Problem Area - Plant Pests

I decided to start the series of Problem Area's off by focusing on Plant Pests that we all encounter in our gardens.

But first ... What exactly is a Plant Pest? 

A Plant Pest gains it's nutritional requirements from the host plant it feeds upon. 

There are various ways which it can gain it's sustenance but broadly speaking it either eats or sucks a plant's sap.

It's a good idea to take note of a pests life cycle as they are more vulnerable at certain stages.

Here you can find all of the Pests in one place that I detailed in the posts.

VINE WEEVIL

Vine Weevil attacks a large range of plants both indoors and outdoors, they are especially common in container plants.

First of all the Vine Weevil comes in two forms, the larvae and the adult beetle.
Here's what you are looking for ... due to me not having this pest personally in my garden (famous last words) I have provided photo's from the RHS website so you know what to look for due to not having any personally.

Photo's from the RHS website.

A LITTLE BIOLOGY 

I won't bombard you with too much information, but here's a brief description of their life cycle.

Vine Weevil over winter outdoors or under un-heated glass as soil / compost inhabiting larvae. Female Weevils (they are all females) emerge during late May / June and begin laying eggs after they've been feeding on plant material for 21-45 days. The eggs hatch within 2 weeks and burrow themselves into the soil. Each female Weevil can lay up to 200 eggs. The Larvae will grow slowly in the soil over the Summer, maturing by Autumn at about 5/8 inch long and will pupate the following Spring. 

Adult Weevils are easier to spot out of the two with them being above ground. However they will hide during the daytime at the base of plants or in mulches as they are shy in nature. Their activity mainly happens at night when they come out to feed on plant foliage. They are slow moving insects that cannot fly, but are good at crawling and climbing.

The Larvae is what causes the most damage out of the two. The Larvae buries down into the soil and eats the roots of plants during Spring and Autumn. In large numbers they can be detrimental to the plant.

SYMPTOMS

An indicator of Larvae in your soil (ground or container soil) will be the condition of the plant. When affected the plant will turn brown, wilt and die. If you lift the plant out of the pot you will notice that the roots have been eaten away.

Adult Vine Weevil chew notches into plant foliage, this can also be an indicator that larvae are present in the soil beneath.

Photo from the RHS website.

CONTROL

If like me you like to garden Organically there are a few things you can do -

* On mild Spring & Summer evening pick the Adult beetles from plant foliage at night. 

Shake affected plants over some paper to dislodge and catch as many as you can.

* In Greenhouses you can check under pots and staging where the adults may be hiding during the day.

* Encourage natural predators such as birds, frogs, hedgehogs and ground beetles.

* Good drainage can be beneficial.

You can gain control over the pest biologically by using Nematodes. 

This is a living bacteria which is watered onto the affected area. Ideally apply this in August / September when the soil is still warm. (5c - 20c) and before the larvae has grown large enough to cause serious damage.

This has been known to be less beneficial in dry and clay soils.

There is also Chemical control available.

APHIDS

I'm pretty sure that every gardener has encountered problems caused by Aphids.
These attack plants both outside and undercover. There are many types of Aphids which all have their preferred host plants and particular life cycles but today I am focusing on the one I find most common and encounter the most problems with them inside my Greenhouse. Green and Black aphids are the most common however you can also get them in orange, red and brown.

Photo from Google.

A LITTLE BIOLOGY 

As mentioned earlier each type of Aphid has it's own life cycle. Aphids can breed at an extremely quick rate with each Aphid being able to start breeding at just a week old. They usually spend the Summer on one host plant moving to another for the Winter and you can usually find them on young plant growth as this is what they favour.

SYMPTOMS

Aphids are sap sucking pests so any weakened or distorted growth can be a sign that a plant is undergoing an Aphid attack. This can lead to Virus Diseases being introduced to your plants as Aphids are carriers and help spread disease. Aphids are very common in nursery stock production so always check any new plants that you are considering buying for any signs of Aphids.

Photo from Google.

CONTROL

If like me you like to garden Organically there are a few things you can do -

* Check the undersides of plant foliage and if you find any, simply squash them with your fingers. You can wear gloves if your a little squeamish! 

* Encourage Natural Predators such as Ladybirds who will feed on many of the Aphids.

* Wash away the Aphids with a strong jet of water, however be careful doing this on delicate plants as you can end up blasting petals off!

* Avoid over feeding plants as this encourages soft growth with is particularly vulnerable to Aphids.

There is also Chemical control available.

CABBAGE WHITE BUTTERFLY

The Cabbage White is something that can cause real frustration to many gardeners!
As the name suggests they are particularly attracted to Cabbages.

Photo from Google.

A LITTLE BIOLOGY 

A Cabbage White Butterfly starts life as eggs laid on the underside of a cabbage leaf. The larvae then proceed to feed on the host plant. The larva gradually turn into Caterpillars then when they have reached maturity attach themselves to a leaf or stalk to pupate. When the pupae matures the wings become visable and a butterfly emerges.

