Asparagus diseases, along with other garden plant ailments, are very frustrating as a gardener. It's so disappointing to have seen beautiful fresh green buds sprouting in the spring only to find that by mid summer your roses have black spot and rust,your gooseberries have mildew or, perish the thought, your asparagus ferns are looking less than healthy!
The three main diseases affecting asparagus are:
1) Rust - cased by Puccinia asparagi
2) Fusarium stem and crown rot - casued by Fusarium moniliforme, and / or F.oxysporum f. sp. aspargi
3) Fusarium wilt and root rot - caused by Fusarium oxysporum f.sp. asparagi
Lets just call them rust or rot!
All three diseases are fungal infections and over time will weaken your plants year on year to a greater or lesser extent depending on how well you control the spread.
An important point to remember when considering the effect of these diseases is that the strong vigorous growth of stem and fern that occurs through the summer enables carbohydrate to be channelled and stored in the roots of your crowns over the winter. It is this store of energy that powers the growth of your plants in the spring. If your ferns are healthy and happy in the summer you will get lots of good healthy spears in the spring. By contract if your ferns are stunted by disease your spear production in the spring will be less vigorous.
Rust has three stages each looking different.
Starting early in spring to early summer the disease shows itself for the first time as 10-20mm oval lesions ( a bit raised) light green in color turning creamy / orange and more sunken in the centre as they develop. They may not be that obvious and there will be more towards the base of the stems than towards the top.
The next stage is when the rust colour develops. This occurs during the summer when the 1st stage of lesions burst and spread rust coloured spores into the air to land on other plants and other parts of the same plant causing further infection. If you rub your hand over your ferns annd come away with a reddish tinge to your hand you've got this problem.
Finally black, over-wintering spores are produced although these may occur at the same time as the rust coloured ones.
The rust spores which land on the feathery tips will give rust coloured spots on the fronds which will grow back down the stems into browny/ red streaks which will weaken the stems growth and may can cause the whole stem to die back.
Stem & Crown Rot
If your asparagus ferns start to look rather sad, go brown and die back before the autumn and you susequently find that the roots are going black you probably have crown rot
Wilt & Root Rot
Again sad looking ferns that are wilting and generally in poor health will inidicate this disease.
If you understand a few things about these fungal diseases it will help you decide what preventative measures to take:
Even if you are starting an asparagus bed in a previously unused location away from other asparagus the fungi can be introduced from diseased crowns. You can try dipping your asparagus crowns in a fungicide solution before planting. Equally seeds can be suface contaminated with spores. An Asparagus Information Bulletin (no 202) issued by the Cooperative Extension at Cornell University suggest disinfecting seed for 2 minutes in a solution of 1 part commercial 5.25% sodium hypochloridte to 4 parts water, rinsing, drying and planting immediately unless pre-soaking is planned.
The spores live over the winter on plant debris so always cut back the ferns as they die back for the winter, remove them from your vegetable patch and burn them. Take a look at our page on
Aspargus Care if you are not familiar with this process.
Spores may also overwinter in the soil. Try not to plant a new bed in the same place as an old one or the spores that took a while to build up in your old bed as it matured will be waiting to spring into action on your new bed whilst it is still young.
The spores infect plants more easily when the plants are damp either as a result of dew or rain. Try to chose a spot for your plants that it not only sunny but has a breeze running through it to keep your plants from being overly damp.
If you know there are other asparagus beds around or you are planting over an old bed (because you have no choice) chose one of the more resistant varieties. Take a look at our Asparagus Plant Page for information on the disease resistance of different varieties of asparagus plant.
Fungi thrive in the damp and asparagus beds that hold too much mositure may lead to the "rots" setting in. If you have planted your bed on heavy soil which is holding a lot of moisture you could well get this problem.
Generally plants that have rust are more susceptible to other asparagus diseases so treat your plants well for rust to help prevent rot!
On top of that if your plants are infested with asparagus beetle they will also be more susceptible to rust and rot. For more information on the Beetles that infest Asparagus plants follow this link .
Even if you have taken all of these preventative measures your plants are still likely to end up suffering from one of these asparagus diseases at some stage in their life. So then what?
Early treatment is the key. Several fungicides are available for the control of rust. If your bed is in its first year or two and not ready for cutting yet you need to start spraying early in the spring, as soon as you have shoots, to prevent the spores from infecting the plants in the first place. Keep an eye out and re-spray as frequently as the products instructions suggest.
If your beds are in their cutting years the act of cutting will keep the beds clear of rust unti you start leaving them to grow. As soon as you have taken your last cut is the time to start spraying, again you are aiming to stop the initial infection.
If you are getting rot to any great extent your best bet is to pray for the sort of weather that enables you to keep your beds at the right moisture level. This means not too wet. If you water in the morning this allows excess water to drain away and / or dry up during the day.
Good Luck, keep those asparagus diseases under control and enjoy some great produce as a result.....
Varieties of Asparagus