. 



INSECT NOTES, 



A SUGGESTED WAY TO DETECT EEL 



WORMS IN (JANE FIELDS. 



In an article published in the Ai/ricu/lural Xetvs, Vol. 

 VIII, p. 138, an account is given of the general life- 

 history of eel worms {nematodes), and special mention is 

 made of one species, Jleterodera radicicota, which attacks 

 the roots of many different plants throughout the world, 

 and causes characteristic galls to appear on them. In the 

 article referred to, the suggestion is made that the roots of 

 the sugar-cane in the West Indies may be attacked by these 

 pests, but that the characteristic swellings are not produced. 

 Cobb, in Bulletin Xo. 6 of the Division of Pathology and 

 Physiology of the Experiment Station of the Hawaiian Sugar 

 Planters' Association, states that the young roots of the sugar- 

 cane in Hawaii are attacked by these worms, and that they 

 exhibit long narrow swellings, in consequence. Although 

 these swellings are present, they might easily be overlooked; 

 and beside.s, when growing under estate conditions, the cane 

 is not a very easy plant to handle for purposes of observa- 

 tion of the roots. Consequently, it is suggested that soils 

 might be tested for the presence of Heterodera radickola 

 by the following method. 



In several places in the field in which the soil is being 

 tested for the presence of eel worms, plant.s should be grown 

 which are exceptionally prone to attack by the worms, and 

 which exhibit large and unmistakable gall.'^ when they are 

 affected by them. The remainder of the field may be planted in 

 cane, in the ordinary way. If the experimental p'ants look 

 unhealthy, or appear to be dying, they should be removed, and 

 their roots examined for swellings. In any case, the roots 

 should be examined v hen the plants are mature and are dug 

 up. If galls are present, it will be a sure sign that the soil is 

 infested with nematodes. 



Among plants suitable for the e.xperiment described above 

 are melons, cucumbers and squashes, more particularly if they 

 are grown from the imported seed of supsrior varieties. Ochros 

 will also serve the purpose. 



If experiments of this kind ai'e systematically carried 

 out, valuable information should be obtained as to the distri- 

 bution, and frequency of occurrence, of Heterodera radicirnld 

 in the West Indies. The whole question is of interest, as it 

 is conceivable that the presence of root diseases of sugar-cane, 

 Indian corn, and even limes, may be dependent to some extent 

 on attacks by these animals. 



A OOTTON-EATING BEETLE. 



A communication which has been received recently from 

 Mr. C. Rey, of Anguilla, states that a certain amount of dam- 

 age is being done to cotton in that island by a small beetle. 

 The effect of this attack is to delay the maturity of the cotton 

 crop for two to four weeks, even when no greater damage is 

 done. 



It is probable that the beetle to which reference is made 

 is the one mentioned as doing damage to cotton, in the Ai/ri- 

 cultural Nevjs, Vols. Ill, p. 357; IV, p. 266. This is Hopat- 

 rinus gemellatus, and it has been recognized as a cotton pest, 

 to some extent, in Anguilla and St. Martins. As is stated in 

 the second arlicle in thf Aiiriculturnl Neivs, this insect is 

 widely distributed throughout the West Indies, having been 

 reported from Antigua, Guadeloupe, St. Vincent, Grenada, 

 and Barbados, as well as from the islands already mentioned. 



The account goes on to show that growing plants are 

 rarely affected by the members of the family to which this 

 beetle belongs; it appears, however, to have acquired the habit 

 of attacking young cotton plants just below the surface of the 

 ground, and it is, therefore, important that measures should 

 be taken for its control, as soon as it appears. 



Mr. Rey state.s, in the communication to which refer- 

 ence is made above, that he has been making trial of 

 means to kill the beetles; these have included the employ- 

 ment of both contact and stomach poisons. The first con- 

 sisted of carbolic acid solution, 1 in 24, and kerosene oil 

 emulsion, 1 in 10, and they were found to be .succe.ssful. 

 The method employed is to raise the stone beneath which 

 the beetles hide during the day, and then to spray them 

 with the insecticide. The chief objection to this means 

 of control is the expense in the matter of the provision of 

 labour. In the trials with a stomach poison, the bait used 

 was that employed for cut worms (see Agricultural News, 

 Vol. V, pp. 167 and 182); no definite results have been 

 obtained, as yet, although some of the beetles have been 

 killed. Mr. Key thinks that the beetles do not feed 

 regularly, so that the mixture is required to be effective o« 

 more nights than one; he therefore suggests that on the 

 second night, the bait, which has become dry in the sun, 

 should be sprayed with clean water. 



It will be of interest if cotton planters in the West 

 Indies will keep a watch for beetles and weevils attacking 

 cotton in the field, and will communicate their results, send- 

 ing specimens at the same time, to the Department. 



LEAD CHROMATE AS AN INSEOTIOIDB. 



The contents of a pamphlet, issued by the Agiicultuial 

 Research Institute, Pu.sa, dealing with the use of lead chrom- 

 ate in the place of arsenial insecticides was given on page 

 159 of the current volume of the Agricultural Neu's. 



Further information as to the experiments which led to 

 the adoption of this insecticide is given in the Agricultural 

 Journal of India, Vol. V, p. 138. It appears that objections 

 had been taken to the use of lead arsenate in India on account 

 mainly, of its poi.sonous nature, both in regard to plants and 

 animals, the fact that it decomposes if it is kept in paste form, 

 and of the difficulty of obtaining it. In consequence, careful 

 trials were made of po.ssible substitutes, and as a result of these 

 it was found that ?uoh bodies fell into four classes: (1) those 

 that killed in twent3'-four hours; (2) those that killed in 

 twenty-four to forty; (3) those that killed, on an average, in 

 from forty to 100 hours; and (4) tho.sc that acted irregularly, 

 or were without effect. 



The quality sought in the insecticides were (1) insolu- 

 bility in water; (2) cheapness; (3) stability, so that compounds 

 may not be lormed which would poison the leaf. Among 

 the substances investigated was a dry paint compound called 

 Lemon Chrome, which is a mixture of gypsum and lead 

 chromate. The consequence ot the discovery of this was that 

 trials were made with lead chromate, as a result of which it 

 exhibited a marked superiority over all other substances, 

 showing the following advantages: (1) it is easily made in 

 paste form; (2) it is yellow and therefore easily seen; (3) it 

 is extremely insoluble; (4) it does not usually decompose, but 

 even if it did, any soluble chromates formed would be less 

 inisonous than arsenical substances; (5) it is not easily wash- 

 ed off; (6) it contains no arsenic. The amount of the insecti- 

 cide (full strength) to fill an ordinary kerosene tin is obtained 

 by mixing 2 oz. of lead nitrate with 1 oz. of potassium 

 bichromate. The usual strength is one-half of this. 



