Epilachna varivestis
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Source: Clemson University - USDA Cooperative Extension Slide Series - IPM Images
Epilachna varivestis Mulsant, 1850 - (Mexican bean beetle)
The beetle is a pest of soybean, beans and other legumes in North America. It is considered to be native to higher elevation areas of southern Mexico and Guatemala and was accidentally introduced into the U.S.A. (first record in Florida in 1933) and Japan (first record in 1997). It has spread to most areas in the U.S. and to southern Canada, being most common in the Mid-Atlantic and southern Appalachian Mountain regions.
Both the adults and the larvae feed in the leaves of legumes, sometimes also on flowers and pods. The larvae are found underneath the leaves and are the most destructive stage. While beans and soybeans can tolerate significant damage to their foliage, the degree of tolerance depends on environmental conditions and these have to be considered when determining threshold levels.
| Vernacular names | |
|---|---|
| • Deutsch: | mexikanischer Bohnenkäfer |
| • English: | Mexican bean beetle |
| • Español: | escarabajo mexicano del frijol |
| • Français: | coccinelle mexicaine des haricots |
Eggs are laid in batches on the leaves and the development from egg to adults lasts around 6 weeks. There can be up to 3 or 4 generations per year. The adults overwinter in plant debris and other locations. Their survival during the winter will again depend on the weather conditions.
Cultural management includes the use of reflective plastic mulches, trap crops, resistant cultivars and timing planting the crop either before or after the overwintering adults emerge. Biological control is also recommended, for example releasing the parasitoid Pediobius foveolatus which is commercially available. For the use of chemical pesticides, the economic threshold depends on the crop, the growing stage of the crop, as well as the environmental conditions. For example for soybeans, a 40% pre-bloom defoliation level or a 15% level during bloom and pod development might be applicable.
The adults are 6-8 mm long, yellowish with 8 dark spots on each elytron arranged in 3 rows. The larvae are bright yellow with black spines. The pupae are also yellowish and are often found in aggregations.
For a review see Nottingham et al., 2016.
- Other images of Epilachna varivestis (Wikimedia Commons, IPM Images, J. of IPM and PaDIL - click to enlarge)
adult and larva on soybean
damage on wax snap beans (right), left resistant lima bean variety
eggs
head
head and pronotum
posterior end
.jpg)
