Impact of leaf mining on the growth of Portulaca oleracea (common purslane) and its competitive interaction with Beta vulgaris (sugarbeet).

Abstract

The combined attack by leaf mining larvae of the argid, Schizocerella pilicornis, and the curculionid, Hypurus bertrandi, typically resulted in >80% defoliation of field-grown Portulaca oleracea plants in the Central Valley of California. Incorporation of aldicarb into the soil prior to planting protected the weed from attack by both insects. A comparison of insecticide-treated and non-treated plants demonstrated that leaf mining reduced weed growth by 60-70%. Under replacement series pot experiment conditions, leaf mining reversed the competitive interaction between sugarbeet and P. oleracea. Sugarbeet grew best in the presence of P. oleracea plants that were attacked by leaf miners; relative crowding coefficients for sugarbeet exceeded 1.0. When P. oleracea was protected from leaf miner attack, relative crowding coefficients for sugarbeet were all below 1.0. P. oleracea caused up to 80% yield loss in sugarbeet in additive field competition experiments. The magnitude of the sugarbeet yield loss increased with increasing density of P. oleracea; between 0.5 and 3.0 P. oleracea plants m^-1 of crop row caused an economic loss depending on year. Soil-applied aldicarb did not alter the competitive interaction in 3 years out of 4, although the insecticide substantially protected P. oleracea from leaf mining. Although P. oleracea was severely damaged by leaf miner feeding, this injury did not result in sufficient biological weed control to reduce the need for use of other weed management techniques.

Key words

• agricultural entomology
• aldicarb
• arthropod pests
• beneficial arthropods
• beneficial insects
• beneficial organisms
• biological control
• biological control agents
• chemical control
• control
• crop losses
• crop weed competition
• crop yield
• economics
• evaluation
• fields
• growth rate
• host plants
• hosts
• insect control
• insect pests
• natural enemies
• pest control
• pests
• sugar crops
• sugarbeet
• weed control
• weeds