Aphids on vegetables — Which? Gardening Helpdesk

Aphids on vegetables

Q What are aphids?
A Aphids are extremely common, sap-sucking bugs. The group includes greenfly, blackfly, root aphids and woolly aphids. There are many kinds, each with different host plants and life cycles. Most occur in small numbers and do little harm. They spread on the breeze and tend to settle in sheltered sites.

Caption: Aphids attack a wide range of plants

Q What damage do aphids do?
A Aphids weaken and stunt plants by sucking plant sap. They excrete a sugary substance called honeydew, which sticks to leaves that then become colonised by sooty moulds. They also spread virus diseases.

If possible, try to live with them, as they mostly do little damage. Natural predators, parasites and diseases will often get rid of them for you.

Q Do aphids turn up every year?
A Aphids survive as eggs on host plants, as adults in sheltered spots, or on plants in greenhouses until the spring. Winged aphids spread by drifting on the wind. This sounds random, but there are so many aphids that few gardens escape.

Some years are much worse than others. Aphid numbers depend on the weather, how many pests and predators attack them and the effect of diseases.

Q Why do some aphids have wings while others do not?
A Aphids have different forms. When their population is high, or predators are about, or at times of the year when they disperse to alternative food plants, winged forms develop. When they find new hosts, the winged forms lose their wings and give rise to wingless aphids again.

Q Which plant diseases do aphids spread?
A Aphids are very important carriers of viruses. For example, willow-carrot aphid carries carrot motley dwarf virus. When it feeds on parsley, the virus causes serious damage and is more harmful than the greenfly. The parsley turns reddish to start with, but soon goes yellow and becomes unusable.

Q Can aphids be sprayed?
A There is a wide number of sprays available to deal with aphids. These include Bayer Natria Bug Control and Westland Resolva.

Check the pack carefully for the harvest interval and what plants it is approved for.

Some aphids are resistant to insecticides. Peach-potato aphid and the melon/cotton aphid, especially those found in greenhouses, are examples of this. If your sprays don’t seem to be working, then switch to ones based on fatty acids.

Q Can aphids be avoided?
A Early and late sowings often escape the worst of the aphid fly-ins. Carrots sown in June are also likely to escape both carrot fly and willow-carrot aphid.

Q What can organic growers do to control aphids?
A Organic aphid killers work very well if carefully applied to cover the whole of the plant. Repeat sprays will be necessary until the aphids are controlled.

It is possible to exclude aphids from plants by covering with horticultural fleece or insect-proof mesh, but the plants must be completely free of aphids before you cover them.

Fleece captures too much warmth for summer sowings. To avoid cooking your plants, use the better-ventilated insect-proof mesh for these sowings. If you raise your young cabbage-family plants in seedbeds covered by fleece or mesh, you will have strong, pest-free transplants to put out. These covers will also protect against flea beetles and cabbage root fly.

Q Are there any biological controls for aphids?
A Natural pests and diseases often kill great numbers of aphids. Sadly, they often fail to do this before the damage is done.

Predators and parasites can be introduced to control greenfly. They are not equally effective against all aphids. They work best in greenhouses, frames and under cloches, where they are less
likely to stray from the plants that you are trying to protect.

Q How do I use biological controls for aphids?
A Introduce the parasites and predators as soon as you see the greenfly, once temperatures are greater than 10°C. Two introductions of Aphidolytes aphidimyza, a tiny (2mm) midge, should be enough. More will be needed if the plants get heavily infested. Each female lays about a hundred eggs during its two-week lifetime. The tiny larvae eat about five adult or 15 juvenile greenfly during their one to two week development time. They work best in warm, well-lit conditions.

Aphidius is a parasitic midge that is good at hunting down and finding greenfly. They lay eggs inside them and the larvae eat the greenfly from the inside. Use this parasitic midge when you only have a few pests.

If you choose biological controls, only use fatty acid-based insecticides. Other chemical treatments may kill the helpful insects.

Q What should I do with plants with aphids?
A Cabbage aphid-infested brassicas should be chopped up and composted thoroughly before the end of May, or they can be burned. Woody stems can be covered with eggs, so, unless the stems are efficiently destroyed, the eggs can hatch and infest new crops. Carrots, parsnips and parsley, left over in the spring, harbour many willow-carrot aphids. These overwintered root vegetables must also be destroyed before May, by thorough composting.

