Potato Aphid
Beginner
Scientific Name
Aphis nasturtii, buckthorn aphid; Aulacorthum solani, foxglove aphid; Myzus persicae, green peach aphid; Macrosiphum euphorbiae, potato aphid
Identification
Aphids are small, soft-bodied, sucking insects 1–4 mm in length, with cornicles or “tail-pipes” near the tip of their abdomen. Aphids affect the potato crop directly by feeding and indirectly by transmitting viruses that cause important diseases.
The most common species of aphids found on potatoes in Ontario are:
- Green peach aphid
- Potato aphid
- Buckthorn aphid
The foxglove aphid is seldom abundant in Ontario.
Buckthorn aphid: Wingless forms are egg-shaped and about 1.2 mm long with a flat, lemon-yellow to green body. The antennal tubercles are not prominent.
Winged forms are approximately 1.4 mm long. The head and thorax are dark brown to black. The abdomen is yellow to yellow-green with a dark stripe behind each cornicle. The cornicles are short and light to dark brown. The antennal tubercles are not prominent.
Foxglove aphid: Wingless forms have a pear-shaped body with prominent, almost parallel, straight- sided antennal tubercles. The body is light yellow-green to dark green or brownish, shiny, usually with darker areas around the bases of the cornicles. The cornicles have dark tips. Legs and antennae have dark joints.
Winged forms have a light yellow brown or green-brown head and thorax. The abdomen is green to yellow-brown with dark bars and spots. The legs have dark joints and the wings have characteristic dark veins. The antennal tubercles are prominent, almost parallel and straight-sided.
Green peach aphid: Wingless forms are teardrop-shaped, 1.7–2 mm long and light yellowish-green to pink. The antennal tubercles are prominent and pointed inward. The cornicles are the same shade as the body and slightly swollen on the apical half.
Winged forms are about 2 mm long, with a dark-brown to black head and thorax. The abdomen is green, pink or reddish with a more or less solid dark patch. The antennal tubercles point inward.
Potato aphid: Wingless forms have elongated, wedge-shaped, yellow-green or pink bodies with long legs and long, slender cornicles. Their length ranges from 2.5–3.5 mm. The antennal tubercles slope outwards.
Winged forms are approximately 2.5–3.5 mm long. The antennal tubercles slope outward. The head and thorax are light yellow-brown or green-brown to dark brown. The abdomen is green or sometimes pink. The darker, pigmented legs and antennae are a distinctive feature of the potato aphid.
Often Confused With
Tarnished
plant bug nymphs
Potato
leafhopper nymphs
Period of Activity
In Ontario, the potato aphid is the first to infest the crop in the growing season. They can be present through most of the growing season.
Scouting Notes
Circles of dead plants are a sign of large aphid populations causing severe damage to the crop.
I. Monitoring aphids in processing and fresh market potato fields by direct counts. Aphids are carried into potato fields by the wind, so they are first found on plants along the windward edge of the field. This is usually the north or west side. Scout border rows separately as is done for CPB. Also, winged aphids tend to land on diseased, yellowing plants growing at the edge of fields.
For the rest of the field, monitor aphids at the same 10 sites that were selected for Colorado potato beetles. Count the aphids on three compound leaves taken from the top, middle and lower canopy. Different species of aphids prefer different parts of the plant. The first species to infest potatoes in Ontario is the potato aphid. The potato aphid prefers to colonize the upper and middle leaves. The green peach aphid begins to infest the crop as early as beginning of July. It is first found on lower leaves. When green peach aphid numbers are very high, this aphid species will also be found on middle and top leaves. If wingless aphids are present, colonies are likely to have been established in the field some time before, and they are reproducing. If only winged aphids are present, however, the aphids likely arrived only recently into the field
Report the average number of aphids per leaf.
II: Monitoring aphids in seed fields by direct counts. It is extremely important to detect the first flights of aphids into seed-potato fields, particularly the first flights of green peach aphid. This will give growers time to spray or to top kill before alrge numbers of plants are infected with viruses. There are several ways to monitor for aphids in seed numbers of plants are infected with viruses. There are several ways to monitor for aphids in seed fields: direct counts, yellow water-pan traps, suction traps and green tile traps.
