Russian wheat aphids are green and relatively small, ranging from 1.6 to 2.1 mm long. The body of the aphids is thin, appearing wider in the middle and thinner on each end. Russian wheat aphids have short antennae and a piercing-sucking mouth part called a stylet on their head. Russian wheat aphids have small cone-shaped tubes on their back end called cornicles. Some have wings. (Hein, et al., 1989; Hodgson and Karren, 2008; Michaud J. P and Sloderbeck, 2005)
The Russian wheat aphid, Diuraphis Noxia, is originally from Asia, particularly southern Russia, Central Asia, and the Middle East. Beginning in the early 1900’s, these aphids began to travel from Asia to other parts of the world. They were blown there on the wind. Russian wheat aphids are now found on every continent in the world except Australia and Antarctica. Most recently, the Russian wheat aphid has invaded Canada and the United States. They are considered one of the most damaging invasive pests in the world. (Dolatti, et al., 2005; Michaud J. P and Sloderbeck, 2005; Zhang, et al., 2012)
Russian wheat aphids live in grasslands and agricultural fields. They are able to survive in a wide range of temperatures. They live inside the rolled leaves of crops and grasses such as wheat and barley throughout the year. They also live in grasses such as crested wheat grasses, intermediate wheat grasses, and wild ryes when the cereal crops have been harvested. (Dolatti, et al., 2005; Hodgson and Karren, 2008; Michaud J. P and Sloderbeck, 2005)
Most Russian wheat aphids are birthed by females by a process called parthenogenesis. This means that the female did not mate, and her offspring are genetically identical daughter aphids. The female does not lay eggs, but gives birth to live daughters. These are called nymphs, and they look similar to the adult aphids, but are covered with a white, waxy material. The time it takes for the nymphs to grow to adults depends on the temperature. When the temperature is cold, development time takes longer. If the temperature is warm, development time is quicker. An aphid can take anywhere from 9 to 55 days to become an adult. In some places, right before winter, males and females will mate and lay eggs. These eggs will stay as eggs for the whole winter, and then hatch in the spring. (Merchant, 2014; Michaud J. P and Sloderbeck, 2005; Sutherland, 2006)
In North America, there are only female Russian wheat aphids, and the reproduce without mating. In other places in the world, males and females will mate in the fall, but there is not much known about their habits. (Hodgson and Karren, 2008; Merchant, 2014)
When the Russian wheat aphid reproduces without mating, female aphids do not lay eggs, and instead give birth to live aphids. These aphids are basically clones of the parent. By reproducing without males, population sizes can grow very quickly. On average during temperatures between 15 and 21 degrees Celsius, a Russian wheat aphid can produce up to 1.5 daughter nymphs per day over the span of a month. In some cases, females can give birth to up to four nymphs in a single day. North American populations reproduce only this way, as there are no males. In non-North American populations, males and females mate in the fall, and females lay eggs that remain as eggs during the winter, and hatch the next spring. It takes Russian wheat aphids anywhere from 9 to 55 days to reach adulthood after birth. (Hein, et al., 1989; Hodgson and Karren, 2008; Merchant, 2014; Michaud J. P and Sloderbeck, 2005)
Most Russian wheat aphids give birth to live young, which takes a large amount of energy from the female parent. In populations that lay eggs, females provide nutrients in the eggs that will keep the offspring alive and well until the following spring when they hatch. However, after birth or after the eggs are laid, Russian wheat aphids do not give any more parental care. (Hodgson and Karren, 2008; Merchant, 2014)
Russian wheat aphids live for about three months. The environmental temperature has a big impact on their lifespan though. Too warm or too cold, and they live for much less time. (Merrill and Holtzer, 2010; Merrill, et al., 2009)
Russian wheat aphids live in large colonies. Each year, there are several batches of winged aphids. Aphids are usually poor fliers and rely on the wind to blow them from area to area as they search for new plants to feed on. The rest of the aphids do not have wings. Aphids spend much of their time searching for plants to feed on. When doing so, they will explore the surface of the plant, and eventually will stick their mouthparts into the right part to suck out its food. Once they have used up all the nutrients in a plant, they move on to a new one. (Caillaud, et al., 1995; Hodgson and Karren, 2008; Merchant, 2014)
