Control of Xylotrechus arvicola (Coleoptera: Cerambycidae) larvae population by inoculating Trichoderma spp. in vine wood

Xylotrechus arvicola (Coleoptera: Cerambycidae) is a grapevine (Vitis vinifera) pest in the Iberian Peninsula causing the spread of wood diseases. Trichoderma (Teleomorph: Hypocrea) is a fast growing opportunistic fungus, which produces antimicrobial compounds¹. Moreover, it can be used as biological control of pests². This study's aim is to evaluate Trichodema spp. efficacy on controlling X. arvicola larvae, simulating field conditions. One millilitre of spore suspension (1 × 10⁷esp/ml) of Trichoderma spp. was applied directly to vine with a manual diffuser. One hour after, four X. arvicola larvae were placed on the vine. Vines were opened 135 days later to count larvae and extract wood samples. Four samples per treatment from rhytidome and galleries per vine in four replicates were incubated on Petri dishes with Rose Bengal-Chloramphenicol Agar medium at controlled conditions during 7 days.

Tab. 1: X. arvicola dead larvae with Trichoderma spp., number of isolations and percentage of isolates showing growth of Trichoderma spp. from vine wood (rhytidome and galleries)

Trichoderma treatment (Isolated number)	Mortality (%) of X. arvicola larvae	Rhytidome isolations	Rhytidome (%) with Trichoderma	Galleries isolations	Galleries (%) with Trichoderma
T. harzianum (T-019)	81.25 ± 6.25A	21	76.19	16	75.00
T. gamsii (T-066)	68.75 ± 23.66A	17	29.41	8	100.00
T. gamsii (T-067)	31.25 ± 11.96B	16	37.50	12	33.33
T. gamsii (T-070)	75.00 ± 10.21A	11	54.54	4	100.00
T. gamsii (T-071)	81.25 ± 11.97A	12	33.33	11	45.45
Control	6.25 ± 6.25B	9	0.00	6	0.00
Different capital letters indicate significant differences among fungal isolates of dead larvae with Trichoderma spp. (Fisher's LSD. p < 0.05).

100% of T. gamsii (T-066) and T. gamsii (T-070) galleries isolates showed Trichoderma growth, confirming the ability of this fungus to move through the vine wood by the galleries created by X. arvicola larvae. T. gamsii (T-071) and T. harzianum (T-019) treatments showed the highest control over insect larvae with a 81.25% mortality. These results indicate Trichoderma should be considered for further studies to evaluate its efficacy to control X. arvicola on field conditions.

[1] Mayo S, Gutiérrez S, Malmierca MG, Lorenzana A, Campelo MP, Hermosa R, Casquero PA. Front. Plant Sci 2015, 6, 685.

[2] Abdul-Wahid, OA, Elbanna, SM. Afr. J. Microbiol. Res. 2012, 6: 1024 – 1032.