Effect of temperature and host plant on survival and development of Altica litigata Fall

Abstract

Altica litigata Fall (Coleoptera: Chrysomelidae) is oligophagus, feeding on numerous plants in the Lythraceae and Onagraceae families which include weeds and cultivated plants, such as primroses (Oenothera spp.) often found in commercial nurseries. Adult A. litigata are important pests of crapemyrtles (Lagerstroemia spp.; Lythraceae) grown in container nurseries in the southern United States. The severity of the pest problem attributed to feeding by these beetles has increased substantially during the past decade. Whereas commonly recommended pesticides easily control these beetles, knowing when to time applications to avoid large defoliation events could focus scouting efforts and prevent economic loss. The objective of our research was to define more closely the relationship between temperature, host plant and development of A. litigata to permit prediction of damaging stages of the beetle on landscape and nursery plants. A. litigata completed development between 15 and 30°C on six weedy or cultivated hosts: Gaura lindheimeri Engelman & A. Gray 'Siskyou pink', G. lindheimeri 'Corries gold', G. lindheimeri 'Whirling butterflies', Oenothera speciosa Nutt., Oenothera laciniata J. Hill and Oenothera missourensis_Simms. Development was optimal on Oenothera spp. Duration of development from eclosion to adult emergence ranged from 13.3 d at 30°C on O. speciosa to 64.0 d at 15°C on G. lindeimeri 'Whirling butterflies.' Duration of egg development ranged from 4.5 d at 30°C to 15.8 d at 15°C. The relationship between temperature and rate of development was expressed as a linear thermal unit model for each stage and for combined larval/pupal development. Development parameters varied with host plant. Averaged among the six hosts, larval and pupal development required 237.3 degree-days (DD) above a threshold of 9.2°C. Eggs required 87.5 DD above a 9.8°C threshold. Observation of beetles or feeding injury on indicator plants such as weedy or cultivated Oenothera spp. in late winter or early spring can alert nursery or landscape managers to anticipate a new generation within 300-400 DD above the approximate 10°C developmental threshold used for many DD calculator models for landscape and nursery pests.