Hollyhock rust

Question 1

what time of year is this most damaging?

Answer 1

wet summers

Question 2

describe the damage

Answer 2

lower surface of lower leaves affected first with raised grey spots.

later in summer raised reddish-orange spots can be produced on lower surface of leaves.

At severe levels of infection, leaves will shrivel and die.

Stems may have a cankerous appearance

infection leads to stunted plants

Question 3

life cycle and spread of hollyhock rust

Answer 3

Two types of spores. Carried by wind and rain droplets.

Teliospores are large and can survive winter so in damp cond. infect young shoots in late spring

in warmer months, infection cycle takes 14days from infection to mature leaf spot and a new cycle takes place if weather damp.

Question 4

cultural control methods

Answer 4

remove and burn heavily infected plants

dont use self saved seed

treat as biennials, remove after flowering period

if rust levels low, cut stem back to ground level in early autumn and dispose of all material.

avoid dense planting and having Malvaceous plants nearby

Question 5

what is a malvaceous plant?

Answer 5

species related to hollyhocks eg:

Hibiscus

Question 6

chemical controls for hollyhock rust are

Answer 6

apply twice a week from mid-may onwards.

eg: myclobutanil