Acetamiprid, chlorantraniliprole, and in some situations the physical barriers MultiPro® or Kvaae® wax, can be alternatives to traditional synthetic pyrethroid insecticides for the protection of young conifers from damage by the large pine weevil Hylobius abietis L.

Figures & data

Table 1. List of products tested.

Active ingredient(s)	Product name	Supplier company	Product type	Experiment number
acetamiprid, 20% w/w	Gazelle SG®	Certis, www.certiseurope.co.uk	Synthetic insecticide	1, 3, 4, 5
acid blue 9 (CI 42090), 40% w/w	Dysol Turquoise®	Brenntag, www.brenntag.com	Marker dye	5
alpha-cypermethrin, 100 g l^−1	Alert®	BASF, www.agricentre.basf.co.uk	Synthetic insecticide	1, 3
alpha-cypermethrin, 60 g l^−1	Alpha C 6ED®	Techneat, www.techneatengineering.co.uk	Synthetic insecticide	4
cardboard, waxed	MultiPro®	Svenska Skogsplantor, www.skogsplantor.se	Rigid physical barrier sleeve	4
chlorantraniliprole, 200 g l^−1	Coragen®	FMC / Syngenta, www.fmc-agro.co.uk / www.syngenta.co.uk	Synthetic insecticide	5
cypermethrin, 100 g l^−1	Forester®	UPL / Arysta, www.upl-ltd.com/uk	Synthetic insecticide	4
wax	Kvaae® wax	Norsk Wax AS, www.kvaae.com	Flexible physical barrier film	1, 2, 3, 4

Table 2. Experiment site details.

Site name	Location national grid reference	Location (Latitude, Longitude)	Elevation (m)	Annual rainfall (mm)*	Accumulated temperature (growing degree days > 5°C)	Soil type	Felling date, previous crop	Experiment planting date
Experiment 1
Headley Research Enclosure, Hampshire, England	SU809379	51°08′05″N, 000°50′42″W	90	645	1840	Podzol	Not applicable, not afforested.	December 2014 January 2015 March 2015
Experiment 2
Headley Research Enclosure Hampshire, England	SU809379	51°08′05″N, 000°50′42″W	90	645	1840	Podzol	Not applicable, not afforested.	May 2014
Experiment 3
Unicorn Knowe, Kielder Forest, Northumbria, England	NY760803	55°06′59″N, 002°22′40″W	290	1030	1106	Peaty surface-water gley	October 2013 to March 2014	December 2014 January 2015 March 2015
Experiment 4
Binky Burn, Kielder Forest, Northumbria, England	NY657839	55°08′54″N, 002°32′23″W	280	770	1152	Peaty surface-water gley / Deep peat	October 2012 to March 2013	May 2014
Wainhope Linn, Kielder Forest, Northumbria, England	NY665927	55°13′39″N, 002°31′42″W	280	710	1126	Peaty surface-water gley	October 2012 to March 2013	May 2014
Experiment 5
Stourcleugh, Spadeadam Forest, Northumbria, England	NY649749	55°04′02″N, 002°33′04″W	280	1200	1113	Peaty surface-water gley / Deep peat	October 2014 to March 2015	May 2016

Notes: *From: – Hollis and McCarthy (2013).

Table 3. Experimental treatments at Headley Research Enclosure (Experiment 1), and Unicorn Knowe, Kielder (Experiment 3).

