Premature defoliation may follow. Conifer species . On conifer species, the two most common needle symptoms are chlorotic mottle and tipburn. In general, mottle of young and older needles is induced by low dose exposures, while tipburn of young needles is induced by high dose exposures. There is, however, considerable overlap depending on species, within-species variation, timing of exposures, and environmental conditions.
Chlorotic mottle develops as small patches of yellow tissue surrounded by apparently healthy tissue.
The tissue, especially in young needles, may also become tan. Necrotic tips result from tip dieback or from necrotic banding, which may develop when medium-aged tissue along an individual needle is most sensitive. Eventually, the rest of the tip portion of the needle may also die, producing necrotic tips with a reddish brown colouration that fades with age. Toward the end of the growing season, these necrotic tips may break off, making affected needles appear much shorter. The tipburn symptom, especially in white pine, usually affects all needles in a fascicle equally.