Outbreaks of the cotton tipworm, Crocidosema plebejana (Lepidoptera: Tortricidae), related to weather in southeast queensland, Australia

The cotton tipworm, Crocidosema plebejana (Zeller), has periodically caused serious damage to seedling cotton in Southeast Queensland. An analysis of data over 11 years revealed that outbreaks of this pest are weather related. A heat/precipitation ratio (weather index) was calculated and compared with population levels of the tipworm. Outbreaks were strongly correlated to cool and wet weather during March-November, the principal growth period of the weed host Malva parviflora (L.). Infestations were minor when conditions were dry. A prediction based on this index is compared with field infestation levels in 1984.