Crops in our field are attacked by many diseases and pests. Among them we can observe one of the stages of pests i.e “Grub Stage”. Grubs are small, white to creamy, c- shaped larva that live beneath the soil. These are larva or immature form of certain species of beetles like May/june beetles, Japanese beetles or Chaffer beetles. Mostly these are found in crops like Sugarcane, Maize, Soybean etc. These are occasional pests which can be seen in some seasons.
Occurance
Grubs are found below the surface of the soil in crop field or lawn. Several species of white grubs can be found in the plant roots which feed on organic matter, roots of crops and grasses. If the soil is moist, they may emerge to feed on the plant roots.
Life cycle
Its has 4 stages in its life cycle.
Egg
Adult beetles lay eggs in the soil between June and August. In warm condition, these eggs will hatch within 2 weeks.
Larva
Once the eggs hatch, a tiny first instar larva(grubs) will emerge out. They begin to eat the roots of the crops as well as grasses. As they grow into 2nd and 3rd instar, they start to feed aggressively. White grub overwinters at the 3rd instar grub, which burrows deep into the soil.
Pupa
Once the larva finsh their feeding schedule, they develop into pupa and remain in the soil for several weeks. Later they grows and transforms into beetle.
Adult
Adults emerge during summer months. These are 1/4th to 1 inch long, with to creamy with brown head and have 6 prominent legs. They start to cause more problems in the crop fields. Adult beetles spend for 2-3 weeks mating before laying eggs. They lay about 60 eggs at a time. Their entire life cycle will be completed in a year. But June beetles completes their life cycle in 3 years.
Reasons for their occurance
Grubs occur in the crop field due to several reasons. It is mainly influenced by condition of soil, lack of organic matter etc. It depends on how the field is managed by farmers. Improper management of land is the most important cause for grubs attack.
Damage Symptoms
- Grubs feed on the roots of seedlings as well as older plants.
- Plants become stunted and discolured.
- This leads to withering and dying of leaves.
- Reduced number of tillers in crops like sugarcane and Maize.
- Later patches develop on the leaves.
- They also feed on mesocotyl region which leads to death of the plant.
Management
There are different management stratergies for grubs. But insecticides plays major role in grubs management.
- Thiamethaxam 30% FS has to be used to control grubs. It has to be drenched if the damage is more. In the initial stages it can be mixed with urea and can be applied to the soil. When it is used in sugarcane crop, other than controlling grubs it also increases tillers. In brinjal crop it controls grub population along with early shoot borer.
- Cartap hydrochloride 50 SP also plays major role in controlling grubs
- Imidachloprid 70%
- Danitol is having Fenpropthrin as its active ingredient which manages the white grubs to greater extent.
