Blackfly Epidemic

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This year the blackfly have run riot on my plot. I normally expect them on my broad beans and usually pinching off the tops of the beans when four trusses have formed controls them to a reasonable level. However this year they have attacked my climbing beans, runner beans, dwarf French beans and my relatively recently planted everlasting spinach and beetroot. This has never happened before!

They are a type of aphid that sucks  sugars from the plant causing it to have stunted and twisted growth. Ants are often seen on the leaves as they harvest some of the sugar and also clear off the larvae of ladybirds which eat the blackfly. Clever!

Heavy infestations can be hard to get rid of. A jet of water can wash them off the leaves or you can remove infested leaves completely. In terms of sprays many people swear by water with a little bit of washing up liquid or soap .There are insecticides available to the gardener that can be used on them but these may need repeat application. You can also buy natural predators that can be effective but these are really intended for enclosed spaces like greenhouses or polytunnels.

For more information about these little pests see this RHS link about them

George Gray 01/06/2023

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Allium Leaf Miner

This pest attacks all members of the Allium family - onions, shallots, garlic & leeks. The small flies suck sap from the leaves then lay their eggs in the ground near the plants in March and April and these hatch out to grubs that eat there way down the leaves and turn into brown pupae. These hatch out to flies which repeat the cycle in October- November. There are no pesticides currently available to gardeners so the only alternative with infected plants is to dig them out and destroy them (and definitely don't put them on the compost heap!). However covering the plants with fleece in March-April and then in October- November prevents the flies from laying eggs and may reduce attacks.For more information click here.

George Gray  02/06/2017
 

 

Diamond Back Moth Epidemic

 

 

Well there is a new caterpillar around in the UK that is chewing away at our brassicas and it has now been found on the site. It’s the larva of the Diamond Back Moth – an insignificant little insect (possibly small enough to get through debris netting!) but it can produce large numbers of very small caterpillars (up to 12mm long). They lay the eggs on the underside of the leaves and the larvae, when they hatch, burrow into the leaves and chew away. As they get bigger they emerge and do more serious chomping. They attack all brassicas (cabbage, cauliflower, broccoli, brussels sprouts) apparently attracted to them by their smell.

It’s originally from the Mediterranean and has been a pest in those countries for many years and to control it they have dosed it with various pesticides. As a result they are usually resistant to most pesticides available to the gardener.

 

Normally we only see it in the UK in small numbers but this year there is an epidemic of them. This seems to happen about every ten years –no one knows why. Fortunately, whilst they set the plant back, they usually don’t kill them off so they should eventually recover

 

If you get them you could try garden pesticides but they may be ineffective. However I have not tried the old organic favourite of soapy water. The alternative is to pick them off individually – a mammoth task on big plants!

 

George Gray Summer 2016

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An Epidemic of Broad Bean Aphid

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This year my broad bean crop has been decimated by black bean aphid. This little bug commonly attacks broad beans as they flower but usually does not cause major damage to the crop so I don’t even bother pinching out the top of the plants after four trusses have grown as recommended in the books. However this year my plants have hardly a single broad bean pod to their name and are covered in the little beggars.
Here is an article about them.
Turns out I am not alone. The last couple of fairly mild winters have lead to an epidemic of them affecting both commercial and home crops. See this link to a newspaper article about it.
The best way of stopping them them is prevention by spraying with insecticide or a soap solution regularly and early on. But at these levels it will be a long process!

George Gray Summer 2015
 

The Broad Bean Nibblers

This time of year we get problems with our broad bean leaves being nibbled at the edges. This is due to the pea and bean weevil-Sitana lineatus. The beetles overwinter in leaf litter, emerge in late spring and lay their eggs near the surface of the soil. The grubs hatch out and live off the nitrogen fixing nodules on the pea or bean plant roots. However generally this does not have a big effect on growth. When they pupate to beetles these nibble away the edges of broad beans and the shoots of peas.Usually, if the plants are big enough, they only put back growth a little bit. However, if the plants are small or with larger plants occasionally in bad years it can kill off entire the plant. Here is an article on the RHS website about it with information on how to control it.
On our site many people have found that spraying with a weak soap solution is a very effective organic way of stopping it in its tracks!

George Gray & Stella Turner Spring 2015

Something’s eating the Sweetcorn!

