Efficacy of Propiconazole for Prevention of Sassafras Mortality from Laurel Wilt Disease Using a Tree Micro-Injection and Micro-Infusion Delivery System

C.W. Johnson; R.O. Olatinwo; J. Hwang; C. Brownie

doi:10.48044/jauf.2023.002

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Figure 1.
Tissue-sample discs collected from inoculated and noninoculated sassafras trees (top); tissue discs plated on potato dextrose agar (PDA) for reisolation of H. lauricola (middle); and inhibition zones from the evaluation of the movement and retention of propiconazole in sassafras tissue samples on PDA pre-inoculated with spores of H. lauricola (bottom).
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Figure 2.
Proportion of trees by treatment 16 weeks post-inoculation with H. lauricola (20 weeks post-injection with propiconazole) using the TREE I.V. Micro-Infusion^TM delivery system.
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Figure 3.
Proportion of trees by treatment 63 weeks post-inoculation with H. lauricola (67 weeks post-injection with propiconazole) using the TREE I.V. Micro-Infusion^TM delivery system.

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Table 1.

The 2019–2020 QUIK-jet^® Micro-Injection^TM system trial. Least squares mean (± 1 SE) for weeks to development of ≥ 50% crown decline and tree mortality among treatments using the Arborjet QUIK-jet^® Micro-Injection^TM system following inoculation with Harringtonia lauricola or sterile agar. Within a column, differing letters denote significant difference (Tukey-Kramer test; α = 0.05). Note: where survival exceeded 62 weeks, values were rounded to 63 for mean calculation and analyses. Standard error (SE); Propiconazole (PZOL); Harringtonia lauricola (HL); agar (AG); standard error of the mean (SEM).

	Tree (n)	Weeks to ≥ 50% crown mortality	Weeks of tree survival	Crown score at final evaluation	HL reisolated at tree death or 12 months
PZOL + HL^a	1	> 62	> 62	2	-
	2	49	62	Dead	Y
	3	49	49	Dead	Y
	4	> 62	> 62	1	-
	5	> 62	> 62	1	-
	6	49	60	Dead	Y
	7	> 62	> 62	1	-
	Mean (± 1 SEM)	57.0 ± 2.3 b	60.4 ± 1.4 b	-	-
HL^b	1	18	49	Dead	Y
	2	4	10	Dead	Y
	3	4	14	Dead	Y
	4	8	14	Dead	Y
	5	4	20	Dead	Y
	6	10	56	Dead	Y
	7	18	49	Dead	Y
	8	4	6	Dead	Y
	9	8	10	Dead	Y
	Mean (± 1 SEM)	8.7 ± 2.1 a	24.9 ± 6.8 a	-	-
AG^c	1	49	> 62	2	Y
	2	49	> 62	2	Y
	3	49	> 62	2	Y
	4	49	> 62	2	Y
	5	60	> 62	1	N
	6	56	> 62	2	Y
	7	60	> 62	1	N
	8	60	> 62	1	Y
	Mean (± 1 SEM)	54.4 ± 2.2 b	61.3 ± 1.4 b	-	-
PZOL + AG^d	1	> 62	> 62	1	Y
	2	49	> 62	2	Y
	3	49	49	Dead	N
	4	60	> 62	2	Y
	5	56	> 62	2	Y
	6	49	60	Dead	Y
	7	60	60	Dead	N
	8	56	60	Dead	Y
	Mean (± 1 SEM)	55.2 ± 2.2 b	59.5 ± 1.4 b	-	-

↵^aTrees injected with propiconazole and inoculated with Harringtonia lauricola
↵^bTrees not injected with propiconazole and inoculated with Harringtonia lauricola
↵^cTrees not injected with propiconazole and inoculated with agar
↵^dTrees injected with propiconazole and inoculated with agar

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Table 2.

The 2019–2020 QUIK-jet^® Micro-Injection^TM and 2020–2021 TREE I.V. Micro-Infusion^TM system trials. The proportion of propiconazole-injected sassafras trees (and percent of total per treatment) exhibiting Harringtonia lauricola inhibition in wood-tissue discs obtained 30 cm above or below inoculation points 3, 12, and 15 months post-inoculation with H. lauricola using the Arborjet QUIK-jet^® Micro-Injection^TM and TREE I.V. Micro-Infusion^TM delivery systems. Propiconazole (PZOL); Harringtonia lauricola (HL); agar (AG).

		3 months		12 months		15 months
Injection system	Treatment	Above	Below	Above	Below	Above	Below
QUIK-jet^® Micro-Injection^TM (2019–2020)	PZOL + HL^a	1/7 (14%)	1/7 (14%)	1/7 (14%)	0/7 (0%)	3/4 (75%)	3/4 (75%)
QUIK-jet^® Micro-Injection^TM (2019–2020)	PZOL + AG^b	5/8 (63%)	6/8 (75%)	1/7 (14%)	5/7 (71%)	1/1 (100%)	1/1 (100%)
TREE I.V. Micro-Infusion^TM (2020–2021)	PZOL + HL^a	5/13 (38%)	6/13 (46%)	10/13 (77%)	8/13 (62%)	N/A	N/A