Garden Pests

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Garden Pests

• http//www.dgsgardening.btinternet.co.uk/aphids.ht
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Aphids

• There are over 500 species in Britain,
  fortunately only a few are garden pests
• most are specific to one or two plant species.
• The Peach - potato aphid (Myzus persicae) is the
  green one which is most often seen on a wide
  range of plants, but can range in colour from
  yellow, all shades of green, to pink, red and
  almost black.

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Root aphids

• There are root aphids which attack below ground
  and with a severe infestation will kill the plant
  by removing the sap before it can rise up the
  stem. They are white and waxy, giving them the
  appearance of a fungus.

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Aphids

• The usual symptom of their presence is distorted,
  weak growth of leaves and shoots.
• A large infestation can cause roots to reduce in
  size due to the sucking activity of the aphids
  increasing the transpiration stream, so the plant
  requires fewer roots to supply the volume of
  water by normal means.
• When their numbers decrease the plant suffers.

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Aphids

• They can be carried for hundreds of miles by wind
  or air currents, and can transfer viruses as they
  move to other plants.
• They need to suck up copious amounts of sap to
  obtain the small amounts of protein it contains.
• The excess, which contains sugars is flicked from
  their bottoms and is given the appetizing name of
  honeydew.

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Aphids

• This sticks to leaves and can be colonised by
  Sooty Mould, which reduces the amount of light
  reaching the photosynthesising cells, so further
  weakening the plant.
• They are attracted by the pale yellowish-green of
  young shoots where they know there is plenty of
  sap in tissues which are easily penetrated.

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Aphids

• One species infests most Lime trees where they
  are joined by Scale insects which add to the
  problem - the honeydew can usually be seen on
  parked cars and plants below them.
• Some colonies of Ants 'herd' the aphids and
  collect the honeydew to feed their larvae they
  protect the aphids and carry them to overwinter
  in their nests.

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Aphids

• In spring and summer only females are present
  reproducing asexually by a process known as
  parthenogenesis, giving birth to live young.
• In the autumn, males are produced and after
  mating the females lay eggs which remain through
  the winter in crevices.
• The population can double in 4 - 6 days
• starting with one aphid, after one year of
  uninterrupted reproduction in perfect conditions
  would produce 250 million tons if none died!
• This means that they are a good source of food to
  other creatures including Ladybirds and their
  larvae, lacewings, hoverfly larvae and parasitic
  wasps.

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Aphid Control

• Where only a few are present they can be rubbed
  off affected shoots, after a while natural
  predators will arrive and remove them.
• A hose with good force can be used to dislodge
  them from tough-leaved vegetables.
• A spray prepared from a couple drops of
  washing-up liquid to a gallon of water as an
  acceptable organic method of control so are
  insecticidal soaps made from plant fatty acids.
• Avoid spraying in sunshine to prevent scorching
  the plant.

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Aphid Control

• Biological controls need a constant supply to
  survive, so there will always be a low-level
  presence, hopefully these will be on nearby wild
  plants. Ladybirds are nocturnal so if they are
  feeding during the day the number of aphids may
  be low.
• For chemical control use pyrethroids or
  bifenthrin - spray as late in the day as possible
  to avoid Ladybirds and other friendly creatures.
• There is evidence that Myzus persicae are
  developing resistance to the pyrethroids and
  Primocarb so it is best to vary the chemicals
  used to reduce the chances of this happening.

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Aphid control

• An acceptable organic spray is made from an
  extract of the Neem tree called Azadiractin
• Companion planting using partner plants which
  deter the aphids, eg. Borage to deter Black Bean
  Aphids.

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Slugs

• Slugs and Snails are molluscs of the class
  Gastropoda which literally translated is 'stomach
  foot'.
• Gastropods form the second largest class in the
  animal kingdom, the largest being insects.
• Of the 29 species in Britain a few are
  carnivorous, but most live on living and decaying
  plant tissue usually the plants we like to look
  at or eat ourselves!