Treatment number	Active ingredient or physical product	Product dosage (g ha^−1)	Product dosage (g stem^−1)	A.i. dosage (g stem^−1)	A.i. dosage (g ha^−1)	Storage period (months)	Planting date	Root Electrolyte Leakage (%)
1	untreated	-	-	-	-	0	December 2014	20
2	untreated	-	-	-	-	1.5	January 2015	15
3	untreated	-	-	-	-	3.0	March 2015	13
4	alpha-cypermethrin	1430 (ml ha^−1)	0.53 (ml stem^−1)	0.053	143	0	December 2014	20
5	alpha-cypermethrin	1430 (ml ha^−1)	0.53 (ml stem^−1)	0.053	143	1.5	January 2015	29
6	alpha-cypermethrin	1430 (ml ha^−1)	0.53 (ml stem^−1)	0.053	143	3.0	March 2015	15
7	acetamiprid	500	0.185	0.037	100	0	December 2014	22
8	acetamiprid	500	0.185	0.037	100	1.5	January 2015	22
9	acetamiprid	500	0.185	0.037	100	3.0	March 2015	16
10	Kvaae® wax	-	-	-	-	0	December 2014	20
11	Kvaae® wax	-	-	-	-	1.5	January 2015	14
12	Kvaae® wax	-	-	-	-	3.0	March 2015	13

Notes: 1. Dosages are given in g ha⁻¹ or g stem⁻¹ unless other units are stated in parentheses.

2. Tree dosages were calculated assuming a restocking density of 2700 stems ha⁻¹.

3. Root Electrolyte Leakage (REL) was determined by sampling plants prior to dispatch to the experiment site, but after any cold storage.

4. Kvaae® wax was applied to 50% of the stem and foliage, as measured from the root collar upwards.

Table 4. Experimental treatments at Headley Research Enclosure (Experiment 2).

Treatment number	Treatment code	Tree species	Seedling size class	Initial height (cm)	Initial root collar diameter (mm)	Stem wax cover (%)
1	QSS S	Sitka spruce	Small	24.3	4.8	0
2	QSS S	Sitka spruce	Small	24.8	6.4	50
3	QSS S	Sitka spruce	Small	24.1	5.8	75
4	QSS S	Sitka spruce	Small	25.1	8.9	100
5	QSS L	Sitka spruce	Large	32.9	7.4	0
6	QSS L	Sitka spruce	Large	33.3	7.5	50
7	QSS L	Sitka spruce	Large	32.4	7.0	75
8	QSS L	Sitka spruce	Large	32.9	6.7	100
9	VPSS S	Sitka spruce	Small	25.3	4.4	0
10	VPSS S	Sitka spruce	Small	23.1	4.3	50
11	VPSS S	Sitka spruce	Small	22.8	4.3	75
12	VPSS S	Sitka spruce	Small	23.5	4.1	100
13	VPSS L	Sitka spruce	Large	35.4	4.5	0
14	VPSS L	Sitka spruce	Large	33.2	4.5	50
15	VPSS L	Sitka spruce	Large	34.5	4.5	75
16	VPSS L	Sitka spruce	Large	34.2	4.7	100
17	NS S	Norway spruce	Small	28.4	5.5	0
18	NS S	Norway spruce	Small	25.4	5.5	50
19	NS S	Norway spruce	Small	29.5	6.7	75
20	NS S	Norway spruce	Small	27.1	5.6	100
21	WRC L	Western red cedar	Large	53.7	8.7	0
22	WRC L	Western red cedar	Large	59.1	8.8	50
23	WRC L	Western red cedar	Large	56.3	9.4	75
24	WRC L	Western red cedar	Large	56.6	10.0	100
25	DF S	Douglas fir	Small	25.3	5.2	0
26	DF S	Douglas fir	Small	23.6	4.9	50
27	DF S	Douglas fir	Small	22.5	4.8	75
28	DF S	Douglas fir	Small	23.8	6.0	100
29	DF L	Douglas fir	Large	36.5	6.4	0
30	DF L	Douglas fir	Large	37.3	6.5	50
31	DF L	Douglas fir	Large	34.2	6.9	75
32	DF L	Douglas fir	Large	36.3	7.1	100
33	SP S	Scots pine	Small	21.5	5.3	0
34	SP S	Scots pine	Small	12.8	4.7	50
35	SP S	Scots pine	Small	12.0	5.1	75
36	SP S	Scots pine	Small	14.3	5.5	100
37	OK L	Pedunculate oak	Large	22.5	5.9	0
38	OK L	Pedunculate oak	Large	27.5	8.1	50
39	OK L	Pedunculate oak	Large	21.9	6.1	75
40	OK L	Pedunculate oak	Large	27.2	5.9	100

Notes: 1. QSS = Sitka spruce, conventional bare root planting stock from improved seed orchards.

