the broadbean story II or wait-and-hose

I had seen ladybirds on my broadbeans and was hoping they would multiply faster than the aphids. this was of course wishful thinking. nothing multiplies faster than aphids under the right conditions. they have mastered the art of asexual reproduction and don´t even need to mate to produce offspring. overwintering eggs hatch female aphids which produce hundreds of clones. however my hopes were not completely unfounded. I spotted quite a few clusters of tiny yellow lady bird eggs carefully stuck under the leaves.

I did get impatient though, when in a very short amount of time a considerable part of my bean plants, stalks , leaves, flowers and all, were covered in black flies. something had to be done. I got the hose out. black flies really don´t like cold water. I hosed each plant individually (carefully, the leaves squish easily), removing the aphids carefully with my fingers. you never get all of them, but apart from me being dripping wet, there were considerably less after my hose treatment. the sugary juice of all the aphids makes the leaves sticky and attracts fungal growth on the plant. the water washes the sugar away and cleans the plants as well as removing the insects. I had checked for lady bird eggs beforehand and tried to avoid the leaves they were attached to. I hosed the plants twice so far and finally some help has arrived. the ladybird larvae have hatched:

they have a massive appetite and I counted at least 30 of them. in the picture below you can see them working away on the first beans to emerge.

had I used an insecticide, my little helpers would not have had a chance. being a scientist I of course have some science to back this up. a couple of guys did some mathematical modelling in 1925 concerning the population dynamics of prey/predator systems (Lotka and Volterra). in our case the aphids are prey, as they get eaten by the ladybird and ladybird larvae predators. they found, that when both prey and predator get equally disturbed (if you want to call poisoning them with insecticide a disturbance), the prey will always recover faster. the predator population (ladybirds) might completely collapse as it suffers twice. they get poisoned themselves, and any survivors die by a lack of food, as their food source got poisoned as well. the aphids however will recover quickly and multiply unchecked by their natural enemies.

my wait-and-hose-method is a bit more selective as the ladybirds move out of harms way and I tried to avoid their eggs. they did a good job so far and hopefully are going to keep the aphid population low for the rest of the season for free.

the broadbean story

it all began in february. it was freezing -10°C cold and there was no way anything could be planted in the garden soon. as broadbeans need to be started as early as possible (in milder climates you plant them in autumn, ideal temperature for germination 5-10°C) I planted mine in milk cartons on the windowsill. when the frost was over and the ground had thawed and warmed up a bit in march, I already had little bean plants to plant out. this is what my broadbeans looked like on the first of april:

you can see what our soil is like. if exposed the grey sand turns into a white sandpit that repells water. together with the amount of rain we are getting at the moment (3-5mm every two weeks or so) it starts to remind me of desert farming. hence the mulch and the black drip irrigation pipe on the picture below.

now, five weeks later in may, the beans have trippled in size and are putting out crazy amounts of flowers.

but nothing is perfect. the imperfectness in this case arrived in form of black bean aphids also known as blackfly. they are the reasons why broad beans need to be planted out early. the beans don´t mind cool weather the aphids do. luckily the garden police has spotted the problem and I have seen several lady birds on patrol already. this yellow and black cutie is munching away on an aphid.

go ladybird go!

one adult ladybird can eat up to 50 aphids a day, but this is nothing compared to the appetite the larvae develop. so I hope for the first eggs to hatch soon and keep the nasty flies in check. this beeing real life the situation is a bit more complex though. this little fellow:

is resting after beeing attacked by three ants. the ants milk the aphids for sugary juice, cary them from plant to plant and as I saw, even defend them agains ladybirds. angry ants are to be recond with, especially when you are bug sized. they can not be everywere though and the ladybirds can fly.

I´ll keep you posted who wins.