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Slugs

• Instead of a shell like the snails, slugs have an
  internal horny plate covering their breathing
  cavity.
• There is a range of colours and sizes of slug
  depending on the species. The Field Slug is 2cm
  and grey, while the Round Back Slug can be
  5-10cm, black or brown and in some cases can have
  an orange colour on their foot.

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Slugs

• They feed by rasping ragged holes in flowers,
  leaves, stems, roots and seeds, with young plants
  the leaf feeding can kill.
• Below soil level some species attack root crops -
  the small Black Keeled Slug being particularly
  destructive, especially to potatoes and the bases
  of plant stems.
• Many species spend most or all of their life
  underground and those seen are only a small
  proportion of those present.

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Slugs

• Slugs begin to move, hatch, feed, and lay eggs
  when the temperature is above 5 C.
• During dry and cold conditions they remain deep
  in the soil.
• The wetter weather and milder winters of late has
  been very beneficial, and most gardeners have
  noticed an increase in their numbers.
• They are usually nocturnal, but will venture out
  on dull, damp days.

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Slugs

• There are three stages in the life cycle eggs,
  immature stage and adults - they can overwinter
  in any stage.
• They are hermaphrodite having both male and
  female organs, so every individual can lay eggs -
  up to 300 each in batches of 10 to 50 in moist,
  but not waterlogged, crevices sometimes down the
  sides of pots.
• One individual has the potential to produce about
  40,000 offspring.

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Slugs

• Eggs are gelatinous, watery, about 3 - 4mm across
  and usually spherical like tapioca.
• The period of development of the eggs varies
  depending on the temperature, during warmer
  weather they hatch after 10 days, but this can be
  up to 100 days in cooler conditions.
• After hatching the slug matures in less than a
  year and can live for two or more years.

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Slug control

• There are many suggestions to kill or deter this
  pest, but even the most diligent collection
  regime has been shown to have little effect on
  the damage caused.
• The best thing is to try and cope with them by
  following some general hygiene methods.

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Slug control

• Remove their hiding places and spots where they
  lay eggs, eg. rotting boards, logs, stones dead
  leaves and other debris.
• Place compost heaps away from vulnerable plants.
• But don't be too tidy as Ground Beetles which
  feed on the eggs, like to hide during the day as
  well, large stones and pebbles will do for them.
• Another creature which appears to eat the eggs is
  the New Zealand Flatworm -.

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Slug control

• use traps, eg. stones, boards, upturned pots
  empty grapefruit skins or wet sacking, the slugs
  take cover underneath and can be collected. They
  will also lay their eggs here so they can be
  destroyed as well.
• go slug hunting at dusk and chop them up or put
  them in hot water, this is the most effective
  method of reducing their numbers, but the most
  destructive species do not emerge often. The
  slimy bodies are not very pleasant to handle so
  use tweezers, chopsticks

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Slug control

• Ordinary table salt is lethal to slugs, but
  overuse is detrimental to plants and other
  creatures. It is probably best to drop them into
  a container of this, rather than sprinkling it
  about.
• A tablespoonful of oats acts as an attractant
  when placed beside more favoured plants. The
  slugs can be collected and destroyed.
• attract hedgehogs into the garden with dog food
  (not bread it clogs their digestive system and
  milk is bad for young hedgehogs). Keep them there
  with a concealed, dry home with straw bedding and
  don't light bonfires without checking for
  sleeping 'hogs.

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Slug control

• beer traps should have the entrance about 3cm
  above soil level to prevent Ground Beetles
  falling in - put a few twigs inside to help any
  which do fall in, to climb out. Beer cans can be
  quite effective,
• An alternative to beer is a mixture of sugary
  water and yeast or milk, but the best bait is
  said to be stout .
• Slugs are also partial to cat and dog food, so
  this too makes a suitable bait.
• A home-made trap can be constructed from an empty
  margarine or ice-cream tub with a hole cut in the
  side near to the top - the lid makes escape more
  difficult and stops the trap filling up with rain
  water.

