The greater false wireworm (GFW) occurs sporadically in the summer rainfall region.
IdentificationThe GFW is the larval stage of dark-colored beetles with long legs, often seen running over the soil surface and hiding under plant litter. The larvae can grow to ca. 35 mm in length and are smooth, hard-bodied with a polished cream to golden-brown appearance.
Feeding position and damage symptomsLarvae feed on the seed and stems of seedlings just beneath the soil surface, causing the stem to have a tattered appearance. Adult beetles may occasionally damage emerging seedlings. Severely damaged plants eventually wilt and die.
ControlCultural practices supporting germination and rapid seedling development will shorten the vulnerable ‘damage period’ of the plant thus limiting seedling loss and retaining plant densities. Targeting the larval stage in the soil through seed treatments can also be used with best effect where seedlings grow actively under moist soil conditions.
Greater False Wireworm adult
Greater False Wireworm larva
The lesser false wireworm (LFW) occurs sporadically throughout the summer rainfall region.
Identification
The LFW is the larval stage of a dark-coloured beetle often referred to as the ‘Dusty Surface Beetle’. The larval stage is thin, 10 - 15 mm long with a dark shiny appearance. Larvae are very active and move away quickly when disturbed.
Feeding position and damage symptoms
Similar to the GFW, larvae of the LFW also feed on the seed and stems of seedlings just beneath the soil surface, causing the stem to have a tattered appearance. Plants then wilt and die, leading to seedling density-loss in the field.
Control
Cultural practices supporting germination and rapid seedling development will shorten the ‘damage period’ of the plant thus limiting seedling loss and retaining plant densities. Targeting the larval stage in the soil through seed treatments can also be used with best effect where seedlings grow actively under moist soil conditions.
DistributionThe black maize beetle occurs sporadically throughout the summer rainfall region.
IdentificationAdult beetles have a shiny black colour and are approximately 12 to 15 mm in length. They are usually found in or on the soil surface layer. Larvae are grub-like, soft-bodied and white with a slightly darker (orange-brown) head. The grubs can reach 25 mm in length.
Feeding position and damage symptomsAdult beetles feed on seedling stems at or just below the soil surface. Big holes with ragged edges can be seen after feeding, resulting in plant death and seedling density-loss. Larvae generally feed on decaying organic material and do not damage the crop.
ControlCultural practices supporting germination and rapid seedling development will shorten the ‘damage period’ of the plant thus limiting seedling loss and retaining plant densities. Chemical seed treatments are registered as pre-plant approach toward control of adult beetles.
Black Maize Beetle (adult)
Black Maize Beetle (grub/larva)
DistributionWestern Province grain worm is a sporadic and unpredictable pest of wheat under intense rainfall conditions in the Western Cape.
IdentificationThe C-shaped larvae are legless and can reach 10 mm in length. They are white to cream coloured with small shiny brown heads. The brown-black adult beetles are known as weevils and average 5 to 6 mm in length. The bodies of the beetles are faintly spotted on the back and they show a characteristic snout on the front of the head. Soft white pupae can be found inside cells in the soil.
Feeding position and damage symptomsLarvae feed on the stems of seedlings just beneath the soil surface, causing the stem to have a tattered appearance. Plants then wilt and die leading to poor plant stand in the field. Adult beetles feed on the leaves but no economically significant damage has been reported.
ControlCultural practices supporting germination and speedy development of seedling will shorten the ‘damage period’ of the plant thus limiting seedling loss and retaining plant densities. No chemicals are currently registered for wheat against this pest.
DistributionThe ‘Sandveld’ grain worm occurs only in the Western Cape Province.
IdentificationThe larva is cream-coloured with a dark brown head and approximately 10 to 12 mm in length. Adult beetles are blue-green to metallic green and approximately 6 mm long. Pupae are present inside cells just below the soil surface.
Feeding position and damage symptomsLarvae feed on the stem of the plant just below the soil surface causing small plants to die. Bigger plants often survive feeding damage but tillering of these plants is reduced.
ControlCultural practices supporting germination and rapid seedling development will shorten the ‘damage period’ of the plant thus limiting seedling loss and retaining plant densities. Currently, no chemicals are registered against this pest on wheat.
