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Saurav Ranabhat, Carlton, Christopher E.
The green cloverworm, Hypena scabra, is a widespread, medium sized moth that is a sporadic defoliating pest of soybeans. Adult green cloverworm moths have a wingspan of 25 mm to 35 mm. They hold their wings in a triangular shape when at rest. Males are larger than females with uniform charcoal-colored bodies. Females are brown with silver patches and less uniform charcoal color on the upper wing surface. Wing color and pattern are highly variable among adult green cloverworms.
Newly hatched green cloverworm larvae are pale yellow but become light green as they mature. Freshly hatched larvae are about 0.5 mm in length and grow to approximately 25 mm when fully developed. Larvae possess two yellowish white stripes that run horizontally along the sides of the thorax and abdomen. Their bodies are covered with sparse, long hairs (setae). They are superficially similar to other soybean infesting caterpillars such as soybean loopers, velvet bean caterpillars and corn earworms. Green cloverworms can easily be distinguished by the three pairs of leglike processes under the abdomen (prolegs). Soybean loopers have two and corn earworm and velvet bean caterpillars have four abdominal prolegs, respectively. Green cloverworms jump and flop when disturbed. Eggs are about 0.5 mm in diameter, and are laid singly on the undersides of leaves.
In many older literature sources, the species is described under the name Plathypena scabra, but the current accepted name is Hypena scabra. The genus Hypena is a large, taxonomically challenging genus, with 29 species recorded in the U.S. Many are similar in appearance to green cloverworm as adults and larvae. In cases where confirmation of species identifications is required, a qualified entomology taxonomist or diagnostician should be consulted.
Green cloverworm moths undergo four life stages (complete metamorphosis), as with all other moths. These are egg, larva, pupa and adult. Larvae hatch within a week and undergo six growth stages (instars) transitioning to the pupal stage. In soybean fields, populations may increase rapidly during flowering, and peak during full bloom to late pod-set. Larval duration is around 19 days during warm weather. Larvae enter a prepupal stage for up to 11 days and burrow into soil or organic ground litter for pupation. Once the pupal stage is completed, adults emerge. Adults are active from March to November with peak egg laying during May or June in soybeans.
Lifespan of adults varies from a few days to several months, depending on temperature, with extended longevity during cooler weather. Multiple, overlapping generations occur throughout the year due to long ovipositional periods and relatively long life cycles. The egg-to-adult development duration is affected by the environmental conditions. The combined male and female development duration can range from 80 days to 29 days at 60 F and 85 F, respectively.
Green cloverworms are widely distributed throughout the United States, from southern Canada to Florida and Texas. Research indicates that the species is largely migratory, with overwintering in southern parts of the U.S., including Louisiana and along the Gulf Coast. Sporadic reports of the species in Great Britain exist.
Green cloverworms feed on a wide variety of plant species (polyphagous), including soybeans, clover, ragweed, raspberries and strawberries. It is an agricultural pest in many crops. In Louisiana, it is an important, voracious defoliating pest in soybeans. Large populations cause stunted growth and yield loss, primarily through reduced pod numbers and secondarily through decreased seed weight. However, damage is usually sporadic and usually does not result in major economic loss. For soybeans, the vegetative and reproductive phenology can be recovered even if the defoliation is more than 30%. The LSU AgCenter has established an economic threshold level at 300 worms in 100 sweeps or eight worms of 12 mm body length or longer per row foot, above which control is necessary.
A range of integrated pest management strategies can be employed for effective management of green cloverworms, similar to those used for other defoliating caterpillars. Each practice targets a specific stage of the insect’s life cycle and focuses on both preventive and control methods.
Monitoring. Regular scouting and monitoring should be done during early stages of plant growth to determine if their population is large enough to consider control. Sweep net sampling is a standard method to sample larval populations. Caging techniques can be used for higher precision in estimating populations. Adults can be monitored using UV light stations and pheromone-baited bucket traps. Regular monitoring for defoliation is also important.
Cultural practices. Implementing crop rotation can help disrupt the life cycle of green cloverworms. Since the population of green cloverworms is generally higher in late planting and late-maturing cultivars, adopting early-maturing varieties with early planting can avoid periods of high infestation. Management of weeds that serve as alternative hosts (legumes, vetch) can also decrease the infestation level.
Biological control. Predatory insects, parasitoids, and birds can help check the population of green cloverworms. Parasitoids may also suppress populations. These include the braconid wasps Cotesia marginiventris, Rogas nolophanae, and Meteorus autographae. Insect pathogens such as the fungus Nomuraea rileyi and granulosis virus disease can also be effective. Conservation of natural habitats of these organisms and minimal use of pesticides can enhance naturally occurring control agents.
Chemical control. A variety of insecticides are recommended by the LSU AgCenter when the population exceeds the economic threshold level. These include Sevin (carbaryl), Lannate (methomyl), Blackhawk (spinosad), Vantacor (chlorantraniliprole), Steward (indoxacarb), Besiege (lambda-cyhalothrin, chlorantraniliprole) and more. They should be carefully selected and applied at their respective recommended doses. Label directions must be followed exactly. Biological insecticides like Bacillus thuringiensis and Beauveria bassiana are also used for their control. Please consult the LSU AgCenter Insect Management Guide for more information.
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Contact Us: For advice about pest identification or diagnosis, contact the LSU AgCenter Department of Entomology.
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4/29/26
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Hypena scabra eggs. Photo by Phil Sloderbeck, Kansas State University, Bugwood.org
Green Cloverworm larva. Photo by Phil Sloderbeck, Kansas State University, Bugwood.org
Adult green cloverworm. Photo by Mark Dreiling, Bugwood.org