Winged Russian wheat aphids fly to plants in new areas to begin new colonies. Since aphids are poor fliers, they do not fly very far unless they get caught in a strong wind. Wingless aphids stay in the same general area. (Hodgson and Karren, 2008; Merchant, 2014)
Russian wheat aphids communicate with each other by producing an chemicals called pheromones. One important pheromone is their alarm pheromone. The alarm pheromone is produced when a predator is threatening aphids. The pheromone lets other aphids nearby that there is danger present, and the aphids respond by dropping off the plant and escaping. (Becker, 2000)
Russian wheat aphids feed on a plant fluid called phloem. They stick their mouthparts into the plant and suck the phloem out. They only feed on certain plants, mainly wheat and barley, but will switch to wheatgrass, intermediate wheatgrass, and Canada wild rye when wheat and barley are not available. They start feeding on the top or edge of the plant, and suck out all the nutrients. Once the plant loses its nutrients, the leaves begin to curl inward. The aphids sit inside of the curled leaves, which protects them from predators and other dangers. Russian wheat aphids also produce a toxin while feeding that hurts the plant and turns the plant white, purple, or yellow. (Hein, et al., 1989; Michaud J. P and Sloderbeck, 2005)
Predators of the Russian wheat aphids include the convergent lady beetle (Hippodamia convergens), the seven-spotted lady beetle (Coccinella sepempuncata), the lady beetle Hippodamia variegata, Aphidiid wasps (Aphidiidae), hover flies (Diptera: Syrphidae), Scymnus beetles, lacewings (Chrysopidae), rove beetles (Staphylinidae), and spiders (Araneae). Russian wheat aphids hide in the curled leaves of wheat plants, making it hard for larger predators to reach them. Convergent lady beetles, seven-spotted lady beetles and Scymnus beetles are small enough to crawl inside the curled part of the leaves and eat the aphids. The aphids also drop off their host plants when a predator is near, and alert the colony of a predators' presence with a chemical called an alarm pheromone. (Adisu, et al., 2003; Knutson, et al., 1997; Michaud J. P and Sloderbeck, 2005)
Russian wheat aphids are an invasive species. This means that they now live in areas and countries where they did not originally live. This causes problems for the plants and animals that live in the area the aphids are invading. The aphids destroy plants by feeding on them, and also use up resources and habitats that these other native animal species used to use.
Like all aphid species, Russian wheat aphids have a bacterium that lives in their bodies called Buchnera. The Buchnera bacteria cannot live anywhere else except inside the aphids. In return, it produces amino acids that the aphids need to survive and do not get anywhere else. Both organisms need the other to survive. This is called an obligate relationship, because both organisms are obligated to the relationship.
Russian wheat aphids are also parasitized by many parasitoid wasp species. The wasps lay an egg inside of the aphid's body, which cause the mummification and death of the aphid. Parasitoid wasps species for Russian wheat aphids include Aphidius species such as Aphidius colemani, braconid wasps, Aphelinus albipodus, and Lysiphlebus testaceipes. (Adisu, et al., 2003; Hodgson and Karren, 2008; Lai, et al., 1996; Michaud J. P and Sloderbeck, 2005; Turanli, et al., 2012)
The Russian wheat aphid feeds on and lives on important crops such as wheat and barley. This kills the crops and causes problems for farmers and people that depend on these crops. Since Russian wheat aphids were first discovered in the United States in 1986, they have caused millions of dollars in crop losses. People have also spent millions of dollars on pesticides to kill the aphids. In recent years, crop damage has not been as bad as it once was, but the aphids are still causing problems in Nebraska, Wyoming, Colorado, Kansas, and New Mexico. (Hein, et al., 1989; Michaud J. P and Sloderbeck, 2005)
Russian wheat aphids do not have any positive effects on humans.
Russian wheat aphids are not an endangered species. Instead, they are considered one of the most invasive pest species. This means that they have invade areas where they originally did not live, and destroy many of the native plants in these habitats. People are trying to get rid of their populations and prevent damage. (Turanli, et al., 2012)
Najma Salah (author), Grand View University, Kassie Sopher (author), Grand View University, Ashley Sowder (author), Grand View University, Felicitas Avendano (editor), Grand View University, Dan Chibnall (editor), Grand View University, Angela Miner (editor), Animal Diversity Web Staff.
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