208 On the Insects affecting the Turnip Crop, 



stopping up the pores of the soil, and so preventing the exit of 

 the fly. 



Nitrate of soda has been tried in two instances on crops of 

 Swedish turnips with very beneficial effects ; and it. probably 

 assists, from its peculiar qualities, in checking the increase of the 

 beetles. The nitrate was sown two or three days after the seed ; 

 and it may be used on all soils excepting on chalk. It should be 

 sown broad cast, mixed with wood-ashes, which enable the sower 

 to spread it more regularly. 



We now come to what may be termed direct remedies. 



The Paul-net, as it is called, after its inventor, although it has 

 been considered as a toy, yet I am of opinion might be use- 

 fully employed ; for I have seen a quart bottle filled with the 

 little turnip-beetles that were all caught with this net. If I 

 remember correctly, Mr. Paul's plan was to sow a small spot 

 with white turnips early, as a decoy, and over that space to draw 

 his net.* It always struck me that vast quantities made their 

 escape by skipping out of the net, which was its greatest defect, 

 but this might be remedied by placing some sawdust at the ex- 

 tremity of the bag, mixed with lumps of common ammonia, or 

 sprinkled with spirits of turpentine, which perhaps would be 

 better ; but either of these would kill a great many, and stupify the 

 remainder, until the contents of the net were subjected to suffi- 

 cient heat to deprive them of life. This process is no doubt 

 troublesome, and requires to be repeated ; and unless, perhaps, 

 some alterations were made, it would not answer on an extensive 

 scale. This, however, is no fatal objection to the principle. 



A board newly painted or tarred, and drawn over the turnips, 

 will catch multitudes of the beetles ; for on being disturbed they 

 leap against it, and cannot release themselves. I should recom- 

 mend white paint ; and the brighter it is the better, as all insects 

 are attracted by light colours. Neither wet nor windy weather 

 would be suited to these operations ; for it is ascertained that the 

 beetles are at such seasons disinclined to move; neither would 

 mid-day in fine weather do, as they are then active, and fly well ; 

 for it is a well-known fact, corroborated also by the flight of swal- 

 lows, that in hot days and sunshine insects fly high;, whilst in 

 damp weather they keep upon or near the ground. 



Fumigation by burning stubble, weeds, &c., to windward of 

 the field, so that the smoke drives along the ground, has proved 

 effectual ; but I should prefer burning to leeward as a preventive, 

 for as the beetles are attracted by the scent of the turnips, and fly 

 towards the wind, they would be baffled by such a manoeuvre. 



* A very good representation of this net will be seen in Kirby and Spence's 

 Introduction to Entomology, pi. 24, fig. 3. 



