Other
Scarab beetles / White grubs
Scarabaeidae sp.
Insect
In a Nutshell
- Wilting and yellowing of the canopy.
- Plants die, easily pulled out from the soil.
- Reduction of yields.
- Adults are dark brown, about 20 mm long and 8 mm wide.
Can also be found in
Other
Symptoms
The grubs damage the rootlets, causing wilting of the plants and yellowing of the canopy. In the case of peanut, pods can also be attacked and damaged. In severe cases, plants ultimately die and can be easily pulled out from the soil. In spite of the attack, the crop often does not show immediate symptoms of damage. However, in the long run, their lifespan is reduced and yields are consistently reduced. In annual plants, the sudden wilting of the plants is the earliest symptom, later followed by premature defoliation. Affected plants are yellowish and wilted and die in patches.
Recommendations
Organic Control
Use extracts of Solanum surattense or Neem leaves as a seed treatment. Spray a liquid suspension of beneficial nematodes (for example Heterorhabditis spp.) at 1.5 billion nematodes per hectare in the early season. Bio-insecticides based on Nuclear Polyhedrosis Virus or the fungus called green muscardine can also work. Treat the kernels with kerosene (1 liter per 75 kg/seeds) before sowing. Make sure to conserve insects of the family of braconids, dragonflies, trichogrammatids.
Chemical Control
Always consider an integrated approach with preventive measures together with biological treatment if available. On emergence from the soil, adults may feed on the foliage of certain nearby plants. Spraying these plants in the night with persistent insecticides reduces the population of adults before egg laying.
What caused it?
The symptoms are caused by a group of white grubs of the genus Holotrichia. Both adults and larvae can damage the plants or trees by feeding on the roots. The adults are dark brown, about 20 mm long and 8 mm wide. Within three to four days after the onset of rain, they emerge from the soil, fly short distances and feed on the surrounding plants. After feeding, they reenter the soil to hide and lay their eggs. Female lays 20-80 white and roundish eggs singly at a depth of 5-8 cm in the soil. The larvae are whitish yellow, translucent and about 5 mm long. The fully grown grubs are stout with strong mandibles. Their head is yellowish and the white colored body is fleshy and 'C' shaped. They feed on organic matter for a few weeks and then feed on fine rootlets and pods. White grubs feed on the roots of a variety of crops such as sugarcane, chili, sorghum, maize, red gram or pearl millet.
Preventive Measures
- Plow deep in the seasons before planting.
- Plant resilient varieties if available.
- Sow early to avoid peaks of grub damage.
- Sow trap crops like sorghum, maize or onion in between your plants.
- Install light traps at the onset of rains and monitor the number of beetles per day.
- Collect and destroy white grub around the field, preferably in the morning.
- Use green manure such as Italian rye grass or legumes to conserve natural enemies.
- Apply potassium as base fertilizer to strengthen root systems and increase tolerance to grub damage.
- Fallow the fields for two years.
- Rotate crops with non-host plants (e.g.
- paddy rice).
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