Insect attractant compositions

Abstract

An attractant composition suitable for attracting Lepidopterous insects, particularly Helicoverpa armigera, for use as an insect lure in a control method aimed at reducing pest damage to crops. The preferred attractant composition comprises phenylacetaldehyde, salicylaldehyde and at least one compound selected from the group comprising: methyl-2-methoxybenzoate, linalool and limonene.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the national phase application of international application no. PCT/GB2010/051716, filed Oct. 12, 2010, which claims priority to Great Britain application no. 1014038.2, filed Aug. 23, 2010, and Great Britain application no. 0917781.7, filed Oct. 12, 2009. The contents of the aforementioned applications are incorporated herein.

The present invention relates to insect attractant compositions and particularly to insect attractant compositions for attracting moth pest species, such as Helicoverpa armigera.

Most larvae of the insect order Lepidoptera are phytophagous, the Lepidopterous moth families Noctuidae and Pyralidae including some of the most economically-important pest species. The American cotton bollworm, Helicoverpa armigera, is a particularly significant polyphagous pest of legume and solanaceous crops, such as chickpea, pigeon pea, lablab bean and tomato. H. armigera has been recorded in the UK but is of greater economic importance in the countries of southern Europe, particularly Spain, where it attacks cotton and tomato crops. Traits such as high mobility of adults and the ability of each female moth to lay between 500 and 3,000 eggs on a host-plant, enable rapid growth and dispersal of H. armigera populations.

Insect pests can be controlled by a variety of techniques, each method having particular advantages and disadvantages. Insecticides are a common control method for reducing pest populations. However, non-selective insecticide use can result in resistance development amongst pest populations. For example, H. armigera has developed resistance to pyrethroid and endosulfan insecticides in Australia and the Indian sub-continent. Use of transgenic plants, which have resistance to a particular pest, is an alternative strategy for minimising insect-mediated crop damage. Transgenic cotton, for example, has been widely used in the USA, South America, India and China.

Other insect control methods include mating disruption and mass trapping. Chemical ecologists have focused on the identification and application of sex pheromones for insect detection, monitoring and control programmes (Witzgall et al., 2010). The specificity of pheromones, however, usually limits their use to situations where there is a single key pest species (due to the prohibitive costs associated with providing a solution for a species-complex). The sex pheromone of H. armigera has been characterised, but its value for control and population monitoring is minimal. Research has shown that control of H. armigera using pheromones to disrupt mating is ineffective because, although adult females will not mate within treatment areas, they may return later to lay their eggs within test areas (Chamberlain et al., 2000). There is some evidence to suggest that mass-trapping male moths using the female sex pheromone can have an effect on populations, but given the mobility of female moths, such an approach is unlikely to form the basis of a comprehensive control method.

Certain plant species have floral attractant properties that have been successfully exploited as trap crops for control of H. armigera. Adult Lepidoptera are attracted to, and feed on, floral nectar. They will usually select a particular plant species for oviposition, but they can select a broad range of flowering plants for feeding. Nocturnal insect species rely on floral odours in order to locate these food sources (Weisenborn and Baker, 1990; Gabel et al., 1992; Heath et al., 1992; Zhu et at, 1993; Dobson, 1994). Therefore, moth species are expected to respond to a broad range of floral odours. Both male and female adult moths, feed on nectar sources and so floral baits advantageously attract both sexes.

Diurnal changes in flowers, such as petal opening and closing, anthesis and the presentation of nectar, are co-ordinated with the release of floral scents (which act as synomones), and the activities of the insect pollinators (Bünning 1967, Hess 1983). Matile and Altenburger (1988) studied fragrances released from four plant species. They found pronounced diurnal changes in the composition of floral fragrances of species such as Odontoglossum constrictum and Citrus medica. Hoya carnosa and Stephanotis floribunda floral emissions were found to be primarily nocturnal. However, not only did the total quantity of material released vary over time, the relative composition also changed. In the case of Stephanotis floribunda, the maximum release of methyl benzoate and linalool occurred at midnight, while the maximum release of 1-nitro-2-phenylethane occurred at noon. Similarly, head-space analysis of floral odours emitted by honeysuckle, Lonicera japonica, showed that much of the odour was emitted in the middle of the night (Ikeda et al., 1994). The odour was found to consist of 150 compounds. However, it was primarily characterised by compounds found in jasmine—(Z)-jasmone, (Z)-jasmine lactone, (E)- and (Z)-methyl jasmonate and methyl epi jasmonate. Nocturnal scented flowers are predominately pollinated by moths and, indeed, L. japonica has long slender nectaries that are inaccessible to day-flying Hymenoptera.

