The white maggot Holotrichia serrata is a soil pest in tropical India that significantly affects sugarcane crops. While its larvae initially feed on decaying plant matter, in later phases, they can cause severe root damage, potentially leading to crop failure. Before the spread of sugarcane cultivation, monoculture, and limited varietal diversity, the pest was only found at high altitudes or in areas with assured rainfall. However, these factors have allowed the pest to expand its range. Effective management strategies are necessary to control this pest and mitigate its impact on sugarcane production.
White Grub Management in Sugarcane
Life Cycle of White Grub
- Sugarcane areas, fallow lands, grassy bunds near water channels, and grubs lay eggs.
- Beetles mate on host trees, eat leaves, and return to the soil.
- After rains, white grubs turn into insects at nightfall.
- First-instar grubs hatch after 10-12 days and feed on grass roots or organic debris before switching to sugarcane in the first two instars, each lasting one month.
- Third-instar grubs consume sugarcane stems for three to four months.
- Adults appear 10-14 days after earthen cells pupate.
- Adult bugs stay underground until early spring rains bring them out.
- The life cycle of white grub lasts one year.
Host range: Sugarcane, corn, rice, sorghum, neem, ailanthus, and cotton host white grubs. They also feed on weeds and grass stems.
Identification of White Grub in Sugarcane in the Field
- Farmers can identify sugarcane fields infested with white grubs by digging up plants and inspecting the roots for the creamy white, C-shaped larvae.
- Mature grubs are on average in the root zone of impacted clusters. Infestation symptoms include leaf yellowing and wilting, gradual leaf browning, and stunted growth of mature stems. As with flooding, white grub infestations can be so extreme that entire fields are wiped out.
Damage Symptoms of White Grub in Sugarcane
- White grub larvae cause damage to sugarcane roots, decreasing the plant’s water and nutrient supply.
- The symptoms are similar to drought damage: initial yellowing and withering of leaves, followed by browning and deterioration of maturing stalks.
- Insects may tunnel into cane stalks, causing additional damage.
- Extreme infestations can cause cane lodging and collapse.
- Seven to ten mature grubs are present in the root zone of clusters with white grub damage.
- The inability to control late-stage damage with pesticides can lead to crop failure.
- In the case of severe infestations and early phases of cane growth, replanting may be required.
- In extreme circumstances, entire fields can be destroyed by damage that typically affects regions.
- As a result of white grub damage, weight loss, and cluster dehydration can also occur.
Factors Favoring Growth/ Causes of White Grub Spread in the Field
- White grub larvae have a creamy white, C-shaped body and become more voracious as they mature, causing damage if left unchecked.
- The quantity of damage caused by white grubs depends on their number, age, sugarcane variety, and growth stage at the time of the attack.
- Attacks on old cane result in a decrease in yield.
- White grubs grow and spread in sugarcane fields where the soil is warm and wet, there is a lot of rain, drainage is bad, and too many organic matter fertilizers are used.
- Crop rotation and legume intercropping can aid in reducing white worm populations.