Keeping blackfly off Broad Beans

Broad beans in the kitchen garden. You can see the first beans are almost ready to pick.

It's the time of year to start planning those broad bean meals, as the first crops should be ready to harvest soon. However, just before the broad beans are ready for eating, also happens to be the exact same time that the dreaded Blackfly (black bean aphid - Aphis fabae) decide to make an appearance. They suck out all the goodness from the plant and can destroy much of your crop if you don't get them under control.

Images: Left - The Vegetable and Herb Expert (2002), Right - RHS website.

The blackfly head for the tips of the broad beans first, as per the picture on the left, and an example of a bad infestation is on the right. It can take only a couple of days to go from just appearing, to a bad infestation, which can destroy the flowers before they even turn into beans.

If you notice that you have ants going up and down your beans, that's because they are also getting read for them. Ants 'farm' them (photo above) and can make an infestation so much worse. These are my tips for getting ahead of the blackfly.

Pinching out the tips
The first tip, is to pinch out the tips of the broad beans. This is because this is where the blackfly will land and start their infestation. By taking out the tips, you are opening up the top of the plant to more light and air, making it a little harder for them to take over.

You want to do this once the plants look like they are a decent size and have plenty of flowers on them. This is usually around early-mid May, but can depend on when you sowed them. Earlier May if you sowed in Autumn, later May if the sowing was done in Spring.

The circle shows the tips in detail.

You can see lots of young leaves and flowers all wrapped up tight.

From another angle, me holding the tip I'll pinch out.

Closer in, you can see I'm going to take out the whole tip.

Use your fingers (or pruners if you like) and snap off the tip.

Remember, the tips are edible and you can add them to salad or a stir fry.

The flowers have been pollinated and the bean pods are developing.

Spray the blackfly
Even with pinching out the tips, the blackfly will most likely still attack the beans, you've just slowed down the process. The second line of defence is soapy water, which works by clogging up the pores which insects breathe through, effectively suffocating them. Technically, it can harm all insects, including the good ones. But it dissipates quickly and doesn't really harm anything which isn't directly sprayed.

Squeeze some washing up liquid into a sprayer (see pic below) then fill to about 3 quarters. Given it a really good shake so it gets all soapy. Then squirt the soapy water directly onto the blackfly. Be really generous and drown the buggers. Also make sure to spray the undersides of the leaves as they can hid there too.

A squirty bottle with soapy water, filled to three quarters.

Make a concerted effort of spraying them morning and evening for a few days, and most will eventually be killed off. A few may hang around, but they will be weakened, and you will have saved most of your crop.

The soapy water won't hurt good bugs like ladybirds (whose larvae eat blackfly), just the bad bugs like blackfly. In fact, you can also use this solution on greenfly.

 Dwarf broad beans, in front of tall ones

Other options
Other options include ordering some ladybird larvae to be delivered to you, as these dine on blackfly quite voraciously, and they could solve your problem. I have yet to try this, so cannot say how well it works.

Some people use Neem oil for a really bad infestation. It's apparently effective, but can be hard on the plant and it can kill 'good' insects, so best kept for when you need the nuclear option.

Both Neem oil and Aspirin contain high levels of salicylates, the plant hormones involved in boosting pathogen-defending protein production in plants. Salicylic acid is also used by some plants as a signalling mechanism when they're under attack. Predatory insects and insect eating birds will follow a trail of salicylic acid, expecting a swarm of aphids or similar. So adding 1 soluble Aspirin to your soapy water is worth trying, and one I will experiment with this year.

An 'untidy' garden, particularly for ladybirds to over winter in, to increase their habitat and numbers, can help. Whilst I do this every year, and I've created a bug hotel, I've still not had much luck with increasing the number of ladybirds in the garden, so I continue to resort to pinching out tips and soapy water.

* * * * *
If you can, try to check your beans daily for blackfly. The sooner you notice and start spraying them, the better chance you have of keeping them under control.

A few days of some dedicated checking and spraying, and you can look forward to eating these!

 Just picked (last year) broad beans

P.S. Thanks to people on Mastodon (you know who you are) for sharing their experience of using Neem oil and Aspirin. To Alx who said their beans are looking much better after just a few days of the washing up liquid spray suggestion, and Xan for the extra information about how the soapy water works on the blackfly.
 
I also recommend reading a short post by a gardening professional, Saralimback, about the negative impacts of neem oil on your ecosystem.

My top tip for keeping cats, foxes and birds off your newly sown beds

Frequently I see people comment on social media about the difficulty of keeping cats, foxes and other creatures, off their newly sown beds. I thought I'd share my tip, which pretty much always works.

Right: Parsnip seed

These are newly sown rows of parsnip and beetroot.

Basically, you need some netting and something to hold the netting down. Ideally, go for finer netting, as this will also keep the birds off the seedlings. And sparrows, in particular, love the fresh germinated leaves of vegetables like beetroot, spinach, chard and lettuce.

Right: netting over young beetroot seedlings. The netting is

held down tightly so birds cannot get under it and get trapped.

When I prepare the netting, I make sure I allow not just enough to cover the space, but also enough space for the young seedlings to grow without squishing up, and then growing through, the netting. Otherwise, when you come to take the netting off, you'll pull out the seedlings. I fold under the extra netting and pin that down, then unfold it once I need to give the seedlings more room. In the picture above, you can see the netting on the bottom part of the picture has been folded over then pinned down.

Below is some netting over some salad seedlings. The glass cloche on the left is because I wanted that cultivar to grow quicker so I would a) have some new lettuce sooner, and b) by trying to get it grow quicker, I'm hoping I'll have time to harvest but also let it go to seed so I can save the seeds before the autumn frosts hit.

The lettuce seedlings (below) are now getting bigger and were just about to start growing through the netting. So I've unfolded the extra netting and have lifted it to give them more space to grow. At this point, they are still a bit young for removing the netting entirely. I've done it too soon in the past and come out the next day to see the seedlings dug up.

The seedlings are now well established and have taken over most of the space, so it's now safe to take the netting off. You can also see how the cloche made a difference, with the lettuce on the right being bigger than that on the left.

The parsnips and beetroot are slower growers, and still too young to take the netting off. It will probably be another month before they'll be established enough.

When it comes to what materials to use, as you can see, I have used plastic netting. I've had this same netting for years and it just last and lasts. Netting is also easy to water and rain through. Because these beds are permanent, I'm cutting the netting to suit each bed, and when I take it off, I'll pin a note to the netting before putting it away, noting which bed it fits for when I need to use it next time. Yes, I'm organised  :)

To hold it down, I use steel ground pegs (see right). Again, these last forever. You could obviously use other similar tools. Some people use old soft drink bottles as individual cloches that protect and encourage germination and growth. I've tried this but found I had to lift them to water the seedlings, and that was just annoying.

I have tried tricks like using hot chilli powder spread around young plants, putting in lots of sticks to keep cats off etc. These can work a bit, but you have to reapply the chilli every couple of days and after rain, and a determined cat can work around sticks. I know, my cat is quite determined!

In the end, I've found the netting and ground pegs keep all creatures off, as well as safe from being trapped under the netting, and my seedlings are protected until they have grown up enough to go net-free.

Looking from the kitchen garden back towards the house