Diurnal Lepidoptera are also known to be sensitive to airborne chemicals originating from oak sap and rotten fruits (Ilse, 1928, Miyakawa, 1976, Scherer and Klob, 1987). It is not clear how important these odours are, since sap and fruit lack the accompanying visual effects produced by flowers. In the case of the diurnal moth, Zygaena, feeding behaviour is stimulated by both visual and olfactory stimuli (Naumann et al., 1991), while for the small white butterfly, Pieris rapae crucivora, visits to flowers of Ligustrum japonicum are thought to be mediated by olfaction alone (Honda et al., 1998).

Preliminary studies carried out by the present inventors, seeking to identify the attractive volatile components of plant species, resulted in the identification of electrophysiologically-active compounds from marigold, Tagetes erecta. Subsequent wind tunnel bioassays confirmed that synthetic blends of these compounds were as attractive as the natural floral extracts (Bruce and Cork, 2001). However, field tests conducted in chickpea crops proved inconclusive since they resulted in low trap catches. Further studies on the volatiles of maize plants have identified phenylacetaldehyde as a strong attractant for female Helicoverpa armigera (Pawar et al., 1993). This compound is also found in many flowering plants and is present in at least one commercially available insect attractant (Magnet®).

Chinese farmers have traditionally used dried leaves of poplar trees to attract Helicoverpa armigera. In 2005, Li et al. demonstrated that leaf extracts of Populus nigra could attract Helicoverpa armigera in cotton crops. This study employed a lure including a basic five-component blend comprising aromatics without phenolics, and containing additional components all present in the steam distillate of the leaves of P. nigra. The blended components were mixed in the proportions found in the steam distillate. The results indicated that volatile components of wilted leaves of P. nigra can also attract H. armigera adults. However, the results of these tests are not entirely clear since several of the components in the blend have also been shown to act as repellents of H. armigera in certain crops.

Following considerable interest in the development of floral odour-baits for insect pests, Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) scientists developed an insect attractant known commercially as Magnet®. This product is based on a blend of volatile plant compounds and an insecticide for controlling H. armigera on cotton. The insecticide contained in Magnet® adversely affects pollinators attracted to the odour bait and can kill natural pest enemies and parasitoids that are important for the control of other cotton pests. Magnet® has a short field life (around three days), which is disadvantageous when the attractant is used with long-duration crops, such as cotton. The Magnet® formulation is not water-fast and so it can be quickly washed away in areas with significant rainfall.

The present invention seeks to provide an attractant that overcomes at least some of the disadvantages of Magnet®. The present invention also seeks to provide a chemical attractant for use in the capture of economically-important moths, particularly Lepidopterous moth families Noctuidae and Pyralidae, which is environmentally friendly.

In its broadest aspect, the present invention provides an insect attractant composition comprising phenylacetaldehyde and salicylaldehyde.

The present invention also provides an attractant composition for attracting insects, the composition comprising: phenylacetaldehyde and salicylaldehyde; and excluding at least one of: benzaldehyde, benzyl alcohol, and phenylethyl alcohol.

In another aspect, there is provided an attractant composition for attracting insects, the composition comprising phenylacetaldehyde and salicylaldehyde, wherein phenylacetaldehyde comprises between 40 and 97% of the total weight of the composition. Preferably, salicylaldehyde comprises between 3 and 60% of the total weight of the composition.

According to the present invention, there is provided an attractant composition for attracting insects, the composition comprising phenylacetaldehyde, salicylaldehyde and at least one of: methyl-2-methoxybenzoate, linalool and limonene.

Preferably, the composition comprises at least two of methyl-2-methoxybenzoate, linalool and limonene. Ideally, at least two of: methyl-2-methoxybenzoate, linalool and limonene, each comprise between 3 and 30% of the total weight of the composition.

In a preferred embodiment, the composition comprises phenylacetaldehyde, salicylaldehyde, methyl-2-methoxybenzoate, linalool and limonene. Preferably, the ratio of phenylacetaldehyde:salicylaldehyde:methyl-2-methoxybenzoate:linalool:limonene is approximately 50:20:10:10:10.

Suitably, the composition further comprises one or more compounds selected from the group comprising: benzaldehyde, benzyl alcohol, phenylethyl alcohol, anisyl alcohol, α-pinene, butyl salicylate (Z)-jasmone, methyl salicylate, diacetone (4-hydroxy-4-methyl-2-pentanone), (E)-myroxide, (Z)-b-ocimene, and (R)-(−)-piperitone.

