GARDEN PESTS IN NEW ZEALAND 



In the case of the slug (Fig. 13, 1-t), the shell is small and incon- 

 spicuous, but the large spiral shell of the snail (Fig. 13, 15) affords 

 the animal adequate protection, into which it withdraws itself in times 

 of danger. Both slugs and snails reproduce by means of eggs ; these are 

 white, spherical and opaque, and are deposited in the soil or under 

 decaying vegetation. 



One of the best means of control is to dust the plants with powdered 

 tobacco. Another method is to treat infested plants with soot or lime, 

 but this must be done at night, and the material used must 'come into 

 actual contact with the pests. An effective poison bait, but one that 

 requires to be carefully handled, owing to its poisonous nature, is a mash 

 made of 61b. of bran mixed with lib. of arsenate of lead and an equal 

 weight of treacle; this is made into a stiff paste, water being added if 

 necessary. Lumps of this mash are placed about the plants to be pro- 

 tected. As a barrier to prevent the inroads of slugs and snails, plants 

 may be surrounded by a belt of calcium cyanide; this would have to be 

 replaced each night, and the utmost care taken in handling, since the 

 substance and the gas evolved from it are highly poisonous ; out of doors, 

 however, the gas, being diluted with air, would not be very injurious as 

 long as one did not stand over the treated ground longer than was 

 necessary for laying the cyanide. 



Apart from the above methods, the key to the control of slugs and 

 snails is "clean farming" that is, the removal of all places, such as 

 rubbish and rank vegetation, where the animals will find shelter; the 

 compost heap is a favourite breeding place, and this should be turned 

 over at intervals and dressed with lime. 



Eelworms. 



Eelworms are minute, unsegmented worms, related to the parasitic 

 thread- worms of animals, and are abundant in soil and water; it is 

 usually the surface layers of the richer soils that are inhabited by them. 

 Of the long list of species, only a few are destructive to vegetation, but 

 these constitute one of the greatest problems of the horticulturist. It is 

 thought that the injury caused to plants by eelworms is toxic rather 

 than mechanical, and some plants apparently are capable of producing 

 anti-toxins, which neutralise the toxins of the eelworms ; such plants 

 possess an immunity. There are three important species in New 

 Zealand. 



The so-called bulb-eelworm (AnguiUulina dipsaci) attacks more 

 than two hundred kinds of plants, but is of especial interest to the horti- 

 culturist on account of its attacks upon hyacinths, daffodil, narcissus, 

 and gladiolus, causing deformity and rotting of the tissues (Fig. 13, 16). 

 It has been found that this eelworm develops from egg to adult within 

 a period of between three and four weeks; the eggs are capable of lying 

 dormant in the soil for as long as seven years. Infested bulbs and cornis 

 should be treated by immersion for three hours in water heated to 

 110 deg. Fahr. 



Potatoes are often damaged by the beet eelworm (Heterodera 

 schaclitii), which causes what is known as "potato sickness/' when the 

 growth is retarded, and wilting takes place; the root-system shows an 

 abnormal development of secondary or "hunger-roots." The eggs are 