Direct counts: Start by checking plants along the windward edges of the field. This is usually the north or west side. Check 50 lower leaves from 50 different plants along the north border, and then repeat this along the west border to get counts for 100 lower leaves. Then, scout the entire field following an X, or criss-cross pattern. Check 100 plants at random, 50 plants on the NE to SW diagonal and 50 plants on the NW to SW diagonal.
Examine three leaves per plant; a total of 300 leaves, from the lower, middle and upper part of the plant because the different species of aphids do not distribute themselves evenly over the plant.
Collect samples of the aphids in vials for later identification under magnification. Continue to monitor for aphids as long as the vines are green and growing.
Report the number of winged aphids found.
III: Other monitoring devices for seed fields are: Yellow water-pan traps. Yellow pan traps are partially filled with soapy water and then placed at least 15 m from the edge of the field on bare ground. Aphids are attracted to yellow, and the pans are put on bare ground to increase the contrast with the surroundings. The sides of the pan can be painted black to increase the contrast. Soap is added to the water to reduce surface tension. Aphids that fly into the pan sink in the water and drown. Yellow pan traps should be checked daily. Aphids are removed from the yellow pan with a small brush and the species identified.
Thresholds
Thresholds in fresh market and processing fields:
| CROP STAGE | AVERAGE NUMBER PER LEAF |
Tuber Initiation to 2 weeks before vine kill |
4 |
Within 2 weeks of vine-kill |
10 |
Thresholds in seed fields:
| Borders: | 3 wingless aphids/100 leaves |
Field: |
9 wingless aphids/300 leaves |
NOTE: Some seed producing areas use a zero-tolerance threshold.
Advanced
Scientific Name
Aphis nasturtii, buckthorn aphid; Aulacorthum solani, foxglove aphid; Myzus persicae, green peach aphid; Macrosiphum euphorbiae, potato aphid
Identification
Aphids are small, soft-bodied, sucking insects 1–4 mm in length, with cornicles or “tail-pipes” near the tip of their abdomen. Aphids affect the potato crop directly by feeding and indirectly by transmitting viruses that cause important diseases.
The most common species of aphids found on potatoes in Ontario are:
- Green peach aphid
- Potato aphid
- Buckthorn aphid
The foxglove aphid is seldom abundant in Ontario.
Buckthorn aphid: Wingless forms are egg-shaped and about 1.2 mm long with a flat, lemon-yellow to green body. The antennal tubercles are not prominent.
Winged forms are approximately 1.4 mm long. The head and thorax are dark brown to black. The abdomen is yellow to yellow-green with a dark stripe behind each cornicle. The cornicles are short and light to dark brown. The antennal tubercles are not prominent.
Foxglove aphid: Wingless forms have a pear-shaped body with prominent, almost parallel, straight- sided antennal tubercles. The body is light yellow-green to dark green or brownish, shiny, usually with darker areas around the bases of the cornicles. The cornicles have dark tips. Legs and antennae have dark joints.
Winged forms have a light yellow brown or green-brown head and thorax. The abdomen is green to yellow-brown with dark bars and spots. The legs have dark joints and the wings have characteristic dark veins. The antennal tubercles are prominent, almost parallel and straight-sided.
Green peach aphid: Wingless forms are teardrop-shaped, 1.7–2 mm long and light yellowish-green to pink. The antennal tubercles are prominent and pointed inward. The cornicles are the same shade as the body and slightly swollen on the apical half.
Winged forms are about 2 mm long, with a dark-brown to black head and thorax. The abdomen is green, pink or reddish with a more or less solid dark patch. The antennal tubercles point inward.
Potato aphid: Wingless forms have elongated, wedge-shaped, yellow-green or pink bodies with long legs and long, slender cornicles. Their length ranges from 2.5–3.5 mm. The antennal tubercles slope outwards.
Winged forms are approximately 2.5–3.5 mm long. The antennal tubercles slope outward. The head and thorax are light yellow-brown or green-brown to dark brown. The abdomen is green or sometimes pink. The darker, pigmented legs and antennae are a distinctive feature of the potato aphid.
