404 



are known also to winter over, but in limited numbers, and hence your observation 

 of their occurrence in such excessive numbers in March is quite interesting. — [No- 

 vember 17, 1890.] 



The Mealy Bug. 



Is there any reliable remedy for the pest known as the Mealy Bug in the green- 

 houses ? All applications seem to be nearly worthless except hand-picking. We have 

 tried all the advertised mixtures and are disgusted. How will the gas from cyanide 

 potassium and sulphuric acid work in them, and can it be safely used by letting it 

 have possession of the house over night and thoroughly ventilating the house the 

 next morning ? Would it be dangerous for the gardener to go into the house to ven- 

 tilate it the next morning ? I am fully aware of the deadly effect. I have used the 

 cyanide jar to kill my specimens for the past three years.— [H. L. Jeffrey, Woodbury, 

 Connecticut, November 21, 1890. 



Reply. — Hydrocyanic acid gas, produced in the way which you mention, is being 

 extensively used on the Pacific coast as a remedy against scale insects. Entire orange 

 trees are covered with tents, and the acid is manufactured under the tent. I am not 

 aware, however, that it has been tried in greenhouses on the scale which you sug- 

 gest, but am inclined to think that there would be some danger in its use in this 

 manner. A copy of bulletin 22 of this division is sent you by accompanying mail, 

 and you will be able to see from the report of Mr. D. W. Coquillett the methods in 

 use in California. From this account you will be able to get some idea as to rigging 

 up a small apparatus for the disinfection of a few of your hothouse plants at a time. 

 In case you attempt anything of the sort it will give us pleasure to learn the result. — 

 [November 21, 1890.] 



The Sweet-potato Root-borer. 



Please find Inclosed a few insects (alive just now) with small piece of sweet-potato 

 (yam variety), in regard to which I would be pleased to have your opinion. They 

 seem to be quite a pest to the potato crop in this section of Louisiana, certainly very 

 destructive to the tubers. — [J. Ed. Blanchard, Thibodeaux, Louisiana, November 16, 

 1890. 



Reply. — The insect which you send is the so-called Sweet-potato Root-borer 

 (Cylas formicarius). It is a very destructive enemy to sweet-potatoes in regions 

 where it occurs abundantly, but fortunately it is rare in most localities. The only 

 remedy which has been suggested is to dig the potatoes as soon as they are found to 

 be infested and to burn those containing insects or feed them to cattle, thus reduc- 

 ing the number and making the chances better for the next crop. You will find some 

 account of this insect in the Annual Report of this Department for 1879, pages 249- 

 250.— [November 19, 1890.] 



Parasites of the Apple-tree Saperda. 



In response to your request for my experience in regard to insect injury or habits, 

 I will mention that I have this fall, for the first time, noticed that the Round-headed 

 Apple-tree borer {Saperda Candida Fabr.) had been parasitized, the larva being 

 destroyed before it had done any damage to speak of. As Saunders, in his '^ Insects 

 Injurious to Fruits," does not speak of any parasites of this species, and thinking 

 it perhaps might be something new, I will endeavor to obtain some specimens for you 

 the coming season if you deem it sufficiently interesting to investigate. 



This borer is the greatest pest we have in our apple orchards here as it works from 

 the base to the top. I have secured the beetle from sections of limbs but little over 

 an inch in diameter. The period of its greatest activity seems to be the latter part 

 of August and the whole of September, and the month of October is the best time for 

 their removal, as they have not many of them eaten through the bark yet. There 

 is no prospect of ever diminishing their numbers by any artificial means, as they come 



