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Subjects · Leaving Cert Agricultural Science

Leaving Cert Agricultural Science: Weeds, pests & crop disease

How often Weeds, pests & crop disease comes up on the Agricultural Science papers, every year it was asked, and questions to try.

HL Asked on 4 of the last 5 Higher Level papers, most recently in 2025. most years

OL Asked on 4 of the last 5 Ordinary Level papers, most recently in 2024. most years

Weeds, pests & crop disease, Higher Level(6 marks)

Quick ones on Weeds, pests & crop disease.

(a)Potato blight is caused by...
  1. A virus spread by aphids flying from plant to plant
  2. Phytophthora infestans, a fungus-like organism
  3. A soil bacterium that enters through roots
(b)Releasing ladybirds to control aphids is an example of...
  1. Cultural control
  2. Chemical control
  3. Biological control
(c)What is a selective herbicide?
  1. One that kills certain weeds, not the crop
  2. One that kills insects on the crop
  3. One that kills every plant it touches
Show the answers

(a) Phytophthora infestans, a fungus-like organism

(b) Biological control

(c) One that kills certain weeds, not the crop

Your turn: Higher Level questions on Weeds, pests & crop disease.

Higher Level

Asked on 4 of the last 5 Higher Level papers, most recently in 2025. most years

Every paper, year by year

YearWhere it came up
2025Q15
2024Q8, Q18
2023Not asked
2022Q18
2021Q2a

Links open the State Examinations Commission’s paper for that year.

More Weeds, pests & crop disease questions

Weeds, pests & crop disease, 2 marks

Which of these is a fungal disease of cereals?

  1. Barley yellow dwarf virus
  2. Aphid damage
  3. Septoria
Show the answer

Septoria

Septoria causes leaf blotch in wheat and is spread by rain splash. BYDV is a virus spread by aphids, and aphids are insect pests.

Ordinary Level

Asked on 4 of the last 5 Ordinary Level papers, most recently in 2024. most years

Every paper, year by year

YearWhere it came up
2025Not asked
2024Q17
2023Q12, Q14
2022Q6
2021Q1b, Q3a, Q3b

Links open the State Examinations Commission’s paper for that year.

More Weeds, pests & crop disease questions

Weeds, pests & crop disease, 2 marks

Potato blight is caused by?

  1. A virus spread by aphids
  2. An insect pest
  3. A fungus-like organism
Show the answer

A fungus-like organism

Blight (Phytophthora infestans) spreads by spores that kill leaves and rot tubers. It caused the Great Famine; spraying protects the crop.

Weeds, pests & crop disease, 2 marks

Potato blight spreads fastest when the weather is?

  1. Hot and very dry
  2. Mild and humid
  3. Cold and frosty
Show the answer

Mild and humid

Blight spores need moisture on the leaves and mild temperatures. Met Éireann issues blight warnings so farmers can spray in time.

Weeds, pests & crop disease, 2 marks

Aphids damage cereal crops mainly by?

  1. Sucking sap and spreading viruses
  2. Eating the roots underground
  3. Boring into the stems
Show the answer

Sucking sap and spreading viruses

Aphids feed on sap and carry viruses, such as barley yellow dwarf virus, from plant to plant. Ladybirds are natural predators of aphids.

Other Agricultural Science topics

All of Leaving Cert Agricultural Science