Often Confused With
Tarnished
plant bug nymphs
Potato
leafhopper nymphs
Biology
Life stages: eggs, wingless forms, winged forms.
Aphid populations may increase rapidly when temperatures are high; a mixed population of young and old aphids can increase five-fold within one week. Natural predators such as ladybeetles and lacewings are very effective in keeping aphid populations at low levels.
The green peach aphid is the most important vector of potato viruses.
Although it prefers to feed on the lower leaves of potato plants, the green peach aphid will feed on the top leaves if populations are high.
The potato aphid is the largest aphid that infests potatoes in the province. This aphid is usually found on the middle and upper leaves of potato plants. High populations will cause wilting and will cover the upper leaves with sticky honeydew.
Period of Activity
In Ontario, the potato aphid is the first to infest the crop in the growing season. They can be present through most of the growing season.
Scouting Notes
Circles of dead plants are a sign of large aphid populations causing severe damage to the crop.
I. Monitoring aphids in processing and fresh market potato fields by direct counts. Aphids are carried into potato fields by the wind, so they are first found on plants along the windward edge of the field. This is usually the north or west side. Scout border rows separately as is done for CPB. Also, winged aphids tend to land on diseased, yellowing plants growing at the edge of fields.
For the rest of the field, monitor aphids at the same 10 sites that were selected for Colorado potato beetles. Count the aphids on three compound leaves taken from the top, middle and lower canopy. Different species of aphids prefer different parts of the plant. The first species to infest potatoes in Ontario is the potato aphid. The potato aphid prefers to colonize the upper and middle leaves. The green peach aphid begins to infest the crop as early as beginning of July. It is first found on lower leaves. When green peach aphid numbers are very high, this aphid species will also be found on middle and top leaves.
If wingless aphids are present, colonies are likely to have been established in the field some time before, and they are reproducing. If only winged aphids are present, however, the aphids likely arrived only recently into the field.
Report the average number of aphids per leaf.
II: Monitoring aphids in seed fields by direct counts. It is extremely important to detect the first flights of aphids into seed-potato fields, particularly the first flights of green peach aphid. This will give growers time to spray or to top kill before alrge numbers of plants are infected with viruses. There are several ways to monitor for aphids in seed numbers of plants are infected with viruses. There are several ways to monitor for aphids in seed fields: direct counts, yellow water-pan traps, suction traps and green tile traps.
Direct counts: Start by checking plants along the windward edges of the field. This is usually the north or west side. Check 50 lower leaves from 50 different plants along the north border, and then repeat this along the west border to get counts for 100 lower leaves. Then, scout the entire field following an X, or criss-cross pattern. Check 100 plants at random, 50 plants on the NE to SW diagonal and 50 plants on the NW to SW diagonal.
Examine three leaves per plant; a total of 300 leaves, from the lower, middle and upper part of the plant because the different species of aphids do not distribute themselves evenly over the plant.
Collect samples of the aphids in vials for later identification under magnification. Continue to monitor for aphids as long as the vines are green and growing.
Report the number of winged aphids found.
III: Other monitoring devices for seed fields are: Yellow water-pan traps. Yellow pan traps are partially filled with soapy water and then placed at least 15 m from the edge of the field on bare ground. Aphids are attracted to yellow, and the pans are put on bare ground to increase the contrast with the surroundings. The sides of the pan can be painted black to increase the contrast. Soap is added to the water to reduce surface tension. Aphids that fly into the pan sink in the water and drown. Yellow pan traps should be checked daily. Aphids are removed from the yellow pan with a small brush and the species identified.
Thresholds
Thresholds in fresh market and processing fields:
| CROP STAGE | AVERAGE NUMBER PER LEAF |
Tuber Initiation to 2 weeks before vine kill |
4 |
Within 2 weeks of vine-kill |
10 |
Thresholds in seed fields:
| Borders: | 3 wingless aphids/100 leaves |
Field: |
9 wingless aphids/300 leaves |
Management Notes
The continuous use of broad-spectrum insecticides may disrupt beneficial insect populations, resulting in aphid resurgence.
