December 1, 2004
Soil acidity and tree stress from flooding can occur simultaneously with Diaprepes abbreviatus (L.) root weevil infestations in citrus groves. We conducted a greenhouse study in 2003 to determine the effect of flooding duration on the outcome of soil liming, and the interaction of soil liming and flooding treatments on Diaprepes larval survival and seedling growth. We used a Floridana sandy soil (pH 4.8) from a citrus grove damaged by Diaprepes root weevil in Osceola County. The treatments consisted of three soil pH levels (non-limed, and target pH of 6 and 7), two citrus cultivars (Swingle citrumelo (Citrus paradisi Macfad. Raf. × Poncirus trifoliata (L.)) and Carrizo citrange (Citrus sinensis (L.) Osb. × Poncirus trifoliata), flooding durations of 0 or 40 days, and Diaprepes larval infestations at 0 or 5 larvae for 55 days. Dolomite (CaCO[sub3] · MgCO[sub3]) was used for liming. Treatments were arranged using 15 replicates in a completely randomized design. Soil pH increased by 0.5-0.9 units for the target pH 6, and 0.7-1.0 units for the target pH 7. The linear effect of liming treatment significantly increased soil pH (P 0.01). Larval survival rate was up to 100% for low soil pH ( 5.1) but decreased to 60% at the highest measured soil pH of 5.7. Total larval weight decreased significantly from 60 mg to 18 mg per seedling when soil pH increased from 5.1 to 5.7. Shoot dry weight was higher at the target pH 7 than at other pH treatments (P 0.05). Our data suggested that increasing soil pH by 1 unit could decrease Diaprepes larval survival while promoting citrus growth.