What do lygus bugs look like?
Adult lygus bugs can range in color from pale green to reddish brown or black and are about 3mm wide and 6mm long. They can be a solid color to mottled and have a distinctive V shape on their backs. They are active bugs and will fly when approached. The immature lygus are light green and wingless, which can be mistaken for aphids. However, lygus are more active than aphids and have harder bodies and have no cornicles or 'tailpipes'. As the young lygus get older they can develop black spots on their backs, most commonly having 5 spots.
What is the Life cycle?
Lygus bugs overwinter as adults. In the spring they find winter annuals on which to feed then proceed to lay their eggs from May to July. The first nymphs will be seen at the end of May. Adults can be seen at the end of June in the South. In the northern prairies, there is only one generation per year. In the southern prairies there may be two generations per year.
What do lygus bugs feed on?
Lygus bugs will feed on almost anything. Their preferred crop choices include alfalfa, canola, lentils, potatoes, flax and fruit trees. Other host plants include weeds such as redroot pigweed, stinkweed, wild mustard and lamb's quarters. In these plants the lygus bugs will feed on the sap of new growth and the reproductive tissue.
What kind of damage can lygus bug do?
Damage is done from the budding to the podding stage. Damaged buds will turn white and fail to develop. The flowers may fall without forming pods, or the pods can fall without maturing. The main economic damage usually occurs at the podding stage. Lygus bugs damage seeds by poking into the seed and sucking out its juice. The damaged seeds collapse, shrink, darken, and lose quality and viability. The adults and oldest nymphs do the most damage. Hot dry weather promotes lygus growth. Adequate rain and good growing conditions from budding to the end of flowering may help the crop outgrow lygus damage. Research also indicates that canola can compensate for Lygus bug damage.
When do I monitor and what is the threshold of Lygus bugs?
Monitoring for lygus bug should be done from bolting to early pod ripening. Spraying should be done at the end of flowering (90 % has flowered) to pod ripening. Spraying once the seeds have ripened is not recommended. The economic threshold for spraying varies depending on estimated value of crop, crop application stage and insecticide costs. Threshold numbers are based on the average per 10 sweep sample.
What products are available for controlling Lygus bugs?
Available insecticides for Lygus bugs in canola include Decis 5 EC TM, Lorsban 4E TM and Matador 120 EC TM. Registered insecticides for mustard and alfalfa include Decis 5 EC TM and Matador 120EC TM. Make sure to note grazing restrictions and pre-harvest intervals for products.
Fact Sheet: Lygus Bugs
Prepared by Kim Zeleny, Ag-Info Centre, Alberta Agriculture & Rural Development