Beating the beetles: Nauni University experts roll out war plan to save orchards

Scarab beetles, particularly in their larval stage known as white grubs, have emerged as a serious threat to horticultural and field crops in several agro-climatic regions. Recent reports of heavy infestations in apple and stone fruit orchards have left growers worried, as these beetles are capable of causing extensive damage to both roots and foliage.

To address this concern, scientists at Dr YS Parmar University of Horticulture and Forestry, Nauni, have issued an advisory outlining integrated pest management (IPM) strategies that incorporate cultural, mechanical, biological and chemical methods. These methods, when tailored to the pest’s biology and local conditions, can significantly reduce beetle populations and limit crop damage.

Defoliating beetles, often called May or June beetles, typically lay eggs in the soil following summer rains. The egg incubation period can range from a few weeks to over a month, depending on the beetle species. Once hatched, the larvae—commonly known as white grubs—initially feed on soil organic matter and humus. As they grow, they begin attacking plant roots, severely affecting high-value crops like apple, peach, and citrus, along with vegetables such as potato, carrot, and tomato. Ornamental plants, too, are not spared.

The white grub is easy to recognise: it has a C-shaped, creamy-white body with a distinct brown head. As temperatures drop in winter, the grubs burrow deeper into the soil and become dormant. Feeding resumes in the spring. By late spring or early summer, mature larvae move further down to form earthen cells, where they pupate and eventually emerge as adult beetles.

According to university experts, root feeding by white grubs weakens plant anchorage and disrupts water and nutrient uptake, leading to wilting, stunted growth, and, in severe infestations, total plant collapse. Adult beetles exacerbate the damage by feeding on tender leaves, significantly reducing the plant’s photosynthetic ability and overall vigor. Some beetles even target the reproductive parts of the plant, consuming flowers, nectar and young fruits—resulting in poor fruit set and lower yields.

The university’s advisory includes several control strategies for managing these pests. As a part of cultural control, fields with a known history of grub infestation should undergo repeated ploughing during April–May or September. This process exposes grubs to predators like birds and allows manual collection, thus reducing pest load. Only well-decomposed farmyard manure should be used, as it discourages grub development while promoting beneficial soil microbes.

Mechanical control is especially effective during the adult emergence stage, which coincides with the first summer rains. Since the beetles feed on foliage after 8 pm, they can be manually collected by shaking tree branches and catching them on cloth sheets spread beneath the canopy. The collected beetles should then be destroyed by immersing them in a 5% kerosene-water solution.

Light traps, though mainly used for monitoring, can also help reduce beetle populations. These should be set up in open areas for maximum effectiveness. Scientists also urge the initiation of mass beetle collection drives soon after the first summer rains.

For farmers practicing natural or organic farming, bio-formulations like Agniastr, Brahmastr, and Dashparniark (at 3 liters per 100 liters of water) can be sprayed for three consecutive days to help curb beetle infestation.

The university stresses that an integrated and timely approach is key to minimising damage caused by scarab beetles. Adopting these strategies not only helps protect current crops but also ensures long-term soil health and agricultural sustainability.