Effective Control of Leaf Eater Pests in Mulberry: Methods and Tools

Mulberry (Morus spp.) is the sole food source for the silkworm Bombyx mori, making the health of mulberry foliage directly linked to the quality and quantity of silk produced. Among the many threats to mulberry gardens, leaf eater pests are particularly damaging – they consume the leaf tissue that silkworms depend on, often stripping plants bare within days. Four key leaf-eating pests – the leaf roller (Diaphania pulverulentalis), the Bihar hairy caterpillar (Spilosoma obliqua), the cutworm (Spodoptera litura), and the wingless grasshopper (Neorthacris acuticeps nilgirensis) – are responsible for significant yield losses in sericulture regions. Understanding their biology, damage patterns, and management options is essential for anyone involved in mulberry cultivation.

Why leaf eater pests are a serious threat in mulberry 🔗

Unlike sap-sucking pests that gradually weaken a plant, leaf eaters directly destroy the leaf surface. In mulberry, this matters more than in most other crops because the leaves are not just a measure of plant health – they are the product. Silkworms at the chawki (early instar) stage require tender, high-quality leaves. When leaf eaters damage or eliminate these leaves, silkworm rearing is disrupted, leading to poor cocoon formation and reduced silk yield. According to research published in the Asian Research Journal of Agriculture, infestations of leaf rollers like D. pulverulentalis have been recorded at up to 100% in some mulberry plantations in Karnataka, making early detection and intervention non-negotiable.

The four major leaf eater pests of mulberry 🔗

1. Leaf roller – Diaphania pulverulentalis (Hampson) 🔗

First reported as a mulberry pest in Karnataka around 1995, the leaf roller (D. pulverulentalis, Family: Pyralidae) has since become one of the most destructive leaf eaters in southern India. The adult moth is greyish brown, about 1 cm in length, with brownish wavy stripes on its wings. Each female deposits around 100 eggs, one or two at a time, near the shoot tips. Eggs hatch in 3-4 days. The greenish-brown larvae, with distinctive black head and black markings along the body, complete their larval development in 10-15 days, then pupate in dry leaves for 8-10 days. The full life cycle takes just 21-29 days, allowing multiple generations in a single growing season.

Young caterpillars secrete fine silky threads that bind the leaf surfaces together, forming characteristic rolled or webbed leaves – the visible sign that gives this pest its name. Older larvae feed voraciously on tender leaves at the shoot tips. Beyond direct defoliation, the pest poses an indirect biological risk: larvae infected with Nosema bombycis (pebrine) spores can contaminate mulberry leaves in the field, potentially transmitting pebrine disease to silkworms. Infestation is observed throughout the year but peaks between July and November.

2. Bihar hairy caterpillar – Spilosoma obliqua (Walker) 🔗

The Bihar hairy caterpillar (Family: Arctiidae) is a polyphagous pest found across India and the Philippines. It infests several crops but is a consistent problem in the sericulture belt, with severe outbreaks occurring from August to January. Adult moths are light brown with brick-red abdomens dotted with dark spots. Females are highly prolific, laying 1,000-2,000 pale green eggs in batches on the underside of leaves. Eggs hatch within 5-7 days, and the larvae go through seven instars over 27-32 days. The fully grown caterpillar reaches 4.5-5 cm in length, with black ends and a reddish-brown midsection covered in bristle-like hairs. Pupation occurs in sheltered locations such as soil crevices, tree trunks, and building corners, and the pupal period lasts 12-14 days. The entire life cycle is completed in approximately 44-53 days.

Young larvae feed gregariously on the soft tissue between leaf veins, leaving behind a skeleton-like mesh visible from a distance. As they mature, caterpillars become solitary and far more destructive, consuming entire leaves. In severe cases, entire branches can be stripped bare, leaving mulberry gardens with dried, dead-looking foliage.

3. Cutworm – Spodoptera litura (Fabricius) 🔗

Spodoptera litura, commonly called the tobacco cutworm or cotton leafworm (Family: Noctuidae), is one of the most widely distributed and damaging agricultural pests in Asia, Oceania, and the Indian subcontinent. According to ScienceDirect, it is known to attack over 87 economically important plant species, and in mulberry gardens it appears sporadically, especially where vegetable crops are cultivated nearby. Peak incidence falls between August and February. The stout adult moth has dark forewings with wavy white markings; hind wings are white with brown margins. Eggs are laid in clusters of 200-300 on the underside of leaves and covered with brown bristles. The incubation period is 4-5 days. The fully grown caterpillar is pale greenish-brown with grey and yellow longitudinal bands, reaching 40-50 mm in length. Larvae are strictly nocturnal – they hide in soil crevices during the day and emerge at night to feed. The life cycle is completed in 36-40 days.

The cutworm caterpillar attacks young mulberry shoots, cutting through them so the severed portion dries and falls off. It also feeds on leaves, and during severe infestations, entire crop fields can be defoliated overnight. The nocturnal habit makes it harder to detect during routine daytime inspection.

4. Wingless grasshopper – Neorthacris acuticeps nilgirensis 🔗

The wingless grasshopper (Family: Acrididae) is a serious concern in rainfed mulberry plantations of Karnataka, with infestation levels ranging from 8% to as high as 95% in affected areas. Unlike winged locusts, this species cannot fly, but it moves actively through the field. Adult grasshoppers are light brown in colour. Gravid females deposit 6-8 egg pods in loose, shallow soil (2-3 cm deep), with each pod containing 8-10 eggs. Hatching takes 28-31 days. The nymphs pass through six instars over 90-95 days, with early instars appearing straw-coloured and later ones turning light green. The full life cycle spans a lengthy 163-186 days. The pest is present throughout the year but causes most damage during July and August.