2. VPSS = vegetatively propagated Sitka spruce clonal progeny.

3. Kvaae® wax was applied to varying percentages of the stem and foliage, as measured from the root collar upwards. Terminal buds were never treated.

Table 5. Experimental treatments at Binky Burn and Wainhope Linn, Kielder Forest (Experiment 4).

Treatment number	Active ingredient or physical product	Seedling size class	Initial height (cm)	Application method	Product dosage (g ha^−1)	Product dosage (g stem^−1)	A.i dosage (g.stem^−1)	A.i dosage (g.ha^−1)
1	untreated	Small	24	-	-	-	-	-
2	untreated	Large	33	-	-	-	-	-
3*	alpha-cypermethrin	Small	25	stem – Electrodyn®	270 (ml ha^−1)	0.100 (ml stem^−1)	0.006	16
4*	alpha-cypermethrin	Large	33	stem – Electrodyn®	270 (ml ha^−1)	0.100 (ml stem^−1)	0.006	16
5	cypermethrin	Small	24	stem	1080 (ml ha^−1)	0.4 (ml stem^−1)	0.040	108
6	cypermethrin	Large	37	stem	1080 (ml ha^−1)	0.4 (ml stem^−1)	0.040	108
7	acetamiprid	Small	25	stem, foliage and roots (5 ml stem^−1)	500	0.185	0.037	100
8	acetamiprid	Small	24	stem, foliage and roots (10 ml stem^−1)	500	0.185	0.037	100
9	acetamiprid	Small	24	stem, foliage and roots (20 ml stem^−1)	500	0.185	0.037	100
10	acetamiprid	Small	25	stem and foliage (5 ml stem^−1)	500	0.185	0.037	100
11	acetamiprid	Small	27	stem and foliage (10 ml stem^−1)	500	0.185	0.037	100
12	acetamiprid	Small	23	stem and foliage (20 ml stem^−1)	500	0.185	0.037	100
13	acetamiprid	Small	20	stem and foliage – seedbed	500	0.0005	0.0001	100
14	acetamiprid	Small	22	stem and foliage – seedbed	30830	0.031	0.006	617
15	Kvaae® wax	Small	24	stem and foliage – 50%	-	-	-	-
16	Kvaae® wax	Small	23	stem and foliage – 75%	-	-	-	-
17	Kvaae® wax	Small	24	stem and foliage – 100%	-	-	-	-
18	Kvaae® wax + acetamiprid	Small	26	stem and foliage – 50% + remainder sprayed	500	0.185	0.037	100
19	Kvaae® wax	Large	32	stem and foliage – 50%	-	-	-	-
20	Kvaae® wax	Large	33	stem and foliage – 75%	-	-	-	-
21	Kvaae® wax	Large	35	stem and foliage – 100%		-	-	-
22	Kvaae® wax + acetamiprid	Large	34	stem and foliage – 50% + remainder sprayed	500	0.185	0.037	100
23	MultiPro®	Small	25	-	-	-	-	-
24	MultiPro®	VPSS small	25	-	-	-	-	-
25	MultiPro® + acetamiprid	VPSS large	34	stem and foliage	500	0.185	0.037	100

Notes: 1. Dosages are given in g ha⁻¹ or g stem⁻¹ unless other units are stated in parentheses.

2. Equivalent rates per hectare were calculated assuming a restocking density of 2700 stems ha⁻¹, except for treatments 13 and 14.

3. For treatments 13 and 14, mechanised sprays were made over nursery seedbeds before lifting at an application rate of 0.5 kg ha⁻¹ Gazelle SG and 30.83 kg ha⁻¹ Gazelle SG respectively, both in a total application volume rate (insecticide plus diluent) of 500 litres ha⁻¹. Equivalent individual tree dosages were calculated assuming an average of 100 trees m² within the nursery seedbeds.

