294 



The Supplement to the Tropical Agriculturist 



ANIMALS ASSOCIATED WITH THE HE* 

 VEA RUBBER PLANT IN CEYLON. 



(A PERADENIYA CIRCULAR.) 



At the present stage of the cultivation of this 

 product in Ceylon we have comparatively few 

 animal pests to combat. The plant is to a very 

 large extent self-protected from insect attack 

 by the presence of the viscid caoutchouc- 

 producing latex, which constitutes its great 

 value. The most vulnerable part of the plant — 

 its " Achilles heel — is the root system, and 

 it is here that we find its more important 

 enemies. Many of the insects included 

 in the following catalogue are but doubt- 

 ful pests, and others are not enemies at 

 all. But in the present state of our knowledge 

 I have thought it advisable to notice every in- 

 sect that is in any way associated with the plant. 



The various pests and negative species will be 

 noticed in sections dealing with (I.) the roots ; 

 (II.) the collar and stem ; (III } the branches 

 and young stems of seedlings ; (IV.) the leaves 

 and terminal buds ; and (V.) latex and prepared 

 rubber. 



I. — Enemies of the Root System. 

 (1) " Cockchafer Grub " (Lepidiota p'iritfitis, 

 Burm.). — It is in the larval or grub stage 

 that these insects are so destructive. The 

 larva is a large white Meshy grub with 

 al reddish head and strong biting jaws. 

 There are six well-developed legs near 

 the anterior extremity. The anterior half of 

 the body is strongly wrinkled, the hinder part is 

 smooth and swollen and curved round towards 

 the head. When full-grown the body measures 

 about three inches in length. The time occupied 

 in the larval stage is not known, but the growth 

 of the grub is probably slow, and it may be more 

 than a year before it attains its full size. It then 

 constructs an earthen cocoon, in which it turns 

 into a reddish pupa, and after another probably 

 somewhat lengthy period appears as a winged 

 beetle. The adult insect is of a dull brown 

 colour with a covering of grayish scaly hairs ; 

 and has a total length of rather more than two 

 inches. The beetle flies at dusk and lays its 

 eggs just below the surface of the ground. The 

 newly hatched grubs burrow down into the soil 

 and attack the roots of the neighbouring plants. 

 The insect by no means confines its attention to 

 Hevea plants. It is probably more or less omni- 

 vorous. It was at one time a notorious coffee 

 pest, and is now a serious enemy of cinnamon in 

 the low-country. Its appearance in large numbers 

 in rubber clearings is probablydueto the facility 

 with which the beetle is able to deposit its 

 eggs in the newly-turned soil immediately sur- 

 rounding the plants. The clean weeding of 

 clearings also tends to concentrate the grubs at 

 the roots of the rubber plants. If there is an 

 insufficiency of food at one spot, the grubs will 

 come up to the surface and wander to neighbour- 

 ing-plants. Specimens of injured plants that have 

 been submitted to me show the tap root eaten 

 clean off to within an inch of the surface of the 

 soil. One correspondent informs me that he has 

 lost 3,000 plants in a single clearing, and has 

 extracted five or six grubs from each hole. I have 

 not received any reports of damage to ojder trees. 



Treatment. — Dead or dying plants in a clear- 

 ing should be pulled up and examined. If the 

 roots show signs of having been attacked by an 

 insect, it will almost certainly be the work of 

 either cockchafer grubs or termites. In the 

 former case the roots will have been bitten oft' 

 clean. The work of the termites, on the other 

 hand, is usually recognisable by the core of the 

 root or stem being left, while the outside part 

 is eaten away. If the damage is attributable 

 to cockchafers, further search should be made 

 for the grubs in the soil at the roots of this and 

 the neighbouring plantf. When a plant shows 

 signs of distress, the damage has usually gone 

 too far to secure that individual ; but damage to 

 the remaining plants may be prevented by 

 forking in either nitrate of soda or " vaporite"" 

 The former is a well-known fertiliser, and has a 

 marked effect in ridding the soil of insects. 

 "Vaporite" is a patent insecticide placed on 

 the market by the Strawson Company, and is 

 specially designed for subterranean insects. I 

 have made some experiments with this mixture, 

 which show that it is rapidly fatal to cock- 

 chafer grub. A number of the grubs were 

 buried in the soil of pots containing gi owing 

 Hevea plants. Half of these were treated with 

 "vaporite" (J oz. to each pot) the other half 

 being left as controls. Within two hours the 

 grubs in the treated pots had come to the sur- 

 face, and they were all dead, by the next 

 morning. The grubs in the other pots remained 

 below. Similar results were observed in a field 

 experiment. The grubs very quickly came to 

 the surface and died or crawled away from the 

 neighbourhood of the " vaporite." 



" Vaporite " has a strong odour of carbolic 

 acid and gas lime. It is claimed by the patentees 

 that the powder " gradually evolves a noxious 

 vapour which fills the interstices of the soil, 

 from which the insects cannot escape, and are 

 consequently destroyed. The development of 

 vapour is slowly promoted by the influence of 

 the soil and remains in force for a long time 

 probably two to six months. •' To protect rub- 

 ber plants in a clearing, from 1 to 1£ oz. should 

 be forked or dibbled in at a distance of about 6 

 inches from the stem. It should not come into 

 direct contact with the roots. 



Nitrate of soda has also been reported upon 

 very favourably, one correspondent writing that 

 the grubs quickly deserted the holes treated with 

 this substance. The nitrate should be applied at 

 the rate of from 1 to 2 oz. for each plant, accord- 

 ing to size. 



The grubs of several other smaller cockchafers 

 attack the roots in a similar manner. They are 

 all very similar in appearance, and will respond 

 to the same treatment. 



(2) Termites (White Ants).— Complaints have 

 been made from time to time of damage to the 

 roots of young plants by white ants. The insects 

 have been found apparently in flagrante delictu ? 

 But it is extremely doubtful if we have really 

 any termitesin Ceylon that attack healthy living 

 plants. In every case that has been examined 

 the roots are found to be invaded by some 

 parasitic fungus, and it is practically certain 

 that the white ants came on the scene only 

 after the death of the affected parts. If at any 



