Combining an HA + Cu (II) Site-Targeted Copper-Based Product with a Pruning Wound Protection Program to Prevent Infection with Lasiodiplodia spp. in Grapevine

Abstract

The genus Lasiodiplodia has been reported from several grape growing regions and is considered as one of the fastest wood colonizers, causing Botryosphaeria dieback. The aim of this study was to (i) evaluate the efficacy of Esquive^®, a biocontrol agent, on vineyard pruning wound protection, applied single or, in a combined protection strategy with a new site-targeted copper-based treatment (LC2017), and (ii) compare their efficacy with chemical protection provided by the commercially available product, Tessior^®. For two seasons, protectants were applied onto pruning wounds, while LC2017 was applied throughout the season according to the manufacturer's instructions. Pruning wounds of two different cultivars were inoculated with three isolates of Lasiodiplodia spp. Efficacy of the wound protectants, varied between both years of the assay and according to the cultivar studied but were able to control the pathogen to some extent. The application of LC2017 did not show clear evidence of improving the control obtained by the sole application of the other products tested. Nevertheless, LC2017 showed a fungistatic effect against Lasiodiplodia spp., in vitro, and has previously shown an elicitor effect against grapevine trunk diseases. Therefore, this combination of two protection strategies may constitute a promising long-term approach to mitigate the impact of Botryosphaeria dieback.

Keywords: Botryosphaeriaceae; Hydroxyapatite-Copper; Trichoderma atroviride strain I-1237; Vitis vinifera; combined strategy.

Figure 1

Mean inhibition percentage of growth radius for Trichoderma atroviride strain I-1237 against Lasiodiplodia theobromae isolates Bt105 and LA-SOL3 and Lasiodiplodia mediterranea isolate CBS124060. Dots and triangles represent data from both experiments, black dots represent the mean percentage of growth inhibition for the total replicates of both experiments and black bars represent the standard error of means. Columns with the same letter (a,b) are not significantly different according to Tukey’s test (p = 0.05).

Figure 2

Dual culture antagonism assay of T. atroviride strain I-1237 and the three Lasiodiplodia spp. isolates under study. (A) isolate Bt105; (B) isolate LA-SOL3; (C) isolate CBS124060.

Figure 3

Monthly rainfall and average temperature for the two years of the trial.

Figure 4

Principal component analysis (PCA) for the interactions of all treatments, 15 variables including all the product/isolate combinations (T represents the treatment numbers which are stated in Table 2), as well as inoculated controls on both variables and the meteorological variables (Figure 2). Red marks represent the observations for Cabernet Sauvignon (CS) and green marks represent the Touriga Nacional (TN) observations. (A)-PCA analysis for 2019; (B)-PCA analysis for 2020.

Figure 5

Diagram showing the several steps of the field assay. Information on the products used can be found in Table 4, and a description of the different treatments can be found in Table 5. (A) Marked sample collected from the field prior to analysis; (B) Sample with the bark removed showing sign of necrosis; (C) Sample collected about 1 cm below the pruning wound, to be divided into four pieces and plated onto PDA; (D) Isolate Bt105 (Lasiodiplodia theobromae) recovered from infected pruning wounds; (E) Isolate LA-SOL3 (Lasiodiplodia theobromae) recovered from infected pruning wounds; (F) Isolate CBS124060 (Lasiodiplodia mediterranea) recovered from infected pruning wounds; (G) Petri dish containing wood obtained from non-inoculated control plants showing no signs of pathogen growth.