Artemisia arborescens “Powis Castle” extracts and α-thujone prevent fruit infestation by codling moth neonates

Figures & data

Figure 1. The codling moth and two examples of fruit damage caused by this pest. (A) The moths immobilized on the sticky board of monitoring trap. The wingspan of the moth equals approximately 2 cm. (B) Codling moth neonate larva, about 1.5 mm long, is the invasive stage. (C) Fruit damage caused by infestation early in the season. (D) Fruit damage caused by infestation late in the season, about 30 d before harvest.

Figure 2. Chemical structure of a secondary metabolite of Artemisia arborescens “Powis Castle”, α-thujone, tested for codling moth deterrence in this study. α -Thujone exhibited weak deterrent effects, which do not explain the level of deterrent activity in A. arborescens “Powis Castle” crude extracts toward codling moth neonates, suggesting the presence of other codling moth deterrent compounds in this plant.

Table 1. Comparative feeding deterrence of extracts isolated from Artemisia absinthium, Artemisia arborescens, Artemisia annua, and Artemisia ludoviciana chromatograms.

		Number of neonates feeding on apple
Artemisia species	Number of neonates tested	Treated with extract	Treated with solvent	Deterrence index
A. absinthium	26	13	13	0
A. arborescens “Powis Castle”	24	2**	22	90.9
A. annua	26	13	13	0
A. ludoviciana “Valerie Finnis”	24	11	13	0

The areas of the chromatograms that co-localized with α-thujone standards were extracted with dehydration alcohol, prepared as described in methods and tested in the bioassay for apple-feeding deterrence against codling moth neonates.

**p < 0.01, Fisher exact test.

Table 2. Concentration-dependent feeding deterrence of α-thujone against codling moth neonates.

		Number of neonates feeding on apple
Concentration tested (mg/ml)	Number of neonates tested	Treated with extract	Treated with solvent	Deterrence index
100	44	8**	36	77.8
30	38	7**	31	77.4
10	34	8*	26	69.2
3	34	16	18	11.1
1	40	20	20	0

**p < 0.01, *p < 0.05, Fisher exact test.

Table 3. Concentration-dependent feeding deterrence of the crude extract from Artemisia arborescens “Powis Castle” against codling moth neonates.

		Number of neonates feeding on apple
Concentration tested (mg/ml)	Number of neonates tested	Treated with extract	Treated with solvent	Deterrence index
10	48	4***	44	90.9
3	38	6**	32	81.3
1	46	8**	38	78.9
0.3	38	12	26	53.8
0.1	38	15	23	34.8

***p < 0.001, **p < 0.01, Fisher exact test.