I recently received this e-mail from Wendy Pietrzak, who oversees the community gardens in Santa Monica, and thought I would pass it along in case anyone else is dealing with the dreaded badraga bug (aka the painted or harlequin bug), which has been attacking cabbage crops in California. Photo is from Mike Lewis of the UC Riverside Center for Invasive Species : 

Several of our diligent Main Street gardeners shared some information on a bug that seems to be infesting kale and other lettuce plants/seedlings in the community gardens and I want to share it with you also. It has been identified as the Bagrada Bug. Here are two links that have more information on the bug:



http://cisr.ucr.edu/bagrada_bug.html

http://www.infonet-biovision.org/print/ct/103/pests

If you are having issues with this bug in your garden here are some organic ways to combat them (click "read more"):

Monitoring

Regular monitoring of the crop is important to detect bagrada bug before they cause damage to the crop. Research in Namibia has shown that control measurements should start if the number of bugs/m² in the early growing stage exceeds one. If the crop is past the early growing stage, a higher threshold level of three bugs/m² can be maintained (Keizer and Zuurbier). However, note that these thresholds are given as examples. Economic thresholds depend on many factors (crop stage, crop age, and socio-economic and climatic conditions) and cannot be adopted without taking into consideration local conditions.

Sanitation

Crop hygiene, in particular removal of old crops and destruction of weeds of the family Cruciferae prevents population build-up.

Hand picking

Handpicking and destruction of the bugs helps to reduce damage. This is particularly important in the early stages of the crop.

Cultivation

Eggs laid in the soil are readily killed by cultivation, so frequent light cultivation (once or twice a week) of the vegetable beds will help in controlling this pest (Keizer and Zuurbier; Horticultural Research Program, Botswana).

Irrigation

Watering and overhead irrigation disturb bugs discouraging them from feeding on the crop. However, note that use of sprinkler irrigation may lead to increase of diseases such as black rot and downy mildew.

Mixed cropping

Growing strong smelling plants such as garlic, onion or parsley near the crop are reported to reduce infestations (Dobson et al, 2002).

Biological pest control
Natural enemies: Eggs of Bagrada bugs are parasitised by tiny wasps. Bugs are parasitised by flies (e.g. Alophora sp.).

Biopesticides and Physical Methods

Plant extracts: A mixture of chilli, soap, garlic and paraffin has shown to be an effective control method in trials in Namibia (Keizer and Zuurbier).

Natural products: In Namibia there are reports that sprinkling the plants with crushed Bagrada bugs repels other bugs. This can be used effectively in combination with frequent soil cultivation (Keizer and Zuurbier).

Soap solution: Spraying plants with a soapy solution (bar soap) has been found effective against Bagrada bugs. It helps to wash off young bugs (Dobson et al, 2002; Elwell and Maas, 1995).