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Slug control

• researchers in Hawaii have found that a 1 to 2
  solution of caffeine will kill slugs and a 0.1
  solution will deter them if is sprayed on leaves.
  However, this latter strength solution also
  scorched the young leaves of cabbages.
• frogs, toads, hedgehogs, some beetles and their
  larvae, centipedes, parasitic flies, birds,
  chickens, and ducks are natural enemies. Attract
  these creatures by providing shelter like a thick
  hedge

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Slug control

• a dry mulch will reduce slug activity, this is
  achieved using a dutch hoe in dry weather.
• Alternatives are grit, sawdust, cocco shells,
  weathered cinders, wood ash or crushed egg
  shells.
• However their protective slime can allow them to
  crawl over a razor blade or sharp glass, so these
  methods are of limited success at best and are
  usually wishful thinking!

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Slug control

• Fito Slug Stoppa granules form a rough barrier
  and absorb slime so make it difficult for slugs
  to move over them, but are quite expensive.
• Diatomaceous Earth is a dry granular substance
  made up of fossilised algae. It is applied as a
  barrier to exclude the slugs. It loses its
  effectiveness when wet, but regains it after
  drying out.

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Slug control

• a copper wire or strip placed in a circle around
  the area is said to deter by creating a
  micro-current as the slug touches it.
• Check for the presence of slugs or their eggs
  first and destroy - there is no point in trapping
  them inside!
• Strips around pots could also be decorative. A
  self-adhesive copper tape is available in some
  garden centres or online.
• There is also a woven mesh which can be erected
  as a small fence, but it must be in contact with
  the soil along its full length otherwise they
  will crawl underneath.

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Slug control

• cut the bottom off a plastic drinks bottle and
  remove the cap, to form a protective cylinder
  around vulnerable young plants.
• a slick of petroleum jelly around the top of
  containers prevents them crossing to the
  contents, but makes handling the pots difficult
  and it becomes covered with dust and leaves.
• for use when on slug patrol, make a half-and-half
  mixture of vinegar and water in a handsprayer.
  One squirt should kill them.
• Also a 1 3 mixture of household ammonia in
  water should work.

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Slug control

• a biological control is the nematode (eel worm)
  Phasmarhabditis hermaphrodita which occurs
  naturally and is used in Slugsure.
• They invade the slug and bacteria which they
  carry cause the slug to stop feeding, go
  underground and die.
• As they decompose the eel worms reproduce.
• This natural control is less effective on surface
  dwelling species as the eel worms live in the
  moist conditions below ground, but they are the
  best treatment for the underground species which
  attack root vegetables.
• Nematodes are unaffected by wet weather. They
  remain active for about 6 weeks, and need a
  minimum temperarure of 5C.
• Another brand is Nemaslug (Phasmarhabditis
  hermaphrodita), which is available by mail order
  or on-line. They can be ordered between March and
  October, and keep in the fridge for a few weeks
  after delivery.

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Slug control

• slug pellets, said to be safe by their
  manufacturers if sprinkled thinly around.
• They are dangerous to pets if they find the
  packet,
• Birds are not likely to eat them directly and
  they do not eat the corpses, but slightly
  affected slugs may be eaten and some studies show
  that the bird's fertility may be reduced.
• The same chemicals, usually metaldehyde, can be
  applied as a drench.

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Slug control

• Another slug bait is one containing ferric
  phosphate which works best in moist conditions.
• It is considered to be organic and although it is
  less effective than metaldehyde, it can be used
  where crops are grown and is not hazardous to
  pets.
• It degrades over time in the soil to iron and
  phosphate.

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Slug control

• some species or varieties of vulnerable plants
  with thicker leaves are said to be resistant.
• sacrificial plants such as lettuce planted near
  to vulnerable ones, may draw the slugs away and
  keep them interested for long enough to be picked
  up and removed.
• keeping vulnerable plants such as Hostas in drier
  conditions makes the leaves tougher and a bit
  less attractive to the slugs.