For crucifers, inspect five sets of 20 seedlings per field to determine the presence and the number of the beetles. An average of five or more beetles per plant prior to the fourth-leaf stage may warrant control (MAF, 2002). Another recommendation is when 10-20% or more of the leaf area shows feeding damage. Seed treatment maybe needed when there is a heavy infestation in the area, as the larva will destroy the developing seedlings (Cranshaw; Al-Doghairi, 2004).
For corn, control may be justified when there is an average of 5 or more beetles per plant prior to the 4-leaf stage. If the infestation is so severe that some plants are being killed, or if more than half of the leaves are whitish, it may be profitable to treat (Ratcliffe; Gray; Steffey, 2004).
For solanaceous crops, control of western potato flea beetle is necessary when there are more than 10 adults per 50 sweeps or the leaves show severe feeding injury, while for tuber flea beetle, 5-6 adults per 25 sweeps or when the adult population averages 2-3 per 7.6 meter of row. Treatment around the border of the field may be adequate to prevent their damage (Berry, 1998: 221).
Cultural and management practices
- Keep fields and surrounding areas free of weeds.
- Remove and destroy all plant residues.
- Sow seeds in a well prepared seedbed to hasten growth and allow seedlings to overcome injury (Cranshaw; Al-Doghairi, 2004).
- Try a high seeding rate and thin plants once established (Cranshaw; Al-Doghairi, 2004). This might be cheaper and safer than using pesticides.
- Plant the barrier crop along the edges of the field ahead of the main crop. Radish and Chinese mustard are good trap crops. Adult flea beetles are attracted to the tallest and earliest crop available (Cranshaw; Al-Doghairi, 2004). Another method is; Chinese mustard (Brassica juncea var. crispifolia) planted every 100 m between rows of crucifers or radish planted every 15 or 30 cm interval among broccoli (Knuepper, 2003).
Remove or treat trap crops when these are infested by pests or else the pests will transfer to the protected crops.
- Flea beetles prefer full sunlight, plant intercrops that provide shade to your susceptible crops (Ellis; Bradley, 1996: p 290).