4. All other treatments were applied after lifting, but before planting, except for treatments 5, 6, 18, 22 and 25, where insecticide was applied immediately after planting in the forest.

5. All insecticide treatments made to individual stems (i.e. not treatments 13 and 14), were made at a volume rate (insecticide plus diluent) of 20 ml stem⁻¹, except for treatments 7 and 10 where 5 ml stem⁻¹ was used, and treatments 8 and 11 where 10 ml stem⁻¹ was used. In these cases, the concentration of the mix was varied so that the amount of acetamiprid applied to each stem remained the same (0.037 g a.i. stem⁻¹ acetamiprid).

6. Kvaae® wax was applied to varying percentages of the stem and foliage, as measured from the root collar upwards. Terminal buds were never treated.

7. Initial root collar diameters were not recorded by treatment, but were in the range of 2–7 mm.

8. VPSS = vegetatively propagated Sitka spruce clonal progeny.

“*” Represents the active control.

Table 6. Experimental treatments at Stourcleugh, Spadeadam Forest (Experiment 5).

Treatment number	Active ingredient	Product dosage (g ha^−1)	Product dosage (g stem^−1)	A.i. dosage (g stem^−1)	A.i. dosage (g ha^−1)
1	untreated	-	-	-	-
2	acetamiprid	125	0.046	0.009	25
3	acetamiprid	500	0.185	0.037	100
4	chlorantraniliprole	70 (ml ha^−1)	0.026 (ml stem^−1)	0.005	14
5	chlorantraniliprole, + acid blue 9 dye	70 (ml ha^−1) + 1080 (ml ha^−1)	0.026 (ml stem^−1) + 0.4 (ml stem^−1)	0.005 + 0.16	14 + 432
6	chlorantraniliprole	140 (ml ha^−1)	0.052 (ml stem^−1)	0.010	28
7	chlorantraniliprole	210 (ml ha^−1)	0.078 (ml stem^−1)	0.016	42
8	chlorantraniliprole	280 (ml ha^−1)	0.104 (ml stem^−1)	0.021	56
9	chlorantraniliprole	350 (ml ha^−1)	0.130 (ml stem^−1)	0.026	70
10	chlorantraniliprole + acid blue 9 dye	350 (ml ha^−1) +1080 (ml ha^−1)	0.130 (ml stem^−1) + 0.4 (ml stem^−1)	0.026 + 0.16	70 + 432

Notes: 1. Dosages are given in g ha⁻¹ or g stem⁻¹ unless other units are stated in parentheses.

2. Tree dosages were calculated assuming a restocking density of 2700 stems ha⁻¹.

3. For treatment 2, which was applied via a prototype pre-treatment machine in the nursery, it was originally intended to apply 0.037 g a.i. stem⁻¹ acetamiprid to provide a direct comparison with treatments 3 and 4, but an error in calibration meant that the final rate used was only a quarter of this.

4. For treatments 9 and 10, the dye Dysol Turquoise® (40% acid blue 9) was applied at 2% of final spray volume following the recommendations in Brown et al. (2003).

Figure 1. Transplant status after one growing season at Headley Research Enclosure, Experiment 1. Notes: (A) Distribution of tree health scores (THS) (1 = healthy; 5= dead) and (B) height growth increment (cm) for Sitka spruce transplants planted in December 2014 (0 months storage), January 2015 (1.5 months storage) or March 2015 (3 months storage) and treated with alpha-cypermethrin, acetamiprid, or a Kvaae® wax barrier coating. For health score data, lettering indicates significant differences in proportion of trees with THS of 1/ 2 versus 3/4/5. For height growth data, lettering indicates significant differences in height growth across all treatments (corrected for multiple comparisons). Error bars = 95% confidence intervals (uncorrected).

