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Pests In The Herbarium
Insects are the chief agents of herbarium destruction .they include beetles , book lice , silver fish , ants .
Fungi is also a pest but does not destroy dry specimens
Insects and fungi can be kept out of herbarium by keeping the specimens dry on a well fitting cupboard
CONTROL OF PEST IN HERBARIUM Paradichlorobenzene (PCB) should be scattered among the specimens . PCB sublimes slowly producing vapour , these affects noxious insects and are repellant to insects but
harmless to humans .
PCB eventually disappears and leaves residues to the specimen which gives protection to the specimen for as long as 6 months .it is sometimes referred to as moth balls .
Insects can also be killed by dip freezing , fumigation using methylene bromine can also be used but also several conditions should be considered before using fumigation because ;
(a) Gas used is deadly /poisonous
(b) Pest control firms should be consulted first
Mercuric chloride can also be used as a preservative especially for specimens to be mounted ( they provide a long lasting solution) . It is prepared as a solution in alcohol . The composition of these solution is as follows
– Mercury chloride -500g
– Phenol – 250
– 95% Ethanol -20l
Mercury chloride dissolves easily. Phenol crystals are melted with gentle heat before storing them in tightly stoppered bottles .
These solution is applied with a soft brush to the mounted specimen which are then left to dry
Care must be taken so that the fluid must not reach the labels
These treatment kills all insect and their eggs present in the specimen and leaves residue solution for severally days . However it sublimes slowly and specimens may become attacked , therefore repeated treatment is necessary
NB LPCP can be used as a substitute for mercuric chloride . It is less poisonous to man but evidence shows that they accumulate in mans tissues
– Silver fish is another pest that attack labels on herbarium specimens . It can be controlled by use of sodium fluorosilicate bait which is applied on labels . it is however dangerous to human health.