Mycosphaerella dearnessii

Brown spot needle blight

Description

Rainfall and temperature are the critical factors for spore dispersal and infection, which occur from June to September. Spores are released only during rainy weather and never at low temperatures (near 2 °C). The major infection period is from late June to early July and moisture on the needle surface is necessary for spore germination. The conidia produce appressoria and penetration occurs via stomata. The incubation period is variable depending on host type and age: from 1–2 months on young needles to 4–7 months on older foliage. Acervuli develop and mature in late August and, although conidia are released in September, infection is restricted, probably due to increased needle resistance. The disease cycle renews the following summer when the overwintering fruiting bodies release conidia as temperature and rainfall increase.

Symptom

The initial signs of infestation include visible light to light yellow resin-stained spots on the needles, which later turn dark brown. The disease is manifested by the presence of brown transverse spots with yellow edging. Infected needles turn brown, dry and fall off, especially from the tops of shoots.

Tree Species: Pine, Spruce

Part of a plant- attacked: Leaf / Needle

Pest significance: Very harmful

Pest Category: Fungi

Invasive Species: Yes

Present in EU: Yes