SYMPTOMS

The larvae and Caterpillars feed on the host plants and damage can be seen on the foliage. The larvae of the Small White feed on the centre of plants on their own. The larvae of the Large White feed in colonies and can cause the most damage.

Photo from Google.

CONTROL

If like me you like to garden Organically there are a few things you can do -

* A layer of protective fleece or film can be laid over your crops creating a barrier preventing the adults laying their eggs. Obviously this is only effective before the pest has arrived.

* Pick off and remove Eggs, Larvae and Caterpillars once spotted.

* Encourage natural predators.

There is also Chemical control available.

* PLEASE NOTE - Try not to confuse the Cabbage White with a different Butterfly species.

TWO SPOTTED MITE

The Two Spotted Mite is also most commonly known as the Glasshouse Red Spider Mite and is a rather common pest. They are mostly found is Glasshouses / Greenhouses and can be quite a troublesome pest to plants under cover. This is a pest that I personally had a problem with earlier in the year.

Photo from RHS.

A LITTLE BIOLOGY 

The life cycle of a Two Spotted Mite depends on the temperature and can be between 3 - 30 days. The females lay the eggs on the underside of leaves which then hatch into 6 legged larvae. The females can become adults in as little as 36 hours and lay 4 - 8 eggs a day! Their colouring is most commonly red but they can also be a straw / green colour, the red colouring appears when they are starved. The mites can over winter on plants and in the cracks / walls of Greenhouses. 

SYMPTOMS

As the photograph above shows one of the easiest ways to spot them is by their webs. The webs are formed when there is a large amount of the mites.
Damage to foliage on plants is also an indicator of the mites presence as they suck the sap from plants.  Yellow speckled foliage which then leads to shrivelling and death of the leaf is common sign that the mites are present.

Photo from Google.

CONTROL

If like me you like to garden Organically there are a few things you can do -

* Maintaining good plant hygiene by removing any affected foliage straight away

* Keeping Greenhouse structures clean

There is also Chemical control available.

GLASSHOUSE WHITEFLY

As the name suggests this pest is most commonly found under glass, although they can be found on plants outside. If left untreated this pest can cause havoc to your plants and is pretty common in all of our gardens.

Photo from RHS.

A LITTLE BIOLOGY 

The Glasshouse Whitefly can breed continuously under cover, the eggs can develop into adults within 3 weeks, a little longer in the Winter. They prefer warm conditions which is why they are most prevalent under cover. 

SYMPTOMS

Damage from this pest to our plants is caused by their piercing mouthparts which withdraw large quantities of sap from plants. This causes mottling to the foliage, yellow discolouration and wilting. If the pest is left to breed and form large quantities the affected plants may be killed.
The pest can also produce a sticky substance on the host plant which can help us gardeners identify them.
Plants that are more susceptible than others are Tomatoes, Cucumbers, Primulas, Dahlia's, Chrysanthemums and Calceolaria (Ladys Purse).

Photo from Google.

CONTROL

If like me you like to garden Organically there are a few things you can do -

* Maintaining good plant hygiene by removing any affected foliage straight away

* Hanging Yellow Sticky Traps under glass - please note that this can however catch the good guys along with the pests.
* Constant checking of plants to remove the pest at first sight

* Biological control can be gained by the introduction of a parasitic wasp (these can be purchased via mail order) at first indication of the pest.

There is also Chemical control available.

RABBITS

To the non gardener these may not seem that problematic, however those that do garden know how much damage these balls of fluff can cause!

You may think that Rabbits only cause damage in gardens out in the countryside but 2 years ago my garden was visited by a rabbit and I live in a cul-de-sac situated within a town.

A LITTLE BIOLOGY 

The main breeding season for Rabbits is between January - May but they can be produced throughout the year. An average litter consists of between 3 - 6 young. Females can become pregnant again after just 1 day from giving birth and produce up to 5 litters a year. 

Rabbits often live together in colonies known as warrens. 

SYMPTOMS

Damage from this pest to our plants can be done to a wide range of plants. One of the most common signs that you have a problem with Rabbits is the damage they can cause to young Tree's, such as ring barking (see photo below). It's also worth noting that plants that aren't susceptible to Rabbits at maturity can be when they are at a young growing stage and eaten away.

Photo's from Google & RHS.

CONTROL

If like me you like to garden Organically there are a few things you can do -

* Young Tree's can be protected by using Tree Guards / Tree Shelters.

* Ensuring that valuable or young plants have physical barrier.

