Blackfly On My Beans

It's that time of year again when the dreaded blackfly takes a shine to your runners, french and broad beans, I have some french climbers and noticed their sap sucking presence this morning. My Dad always planted French Marigolds in the bean row and that does have a good affect, it encourages hover fly and other predatory insects fond of aphids, the problem I have is they aren't in flower yet. so I set about squashing them on the plant, this is time consuming and definitely you will miss some.

So what to do, the immediate thought is reach for the chemicals. This is not advised if your plants are in flower as it can affect the pollinators and remember the predators too.  Also some chemical controls (systemic) are not to be used on food plants and others are bad for the amphibian and fish population (garden ponds, canals etc), unless you are commercial better to avoid chemicals.

Are there any other remedies out there? Time to reach for the google search.

  First an intro from the RHS

 

Quick facts - Common name Blackfly including the black bean aphid

Scientific name Aphis fabae species group
Plants affected A very wide range including broad, French and runner beans, nasturtium, dahlia, philadelphus, viburnum and euonymus
Main cause A black sap-sucking insect
Timing April-August


The best alternative remedies I found were on this website http://www.gardenfocused.co.uk/vegetable/runner-beans/pest.php they have a page dedicated to treating for aphids which can be found here.

This list of their do it yourself remedies looks excellent.

 THE GARLIC DRENCH
It's well known that simply spraying you plants with slightly soapy water will reduce the number of aphids. This method involves leaving three or four crushed garlic cloves to soak in the water before spraying it on. The theory is that insects don't like garlic so garlic in the water will repel them.
SUNFLOWERS
If ants are farming the aphids then a couple of sunflowers grown nearby may well interest the ants more than the runner beans. The ants will then herd the aphids to the sunflowers.
SEMOLINA AND FARMING ANTS
Many gardeners report that simply killing farming ants (ant powder will do the job) reduces the amount of aphids. One recommendation for killing ants is to  put a small piece of semolina near the ants. Apparently they take it back for the queen ant to eat but she cannot actually digest it and explodes!
OXALIC ACID
Rhubarb leaves contain a fair amount of oxalic acid (enough to cause severe discomfort if humans eat them) which can be used to kill aphids. Cut the leaves into bits and boil them then leave them to simmer for five minutes. Add a tablespoon of washing up to the liquid and spray over the aphids.

The BBC had some good advice 

 -  http://www.bbc.co.uk/gardening/advice/pests_and_diseases/identifier.shtml?black_bean_aphid

Organic

• Inspect plants regularly and deal with early symptoms immediately.
• Remove as many aphids as you can by hand or, if possible, cut off infested shoots and stems on susceptible shrubs.
• Spray the infested areas of a plant with a strong jet of water to keep aphid numbers down.
• Use nettings and fleeces to stop aphids spreading to susceptible plants.
• Encourage natural aphid predators such as ladybirds, Aphidoletes, hoverfly and lacewing larvae. These can be obtained from commercial suppliers and released on to affected plants outdoors.
• For greenhouse plants use parasitic wasps of aphids such as Aphidius matricariae and Aphidius ervi which can be purchased for release in a contained space.

Prevention

• Regularly check plants for signs of aphid infestation and deal with them as soon as they appear.
• Encourage natural enemies.
• Avoid using broad spectrum insecticides which will kill beneficial insects as well as aphids.
• Encourage insectivorous birds by hanging feeders during the winter months and provide nesting boxes in the spring.

 Hopefully some of the above will help, good luck.