English grain aphid – adult, nymph Tyler Wist, AAFC
Wheat, barley, oats, rye, canaryseed.
Identification
ADULTS: 1.5–2 mm long, bright green to yellowish-green to reddish-brown with long black legs and cornicles; antennae are as long as or longer than its body. MATURE NYMPHS: Similar appearance to adults but smaller.
Aphid, English grain
Sitobion (Macrosiphum) avenae (Fabricius)
Jan
Feb
Overwintering
Mar
Apr
May
Nymphs
June
July
Aug
Sept
Oct
Life Cycle
Nov
Dec
Migrating Adults
Migrating Adults
Nymphs
Jan . Feb . Mar . Apr . May . June . July . Aug . Sept . Oct . Nov . Dec !
Not known to overwinter in Canadian prairies; blow in from U.S. Several nymphal generations are produced asexually until late summer. Populations die off in the fall.
Feeding Damage
ADULTS AND NYMPHS: They are very efficient vectors of barley yellow dwarf virus. Feed on leaves of winter cereals in the fall; in the spring colonize leaves then move to the heads to feed on developing kernels, causing some to shrivel. Populations drop quickly as heads mature.
Monitoring/Scouting
Prior to the soft dough stage, count the number of aphids present on each of 20 randomly selected tillers at 5 sites across a zigzag transect of the field. Calculate the average number/tiller. In canaryseed, the head should be bent and closely inspected for aphids hiding inside along the small stem.
Economic Threshold
SMALL GRAINS: 12–15 aphids/stem prior to the soft dough stage. CANARYSEED: A nominal threshold of 10–20 aphids on 50% of the stems prior to the soft dough stage.
Management Options
BIOLOGICAL: Similar to other aphid pests, several species of parasitoids, predators (especially lady beetles (p. 116)), and fungal pathogens attack this aphid. CULTURAL: Specific cultural methods have not been developed; see also IPM section. CHEMICAL: Apply products least toxic to natural enemies if treatments are required.
Homoptera
Hosts
PESTS
Similar Species
See greenbug (p. 65).
Descriptions of Field Crop Pests
57
Corn leaf aphid – adult, nymph
Indian Council of Agricultural Research-National Bureau of Agricultural Insect Resources (www.nbair.res.in)
Hosts
Barley, corn, occasionally winter wheat; wild and cultivated grasses.
Identification
Aphid, corn leaf
Rhopalosiphum maidis (Fitch)
Jan
Feb
Homoptera
Overwintering
Mar
Apr
May
June
Nymphs and adults
Migrating Adults
July
Sept
Oct
Nov
Dec
Migrating Adults
Nymphs and adults
Jan . Feb . Mar . Apr . May . June . July . Aug . Sept . Oct . Nov . Dec !
See descriptions of other species of grain aphids.
Monitoring/Scouting
ADULTS: 1.6–2 mm long, blue-green or gray with black legs, cauda and short broad black cornicles surrounded by a dark spot around their bases.
Prior to the soft dough stage, count the number of aphids present on each of 20 randomly selected tillers at 5 sites across a zig-zag transect of the field. Calculate the average number/tiller.
MATURE NYMPHS: Similar appearance to adults but smaller.
Economic Threshold
Life Cycle
Aug
Similar Species
Passes the winter on fall planted and volunteer barley and corn and grasses in the southern U.S. It migrates north in the spring, and passes through several generations during migration. Once arrived, it colonizes available host crops and passes through several asexual generations before dying off in the fall. Winged females are produced throughout the summer to seek out new hosts to colonize. Populations die off in the fall.
Feeding Damage
ADULTS AND NYMPHS: Are a vector of barley yellow dwarf virus. Produce sticky clear “honey dew” which supports growth of black sooty mold. Feeding causes mottling and discoloration of leaves. Heavily infested leaves turn red or yellow, shrivel, and die. The important damage usually occurs during and after flowering. Barley is not susceptible to damage from high infestations after the boot stage. Feed on corn tassels and silks.
SMALL GRAINS: 12–15 aphids/stem prior to the soft dough stage. FIELD CORN: The critical period for injury by corn leaf aphid is during tassel emergence through pollination. Treatment is suggested only when 50% of the corn plants have 100+ aphids per plant during tassel emergence and plants are drought stressed.
Management Options
BIOLOGICAL: Several species of parasitoids, predators, and fungal pathogens attack this aphid. CULTURAL: Specific cultural methods have not been developed; see also IPM section. CHEMICAL: Apply products least toxic to natural enemies if treatments are required.
Corn leaf aphid – damage
Department of Plant Pathology Archive, North Carolina State University, Bugwood.org
56
Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Management Field Guide
Oat-birdcherry aphid – adult, nymph
John Gavloski, Manitoba Agriculture, Food and Rural Development
Hosts
Similar Species
Identification
Monitoring/Scouting
ADULTS: 2 mm long, olive-green with black antennae and cornicles, and a red-orange patch between and around the base of each cornicle. MATURE NYMPHS: Nymphs turn from pale yellowish green to dark olive as they mature.
