Source document: https://docs-lawep.s3.us-east-2.amazonaws.com/1696578414138.pdf (Zimbabwe)
The Larger Grain Borer (Prostephanus truncatus) Introduction • Larger Grain borer is a primary storage pest of maize and dried cassava.

It belongs to the order Coleoptera and family Bostrichidae It is a wood boring beetle originating from Central America.

• • Identification Mophology of LGB • Like other coleopteran beetles the LGB is divided into three • main body parts, the head, thorax and abdomen.
The head, which points downwards, has distinctive eyes and a pair of antenna which is divided into three segments.

• The thorax covers the head and its front rim has teeth-like • • indentations.

The abdomen is covered by hard wing covers called elytra.

The wing covers are heavily punctated and drop off sharply at the back, giving the impression of a square-cut end when viewed from above.

• The adult beetle is about 3-5 mm long and dark brown or black in colour, with a cylindrical shape.
Labeled Diagram of LGB Thorax Abdomen Head Antenna Eye Elytra(Heavily punctated) Comparison of LGB to other Important Storage Grain beetles LGB Compared to Lesser grain borers The slope of the back of LGB compared to lesser grain borer Larger Grain Borer (P. Trancatus) Lesser Grain borer ( R. Dominica) The back of the LGB drops sharply where as that of the lesser grain borer drops gently.
The slope of the back of LGB compared to lesser grain borer The slope of the back of LGB compared to lesser grain borer Larger Grain Borer (P. Trancatus) Lesser Grain borer (R. Dominica) •The back of the LGB has a square cut where as that of the lesser grain borer is concave.

The size of the head of the LGB when compared to that of the lesser grain borer.

Larger Grain Borer (P. Trancatus) Lesser Grain borer ( R. Dominica) •The head of the LGB is bigger than that of the lesser grain borer.
LGB Compared to the bamboo borer The shape of the elytra of the LGB compared to that of the lesser grain borer.

Larger Grain Borer ( P. trancutas) Bamboo borer (Dinoderus ) •The LGB has edged elytra where as the bamboo borer has concave elytra LGB compared to the maize weevil Comparison of the head of the LGB and maize weevil.

P. trancatus Maize weevil S. zeamais The head of the LGB points downward and cannot be seen from above whereas that of the weevils and flour beetle points forward.
The biology and ecology • LGB lives and breeds in dry food commodities, maize stalks, cob remnants and timber • The females lays between 50-600eggs either singly or in pockets of twenty eggs in maize kernel or cob core • The eggs hatch into larvae after 3-7 days • Under favourable conditions the life cycle is completed within 25 days( temp 27oc and 70% relative humidity.

• The male adult lives for about 45days while the adult female lives for about 61 days.
Life cycle of LGB Inside and outside the grain Inside the grain Inside the grain Inside the grain Damage • When LGB attacks stored maize, it makes neat round holes and produces lots of dust • LGB will also damage a wide range of food commodities and will bore into non- food materials such as leather, plastic, soap and wood.

Picture showing damage LGB damage on maize grain (too much flour produced) and wood.
Losses caused by LGB • Loss of weight of grain (quantitative loss • Loss of quality of grain ( qualitative loss) • Loss of nutritional value of grain (nutritional loss) • Economic losses to the farmer and trader (economic losses) Management of LGB • Chemical control (use of fumigants e. g. Phostoxin )and use of grain protectants • Cultural control – timely harvesting of maize and Post- Harvest Farm Hygiene • Use of resistant /tolerant varieties • Biological control-Manipulation of beneficial organism with the goal of reducing pest population to economically acceptable levels • Bio-agents used are: pathogens, parasites, parasitoids and predators(A beetle Teretriosoma nigrescens,has been used successfully to control LGB in Benin, Togo and Kenya).