* Growing Plants known to be 'Rabbit Proof' such as -
Monksood - Acontium carmichaelii 'Kelmescott'
Lily - of - the - Valley - Convallaria majalis
 Day Lily - Hemerocallis atrina
Michaelmas Daisy - Aster amellus 'King George'
                                     Aster cordifolius 'Silver Spray'
                                    Aster novi-belgii 'Royal Ruby'
Crane's Bills - Geranium himalayense
                                           Geranium endressi 'Wargrave Pink'
Japanese Anemone - Anemone hupehensis var. japonica

There is also Chemical control available in the form a repellent spray, which may need to be re-applied after rainfall.

STEM / BULB EELWORMS

These can be particularly problematic to the roots, tubers, bulbs leaves or stems of a plant.
This is most common between the months of March - May.
One of the tell tale signs is that the plant growth is stunted and foliage has a chlorotic (yellow/green) appearance that may appear wilted / droopy.
Narcissus bulbs are particularly susceptible and may be come soft when infected.
These can be hard to find as they live inside the tissue of the plants / bulbs and can only be seen with a microscope. However if you cut a bulb in half and can see tell tale signs of brown rings without any sings of maggots then you can see that this pest is present.
To get rid of this disease you need to dig up and dispose of any affected bulbs and any others that may not even seem affected in a 1m radius as the eelworms can spread via leaf contact or the soil if left untreated.

Photo from RHS

CONTROL

If like me you like to garden Organically there are a few things you can do -

* Always ensure that you buy good quality, firm bulbs and check them all before planting.

SLUGS & SNAILS

Pretty much everyone, gardener or not can identify these two pests in their gardens. They can cause damage all year round to plants but they are most problematic in the Springtime to seedlings and emerging young growth.

Photo's from RHS

A LITTLE BIOLOGY

Slugs are soft bodied molluscs that mostly feed at night and leave tell-tale slime trails which can alert you to where they may be. They can vary in size and colour and they live on or just below the soil surface. Unlike snails, slugs remain active throughout the year, even more so in milder, wet conditions and reproduction happens mostly in the Spring and Autumn.

Snails are easy to spot because of their shells, are less common on acid soils and can move more freely over dry terrain than slugs.
As I mentioned above Snails are dormant in late Autumn / Winter time often clustering together in protected areas. Reproduction also occurs mostly in the Spring and Autumn.

SYMPTOMS

A great deal of damage can be caused by these pests as they will eat the soft tissues of leaves, stems and roots and can climb up to a fair height above ground level. Most of the damage will be done at night, especially to seedlings and young plants.
The slime they produce can reduce the quality of your crops and lead to fungus / rot.

Photo from Google.

CONTROL

If like me you like to garden Organically there are a few things you can do -

* Pick off and remove the pests after nightfall when they are easier to find.

* Ensuring that valuable or young plants have physical barrier.
* Grow on any young plants so that they have good strong, healthy growth before planting out.
* Turn over any hiding places for predators (e.g. birds) to find.
* Growing Plants known to be less likely to be eaten, there are quite a few varieties that can be found over on the RHS website.
* Biological control can be gained against slugs by the use of Nematodes.

There is also Chemical control available.

LILY BEETLE

As the name suggests these are common pests to Lillies and Fritillaries and are distinguishable by their red colouring. As you can see from my photo below the adults can be found on and near other plants but it's only on Lillies and Fritillaries that their eggs are laid and grubs develop upon.

A LITTLE BIOLOGY

Lily Beetles or Red Lily Beetles as there otherwise known overwinter as adults under the soil, leaves and other sheltered places. This can be anywhere and not always near the plants that they favour. The beetles emerge on sunny days during March / April time when they start to look for foliage on host plants. Adults lay their eggs on the underside of leaves from April to mid - summer which hatch and the larvae then feeds on the foliage. When fully fed the larvae will go under the soil to pupate and emerge as adults during the summer. There is only one generation per year so unlike other pests these new adults will not mate until the following year.

SYMPTOMS

Foliage on Lillies and Fritillaries is eaten away by the grubs hatched from eggs on the underside of leaves. The eggs are in clusters of orange/red and are sausage shaped, the larvae are about 6-8mm long and reddish brown, usually covered in their own black excrement. These grubs usually graze on the underside of leaves, resulting in dry white / brown patches and older grubs can devour whole leaves starting at the tips working back towards the stem.
Adults make rounded holes in the leaves when feeding and will also feed on petals & seed pods.
These attacks in Summer can lead to undersize bulbs developing which can hinder flowering the following year.

Lily Beetle Larvae Photo from Google.

Adult Lily Beetle Photo from Google.

CONTROL

If like me you like to garden Organically there are a few things you can do -

* Pick off and remove the pests as soon as you spot them.
If you only grow a few of these plants start inspecting them regularly from March onwards for any signs of the pest.
* Grow a variety that is claimed to be Lily Beetle tolerant -
Lillium (Lily 'Defender Pink').

There is also Chemical control available however please note that if you choose to use this please avoid spraying on plants in flower to avoid harming any innocent pollinating insects.
These products are also usually only beneficial on the young newly hatched larvae rather than the adults.