Life Cycle
Rhopalosiphum padi (Linnaeus)
Jan
Feb
Overwintering
Mar
Apr
May
Nymphs
June
July
Aug
Sept
Oct
Nov
Dec
Migrating Adults
Migrating Adults
Nymphs
Jan . Feb . Mar . Apr . May . June . July . Aug . Sept . Oct . Nov . Dec !
Not known to overwinter in Canadian prairies; blow in from U.S. Several nymphal generations are produced asexually until late summer. Populations die off in the fall.
Feeding Damage
ADULTS AND NYMPHS: Although feeding causes no yellowing or other visible damage to wheat plants, heavy infestations can reduce grain quality and affect protein content and test weight. Spring wheat is more susceptible to injury than winter wheat. They are very efficient vectors of barley yellow dwarf virus which can stunt barley and oat plant growth and reduce seed weights in some varieties. Large colonies on wheat plants past the boot stage can cause the flag leaf to twist into a corkscrew shape that can trap the awns, resulting in “fish-hooked” heads.
See descriptions of other species attacking wheat.
Prior to the soft dough stage, count the number of aphids present on each of 20 randomly selected tillers at 5 sites across a zig-zag transect of the field. Calculate the average number/tiller. In canaryseed, the head should be bent and closely inspected for aphids hiding inside along the small stem.
Economic Threshold
SMALL GRAINS: 12–15 aphids/tiller prior to the soft dough stage. CANARYSEED: A nominal threshold of 10–20 aphids on 50% of the stems prior to the soft dough stage.
Management Options
BIOLOGICAL: Several species of parasitoids, predators, and fungal pathogens attack this aphid. CULTURAL: Specific cultural methods have not been developed; see also IPM section. CHEMICAL: Apply products least toxic to natural enemies if treatments are required.
Homoptera
Wheat, barley, oats, canaryseed.
Aphid, oat-birdcherry
PESTS
Oat-birdcherry aphid – winged adult Andrew Jensen, Flickr
Descriptions of Field Crop Pests
59
Russian wheat aphid – adult, nymph
Frank Peairs, Colorado State University, Bugwood.org
Hosts
Wheat, barley, and many cool season grasses.
Identification
ADULTS: 1.6–2.1 mm long, spindle-shaped, and lime green in colour. Shortened antennae and reduced cornicles at the end of the abdomen are distinguishing characteristics. Adults also have a “double cauda” from the side view.
Aphid, Russian wheat Diuraphis noxia (Mordvilko)
Jan
Feb
Homoptera
Overwintering
Mar
Apr
May
Nymphs
June
July
Aug
Sept
Oct
Nov
Dec
Winged Adults
Nymphs
Jan . Feb . Mar . Apr . May . June . July . Aug . Sept . Oct . Nov . Dec !
Prior to the soft dough stage, count the number of infested plants among 20 randomly selected plants at 5 sites across a zig-zag transect of the field. The % infested = total number of infested plants. Crops should be checked weekly up to soft dough stage.
Economic Threshold
MATURE NYMPHS: Similar to adults but smaller.
WINTER CEREALS (After Oct. 1st): 15–20% seedlings infested.
Life Cycle
SPRING CEREALS: 10–15% of seedlings, 15–20% of plants at boot stage.
No male aphids have ever been found, thus no eggs are produced. Females reproduce asexually all year long and give birth to live young over 60–80 day life span (egg to adult, 10–14 days). Throughout the season, winged forms are produced which search out new hosts.
Feeding Damage
Migrating Adults
Monitoring/Scouting
ADULTS AND NYMPHS: Suck sap from leaves causing characteristic white, purple or yellow streaks between leaf veins. Feeding can cause discolouration and prevent normal unrolling of leaves, plant and head stunting, and bleached heads with poorly formed grain.
Management Options
BIOLOGICAL: Several species of parasitoids, predators, and fungal pathogens attack this aphid. CULTURAL: Control volunteer host plants; plant spring grains early and fall grains late to reduce establishment of colonies. CHEMICAL: Apply products least toxic to natural enemies if treatments are required.
Similar Species
The western wheat aphid, D. tritici (Gillette), is similar in appearance and also damages wheat, but is covered with wax and has a regular cauda.
Russian wheat aphid – damage International Maize and Wheat Improvement Centre (CIMMYT), Flickr
Russian wheat aphid – damage
Frank Peairs, Colorado State University, Bugwood.org
62
Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Management Field Guide
Field Crop and Forage Pests and their Natural Enemies in Western Canada IDENTIFICATION AND MANAGEMENT FIELD GUIDE
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