''Rhopalosiphum maidis'', common names corn leaf aphid and corn aphid, is an

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

, and a pest of

maize Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout grass that produces cereal grain. It was domesticated by indigenous peoples in southern Mexico about 9,000 years ago from wild teosinte. Native American ...

and other

crops A crop is a plant that can be grown and harvested extensively for profit or subsistence. In other words, a crop is a plant or plant product that is grown for a specific purpose such as food, fibre, or fuel. When plants of the same species a ...

. It has a nearly worldwide distribution and is typically found in agricultural fields, grasslands, and forest-grassland zones. Among aphids that feed on maize, it is the most commonly encountered and most economically damaging, particularly in tropical and warmer temperate areas. In addition to maize, ''R. maidis'' damages

rice Rice is a cereal grain and in its Domestication, domesticated form is the staple food of over half of the world's population, particularly in Asia and Africa. Rice is the seed of the grass species ''Oryza sativa'' (Asian rice)—or, much l ...

sorghum ''Sorghum bicolor'', commonly called sorghum () and also known as great millet, broomcorn, guinea corn, durra, imphee, jowar, or milo, is a species in the Poaceae, grass genus ''Sorghum (genus), Sorghum'' cultivated for its grain. The grain i ...

, and other cultivated and wild

monocots Monocotyledons (), commonly referred to as monocots, ( Lilianae '' sensu'' Chase & Reveal) are flowering plants whose seeds contain only one embryonic leaf, or cotyledon. A monocot taxon has been in use for several decades, but with various ranks a ...

Description

The bodies of wingless

parthenogenetic Parthenogenesis (; from the Greek + ) is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization. In animals, parthenogenesis means the development of an embryo from an unfertiliz ...

females are green or whitish-green. The head, antennae, legs,

cornicle The cornicle (or siphuncule) is one of a pair of small upright backward-pointing tubes found on the dorsal side of the 5th or 6th abdominal segments of aphids. They are sometimes mistaken for cercus, cerci. They are no more than pores in some spe ...

s, tail, and transverse bands on the abdomen are black-brown. The body has sparse short hairs. The length of the antennae is less than half the length of the body.

Cornicle The cornicle (or siphuncule) is one of a pair of small upright backward-pointing tubes found on the dorsal side of the 5th or 6th abdominal segments of aphids. They are sometimes mistaken for cercus, cerci. They are no more than pores in some spe ...

s are not longer than the finger-like tail. In winged females, the head and thoracic section are black-brown and the

s are shorter than in the wingless females. Most ''R. maidis'' populations are anholocyclic, ''i.e.'' reproduction occurs entirely by

parthenogenesis Parthenogenesis (; from the Greek + ) is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization. In animals, parthenogenesis means the development of an embryo from an unfertiliz ...

. However, sexual reproduction has been reported in

Pakistan Pakistan, officially the Islamic Republic of Pakistan, is a country in South Asia. It is the List of countries and dependencies by population, fifth-most populous country, with a population of over 241.5 million, having the Islam by country# ...

and

Korea Korea is a peninsular region in East Asia consisting of the Korean Peninsula, Jeju Island, and smaller islands. Since the end of World War II in 1945, it has been politically Division of Korea, divided at or near the 38th parallel north, 3 ...

, with ''

Prunus ''Prunus'' is a genus of flowering plant, flowering trees and shrubs from the family (biology), family Rosaceae. The genus includes plums, cherries, peaches, nectarines, apricots and almonds (collectively Drupe, stonefruit). The genus has a cosm ...

'' ssp. as the primary host. In populations in

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

and

Kenya Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...

, males but not sexually reproducing females have been found.

Agricultural interactions

In winter, winged

females and larvae survive on wild-growing

, from which they move to agricultural fields in the spring. Fields populate gradually, starting from the edges to the center. Reproduction is rapid, with up to twelve generations per year. The aphid population reaches a maximum late in the summer. Dense populations of ''R. maidis'' on maize (''

Zea mays Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout Poaceae, grass that produces cereal grain. It was domesticated by indigenous peoples of Mexico, indigenous peoples in southern Mexico about 9,000 years ago ...

'') can cause direct damage through the removal of photosynthates. Large amounts of honeydew that is deposited by aphid feeding on maize tassels can prevent pollen shed and decrease yield by up to 90%. Several damaging maize viruses, including ''Maize yellow dwarf virus'', '' Barley yellow dwarf virus'', '' Sugarcane mosaic virus'', and '' Cucumber mosaic virus'', are transmitted by ''R. maidis''. In addition to feeding on maize, ''R. maidis'' infests a variety of cultivated grasses, including

wheat Wheat is a group of wild and crop domestication, domesticated Poaceae, grasses of the genus ''Triticum'' (). They are Agriculture, cultivated for their cereal grains, which are staple foods around the world. Well-known Taxonomy of wheat, whe ...

barley Barley (), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains; it was domesticated in the Fertile Crescent around 9000 BC, giving it nonshattering spikele ...