Identifying common types of aphid

1 Black bean aphid (Aphis fabae) A typical blackfly that appears first on the young growing tips of broad beans and spreads very rapidly if unchecked, eventually weakening the plants. When first seen, in May and June, nip out the growing tip carefully, complete with blackfly colonies. Any stray aphids can be squashed. It can also attack French and runner beans later in the summer, and can spread bean yellow mosaic virus.
2 Cabbage aphid (Brevicoryne brassicae) is blue-grey and forms dense colonies with a mealy look, because of the waxy covering the greenfly produce. They feed on the undersides of leaves of the cabbage family, including weeds such as shepherd’s purse, and make the leaves curl and distort. However, they can also infest Brussels sprouts and cabbages more severely, making them inedible.
3 Willow-carrot aphid (Cavariella aegopodii) is an ordinary-looking greenfly that’s quite hard to see. It
attacks celery, carrots and parsnips in May and June. The plants become stunted and covered in honeydew, which gets covered with dead greenfly. After July, the greenfly disperse to their winter host plants: willows.
4 Peach-potato aphid (Myzus persicae) looks similar to other greenfly. Seldom builds up to the large numbers seen with cabbage aphids, but it’s effective at passing on viruses. Potatoes and lettuces are particularly at risk, so using your own potato ‘seed’ tubers can be unwise. The virus won’t have much effect on the current year’s crop, but plants raised from infected ‘seed’ will be heavily infected and are likely to crop poorly. Bought ‘seed’ potatoes are raised in cool, northern areas, where aphids don’t thrive, and should be virus-free.

gardening.which.co.uk

Carrot-Aphid

Bean aphid (Aphis fabae)

Green peach aphid (Myzus persicae)

Willow-carrot aphid (Cavariella aegopodii)

Pest description and crop damage The green peach aphid is slender, dark green to yellow, and has no waxy bloom. The wingless form of the green peach aphid is pale green. The winged form has a black head and thorax. It is primarily an early season pest and transmits virus diseases. The willow-carrot aphid is pale greenish yellow. The winged form is pale yellow marked with black. Its primary host is willow, but it feeds on carrots during the summer. The bean aphid is dark olive green to black with light-colored legs. It is usually more of an early season pest.

Aphids feed on carrot foliage, but they are a key pest because they can transmit diseases such as motley dwarf virus. In general, aphids damage plants by sucking plant sap, which causes heavily infested leaves to curl and stunt; by excreting honeydew, which causes sticky, shiny leaves to turn black because of a sooty-mold fungus growth; and by spreading plant diseases (a large number of viruses are spread by aphids).

Biology and life history

Pest monitoring Check fields frequently after seedlings emerge. If aphids become numerous, increase the frequency of sampling. Aphids often are concentrated in hot spots or near the field margin. Note the presence of any hot spots but avoid sampling only those areas. Also, be sure to look for evidence of biological control; i.e., the presence of predators, parasites (aphid mummies), and disease. Aphid flights are most common during periods of moderate temperatures (60 ° to 80 ° F). Monitor fields particularly closely during April and May.

Many parasites and predators attack aphids. Early year aphids have many natural enemies that frequently bring them under control later in the year. Among the more common predators are lady beetles and their larvae, lacewing larvae, and syrphid fly larvae. Populations of green peach aphids are reduced in winter by a parasitic fungus, Entomophthora aphidis.

Monitor the proportion of aphid mummies relative to unparasitized aphids and the numbers of predators such as lady beetles. If the proportion of mummies is increasing, or predators appear to be gaining control, and aphid populations are not yet damaging, avoid sprays that will disrupt these natural enemies. Most materials for aphid control are highly disruptive of natural enemy populations.

Destroy infested crops immediately after harvest to prevent aphid dispersal. Destroying weed hosts late in the year may help destroy overwintering populations. Populations tend to be higher in crops that are fertilized liberally with nitrogen. Home gardeners can often get effective control by washing aphids with a strong stream of water.

