138 



THE AGKICULTURAL NEWS. 



April 22, 1916. 



INSECT NOTES. 



FIGHTING THE SUGAR-CANE BORER 

 WITH PARASITES AND POISONS. 



In the Louisiana Planter for December 18, 1915, an 

 article appeared under the heading given above, in which 

 methods were discussed for the control of the moth borer of 

 the sugar-cane (Diatrata gacc/iaralis). The article referred to 

 was by Mr. T. E. Holloway, in charge of Sugar-cane 

 Investigations, Bureau of Entomology, U. S. Department 

 of Agriculture. 



The moth borer of sugar-cane has been known as a pest 

 in Louisiana for many years. Until recently the trash in 

 cane fields was burned, but now it is coming to be recognized 

 that the non-burning of trash may have some influence on 

 the abundance of the egg parasite of the moth borer 

 (Trichogranin^a pretwsa), and planters are being advised to 

 make trials on a limited scale of saving the trash and 

 ploughing it under in the Spring. In the experiments carried 

 out in the 1911-15 season, however, it was found, by careful 

 counts made to determine the relative abur dance of the 

 parasite in burned and unburned fields, that there was no 

 difference, and that the results of the experiment were 

 negative. This was believed to be due to the long period of dry 

 weather which was experienced, the drought lasting from sixty 

 to 120 days in different places. It is mentioned that Walcott* 

 found that the amount of rainfall exercised a direct influence 

 on the abundance of moth borer in sugar-cane fields in Porto 

 Rico; the greater the rainfall the less severe wore the attacks 

 of the moth borer, and the less ihe rainfall the greater the 

 attacks of this insect. The question is raised as to whether 

 it may not be that dry weather is unfavourable to the parasite, 

 Trichogramma pretiosa. 



As a result of an expedition to Cuba in search of other 

 parasites of the moth borer, species of Tachinid tiies, 

 Tachimphyto, were collected and sent to the Experiment 

 Station at Audubon Park. 



These flies are parasitic on the Diatraea larvae, and they 

 have been found to breed in Louisiana. It now remains to 

 be seen whether they are capable of enduring the winter in 

 Louisiana, which is severe in comparison with the climatic 

 conditions in Cuba. 



In addition to a discussion of parasites, the article 

 refers to the use of stomach poisons on cane plants as 

 a means of control of the moth borer. 



It is well known that the Diatraea female deposits eggs 

 in clusters on the leaves of tut- cme plant, and that when the 

 caterpillars issue from th(- egg.- they feed at first on the leaf 

 tissue before boring into tlif heart of the plant 



It is stated that very good results have been obtained by 

 dusting arsenate of lead on the cane plants from a cloth bag 

 in the same way as cotton is dusted for the control of the 

 cotton worm. Two applications of arsenate of lead were 

 made on young cane plants which gave very good results in 

 the decreased numbers of the dead hearts. 



The lines of work discussed are summarized under three 

 heads: (1) non-burning of cane trash, (2) the introduction of 

 new parasites from Cuba, and (.3) the aitplication of powdered 

 arsenate of lead to kill newly hatched larvae and prevent the 

 occurrence of dead hearts. 



♦Geo. N. Walcott. The Influence of Rainfall and the noii- 

 V)urnin<' nf trasli on the abundance of D'at'oea .lacdiaralh. 

 Cixcular No. 7, Hoard of Coimuissioncrs of Agriculture, Porto 



Rico. 



SLUGS. 



Recently there have been rather frequent references in 

 the ditterent islands of the Lesser Antilles to the abundance 

 and destructiveness of the Slug or Palut ( Veronicella 

 occident(ilis). A statement now comes from a planter in 

 Antigua that this slug has disappeared from a certain 

 locality in that island; he also says that the craupaud eats 

 the slugs. The slug, or palut, as it is generally called, is 

 an air-breathing mollusc without a shell, the body being 

 covered by a coriaceous mantle. The length of this slug 

 often reaches and sometimes exceeds 1^ inches. 



The palut is widely distributed in the West Indies and 

 has at times caused damage to a variety of plants. It is 

 recorded from Antigua, Montserrat, Dominica, St. Lucia, 

 St. Vincent, and Barbados.. 



Very little seems to be known about the habits and 

 food plants of this slug. The following notes are presented 

 in order that planters and agricultural officers may know 

 what is recortled, and be encouraged to add to the known 

 facts by submitting their observations. 



In Montserrat the slug appeared in great numbers at 

 the Botanic Station in 1914, where they destroyed germinating 

 ground nuts which were planted in a plot from which sweet 

 potatoes had been harvested a short time before. 



Hand collecting was tried on this plot, which was ^-acre 

 in area, with the result that the following numbers were 

 collected on five consecutive days, May 26.30, 1914: 2,800 

 2,000, 1,000, 1,654, and 1,-360. This gives a total of 8,814 

 slugs collected in five days on |-acre. 



It has been troublesome in the mountain lands, where it 

 attacks the potatoes and other crops in the peasants' provision 

 grounds. 



In St. Lucia, a few years ago the garden plots at the 

 Experiment Station at Union were badly infested by slugs, 

 cassava, cabbage, beans and other garden produce being 

 almost completely destroyed. If the slugs had been collected 

 here, probably the numbers would have been fully as large 

 as in the Montserrat results given above. 



In .Montserrat, during the dry season a few years ago, 

 forty-eight slugs were found at the base of a lime tree, twenty- 

 five being closely packed together in one mass. 



In St. Vincent, ground nuts have recently (1915) been 

 severely attacked by this slug, especially in the fields bordered 

 by wild land. The slugs appear to come into the cultivations 

 from the bush or pasture, and they destroy the ground nuts 

 in strips of varying width along the borders of the fields. 



Sweet potatoes appear to be most attacke<l when the 

 slips are first ])lanted out. 



Ferns and other plants in the ferneries and plant housea 

 are sometimes severely attacked. 



No records of satisfactory remedies seem to be available; 

 Hand collecting has been tried as noted above. This is done 

 by the use of a skewer or long, pointed iron rod, the slug being 

 impaled; and when a certain number have been collected on 

 the rod,'they arc slipped ofl' into a suitable receptable 



Their habit of feeding does not appear to have been 

 carefully observed. If they feed on the foliage of plants, they 

 might be killed by means of the firdinary poisons sj)rayed or 



dusted on. 



After a crop is harvested the ground might be thorough- 

 ly cleared of weeds and all plant growth, and the slugs trapped 

 by providing suitable hiding places such as old bags and 

 boards on the surface of the ground or heaps of trash which 

 would afford protection from light and heat. The examination 

 of these traps from day to day would result in the capture of 

 large numbers of the slugs. 