, oat,

rye Rye (''Secale cereale'') is a grass grown extensively as a grain, a cover crop and a forage crop. It is grown principally in an area from Eastern and Northern Europe into Russia. It is much more tolerant of cold weather and poor soil than o ...

sugarcane Sugarcane or sugar cane is a species of tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall with stout, jointed, fib ...

, and

. Barley is a particularly suitable host for ''R. maidis'', though there also is considerable within-species variation in resistance.

Chemical ecology

Under enhanced CO₂ conditions, the growth rate and reproduction of ''R. maidis'' on barley were significantly decreased. Volatiles of barley grown under enhanced CO₂ were also less attractive than those from plants grown under atmospheric CO₂. Temperature and crowding have differential effects on wing formation in parthenogenetically reproducing ''R. maidis'' on barley. Maize inbred lines vary in their resistance to ''R. maidis'' and other insect pests. Relative to other maize-feeding aphids ('' Rhopalosiphum padi'', '' Schizaphis graminum'', '' Sitobion avenae'', and '' Metopolophium dirhodum''), ''R. maidis'' exhibits a greater tolerance of benzoxazinoids, the most abundant class of maize defensive metabolites. Nevertheless, lineage-specific variation in maize resistance to ''R. maidis'' was associated with differences in the abundance of 2,4-dihydroxy-7-methoxy-l,4-benzoxazin-3-one glucoside ( DIMBOA-Glc), an abundant maize benzoxazinoid. Both increased DIMBOA-Glc synthesis and reduced conversion to 2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one glucoside (HDMBOA -Glc) can enhance maize seedling resistance to ''R. maidis''. Maize mutations that knock out benzoxazinoid biosynthesis increase ''R. maidis'' reproduction. In some instances, caterpillar feeding can enhance the conversion of DIMBOA-Glc to HDMBOA-Glc, thereby increasing maize resistance against ''R. maidis''. The defense signaling molecules 2-oxo-phytodienoic acid (OPDA) and ethylene are involved in regulating maize resistance to ''R. maidis''. In olfactometer experiments, ''R. maidis'' were repelled by volatiles from damaged maize plants. One of the major volatiles emitted by damaged maize is the terpene (''E'')‐β‐farnesene, which also functions as an alarm pheromone for

aphid Aphids are small sap-sucking insects in the Taxonomic rank, family Aphididae. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white Eriosomatinae, woolly ...

s and thus may be repellent. Mutations of a maize terpene synthase, ''TPS2'', made the plants more attractive for ''R. maidis.''

Genome sequencing

There is within-species variation in the chromosome numbers of ''R. maidis'', with karyotypes of 2n = 8, 9, and 10 having been reported. Whereas ''R. maidis'' strains on maize tend to have 2n = 8, those on barley generally have 2n = 10. To better enable research related to ecological interactions, virus transmission, pesticide resistance, and other aspects of the species biology, a high-quality genome was assembled from a

''R. maidis'' lineage collected from maize. Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License. The assembled genome is 321 Mb in size and features a total of 17,629 protein-coding genes. Assembly of the genome was facilitated by the extremely low level of heterozygosity in the sequenced ''R. maidis'' isolate.

Hosts

Barley Barley (), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains; it was domesticated in the Fertile Crescent around 9000 BC, giving it nonshattering spikele ...

Millet Millets () are a highly varied group of small-seeded grasses, widely grown around the world as cereal crops or grains for fodder and human food. Most millets belong to the tribe Paniceae. Millets are important crops in the Semi-arid climate, ...

s *

Rice Rice is a cereal grain and in its Domestication, domesticated form is the staple food of over half of the world's population, particularly in Asia and Africa. Rice is the seed of the grass species ''Oryza sativa'' (Asian rice)—or, much l ...

* Several

Gramineae Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and species cultivated i ...

species *

Sorghum ''Sorghum bicolor'', commonly called sorghum () and also known as great millet, broomcorn, guinea corn, durra, imphee, jowar, or milo, is a species in the Poaceae, grass genus ''Sorghum (genus), Sorghum'' cultivated for its grain. The grain i ...

s *

Sugarcane Sugarcane or sugar cane is a species of tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall with stout, jointed, fib ...

Wheat Wheat is a group of wild and crop domestication, domesticated Poaceae, grasses of the genus ''Triticum'' (). They are Agriculture, cultivated for their cereal grains, which are staple foods around the world. Well-known Taxonomy of wheat, whe ...

References

{{Taxonbar, from=Q3703370 Aphidini Agricultural pest insects Insects described in 1856 Taxa named by Asa Fitch Hemiptera of Asia Insect pests of millets