R2103 3.2 Describe the life cycle of garden pests

Question 1

Lifecycle: Cabbage White (Large White) Butterfly

Answer 1

• Adults butterfly lay eggs on underside of brassica leaves. Up to 20-100 yellow eggs
• Have two generations during the summer
• When fully fed caterpillars leave the plants to pupate
• Pupate on suitable vertical surfaces above ground level
• Egg>larva hatches>growth of larva>pupa>adult

Question 2

What is complete metamorphosis?

Answer 2

Egg>larva>pupa>adult

Question 3

What is incomplete metamorphosis?

Answer 3

Egg>nymph>adult

Question 4

What is an instar?

Answer 4

The stage between each moult. The newly hatched larva is called a first instar.

Question 5

Lifecycle: Black Bean Aphid

Answer 5

1. Much of the year colonies consist of wingless females that give birth to live young
2. Winged forms develop when over crowding or deterioration in the host plant induces a need to move to another plant
3. Most aphid species overwinter as eggs, but some can remain as active Aphids in mild winters or on indoor plants
4. Annual cycle involves two different host plants
5. The plant on which overwintering eggs are laid is usually a tree or shrub. In spring eggs hatch and feed on young foliage.
6. By early summer foliage is older and tougher. So winged forms of the aphid migrate to summer host plant. This is usually a non-woody plant with soft succulent foliage.
7. Females may have five young per day, and they can produce new young within 14 days.

Question 6

Lifecycle: Glass house whitefly

Answer 6

1. Both adults and eggs are found on the underside of leaves
2. Each female adult with lay up to 200 rugby balled shaped eggs on underside of leaves, often in neat circles.
3. Eggs start as white but darken to almost black before hatching
4. Legs of nymph degenerate and the nymph becomes and immobile scale (pupa), feeding for two weeks before pupating.
5. Adults emerge 10 days later
6. Egg to adult and take 3 weeks at 21 degrees

Eggs>crawler>second instar nymph>third instar nymph>fourth instar nymph>adult

Question 7

Lifecycle: Vine weevil

Answer 7

1. Adults are dull black beetles and cause some damage.
2. Soil dwelling larvae cause massive damage to roots. Can kill plants.
3. Females lay hundreds of eggs between April to September, next to roots of preferred plants. Eggs are brown and leff 1mm diameter
4. Larvae pupate in the soil before developing into an adult

Question 8

Life cycle: Slug

Answer 8

1. They are hermaphrodite
2. Mate in spring and summer
3. Lay up to 50 spherical yellowish-white eggs under logs, stones and pots
4. After 3-4 weeks slugs hatch out and cause damage immediately
5. Overwinter as young or adult slugs or as an egg
6. Life expectancy 6-12 months

Question 9

Life cycle: Potato cyst eelworm

Answer 9

1. Females kay microscopic eggs in the soil or within affected plants
2. Larvae hatch and mature in about 3 weeks in summer
3. If plant dies eelworms move out in search of new plants to feed on.
4. The white, yellow or brown cysts are the swollen bodies of the female eel worms each containing up to 600 eggs.
5. Eggs hatch when stimulated by chemicals released from potatoes
6. On finding a potato root they invade them
7. Females grow and swell within the root to erupt though the root wall, whilst the head remains embedded in the root
8. When mature they release a chemical that attracts males
9. After mating the body wall of the female hardens to form the cyst which protects the fertilsed eggs within.
10. Eventually female dies and falls off roots or is dislodged.
11. Can be wind blown and transferred to other sites by dirty equipment or soil