2.3 Insects and Pests

Aphids

-aphids are small, pear-shaped insects with soft bodies that use their mouth to pierce the plant and suck out nutrients

-they range in color from green to black, depending on species.

-a pair of tube-like structures protrude out of its hind quarters, called a cornicle (Distinguishing factor)

• Symptoms

  -They typically congregate and feed around the stem and leaves, leaving their skin casts on the underside of leaves

  -unlike other pests, they do not rapidly disperse when disturbed

  -They excrete a sticky substance called honeydew that turns black and moldy.

  -leaf curling and distortion is also a symptom of aphids

• Prevention

  -check plants regularly

  -hose or prune off sections that show signs of infestation

• Treatment

  -chemically - insecticide

  -culturally - parasitic wasps

Fungus Gnats

-the full-grown fungus gnat is a small black pest that resembles a mosquito

-they are a nuisance but don’t pose a threat to humans or plants

-the larvae, however is laid in the soil and will damage roots and prevent growth.

• Symptoms

  -fungus gnats are not strong fliers so they are seen crawling or hovering around growing media, foliage or wet mulch.

  -The larvae thrive in moist environments like soil and leave shiny trails from their excretion

• Prevention

  -Use sticky pads to capture adults

  -reduce soil moisture

  -clean up plant debris

• Treatment

  -chemically - insecticides

  -culturally - nematodes

Leaf Miner

-at 1.8mm adult leaf miners are brightly colored and have clear wings

-females puncture the leaves and lay their eggs inside the tissue

-then they hatch, the larvae feed on the leaf till they are ready to pupate in the soil

-during an infestation the punctures from egg laying and larvae mines will damage the plant and take away from aesthetic value

• Symptoms

  -larvae form mines inside the leaf during their feeding, usually following the veining pattern

  -depending on species of leaf miner, the mines can be visible from either the top or bottom of the leaf

• Prevention

  -Use sticky pads to capture adults

  -check plants regularly

  -keep area free of weeds

• Treatment

  -Chemically - insecticides

  -Culturally - predatory mites

Leaf Hopper

-almost a quarter inch in length, very fast moving and jump when disturbed

-females lay their eggs inside the plant tissue, which causes pimple-like sores to form.

-once the eggs hatch, the nymphs will molt several times, leaving skin castings on the underside of the leaf until fully grown

• Symptoms

  -speckled white marks on the leaves from their feeding

  -eventually too much feeding will cause the leaves to curl and brown.

• Prevention

  -check plants regularly for castings

  -keep area free of weeds

• Treatment

  -chemically - insecticide

  -culturally - predatory wasps or ladybird beetles

Mealy Bugs

-tiny wingless, soft-bodies insects that measure only 1/20 to 1/5 an inch

-oval shaped and covered in a mealy or cottony wax, causing them to get mistaken for wooly aphids

• Symptoms

  -when mealy bugs congregate on a plant they cover it in a white cottony mass as they feed on the plants stems and leaves

  -in some cases they produce a sticky substance called honey dew that will eventually turn black and moldy

  -overtime an infestation will slow growth of the plant

• Prevention

  -check plants regularly

  -hose or prune off sections that show signs of infestation

• Treatment

  -chemically - insecticide

  -Culturally - parasitic wasps

Scale

-There are many species but the females are round and wingless with no recognizable body parts.

-stick their mouthparts into the plant and suck the nutrients out

-males are rarely seen they are small yellow or white winged flies with an antenna

-females scales are either armored or soft

• Symptoms

  -an infestation will cause the plants growth to slow and leaves to appear dehydrated

  -some scales produce a sticky substance called honeydew that will eventually turn black and moldy

  -a few scales, and even high concentrations of certain species, will not harm plants

• Prevention

  -monitor the plants for signs of honeydew

  -set tape traps

• Treatment

  -Chemically - insecticide

  -Culturally - ladybird beetle

Shore Flies

-smaller then the typical house fly, shore flies have short legs, an antenna and their wings have white circles on them

-they breed in overwatered areas that have a good source of algae

• Symptoms

  -they are not harmful to plants

  -their excrement will form small specs on the leaves, lowering the aesthetic value

  -they can also spread fungal diseases inside the greenhouse

  -typically they congregate near irrigation equipment and under benches where algae can grow

• Prevention

  -avoid over watering

  -use sticky pads

• Treatment

  -chemically - insecticide

  -culturally - correct / adjust watering

Snails / slugs

-both these pests belong to the mollusca phylum and share similar characteristics

-snail has a spiral shell snail does not

-both secrete mucus to help them move which create a slime trail

-both are sensitive to the sun / they typically only come out at night or cloudy days

• Symptoms

  -snails and slugs chew on plants and leave holes with smooth edges in the plants.

  -they also like to eat decaying plants, fruit and flowers.

  -to tell if the bite marks where made by a mollusk and not another kind of pest, look for the slime trail

• Prevention

  -check in cool, moist areas for hiding snails/slugs

  -routinely check plants and pick snails/slugs off by hand when necessary

  -create a copper barrier

• Treatment

  -Chemically - molluscicide

  -Culturally - no treatment listed

Spider Mites

-spider mites live in colonies and usually move on the underside of leaves.

-the webs they spin help distinguish a spider mite infestation from other pests

-adults are oval shaped with 8 legs and red eye dots near their head

• Symptoms

  -spider mites suck nutrients from the leaves and in high concentrations they can severely damage the plant.

  -The first sign is white speckles or stippling effect on the leaves and then webbing will begin to appear.

  -The plant can show signs of dehydration, causing leaves to yellow and drop off

• Prevention

  -Prevent dust from accumulating by sweeping or spraying

  -routinely check the undersides of leaves

• Treatment

  -chemically - miticide

  -culturally - predatory mites

Thrips

-suckling insect that measures 1mm in length and has fringed wings

-they feed on plant tissue, fungal spores and pollen.

-range from bright red or yellow to a dark brown or black

-sometimes they are introduced on purpose to help control other pests but once all the other pest is gone they will start eating plant material

-they also transfer diseases among plants

• Symptoms

  -Thrips cause white speckles or stippling, which gives the leaves a silver look. they also leave black dots from their excrement

  -plants suffering from tospovirus will typically have western flower thrips present.

  -an infestation will lead to scaring, distorted growth and lower aesthetic value.

• Prevention

  -gently shake plants that you suspect to be affected

  -use sticky pads

  -prune off sections that show signs of infestation

  -keep area free of weeds

• Treatment

  -chemical - insecticides

  -culturally - parasitic wasps

Whiteflies

-not actually flies, they are winged insects that have a waxy white covering on their bodies and their wings are held in a roof like manner

-they reproduce rapidly in warm weather and little can be done once a large colony has been established.

-they suck the sap out of plants and secrete a sticky substance called honeydew which eventually molds and turns leaves yellow

• Symptoms

  - tend to congregate on the underside of leaves

  -they will cause symptoms similar to dehydration in plants

  -they also cause plant discoloration and distortion

• Prevention

  -prevent dust accumulation

  -use sticky pads

  -hose or remove sections of the plant that show infestation

• Treatment

  -chemically - insecticide

  -culturally - ladybird beetles