130 THE DATE PALM. 



The damage done to date trees by red weevil is done by the 

 grubs only. After hatching, the grub begins to feed on the plant 

 tissues and forms a tunnel in them. This tunnel increases in 

 diameter as the grub grows. The grub prefers the inside of the 

 stem where the tissues are softer and where it can keep away 

 from the light. Therefore the stem from outside may appear 

 unaffected although the tree is badly attacked. A cross section 

 of a date palm stem shows it to be made up of a large number 

 of fibious strands lying side by side and more cr less firmly bound 

 together by other and usually softer tissues. Some of these 

 fibres can be followed into the old leaf scars of the tree trunk, 

 and others into the green leaves which crown the tree (see illus- 

 tration No. 7, page 6a). The function of the strands connected 

 with the green leaves is to conduct the food material from the 

 soil to the leaves and the elaborated foods from the leaves back 

 to the various parts of the plant. The leaves of a palm may 

 therefore look healthy after the plants are badly affected if a 

 sufficient number of the strands of tissues which feed these leaves 

 remain uncut by the insect. Consequently also we sometimes 

 see the sudden collapse of apparently healthy trees when at 

 length these fibres are cut. At points where the insects have 

 bored to the outside of the stem, a thick resinous juice has been 

 found to ooze out and harden on drying. 



The damage caused by the imago (adult weevil) is insigni- 

 ficant. When the adult weevils emerge from the cocoons they 

 may fly to other trees and infect these. Apparently they are 

 capable of flying great distances. They are recorded to have 

 been seen on the wing in the insectary for 2-3 minutes at a time. 



It has been advised by some writers that the leaves should 

 not be pruned from the trees, but that they 

 should be allowed to dry and fall off themselves. 

 In my opinion that advice should not be followed 

 in the case of date trees in the Punjab as (a) if there is any leaf 

 disease such as the scale insect referred to on page 137 on the 

 palms, the old leaves often become very badly infected and these 

 spread the disease to the fresh young leaves coming out of the bud. 