Management-chemical control: HOME USE

Apply to both tops and undersides of leaves.

  • azadirachtin (neem extract)-Some formulations are OMRI-listed for organic use.
  • Beauvaria bassiana -Some formulations are OMRI-listed for organic use.
  • carbaryl
  • cyfluthrin
  • deltamethrin
  • esfenvalerate
  • imidacloprid
  • insecticidal soap-May require several applications. Some formulations are OMRI-listed for organic use.
  • kaolin-Applied as a spray to foliage It acts as a repellent to some insect pests. Some formulations are OMRI-listed for organic use.
  • malathion
  • plant-derived essential oils (clove, rosemary, etc.)-Some have demonstrated efficacy on aphids. Some formulations are OMRI-listed for organic use.
  • pyrethrins (often combined with other ingredients)-Some formulations are OMRI-listed for organic use.
  • zeta-cypermethrin

Management-chemical control: COMMERCIAL USE

  • Beauveria bassiana (Mycotrol ESO) at 0.25 to 1 quart/100 gal spray volume. PHI 0 days. REI 4 hr. OMRI-listed for organic use.
  • bifenthrin (Brigade) at 0.08 to 0.1 lb ai/a. PHI 21 days. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.5 lb ai/a per season.
  • borate complex (Prev-Am) applied as a 0.8% solution. Spray to complete coverage. PHI 1 day. REI 12 hr. Retreatment interval 7-10 days. OMRI-listed for organic use.
  • Chromobacterium subtsugae (Grandevo) at 0.6 to 0.9 lb ai/a per 100 gal. PHI 0 days. REI 4 hr. OMRI-listed for organic use.
  • deltamethrin (Battalion) at 0.012 to 0.028 lb ai/a. PHI 3 days. REI 12 hr. Retreatment interval 3 days. Do not exceed 0.14 lb ai/a per season.
  • flonicamid (Beleaf) at 0.062 to 0.089 lb ai/a. PHI 3 days. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.267 lb ai/a per season. Limit to 3 applications.
  • flupyradifurone (Sivanto) at 7 to 10.5 fl oz/a. PHI 21 days. REI 4 hr. Do not exceed 0.365 lb ai/a per year. Minimum of 10 days between successive applications.
  • imidacloprid (Admire) at 0.156 to 0.375 lb ai/a, or 0.011 to 0.027 lb ai/1,000 row feet. Soil application only. PHI 21 days. REI 12 hr. One treatment per season only. Do not exceed 0.375 lb ai/a per year.
  • imidacloprid (Provado, Prey) at 0.044 lb ai/a. PHI 7 days. REI 12 hr. Do not exceed three treatments per season. Do not exceed 0.13 lb ai/a per season.
  • insecticidal soap (M-Pede) at 1 to 2% solution. Potassium salts of fatty acids. See label for gal/a. PHI 0 days. REI 12 hr.
  • malathion (numerous products) at 1 to 1.25 lb ai/200 gal. PHI 7 days. REI 12 hr.
  • thiamethoxam (Actara) at 0.023 to 0.047 lb ai/a. REI 12 hr. PHI 7 days. Do not exceed 0.125 lb ai/a per year. Retreatment interval 7 days.
  • thiamethoxam (Platinum) at 0.078 to 0.188 lb ai/a soil applied. REI 12 hr. Do not exceed 0.188 lb ai/a per season.
  • sulfloxyflor (Transform WG) at 0.75 to 1.0 oz/a. Do not exceed 8.5 oz/a. PHI 7 days. REI 24 hr. If blooming vegetation is present 12 out from the downwind edge of the field, a 12 foot in-field down wind buffer must be observed. Not for use on seed crops.
  • zeta-cypermethrin (Mustang) at 0.04 to 0.05 lb ai/a. PHI 1 day. REI 12 hr. Do not exceed 0.3 lb ai/a per year.

pnwhandbooks.org

How to Manage Pests

UC Pest Management Guidelines

Carrot

Willow Carrot Aphid

Scientific Name: Cavariella aegopodii

(Reviewed 1/09 , updated 1/09 )

In this Guideline:

DESCRIPTION OF THE PEST

The wingless summer form of the willow carrot aphid is pale green with the cornicles, cauda (tail-like structure), and legs pale to slightly dusky. They are medium-size aphids with rather elongate oval-shaped bodies that are flattened front to back. The upper surface of the body may be roughened by numerous small depressions. The wingless forms have a second tail-like process called the supracaudal process directly above the cauda giving the aphid the appearance of having twin tails when viewed with a hand lens. This supracaudal process may be triangular or fingerlike in shape.

