Legume pod borer (Maruca pod borer)

Maruca vitrata Maruca vitrata (Fabricius, 1787) · formerly or also: Maruca testulalis

spotted pod borer · English, South Asia
bean pod borer · English, Americas and Pacific
foreur des gousses · French, West Africa
豆荚野螟 (dòujiá yěmíng) · Chinese, East Asia

The legume pod borer is a moth whose caterpillars web together the flowers, buds and young pods of cowpea, pigeon pea, mung bean, beans and other legumes, then bore into the pods and eat the seeds. It is one of the most damaging pests of cowpea in Africa and of pigeon pea and other pulses in Asia. Because the caterpillars feed hidden inside webbed flowers and pods, sprays must be well timed.

Adult legume pod borer moth (Maruca vitrata) with brown and translucent white wings spread. Photo: Ravi Vaidyanathan, CC BY 3.0, via Wikimedia Commons.

Type: Insect · Insect (moth; the caterpillars bore into flowers and pods)
Classification: Animalia › Insecta › Lepidoptera › Crambidae
Main crops: Cowpea, Pigeon pea, Mung bean, Black gram, Common bean, Lima bean, Lablab, Soybean
Found in: Africa, South and South-East Asia, Americas, Oceania
Chemical groups: IRAC 28, IRAC 5, IRAC 6, IRAC 11A (mode-of-action groups, not products)
Last reviewed: 2026-10-20

Legume pod borer scientific name, order and family

The scientific name of legume pod borer is Maruca vitrata Maruca vitrata (Fabricius, 1787), in the order Lepidoptera, family Crambidae.

Older or alternative scientific names: Maruca testulalis.

Where it occurs

Found throughout the tropics and subtropics of Africa, Asia, the Americas and Oceania.

Region	Status
Africa	Widespread; major pest of cowpea
South and South-East Asia	Widespread; major on pigeon pea and pulses
Americas	Present in tropical and subtropical areas
Oceania	Present

Symptoms and identification of legume pod borer

Legume pod borer moth (Maruca vitrata), museum specimen. Photo: Komal et al. (2021), CC BY 4.0, via Wikimedia Commons.

The organism

Moths have a wingspan of about 2.5 cm, brown forewings with white, see-through bands and spots, and whitish hindwings with a brown border; they rest with wings spread flat under leaves. Caterpillars are pale greenish-white with rows of paired dark spots on each segment, growing to about 1.8 cm.

Signs in the crop, stage by stage

Crop stage	What you see
Flower buds and flowers	Flowers and buds webbed together with silk and droppings; flowers drop.
Pods	Pods webbed to each other or to leaves; round entry holes with droppings at the hole; seeds eaten inside.
Shoots	Webbed and bored tender shoots and leaves, especially in pigeon pea.

Life cycle of legume pod borer

Life cycle of Legume pod borer (Maruca pod borer) — diagram drawn by Laisha from the stages below. Durations depend on temperature.

Females lay eggs on flower buds, flowers and young leaves. Young caterpillars feed inside flowers, and older ones move to pods, webbing them together. There are five instars. Mature caterpillars pupate in a silk cocoon in webbed leaves or in the soil.

Stage	Duration	Notes
Egg	About 2-3 days	On buds and flowers.
Caterpillar (5 instars)	About 8-14 days	Flowers first, then pods.
Pupa	About 6-9 days	In webbed leaves or soil.
Adult moth	About 1 week	Night-active; may migrate.

Temperature

Egg to adult takes about three to four weeks in warm weather; outbreaks follow the flowering of host crops, often in humid seasons.

Generations

Several generations per year, moving between cultivated and wild legumes.

Conditions that favour it

Large areas of flowering legumes, staggered plantings, wild legume hosts near fields, warm humid weather and loss of natural enemies after broad-spectrum sprays.

Economic threshold level (ETL)

There is no single international threshold. Programmes use counts of caterpillars per number of flowers or plants at flowering, which differ between countries and crops; check with your local extension service.

Thresholds are local. They depend on crop price, control cost, variety and natural-enemy activity, so use the figure your local extension service publishes where one exists.

Damage and yield loss from legume pod borer

Yield losses of 20-80% are reported in cowpea in Africa, and heavy losses in pigeon pea and mung bean in Asia, especially when flowering coincides with peak moth numbers.

