Field Guide 
Pest Management Threecornered Alfalfa Hopper
Threecornered Alfalfa Hopper
CROPS IMPACTED: alfalfa, sweet clover, soybean, cowpea, bean, barley, wheat, oat, tomato
About the Threecornered Alfalfa Hopper
Reproduction and Life Cycle
This pest may overwinter as an adult in grass clumps, or as an egg hidden within plant stems. In the spring, nymphs will hatch from the overwintered eggs and adults will emerge from the grass. They both begin to feed on weeds that line the fields. Between May and June they will travel to young soybean plants. This is when the female adults will begin depositing her eggs. They will usually place up to 40 eggs within the tissue of host plants. They are laid singly and will take 2 to 6 weeks to hatch. The nymphs have 5 instars; this stage of development takes anywhere from 3 to 10 weeks to complete. The entire development cycle from egg to adult will take an average of 50 days. This pest has 2 generations per year.
Threecornered Alfalfa Hopper Identification and Habitat
Identification
The adults are considered to be treehoppers and can migrate easily to new fields with their strong ability to fly. They are wedge-shaped and about 6mm long with the females being slightly larger than the males. Threecornered alfalfa hoppers are green and have a red-orange stripe running along its shoulder area. Their wings are transparent and they have a triangular area located over the thorax, giving them the name ‘threecornered’. The eggs are oval to oblong shaped, are white in colour, and are between 0.9 and 1.3mm in length. The larger end of the egg has a surface that is slightly rough in texture. The nymphs are gray to green and resemble a similar shape to that of the adult. They are soft bodied, and have spines on their back. Their legs, abdomen, and antennae are white. When the nymphs have reached full maturity, they will be about 4.6mm in length.
Habitat
The threecornered alfalfa hopper is most dominant from North Carolina to Southern California, especially in soybean fields that have been planted early. However, they will also present themselves occasionally in Canada and throughout the southern states. While they prefer plant types such as soybean and alfalfa, they will also feed on numerous other plant varieties like tomato, melon, wheat, and different grass and tree types. Both the nymphs and adults can cause plant injury from piercing the stem with their mouthparts and sucking out the juices. Nymphs are usually limited to the base stems. Additionally, females will place their eggs in the stems, which can cause a significant amount of damage. This causes the stem to girdle, turning the parts of the plant above the injury yellow, purple, or red in colour. This may not happen until weeks following the damage.
Threecornered Alfalfa Hopper Management and Control Methods
Cultural Control
To help suppress threecornered alfalfa hopper populations, ensure that weeds in, and around your alfalfa and soybean fields are destroyed. This helps to eliminate overwintering sites for this pest. Also, practice crop rotation so soybeans are not planted in a field 2 years in a row. Plan to seed your fields more heavily, which can give leeway for a few seedlings to die and will not make a major difference to total yield. Note that low tillage systems will often have a higher hopper population. This pest does not usually present as a considerable problem; however, when they do cause severe damage, having satisfactory control is often dependent on using an integrated management system that includes the use of cultural and chemical methods.
Chemical Control
Insecticides used to treat the threecornered alfalfa hopper: Cyfluthrin (If alfalfa is grown for seed, do not apply as this can kill bees), Lambda Cyhalothrin, Methomyl (cattle cannot graze where this chemical has been used for at least 7 days), and Permethrin. Be sure to carefully read the label for cautions and proper application. It is extremely important to never spray on days that are windy. After applying insecticides it is important to irrigate sprayed area to increase the insect control. That being said, a large rainfall or irrigation soon after the application can reduce the concentration insecticides.
Latin / Alternative Threecornered Alfalfa Hopper Names
Sources
http://ipm.ncsu.edu/AG271/soybeans/threecornered_alfalfa_hopper.html
http://www.ipm.ucdavis.edu/PMG/r1301611.html