Aphids are a potential danger to bean crops, which they devastate without hesitation with their voracious appetite for sap.  In addition to that, the harmful effects of their saliva and honeydew droppings on the plants’ leaves and stems do not really improve the situation.  For the sake of preserving the crops, provide them with all the required preventive care and treatments on time.

To expect a good harvest, there is no denying the fact that having the right protection strategy against destructive plant pests is of crucial importance.  It is with this state of mind that the farmer must protect his bean crops against aphids, which constitute their greatest threat.  It is necessary to start the fight against their proliferation from the moment they begin to invade the plants.  This targeted action offers the advantage of quickly impairing their reproduction and proliferation.  Since the aphid becomes sexually mature after 10 to 12 days, a single female aphid can have billions of offspring during its life cycle which lasts 9 months under good conditions.  Spring is the best time to treat against aphids, as it is the time period during which the eggs laid in the fall will hatch.

The resulting damages

Aphids are small insects of the Hemiptera order and Aphidoidea family that suck sap from plants.  There currently exist no fewer than 6,000 species of aphids. They are often green-coloured, but they can also be grey, yellow, red, black or white.  Aphids reproduce in two successive ways during their life cycle: by parthenogenesis between the months from March to August and by sexual reproduction in the months of September and October.  During the winter, all adult aphids perish and only the eggs resulting from sexual reproduction will survive.  The black bean aphid are the species most likely to attack beans. They migrate from some shrubs, such as the common spindle and the mock-orange.  They measure between 2 and 2.5 mm and have a matt black colour. These aphids start looking for beans from the month of March and during the whole summer.  Using their proboscis (needle), they remove the plant’s sap while injecting them with their saliva which is a potential carrier for viruses and diseases. They then secrete honeydew, a carrier for sooty mould which is a fungus harmful to beans.  Damages to plants are numerous: embossing, bending, rolling, crumpling, curling, mottle, mosaic, jaundice, variegation and/or leaf drop.  During more severe attacks, there may be stunting, wilting, drying of the stems and sometimes plant death.

Control strategies

Enemies of beans, aphids can be eradicated in two different ways: physical treatment and biological treatment.  The physical treatment is only appropriate at the beginning of the plants’ invasion by insects.  Proceed by completely immersing seedlings in water for a few minutes and washing larger plants with a water jet to drown and get rid of aphids.  The plant’s damaged parts must then be removed.  Later on, remember to buy a grease band to be laid down at the base of the bean’s main stem.  In regard to biological treatment, it is more effective in the case of a much larger aphid invasion.  This consists of concocting a small home-made recipe.  Dip a whole pack of cigarettes in about 2 pints of water and leave the cigarettes immersed for 24 h. Meanwhile, prepare a mixture containing 1.2 gills of vinegar and 1.2 gills of linseed oil soap. Pour that mixture in the tobacco water after it has been filtered. Spray the whole solution on the beans’ leaves and stems.  Another recipe consists of preparing a mixture containing 2 pints of water and 5 ounces of soap to be sprayed directly on the attacked plants.  Another recipe requires the use of garlic. Dip and marinate 6 cloves of garlic in a closed bottle containing 2 pints of water during 48 hours. Then, add 2 tablespoons of linseed oil soap and spray the solution on the beans’ stems and leaves.

Other creative solutions

The fight against bean aphids can also be conducted by the use of ladybird larvae found in specialized stores.  These larvae can eat up to 800 aphids each from their larval stage until adulthood, that is to say, for a period of 2 to 3 weeks.  Once they reach adulthood, they will each eat daily from 100 to 150 aphids.  This is also true in the case of lacewing larvae which can devour 60 aphids a day from their larval stage until adulthood, that is to say, for a period of about 1 month.  Another way to control bean aphids is to grow plants that have a deterrent effect on insects.  This means planting mint, thyme, French marigold, wormwood, lavender and savory.  These deterrent plants should be planted near the beans.  Thus, aphids will not dare approach the plants to attack them.

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Published in Care by Alexander on 06 Jul 2011