Aster leafhopper and aster yellows
Order: Hemiptera
Family: Cicadellidae
Description
Aster leafhopper (Macrosteles quadrilineatus) is a vector of a plant pathogen, the aster yellows phytoplasma, which can cause severe disease in susceptible plants. Aster leafhoppers are small insects that measure about 3 mm (1/8 inch) in length when fully grown. Their wedge-shaped bodies range in color from olive-green to tan, and they have three pairs of spots on the top of their head. They have grey or opaque wings and are active at temperatures above 15°C (59°F). When disturbed the adults will jump or fly to escape danger. Nymphs are similar to adults in appearance but are smaller and lack wings. Leafhoppers have piercing-sucking mouthparts, which they use to pierce green plant tissues and extract plant fluids.
Aster yellows phytoplasma
Aster leafhopper is one of 24 leafhopper species that can transmit the aster yellows phytoplasma, which causes aster yellows disease. Of these, the aster leafhopper is considered the primary vector of this plant pathogen, which can infect over 350 different plants, including many vegetables such as carrots, celery, cucurbits, potato, sage, tomato, garlic, beets, and onions, as well as many different weeds and flowering plants such as dandelions, quackgrass, chickory, knotweed, sowthistle, ragweed, Kentucky bluegrass, wild carrot, coneflower, aster, marigold, petunia, and zinnia. Infection rates near 100% in carrot fields have been documented Texas during a major outbreak in 2000, which is attributed to a high influx of migrating aster leafhoppers. Therefore, controlling the incidence of aster yellows requires effective management of aster leafhoppers.
Quick Facts
- Aster leafhoppers are vectors of the aster yellows phytoplasma, which is a plant pathogen that can infect around 300 species of flowering plants, vegetables, and weeds.
- The susceptibility and symptoms of aster yellows will differ depending on the host plant. For example, leaf lettuce is less susceptible and shows fewer symptoms of aster yellows infection when compared with head lettuce.
- Insecticide applications should coincide with peaks in the aster leafhopper population. Effective scouting will help inform decisions related to chemical control.
Adult of the aster leafhopper. Note the tan body and the presence of spots on top of the head. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org
A head of lettuce infected with aster yellows. Note the twisting and distortion of the leaves. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org
Carrots showing a range of symptoms due to aster yellows. A healthy carrot (right) and a carrot with a severe infection of aster yellows (left). Note the abundant root hairs on the infected carrot. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org
Marigold flowers showing a range of symptoms due to infection by aster yellows. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org
Life history
The aster leafhopper has three life stages: egg, nymph, and adult. This species does not overwinter in Colorado, and laboratory experiments suggest that temperatures between 5-20°C promote optimum survival and reproduction. Substantial numbers migrate north each year after overwintering in southern regions along the Gulf of Mexico. In 2012, unusually early flights raised concerns in wheat fields in certain regions of the Great Plains, including South Dakota, North Dakota, and Minnesota. As these insects disperse, they can feed on host plants infected with the aster yellows. While aster leafhoppers that acquire the aster yellows phytoplasma will remain infective for life, it takes two to three weeks for the pathogen to circulate to the leafhopper’s salivary glands before the leafhopper can infect healthy host plants. Nymphs and adults can acquire the plant pathogen, which survives and multiplies in various organs of the insect host. Research suggests that aster leafhoppers infected with aster yellows phytoplasma live longer than uninfected individuals. Significant outbreaks of aster yellows occur when large numbers of aster leafhoppers migrate in the spring, during warm weather in May and June, and during conditions with sufficient precipitation and soil moisture for leafhopper development and reproduction. The percentage of infection in an aster leafhopper population is typically around 2-3% but can be as high as 10-15%.
Injury
While feeding injuries of aster leafhopper are not usually a cause for concern, large numbers of migrating leafhoppers can result in significant outbreaks of aster yellows. Typically, symptoms of aster yellows appear more rapidly in warmer weather. The exact symptoms and severity of an infection depend on the host plant, but generally begin with loss of green pigmentation in leaf veins. Other symptoms include bronzing and twisting of new growth, stunted growth of new shoots and flowers, the development of adventitious roots, and failure of seeds and fruit to develop.
Scouting
Scouting is especially important after applications of herbicides for leafy weeds, as the leafhoppers will migrate from dying weeds to healthier host plants. Sweep nets and yellow sticky traps can be used to monitor the leafhoppers population, beginning in spring, and continuing weekly through mid-August. Plants can be visually inspected for adults, nymphs, and molted skins. While no treatment thresholds have been established for aster leafhopper, insecticide applications are recommended when young upper leaves are infested.
Cultural control
Effective weed control is an important approach for managing populations of aster leafhopper, especially when weeds are showing signs of aster yellows infection. Significantly lower rates of aster yellows infection have been documented in the carrot varieties Charger, Gold King, Hi Color, Impak, Royal Chantenay, Scarlet Nantes, and Six-Pak, while susceptible carrot varieties include Bonanza, Candy Pak, Danvera 126, Goldpak, Lucky’s Gold, Nantes, Nantes Superior, Orlando Gold, Red-core Chantenay, and Spartan Bonus. Seeding with the cloves of garlic infected with aster yellows phytoplasma should be avoided.