Figure 2. Transplant status after one growing season at Headley Research Enclosure, Experiment 2. Notes: (A) Distribution of tree health scores (THS) (1 = healthy; 5= dead) and (B) height and root collar diameter (RCD) growth (cm) for transplants treated with Kvaae® wax coating covering 0%, 50%, 75% and 100% of the length of the stem. For health score data, lettering indicates significant differences in proportion of trees with THS of 1/2 versus 3/4/5. For growth data, lettering indicates significant differences in height and RCD growth within each species/size combination (corrected for multiple comparisons). Error bars = 95% confidence intervals (uncorrected). Species codes are: QSS, Sitka spruce (seed orchard); VPSS, Sitka spruce (vegetatively propagated); NS, Norway spruce; WRC, western red cedar; DF, Douglas fir; SP, Scots pine; OK, pedunculate oak.

Figure 3. (A) Transplant status after one growing season at Unicorn Knowe, Kielder Forest in 2015, Experiment 3. Notes: Sitka spruce transplants planted in December 2014 (0 months storage), January 2015 (1.5 months storage) or March 2015 (3 months storage) and treated with alpha-cypermethrin, acetamiprid, or a Kvaae® wax barrier coating. Lettering indicates a statistical difference in the proportion of treatment survival (alive/alive (damaged) versus dead (Hylobius), corrected for multiple comparisons (note: tested at the treatment level, as there was no significant treatment : storage interaction). Other mortality and missing transplants were excluded from the statistical analysis. (B) Transplant status after two growing season at Unicorn Knowe, Kielder Forest in 2016, Experiment 3. Notes: Transplants were planted and treated as for Figure 3a. Lettering indicates a statistical difference in the proportion of treatment survival (alive/alive(damaged) versus dead (Hylobius), corrected for multiple comparisons (note: tested at the treatment level, as no significant treatment : storage interaction). Other mortality and missing transplants were excluded from the statistical analysis.

Figure 4. (A) Transplant status at Binky Burn and Wainhope Linn, Kielder Forest in mid-2014, Experiment 4. Notes: Transplant status including damage caused by Hylobius, across 25 treatments. Lettering indicates a statistical difference in the proportion of treatment survival (alive/alive(damaged) versus dead (Hylobius)); * = significant difference to active control (p < 0.05; grouped mean of treatment 3, Alpha-cypermethrin small size class, and treatment 4, alpha-cypermethrin large size class); † = significant difference to untreated control (p < 0.05; grouped mean of treatments 1 and 2). Other mortality and missing transplants were excluded from the statistical analysis. Treatment effects were consistent across sites, with main effect of site only (% dead due to Hylobius greater overall at Binky Burn). (B) Transplant status at Binky Burn and Wainhope Linn in mid-2015, Experiment 4. Notes: Transplant status including damage caused by Hylobius, across 13 of 25 treatments (for reasons of economy it was not possible to reassess all treatments, and so the decision was taken to focus only on those which included acetamiprid). Lettering indicates a statistical difference in the proportion of treatment survival (alive/alive (damaged) versus dead (Hylobius)); † = significant difference to untreated control (p < 0.05; grouped mean of treatments 1 and 2). Other mortality and missing transplants were excluded from the statistical analysis. Treatment effects were consistent across sites, with main effect of site only (% dead due to Hylobius greater overall at Binky Burn).

Figure 5. (A) Transplant status after one growing season at Stourcleugh, Spadeadam Forest, in 2016, Experiment 5. Notes: Lettering indicates a statistical difference in the proportion of treatment survival (alive/alive (damaged) versus dead (Hylobius), corrected for multiple comparisons. Other mortality and missing transplants were excluded from the statistical analysis. (B) Transplant status after two growing seasons at Stourcleugh, Spadeadam Forest, in 2017, Experiment 5. Notes: Lettering indicates a statistical difference in the proportion of treatment survival (alive/alive (damaged) versus dead (Hylobius), corrected for multiple comparisons. Other mortality and missing transplants were excluded from the statistical analysis.

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