Black & Green Gram
Soybean Looper
Chrysodeixis includens
Insect
In a Nutshell
- 'Window panes' on leaves.
- Irregular holes and ragged leaf margins.
- Adult moths are dark brown, forewings are mottled brown with bronze to golden glitter.
Can also be found in
Black & Green Gram
Symptoms
Damage comes from caterpillar feeding on plant parts. Young larvae feed first on the underside of leaves and spare the upper part, resulting in a clear window-like feeding pattern sometimes referred to as ‘feeding window'. Older larvae feed on the entire leaf from its margins, avoiding large lateral veins, resulting in irregular holes and ragged margins. Unusual defoliation pattern, feeding from the lower part of the plant, inside canopy, and moving up and outwards. They rarely attack flowers or pods. However, in case of defoliation of the plant, the larvae will often continue feeding on soybean pods.
Recommendations
Organic Control
Natural enemies include the parasitoid wasps that feed on larvae of the soybean looper: Copidosoma truncatellum, Campoletis sonorensis, Casinaria plusiae, Mesochorus discitergus and Microcharops bimaculata, Cotesia grenadensis and the parasitoid flies Voria ruralis, Patelloa similis, as well as some species of Euphorocera and Lespesia. Products based on the Baculoviruses, Bacillus Thuringiensis or Spinosad have also been used to control soybean loopers.
Chemical Control
Always consider an integrated approach with preventive measures together with biological treatment if available. Soybean looper on their own are not likely to be a threat to the crop. Take into account the damage inflicted by other potential defoliating insects when making a management decision. Treatments are recommended if defoliation reaches 40% pre-bloom, 20% during bloom and pod-fill, or 35% from pod-fill to harvest. Products containing indoxacarb, methoxyfenozide or spinetoram could be used. Avoid insecticides of the family of the pyrethroids since resistance to these products have been described.
What caused it?
The damage is cause by the larvae of the soybean looper Pseudoplusia includens. Adult moths are dark brown, the forewings are mottled brown with a bronze to golden glitter. Two conspicuous silver markings are visible at their center. The female moth deposits eggs on the undersides of eaves, in the lower part of the plant and inside the canopy. The larvae are green in color with white stripes along their flanks and back. They are characterized by three pairs of special legs unevenly distributed along the body (2 in central part of the body, one at the tail). This arrangement causes the larvae to hump their back when moving, thereby their common name 'looper'. Pupae spin a loose cocoon on the underside of leaves.
Preventive Measures
- Use tolerant or resistant varieties if available.
- Plant early and use varieties that mature early to avoid worst damage.
- Monitor fields for signs of the pest, particularly on lower canopy.
- Remove and destroy larvae or affected plants.
- Keep plants healthy and vigorous during the season.
- Control insecticide use in order not to influence populations of beneficial insects.
- Build perches and open space for birds that will feed on the larvae.
- Use traps to monitor and catch the moths.
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