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Many allotment holders grow sweetcorn on the site. It used to be a touch and go plant in the past but nowadays with seeds available that are suited to our climate you can usually guarantee several sweet and juicy cobs – ideal with lashes of butter.
However this year and over the last few years we have noticed a problem. When we come to pick our corn we find the cobs have been eaten away on the plant. The whole or most of the cob has had the outer husk stripped off it and all or most of the seeds taken.
The trouble is of course while we find freshly picked cobs irresistible so do many other birds and animals. Rats, mice and badgers can attack sweetcorn.  However the consensus seems to be that the culprits on our site are birds – probably wood pigeons, crows and magpies (we have a lot of all three on the site).
They perch on the cob, use their beaks to strip open the husks and eat away.
Not all plotholders sweetcorn is affected and I think this is down to the variety. I grew both "Rising Sun" and "Extra Earl" this year. "Rising Sun" was decimated but "Extra Early" only had a few small areas of husk attacked as was otherwise OK. I suspect the reason is that for the birds some varieties of sweetcorn have husks that are harder to strip than others.
Well what can we do about it! We can cover the corn in netting (we only should need to do this when the cobs are beginning to ripen). If we grow dwarf varieties it will make the netting easier.
Alternatively we can cover the cobs to protect them. One thing I have heard of people using is old 1 litre pop bottles cut off at the base. Others have used paper bags but I suspect birds would peck through these!

George Gray

 

Leek Moth

 
Several Plotholders have found that their leeks have tunneled leaves and contain small green/yellow grubs. These are due to the leek moth which lays its eggs at the base of the plants, usually twice a year -  in Spring and then Late Summer. At its worst the leeks are turned into a squidgy mess and are unusable.This is the first time I can remember anyone finding these little beasties on our site. They only came to the UK in the 1990s and are slowly working their way inland from the South East Coast  and now it looks like thay have reached the Midlands. They can also attack onions and garlic so keep an eye out!
Click here for a fact sheet from the RHS about them.
Control is not easy as apparently most insecticides available to gardeners are not supposed to be very effective - although we would be interested to know if any of our non-organic gardeners have had any success!. The usual advice is to remove and destroy all plants and of course not to put them on the compost heap! Prevention is similar to that for carrot root fly i.e cover the plants with Enviromesh to prevent the moths getting in to lay their eggs.

 

George Gray

Potato Blight

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This year potato blight came early to the site due to the exceptional prolonged wet weather. Some plotholders have had early evidence of blight but at the time of writing most people seem free.This devastating plant is disease due to a fungus that spreads in the air. When it lands on wet leaves and stems of potato and tomato plants it enters them and quickly kills them off. If left unchecked the fungi fall to the ground and infect the tubers turning them into an inedible mushy mass. When does it happen? The key thing is to be on the look out for it and catch it early. Usually it only appears when it is fairly warm - when the daily temperature is never below 10ºC and when we have had high humidity and rainfall for at least two days. These are called “Smith Periods” and you can get warnings of Smith periods in your area from the Potato Council. Just because you have had a Smith Period doesn’t mean you are going to get the blight but it alerts you to look out for it. What to look for? The next thing is to check your plants for evidence of attack. In the early stages blight can be confused with other things such as other fungal infections, the natural die back of plants ending their growth period and magnesium deficiency. Here is an organic gardening website with details of what to look for on the leaves and stems. Blight Resistance I have found that outdoor tomato plants get them first as they have very little resistance – so they act like an early warning sign! In the past many varieties of potatoes had resistance to the blight fungus but in the last few years a new variety of fungus has emerged and these varieties now have much less resistance to this new form. The Savari Research Trust in Wales has produced some new potato varieties with good resistance that are available to the grower but they are said to have a flavour some people like and others don’t! JBA Seed Potatoes is a company that sells specialist poatoes to the amateur grower with resistance to blight and other of teh many pests potatoes seem to be plagued by. What to do about it? If you find a few blighted leaves cut them off and dispose of them. If you have a dry period it may stop the blight in its tracks as it needs to land on wet leaves to spread.
If the attack is bigger then you could try spraying with fungicides. Amateur gardeners have a more limited range of these available compared to commercial growers. The ones we can used are copper based such as good old fashioned Bordeaux Mixture or the more recently available Bayer "Fruit and Vegetable Disease Control"(copper oxychloride) which you can get in Garden Centres. However if you wish to be totally organic or the damage is extensive then the only answer is to cut off the potato stems at the base and dispose of them. This stops the fungus spreading to the tubers. You may have a reduced crop but at least you will have some potatoes this year!

George Gray Plot 32

Moles

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I hadn't heard of these being a problem on the site before but people tell me them have been around for a while but have recently become particularly invasive. They seem to throw up their molehills mainly on plots near the railway line but recently have crossed the path and started digging on the other side of the path. They don’t eat plants of course but can damage the roots of plants and one plotholder thinks they are the cause of a poor showing for this years first early potatoes. However on unused areas they actually help to turn the soil over – they are nature’s rotovators!
Here is a link to an RHS webpage giving advice on how to get rid of moles. If they are a problem to you I would suggest you talk to one of the Committee members before doing anything as you may simply move them