Biological control
Natural enemies are important in managing aster leafhopper populations. One species of wolf spider, Pardosa ramulosa, has been shown to significantly reduce aster leafhopper numbers in nearby states like California.
Chemical control
Insecticides that are effective against potato leafhopper (Empoasca fabae) are generally effective against aster leafhopper. For effective control of aster leafhopper, only one to four insecticide applications are required when the pest population peaks. However, when pesticides are applied too frequently it can result in high costs and increase the likelihood of insecticide resistance of the pest population while failing to provide adequate control.
References
Bahar, M., T. Wist, D. Bekkaoui, D. Hegedus, and C. Olivier. 2018. Aster leafopper survival and reproduction, and Aster yellows transmission under static and fuctuating temperatures, using ddPCR for phytoplasma quantification. Nature Scientific Reports. 8(1): 1-11. Available https://www.nature.com/articles/s41598-017-18437-0.pdf
Beanland, L. C. Hoy, S. Miller, and L. Nault. 2000. Influence of Aster Yellows Phytoplasma on the Fitness of Aster Leafhopper (Homoptera: Cicadellidae). Annals of the Entomological Society of America. 93(2): 271-276. Available https://academic.oup.com/aesa/article/93/2/271/77344
Cranshaw, W. 2009. Lettuce Aster Leafhopper. Available https://wiki.bugwood.org/HPIPM:Lettuce_Aster_Leafhopper
CSU. (n.d.). Aster Yellows. PlantTalk Colorado – Colorado State University. Available https://planttalk.colostate.edu/topics/insects-diseases/1452-aster-yellows/
Delahaut, K. (n.d.). Aster Leafhopper. University of Wisconsin Madison – Extension. Available https://vegento.russell.wisc.edu/pests/aster-leafhopper/
Frost, K., P. Esker, R. Van Haren, L. Kotolski, and R. Groves. 2013. Seasonal Patterns of Aster Leafhopper (Hemiptera: Cicadellidae) Abundance and Aster Yellows Phytoplasma Infectivity in Wisconsin Carrot Fields. Journal of Environmental Entomology. 42(3): 491-502.
Available https://colostate.primo.exlibrisgroup.com/discovery/fulldisplay?docid=cdi_webofscience_primary_000320109500011&context=PC&vid=01COLSU_INST:01COLSU&lang=en&search_scope=MyCampus_FC_CI_PU_P&adaptor=Primo%20Central&tab=Everything&query=any,contains,aster%20leafhopper&facet=searchcreationdate,include,2000%7C,%7C2023&offset=0
Godfrey, L., L. Espino, and S. Lawler. (n.d.). Aster Leafhopper. University of California – Agriculture and Natural Resources. Available https://ipm.ucanr.edu/agriculture/rice/aster-leafhopper/
Manitoba Government. (n.d.). Aster Leafhoppers and Aster Yellows. Available https://www.gov.mb.ca/agriculture/crops/insects/aster-leafhoppers-yellows.html
Martini, I., K. Bottner, R. Dane, M. Black, and N. Troxclair. 2003. Ecological Implications from a Molecular Analysis of Phytoplasmas Involved in an Aster Yellows Epidemic in Various Crops in Texas. Phytopathology. 93(11): 1368-1377. Available https://apsjournals.apsnet.org/doi/epdf/10.1094/PHYTO.2003.93.11.1368
Mollov, D., B. Lockhart, E. Saalau-Rojas, and C. Rosen. 2014. First Report of a 16SrI (Aster Yellows) Group Phytoplasma on Garlic (Allium sativum) in the United States. APS Publications. 98(3). Available https://apsjournals.apsnet.org/doi/10.1094/PDIS-07-13-0689-PDN
Schwartz, H., and D. Gent. 2016. High Plains Integrated Pest Management. Available
https://wiki.bugwood.org/HPIPM:Aster_Yellows
Szczepaniec, A., and N. Spomer. 2016. Effects of Chlorpyrifos and Lambda- and Gamma Cyhalothrin on Suppression of Aster Leafhoppers, Macrosteles quadrilineatus (Hemiptera: Cicadellidae) in Spring Wheat. Journal of Agricultural and Urban Entomology. 32(1): 25-34. Available https://bioone.org/journals/journal-of-agricultural-and-urban-entomology/volume-32/issue-1/JAUE15-15.1/Effects-of-Chlorpyrifos-and-Lambda–and-Gamma-Cyhalothrin-on/10.3954/JAUE15-15.1.full
UNL. (n.d.). Aster Leafhopper. University of Nebraska-Lincoln. Available https://cropwatch.unl.edu/potato/aster_leafhoppers
USU. (n.d.). Aster Leafhopper. Utah State University – Extension. Available https://extension.usu.edu/pests/ipm/notes_ag/veg-aster-leafhopper