Relatively low populations can cause economic damage when plants are in the cotyledon or first leaf stages. Baits are not effective. No economic thresholds are available, but treatments, especially on young plants, should be considered if damage reaches a moderate level. Insecticide treatment should rarely be required, but if it is, one application should suffice. Once plants have several true leaves, they can tolerate several beetles per plant without damage.
Older plants are even more tolerant.
However, chemical treatment may disrupt biological control of aphids and whiteflies. Do not apply within this many days of harvest. Permit required from county agricultural commissioner for purchase or use. Artichoke M. A. Bari, USDA Ag. The Regents of the University of California.