Black Bean Aphid

Species


Black Bean Aphid or Blackfly (Aphis fabae)

Host/site


  • Black bean aphids affect a wide range of garden plants, trees, and shrubs but primarily attack certain beans, peas, and celery. There are different hosts for the winter and summer. Winter hosts include the spindle tree (Eunomys europaeus), Viburnum or Philadelphius plants. In summer, hosts include beans, docks, celery, peas, corn and spinach.
  • They feed on plant sap and excrete plant sugars as honeydew. The honeydew often covers leaves which then become infested with black sooty moulds. This is less common where ants are collecting the honeydew.

Identification


Appearance
  • The adult wingless form is 1.5 - 3.1mm long, usually sooty black or very dark olive green, with some individuals having distinct white waxy stripes on the upper surface of the abdomen.
  • The two tubes (siphunculi) at the rear end are the openings of wax glands, which are black, short and taper slightly towards the tip. This wax protects the aphid from certain predators.
  • The tail (cauda) is black, blunt finger shaped and short.
  • The antennae are about half the length of the body.
  • The winged form is 1.3 - 2.6mm long, also very dark, with some barely discernible black cross-bars on the upper surface of the abdomen.
Indicators
  • Black bean aphid colonies can usually be found on the underside of leaves and on new shoots and buds. They become noticeable due to their clustering and dark coloring - white cast skins might also be present leftover from prior generations.
  • When feeding, they secrete a sticky, honeydew substance, which drips onto lower foliage, often a black mold forms on the honeydew.
  • Black garden ants are strong indicators for the black bean aphid. The ants manage and tend to the aphids and 'milk' the honeydew produced by the aphids.
  • Plants will suffer stunted growth, low production, and become more susceptible to disease when infested by these aphids. Leaf curling, yellowing, and wilting will occur.
  • In celery plants, black bean aphids inflict three types of damage; stunt growth and reduce yield; transmit virus diseases such as western celery mosaic, celery calico, cucumber mosaic or celery yellow spot; and contaminate fresh market produce.
Life cycle
  • Winter: eggs overwinter on certain host plants including the spindle tree (Eunomys europaeus), snowball bush (Viburnum), burning bush (Euonymus) or Philadelphius plants.
  • Spring: Aphids that hatch from these eggs are known as "stem mothers" which, are all female and asexual, meaning they do not need a mate to reproduce. Furthermore, these aphids do not lay eggs but give birth to live, all female, offspring who are also asexual. This continues for about 2-3 generations.
  • Summer: The following generation is typically born with wings and migrates to new plants. Summer hosts include a range of species, which are different than the winter host species, such as beans, docks, spinach, corn sugarbeets, lambsquarters, and pigweed. Aphids continue to reproduce asexually and have live births, allowing for large populations to build quickly. Both winged and wingless forms are produced throughout the summer. Winged forms disperse and migrate to new plants.
  • Fall: Winged asexual females and winged sexual males return to the winter hosts where one generation of sexual females are produced to mate with males and lay the eggs, which will overwinter.

Natural Enemies


Black bean aphids have many natural enemies. There are several parasitic wasps, which control aphids populations in celery, most notably species in the genera Diaeretiella and Lysiphlebus. In some cases, these parasites can eliminate high densities of aphids over a few weeks period. Other predators include ladybeetles, syrphid flies and lacewing.

Monitoring


Visually inspect individual plants each week and estimate the average percent of leaf area with aphids. You can also rate plants as infected or non-infested based on the number of new leaves with aphids. In larger fields of crops infestations tend to be erratic, so sample several locations. Sample intermediate-age crops because this is where the highest population levels of aphids are found. Concentrate on the plants that border other crops susceptible to aphid infestation.

Action Thresholds


Aphid survival and development are historically greatest during periods with temperatures that are less than 80°F. However, the black bean aphid is more tolerant of hot temperatures than other species, and therefore can cause problems into summer. For young celery plants, usually black bean aphids can be tolerated.

Cultural and Physical Controls


  • Destroy crop residue immediately after harvest.
  • Avoid other aphid-favored crops, such as lettuce, in adjacent areas.
  • Intensify monitoring for aphids when adjacent aphid-favored crops are harvested.

Biological Controls


  • Several parasitic wasps provide natural control of aphids in celery, most notably species in the genera Diaeretiella and Lysiphlebus. In some cases, these parasites can eliminate high densities of aphids over a few weeks period.
  • Predators such as ladybeetles, syrphid flies and lacewing also attack aphids. You can preserve these predators and parasites by not applying unnecessary amounts of insecticides and providing acceptable habitats.

Chemical Controls


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

References


"Black Bean Aphid - Aphis Fabae - Information - ARKive." ARKive - Discover the World's Most Endangered Species. Environment Agency - Abu Dhabi, 2009. Web. 24 May 2010. <http://www.arkive.org/black-bean-aphid/aphis-fabae/info.html>.

Godfrey, L. D., and J. T. Trumble. UC Pest Management Guideline - Celery - Black Bean Aphid. Guideline. Comp. W. E. Chaney. University of California, Davis - Agriculture and Natural Resources, Oct. 2005. Web. 23 May 2010. <http://www.ipm.ucdavis.edu/PMG/r104300211.html>.

Pest Management Center - Sugarbeets Black Bean Aphid. Fact Sheet. University of Idaho. Web. 23 May 2010. <http://www.uihome.uidaho.edu/default.aspx?pid=112863>.

"Rothamsted Insect Survey." Rothamsted Research. The Horticulture Development Council, UK. Web. 24 May 2010. <http://www.rothamsted.ac.uk/insect-survey/STAphis_fabae.php>.

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