Groundnut crop is infested with sucking type of insects pests like aphids, leaf minor thrips, leaf eating caterpillars, leaf webber, etc in the initial and active growth stages. In the later stages, the crop may be attacked by pests like Groundnut earwig or pod borer which punctures the developing pods causing heavy damage.
6. 1. Cercospora arachidicola is a fungal ascomycete plant pathogen that causes early leaf spot of peanut. All cultivars of peanuts are equally susceptible to peanut fungal pathogens; however, C. arachidicola is an economically important peanut pathogen and is responsible for significant economic losses in the peanut industry, more specifically in the Southeastern, Eastern, and the Southwestern United States. Early leaf spot of peanut can drastically reduce yields, leading to economic downturn of the peanut crop economy. Annual crop losses in the United States range anywhere from less than 1% to greater than 50% depending on disease management and treatment.
Symptoms
Cercospora arachidicola only infects peanut plants, causing symptoms of brown lesions with chlorotic rings on the stems, leaves, and petioles. The first macroscopic symptoms usually appear on the adaxial surface of the lower leaves about 30 to 50 days after planting. Further damage can lead to premature defoliation and even yield loss. Signs include tufts of silvery, hair-like spores on lesions during humid weather.
Control
Early leaf spot of peanut can be treated through:
Ibimenyetso by’indwara y’ibidomo by’ikigina ku mababi y’ubunyobwa
2. Groundnut rosette virus (GRV) is a peanut pathogenic virus found in Sub-Saharan Africa. It is transmitted between plants by insect vectors such as the ground aphid (Aphis craccivora).
Groundnut rosette virus was first described in Africa in 1907 and causes serious damage to groundnut crops on that continent. In 1939 it was reported to infect 80 to 90% of plants in the Belgian Congo causing major losses in yield. The virus can spread rapidly through a crop.
Groundnut infected by Rosette disease
Control:
3. Ground nut Aphid: Aphis craccivora Koch.
Ground nut aphid injects a powerful toxin into the plant while feeding and, when populations are large, this can stunt or kill plants. While feeding, this aphid produces a considerable amount of honeydew upon which sooty mold grows. The black sooty mold reduces photosynthesis and may make leaves unpalatable to livestock. Damage symptoms include yellowing, wilting, and dieback. In general, legumes can be seriously damaged, either by direct insect feeding or by the transmission of virus diseases (Rossette & Peanut strip virus.)
Control
4. Thrips: (Scirtothrips dorsalis, Thrips palmi)
Nymphs and adults lacerate the surface of the leaflets and suck the oozing sap resulting in white patches on lower surface of the leaves and distortion of young leaflets. Severe infestations cause stunted plants.
Cultural Control
5. Leaf miner Aproaerema modicella
Nature of damage
Small blister like mines are seen on the upper leaf surface near mid rib. As the feeding advances, the mines increase in size and the entire leaflet becomes brown, rolls, shrivels and dries up. In severe cases the affected crop presents a burnt up appearance. Later stages larvae web the leaflets together and feed on them, remaining within the folds.
Control:
6. Pod borer: Helicoverpa armigera
Damage
Larvae feed on the foliage, prefers flowers and buds. When tender leaf buds are eaten symmetrical holes or cuttings can be seen upon unfolding of leaflets.
Cultural Control
7. Ground nut White grub: Holotrichia consanguinea
Adults are 18-20 mm long and 7-9 mm wide. The eggs are white, almost round. The young grubs are translucent, white and 5 mm long. Beetles emerge out of the soil within 3-4 days after the onset of rain. Install light traps with the onset of rains and count the number of beetles per day. Dig 100 X 100 X 20 cm pit @ 10 pits per ha, collect and count the number of beetles per pit.
Both adults and larvae are damaging stage.The larvae feeds roots and damage pods. Grubs feed on fine rootlets, resulting in pale, wilted plants dying in patches.
Mechanical Control
Collection and destruction of white grub adults from host trees around the field. In areas where white grub is persistent problem, deep ploughing after harvesting the crop can reduce the population as birds can pickup the grubs, and destruction of pupae.
Control
8. Termite
Termites are white translucent ant like insects. They enter the root system and burrow inside the root and stem; this usually kills the plant. They bore holes in the pods and damage the seed. They remove the soft corky tissue from between the veins of the pods (scarified). They do not usually damage the seed. But scarified pods are more susceptible to infestation by Aspergillus fungus, which produces health hazard aflatoxins.
Management
9. Millipedes (Peridontopyge spp.)
Millipedes are among the economically important soil pest of groundnuts. They are brown to blackish in colour and curl when disturbed. They attack groundnut seedlings, between planting and approximately 20 days after planting, feeding on the emerging cotyledons and moving to the root system at the collar region. The cortex is often damaged serving as an entry point for secondary infection by microorganisms. The development of plants surviving the attack is often retarded.
Millipedes also attack maturing groundnut during pod formation, i.e. when the pods are still soft. Immature pods from severed pegs are often perforated and thus suffer secondary infection or invasion by rot-causing organisms such as Aspergillus flavus. Millipedes may also damage flowers.
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Control:
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