Both nymphs and adults feed voraciously on sprouting buds and freshly emerged leaves. In severe infestations, mulberry plants can be left entirely without foliage. Because this pest lacks wings, it spreads by walking – which makes field-level containment somewhat more feasible than for flying insects, but also means it can quietly build up large populations in localized patches before being noticed.

Integrated management of leaf eater pests 🔗

Because mulberry leaves are fed directly to silkworms, pest management in mulberry gardens must balance effectiveness with safety. Any insecticide applied to the leaves carries a residue risk to silkworms. This is why Integrated Pest Management (IPM) – combining mechanical, chemical, and biological methods within a structured safety framework – is the recommended approach for leaf eater control.

Mechanical and physical control 🔗

For all four pests, mechanical methods form the first line of defence, particularly when populations are in early stages. These include collecting and destroying egg masses as soon as they are spotted, clipping infested shoots and dipping them in a 0.5% soap solution or burning them, and installing light traps to attract adult moths of the Bihar hairy caterpillar and cutworm. For the cutworm specifically, deep ploughing of the garden and flood irrigation after pruning are effective in exposing and killing pupae that shelter in the soil. For the grasshopper, deep ploughing also serves to expose egg pods to sunlight and natural predators. Providing small containers of water around the plantation encourages insectivorous birds, which naturally prey on the leaf roller larvae.

Chemical control and safety periods 🔗

DDVP (Dichlorvos) is the most commonly recommended chemical for leaf eater management in mulberry. It is effective against multiple species and breaks down relatively quickly, which is critical given the need to feed leaves to silkworms after treatment. Recommended application rates and safety periods are as follows:

For the leaf roller and Bihar hairy caterpillar: spray 0.2% DDVP (2.5 ml/litre of water) on the plants. Treated leaves can be used for silkworm rearing after a safety period of 7-10 days. For the cutworm: spray 0.15% DDVP (2 ml/litre of water) during evening hours, about 20 days after pruning, with a safety period of 10 days. Dusting 5% Malathion near the base of plants immediately after pruning is also effective. For the wingless grasshopper: apply 0.15% DDVP when the pest reaches late-stage nymphal or adult populations, observing a safety period of at least one week before harvesting leaves for silkworm feeding.

It is important to never spray insecticides immediately before or during silkworm rearing cycles. Strict adherence to safety periods is not optional – it is a biological necessity, as UC IPM guidance on mulberry pest management and sericulture extension literature consistently emphasise.

Pheromone traps for cutworm monitoring 🔗

For Spodoptera litura, pheromone traps (spodolure) offer a targeted and residue-free monitoring and mass-trapping method. The recommended rate is 2 lures per acre, deployed twice at 15-day intervals beginning from the 25th day after pruning. These traps attract and capture adult male moths, reducing mating success and helping growers monitor population pressure before it reaches damaging levels.

Biological control 🔗

Biological control is a central pillar of IPM in mulberry precisely because it leaves no chemical residue on leaves. The egg parasitoid Trichogramma chilonis is the most widely deployed biocontrol agent against both the leaf roller and the cutworm. It is applied at 1 Tricho card per week for 4 consecutive weeks for the leaf roller, and at 30 egg cards per acre for cutworm management. Importantly, no insecticides should be sprayed after releasing Trichogramma parasitoids, as this would kill the beneficial insects.

The parasitoid wasp Tetrastichus howardii has also been identified as a natural enemy with potential in managing mulberry leaf-eating pests. Research through institutions such as the Central Sericultural Research and Training Institute (CSRTI), Mysore has documented its parasitic activity against lepidopteran pest larvae in mulberry gardens. Additionally, an IPM study on mulberry leaf webber management demonstrated that neem oil applied at 1-3% concentrations at 10-day intervals significantly reduced leaf roller infestation while preserving beneficial insect populations such as spiders and coccinellids.

Key IPM principles for mulberry leaf eater management 🔗

Effective management of leaf eater pests in mulberry is not about using a single product – it is about combining strategies at the right time. A few guiding principles make a practical difference. Regular monitoring of the garden from the 15th day after pruning helps catch early infestations before they escalate. Egg mass destruction during scouting visits prevents population explosions. Chemical sprays, when required, should always be applied immediately after pruning or leaf harvest – never just before the next harvest cycle. Biological control agents should be released after any mandatory chemical spray window has passed, not concurrently. Finally, avoiding the cultivation of alternate host plants (such as vegetables) near the mulberry garden reduces the risk of cutworm migration into mulberry plots.

When these practices are followed consistently and in the correct sequence, leaf eater damage can be kept well within manageable limits, protecting both the mulberry yield and the silkworms that depend on it.

What do you think? Given that silkworm safety is the primary constraint on mulberry pest management, do you think pheromone traps and biological agents like Trichogramma could fully replace chemical sprays in modern sericulture farms – or will DDVP remain a necessary fallback? And which of these four leaf eater pests do you consider the hardest to manage in practice, and why?

References

1. https://journalarja.com/index.php/ARJA/article/view/646
2. https://www.researchgate.net/publication/295628793_Integrated_Pest_Management_IPM_module_for_Tukra_mealy_bug_Maconellicoccus_hirsutus_Green_and_leaf_webber_Diaphania_pulverulentalis_Hamp_in_mulberry
3. https://hbmahesh.weebly.com/uploads/3/4/2/2/3422804/pests_of_mulberry.pdf
4. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/spodoptera-litura
5. https://bioprotectionportal.com/resources/spodoptera-litura-identification-damage-and-control/
6. https://ipm.ucanr.edu/PMG/GARDEN/PLANTS/mulberry.html
7. http://www.csrtimys.res.in