100 



Commercial Gardening 



March and April, the little plants being afterwards pricked out 3 or 4 in. 

 apart in boxes of light rich soil, or in an old hotbed. By the end of May, 

 or early in June, they will be ready to plant in the open air, 1 to 1J ft. 

 apart every way, in rich and deeply worked soil. The swelling of the 

 stems is hastened in autumn by removing the lower leaves that are turn- 

 ing yellow; and from the end of September onwards they may be lifted 

 and stored for use in dry, airy places; or they may be left in the ground 

 if protected with litter, &c., till required. 



Pests. The Celery crop is liable to be attacked by maggot of the 



Celery Fly (Acidia heraclei, or, as it is better known, Tephritis Onopor- 

 dinis). The insect (fig. 472) appears in April, and is of a tawny brown 



colour. The wings, which have an expanse 

 of about \ in., are transparent and irides- 

 cent, with oblique lines of brownish or rusty 

 spots running through them. The larva 

 varies from white to very pale green in 

 colour, and has no legs. The eggs from 

 which the larvae arise are laid singly upon 

 the upper surfaces of the leaves of the 

 Celery and also of the Parsnip, which is 

 closely related botanically. The eggs hatch 

 out in six or seven days, and the young 

 maggots at once bore through the skin of 

 the leaves into the tissues, the substance of 

 which they feed upon, thus forming "mines" 

 between the upper and lower surface. In 

 about fourteen days the maggot changes into 

 a pupa either in the leaf or in the soil. A 

 few days later a new and perfect insect is 

 hatched out, and several broods may be born 

 in the course of the year, the last one, how- 

 ever, remaining in the puparium stage in the soil, or in pieces of stalk or 

 leaf, during the winter. 



From the nature of the attack the maggots must either be prevented 

 from tunnelling in the leaves of Celery and Parsnips, as, when once inside, 

 they can only be destroyed by picking off the diseased portions and having 

 them burned. On no account should stalks or leaves of Celery and Par- 

 snip containing grubs of the Celery Fly be thrown on the manure heap, 

 as the pest will mature there as readily as elsewhere. 



One of the simplest and best remedies is to spray the foliage early in 

 the season with a mixture of soft soap and paraffin. A quart of paraffin 

 and \ Ib. of soft soap, well churned up in warm water at first, and then 

 diluted with water to 10 gall., makes an excellent solution. Large 

 quantities, of course, would be necessary for field work, and it would be 

 best to spray with a knapsack or other distributor. Two or three 

 applications during the year may be necessary as a preventive. 



Fig. 472. Celery Fly (Tephritis 

 Onopordinis) 



1, Fly (magnified). 2, Lines showing 

 natural size. 3, Larva and pupa figured 

 on blistered leaf. 



