California Red Scale Insecticide Trial, 2015*

CRS infestations cause downgrading of fruit and in extreme cases yield loss due to twig dieback. A field trial was conducted in a 27-yr-old ‘Old Line Washington’ navel orange orchard at the Lindcove Research and Extension Center, Exeter, CA, to test the efficacy of various pesticide treatments and water volumes applied to control CRS. Treatments were assigned to 10 individual trees in an RCB design based on CRS population densities found on twigs collected on 16 Mar 2015. CRS densities were determined by counting all live first- and second-instar scales as well as third-instar and mature female scales on five 1-yr-old twigs (23-cm long) and five fruits (when available) randomly selected from around the outside canopy of each sample tree. CRS densities were evaluated on 16 Mar, 12 May, and 28 Jul on twigs and Nov 9 on fruit. Treatments were applied with a 100 gal high-pressure D30 diaphragm pump sprayer with mechanical agitation with a hand wand sprayer containing a D6 nozzle was used at 450 psi to apply foliar insecticide treatments in 100, 250, or 1,000 gal of water per acre. Four of the treatments were applied to the first generation of crawlers (10 Apr) and two of the treatments were applied to the second generation of crawlers (25 Jun) as detected by double sticky tape wrapped around 1-yr-old wood. All fruits were harvested from each experimental tree on 22 Feb 2016 and examined to determine the percentage of fruit infested with CRS and the percentage of fruit with > 10 CRS (those likely to receive downgrading in the packing house). Data were analyzed using ANOVA, and the means were separated according to Fisher’s LSD (P = 0.05) after log₁₀ (x + 1) transformation of mean scales per fruit or twig or arcsine (square root (x)) transformation of proportions.

Only Movento applied in 250 gpa water significantly reduced scales on twigs (Table 1). Both treatments of Movento significantly reduced the mean number of scale per fruit compared to the untreated control on 9 Nov and the percentage of fruit with CRS at harvest on 22 Feb 2016. None of the treatments significantly reduced the percentage of fruit with > 10 CRS on 22 Feb below the control.

Author notes