Monitoring

From the start of flowering, open a sample of flowers and count caterpillars, and look for webbed flower clusters.
Use light traps or pheromone traps where available to follow moth activity.
Check pods for entry holes with droppings.

How to control legume pod borer (integrated management)

Control works best as a sequence: prevent, monitor, then act only when a threshold or a risk forecast says so, using the least disruptive option that works.

Cultural control

Plant early and in a short window across an area so that flowering does not coincide with peak moth numbers.
Intercrop cowpea with cereals such as maize or sorghum, which can reduce pod borer damage.
Remove wild legume hosts near fields where practical and destroy crop residues.

Mechanical and physical control

On small plots, shake infested plants or hand-pick webbed flowers and pods.

Biological control

Natural enemies include parasitic wasps (such as Apanteles taragamae, introduced in West Africa), predators and a specific nucleopolyhedrovirus (MaviMNPV); neem extracts and Bacillus thuringiensis are used by many farmers.

Host resistance

Bt cowpea expressing a Cry protein against Maruca was approved in Nigeria in 2019 and in Ghana later; conventional resistance in cowpea is limited, while some pigeon pea and mung bean varieties are less attacked.

Chemical control of legume pod borer — by mode-of-action group only

Laisha names chemical options only by their resistance-committee mode-of-action group (IRAC for insects, mites and nematodes, FRAC for fungi, oomycetes and bacteria, HRAC for weeds), never by active ingredient or product. What is registered differs by country and changes over time; the label and your local plant-protection authority decide what may be used, on which crop, at what rate and with what pre-harvest interval.

Sprays are timed to the start of flowering and early podding, when caterpillars are small and exposed; repeated broad-spectrum sprays kill natural enemies. What is registered differs by country and changes over time; follow the label and your local plant-protection authority.

Scheme	Group	Mode of action	Notes
IRAC	28	Ryanodine receptor modulators (diamides)	Rotate.
IRAC	5	Nicotinic acetylcholine receptor allosteric modulators, site I (spinosyns)	Selective.
IRAC	6	Glutamate-gated chloride channel allosteric modulators	Rotate.
IRAC	11A	Microbial disruptors of insect midgut membranes (Bacillus thuringiensis)	Selective; best on young caterpillars.

Resistance management

Rotate groups between generations, follow refuge rules where Bt cowpea is grown, and protect natural enemies.

Look-alikes and how to tell them apart

Cotton bollworm on legumes — Larger caterpillars with stripes rather than paired spots, boring into pods without webbing them together.
Pod-sucking bugs — Shrivelled pods and seeds with tiny punctures, no holes or droppings.
Legume flower thrips — Flower drop with tiny thrips inside flowers, no webbing or caterpillars.

Host range

More than 30 legumes, including cowpea, pigeon pea, mung bean, black gram, common and lima beans, hyacinth bean, soybean, yard-long bean and wild legumes and shrubs that support it between seasons.

What is still uncertain

Maruca populations in different continents may belong to different genetic groups with different behaviour.
Long-term durability of Bt cowpea is not yet known.

Grow guides for its host crops

How to grow the crop well is the first line of defence. Laisha's free grow guides cover each crop from sowing to harvest:

How to grow Cowpea How to grow Pigeon pea How to grow Mung bean How to grow Black gram How to grow Common bean How to grow Lima bean How to grow Lablab How to grow Soybean

Not sure this is what you are seeing?Ask Laisha: describe the symptoms or send a photo, and get a reasoned first read with what to check next — for your crop, your stage and your region.Ask Laisha

Sources

Maruca vitrata (lima bean pod borer) datasheet — CABI Compendium. https://doi.org/10.1079/cabicompendium.32566
Maruca vitrata (MARUTE) — EPPO Global Database. https://gd.eppo.int/taxon/MARUTE
Bionomics, host plant resistance, and management of the legume pod borer, Maruca vitrata — a review — Crop Protection (Elsevier). https://doi.org/10.1016/s0261-2194(98)00045-3
Parasitoid complex of legume pod borer, Maruca vitrata, on different pulses — Indian Journal of Experimental Biology. https://doi.org/10.56042/ijeb.v61i01.69783

Written by Laisha from the sources above, in its own words. This page is general reference, not a prescription: confirm identification locally and follow the label and your plant-protection authority.