The winged forms have a black head and thorax. The abdomen is pale green with dark areas on the sides and dark bands on the top. The antennae are black. The legs are pale in color and black at the tips. The cornicles are somewhat swollen near the tip.

DAMAGE

Willow carrot aphid is primarily of concern because of its efficiency in vectoring a number of serious virus diseases. It transmits carrot motley dwarf, carrot red leaf, and parsnip yellow fleck. It is also a vector of Celery mosaic virus, Sugarbeet mosaic virus, and Cauliflower mosaic virus. It seldom reaches numbers that trigger the need for chemical intervention.

MANAGEMENT

Biological Control

Little is known regarding the parasites of willow carrot aphid. The presence of bloated mummies indicates parasite activity. Predators such as green lacewing larvae, lady beetles, and syrphid fly larvae prey on this aphid as well as on other aphid species.

Cultural Control

Sanitation is important in curbing the spread of the viruses that this insect vectors. Disc all crop residues under as soon as harvest is complete. Keeping fields, ditch banks, and fence lines weed-free may also help in reducing virus inoculum.

Organically Acceptable Methods

Biological and cultural controls are acceptable for use on organically grown produce.

Monitoring and Treatment Decisions

No treatment thresholds have been established. Chemical treatments are not effective in preventing virus transmission and this aphid rarely builds up in numbers high enough to cause economic damage by direct feeding.

PUBLICATION

UC IPM Pest Management Guidelines: Carrot
UC ANR Publication 3438

Insects
  • E. T. Natwick, UC Cooperative Extension, Imperial County
  • D. R. Haviland, UC IPM Program, Kern County
  • C. G. Summers, Entomology, Kearney Agricultural Center, Parlier
Acknowledgment for contributions to Insects:
  • W. E. Chaney, UC Cooperative Extension, Monterey County

Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright © 2017 The Regents of the University of California. All rights reserved.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance.

Agriculture and Natural Resources, University of California

ipm.ucanr.edu

Willow-Carrot Aphid

On This Page

Description of the Pest

The wingless summer form of the willow carrot aphid is pale green with the cornicles, cauda (tail-like structure), and legs pale to slightly dusky. They are medium-size aphids with elongate oval-shaped bodies that are flattened front to back. The upper surface of the body may be roughened by numerous small depressions. The wingless forms have a second tail-like process called the supracaudal process directly above the cauda, giving the aphid the appearance of having twin «tails» when viewed with a hand lens. This supracaudal process may be triangular or fingerlike in shape.

The winged forms have a black head and thorax. The abdomen is pale green with dark areas on the sides and dark bands on the top. The antennae are black. The legs are pale in color and black at the tips. The cornicles are somewhat swollen near the tip.

Damage

Willow carrot aphid is of concern primarily because of its efficiency in vectoring a number of serious virus diseases. It transmits carrot motley dwarf, carrot red leaf, and parsnip yellow fleck. It is also a vector of Celery mosaic virus, Sugarbeet mosaic virus, and Cauliflower mosaic virus. It seldom reaches numbers that require the need for chemical intervention.

Management

Biological Control

Little is known regarding the parasites of willow carrot aphid. The presence of bloated mummies indicates parasite activity. Predators such as green green lacewing larvae , lady beetles , and syrphid fly larvae prey on this aphid as well as on other aphid species.

Cultural Control

Sanitation is important in curbing the spread of the viruses that this insect vectors. Disc all crop residues under as soon as harvest is complete. Keeping fields, ditch banks, and fence lines weed-free may also help in reducing virus inoculum.

