Lygus bug

Lygus keltoni

Plant bugs belonging to the genus Lygus are small, oval-shaped insects that feed on a variety of crops and weeds. Commonly referred to as lygus bugs with as many as 4 different species found on the Canadian prairies, they feed on the sap of new growth and reproductive tissue. Host plants of lygus bugs include alfalfa, canola, lentils, potato, strawberries, vegetable crops, flax, hemp, fababean, tree fruits, and weeds such as redroot pigweed, stinkweed, wild mustard and lamb's-quarters. Lygus bugs are important pests of canola with both adult and juvenile (nymph) stages causing economic damage that can reach levels where insecticidal control is necessary.
Life cycle. Lygus bugs overwinter as adults by finding shelter under plant litter in shelterbelts, headlands, uncultivated areas and field margins. Field experiments conducted in southern and northern Alberta showed that in these insulated areas, temperatures can remain above -5 degrees C although air temperatures can dip below -30 degrees C. Lygus bugs are sufficiently cold-hardy and do not experience significant mortality till temperatures drop below -10 C. In northern Alberta, overwintered adults emerge in the early spring (e.g., early May) to seek out early growing vegetation such as willows breaking bud, and then move onto rapidly growing winter annual weeds like stinkweed or flixweed. Overwintering adults can also be abundant in volunteer canola, early spring seeded canola, especially if these crops are in bud or flower and other hosts are not yet available. After mating in May through early July females seek suitable host plants, such as budding alfalfa or canola, on which to lay their eggs. Eggs are laid individually into the stems and leaves of host plants. The first nymphs appear by about the end of May. In the south, the new generation adults first appear by about the end of June. Nymphs (first to fifth instars) can emerge and develop on these earlier season weed hosts, but usually adults relocate to or even emerge from overwintering in alfalfa and clovers in mid-spring.
Identify. Adult lygus bugs are about 3 mm (0.1") wide and 6 mm (0.2") long. They have relatively long antennae and legs. They vary from pale green to reddish brown to black and can be fairly uniform colour ranging to a mottled appearance. Lygus bugs have a distinctive triangle or "V" shaped marking in the upper centre of their backs and membranous wing tips. Adults are active and fly readily when approached.
Immature lygus bugs (nymphs) are light green and wingless. Young nymphs are often mistaken for aphids, which are similar in size and shape. However, lygus bug nymphs are much more active, are harder bodied and lack the cornicles ("tail pipes") of aphids. Nymphs feed on new growth and reproductive parts of the plant. Several black spots, usually five, become noticeable on the backs of nymphs as they moult or mature through five instars (growth stages) before becoming adults. Wing buds are evident on the dorsal side of fourth and fifth instars.

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