Organically Acceptable Methods

Biological and cultural controls, applications of insecticidal soaps, narrow range oils, entomopathogenic fungi (such as Beauveria bassiana), azadirachtin (Neemix), and neem oil (Trilogy) are acceptable for use on organically certified cilantro and parsley.

Monitoring and Treatment Decisions

Treatment thresholds have not been established for this pest. Pesticides do not prevent virus transmission, and this aphid rarely builds up in numbers high enough to cause economic damage by direct feeding.

Common name Amount per acre** REI‡ PHI‡
(Example trade name) (hours) (days)
Pesticide precautions Protect water Calculate VOCs Protect bees
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees , and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide’s properties and application timing. Always read the label of the product being used.
A. AZADIRACHTIN
(Neemix 4.5)# Label rates 4 0
(Aza-Direct) 2–3.5 pts 4 0
MODE-OF-ACTION GROUP NUMBER 1 : un
B. NEEM OIL#
(Trilogy)# 1–2% 4 0
MODE-OF-ACTION GROUP NUMBER 1 : un
C. BEAUVERIA BASSIANA
(BotaniGard ES)# Label rates 4 0 MODE-OF-ACTION GROUP NUMBER 1 : un
** See label for dilution rates.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
1 Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode-of-action group numbers (un = unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee).
# Acceptable for use on organically grown produce.
Not recommended or not on the label.

UC IPM Pest Management Guidelines: Cilantro and Parsley
UC ANR Publication 3476

www2.ipm.ucanr.edu

Carrot Root Fly

1. Carrot root fly larva and damage.
2. Carrot root fly mines on carrots.
3. Carrot root fly damage — treated vs. untreated.

Identification

The adult flies are 8 mm in length and are a shiny black colour with a reddish head and light orangey coloured legs. The larvae are cream coloured, slender and up to 1 cm in length.

Symptoms

The larvae emerging from newly laid eggs feed on the root hairs, rootlets and tap roots of the host plant. Early symptoms are wilting and a reddish/yellow discolouration of the outer leaves. Early attacks can result in plant loss but the more common outcome is that surviving plants are distinctly stunted. As the plant roots develop and enlarge the larvae mine into the roots leaving unsightly characteristic reddish/brown tunnels below the skin surface.

Life-cycle

First generation adult flies are often on the wing when cow parsley is in full flower at the end of April. They migrate into crops from nearby sheltered areas such as hedgerows. The adults are very weak fliers and rarely rise above a height of 50 cm. Eggs are laid into soil crevices around the base of host plants. Depending on temperature the larvae usually hatch in about one week and feed on the plant roots. Further damage can be caused by the larvae moving from plant to plant. After completing three growth stages (moults) the larvae pupate in the soil. The transition from egg to adult can be completed in 3 months. Carrot flies can survive the winter in a variety of different ways. The adults can survive by sheltering in warm protected environments, the pupae can overwinter in the soil or the larvae can survive in the roots of host plants, especially in crops which have been covered with straw for protection from cold weather. There are usually two generations per year but a third generation is possible especially if temperatures remain high into the autumn. The first generation arises in late April/early May and the second is on the wing in late July. It is the first two generations which are responsible for economic crop damage.

Importance

Crops growing in exposed sites and fields with no adjacent sheltered habitats will be less at risk. Crop establishment can be adversely affected but where pest pressure is severe crops can be rendered unmarketable. Carrot root fly larvae can also invade the roots of parsnips, parsley, celery and other herbaceous plants.

Threshold

Sticky traps located in crops can give an indication of fly emergence which assists with the timing of insecticide sprays. This information can also be valuable for making agronomic decisions on sowing dates and harvesting. Tefluthrin seed treatment can give early protection and repeat applications of pyrethroids can control adults before eggs are laid. These insecticide sprays will not control larvae feeding below ground. Sprays should be applied in the late afternoon or early evening when the adults are most active. Complete protection can be achieved by covering the carrot crop with polythene insect netting which prevents the adults from laying eggs in the rows. This is particularly useful in the organic and amateur market. In the amateur market some progress has also been made with plant breeding. Partial resistance has been successfully bred into some newly released varieties such as ‘Flyaway’.

Identify Pests

Find out more information and help identify the pests found on your crops.

cropscience.bayer.co.uk

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