Advantageously, the composition further comprises an antioxidant. Preferably, the antioxidant is at least one of: α-tocopherol, a related tocotrienol (vitamin E) and butylated hydroxytoluene. Suitably, the amount of the antioxidant is between 10% and 100% of the total weight of the composition, based on the amount of phenylacetaldehyde.

Optionally, the composition further comprises at least one of: a UV screener, preferably carbon black, and a UV absorber, preferably at least one of o-hydroxybenzophenones and benzotriazoles. Alternatively or additionally, the composition further comprises at least one carotenoid, preferably vitamin A.

In one embodiment, the composition further comprises one or more insecticides. Preferably, at least one insecticide has a vapour action. More preferably, at least one insecticide is a pyrethroid or dichlorvos. In another embodiment, the composition comprises an insect-specific microbial pesticide. Preferably, the microbial pesticide is at least one of: a virus (preferably nucleopolyhedrovirus), fungus (preferably Metarhizium anisopliae, Beauveria bassiana) and bacteria (preferably Bacillus thuringiensis).

Optionally, the composition comprises a Hymenoptera deterrent.

According to a further aspect of the present invention, there is provided a lure comprising an insect attractant composition as described above.

Another aspect of the present invention provides use of a composition as described above to trap Lepidoptera.

A further aspect of the present invention provides use of an attractant composition comprising phenylacetaldehyde to trap Diaphania indica. Preferably, the composition further comprises salicylaldehyde. More preferably, the attractant composition further comprises at least one of: methyl-2-methoxybenzoate, linalool and limonene.

The above and other aspects of the present invention will now be illustrated in further detail, by way of example only.

EXAMPLE 1

Field Trials in Bangladesh

Lures were prepared from heat-sealed low density polyethylene sachets formed from ‘layflat plastic’ tubing. In early field work, the lures were prepared on site, with each lure comprising a single compound in a dose of 0.1 ml. The release rate of compounds from the polyethylene sachets is independent of the amount of material in the sachet and so a particular dosage affects longevity only. Longevity, in turn, is dependent on ambient temperature, with an increase of 7-10° C. leading to a doubling of the release rate. Water traps were placed at crop height and trap catches were taken as a crude measure of attractiveness to the compounds. As the compounds mimic ‘floral odours’ generally, they were not expected to be species-specific in their effect.

During testing, different combinations of floral odours, together with H. armigera pheromone, were used as attractants. The chemicals were put inside sealed plastic sachets (10×5 cm) and the sachets were hung inside traps prepared from clear plastic pots (19 cm height, 15 cm dia.) with two triangular holes (12 cm base, 9 cm height) at opposite sides. The traps were set at 1 m height with an inter-trap distance of 10 m. Insects that were trapped by the lures were collected, identified and recorded at weekly intervals.

TABLE 1
Effect of increasing relative amount of minor components on catch of adult
H. armigera
			Methyl 2-
Blend	Limonene	Phenyl	methoxy	Linalool	Salicylaldehyde	H. armigera
code	(μl)	acetaldehyde	benzoate (μl)	(μl)	(μl)	Catch
1.1	0	150	0	0	0	9
1.2	3	150	5	5	5	18
1.3	7	150	15	15	15	17
1.4	15	150	30	30	30	28
1.5	30	150	60	60	60	26
1.6 Pheromone						29

In Table 1, the importance of the minor components to the floral attractant composition for increasing attraction of H. armigera is illustrated. Trap catches doubled with the addition of 13% w/w (percentages are given with respect to phenylacetaldehyde) of the minor components (blend 1.2) compared with phenylacetaldyde alone (blend 1.1), and the catch continued to increase as the proportion of minor components was increased up to 70% w/w of phenylacetaldehyde (blend 1.4) beyond which (140% w/w of phenylacetaldehyde) the catch leveled out (blend 1.5). In addition, the total catch from the floral blends containing 70 and 140% w/w of minor components yielded comparable catches to the pheromone-containing lure (blend 1.6). A limitation of this trial is that it provides no indication of which of the minor components is responsible for the increase in catch. The trial did, however, provide a standard composition (blend 1.4; in bold) with which other blend combinations can be compared.

TABLE 2
Effect of removing single components from total blend on catch of adult
H. armigera
			Methyl 2-
Blend	Limonene	Phenyl	methoxy	Linalool	Salicylaldehyde	H. armigera
code	(μl)	acetaldehyde	benzoate (μl)	(μl)	(μl)	Catch
2.1	15	150	30	30	30	13
2.2	0	150	30	30	30	19
2.3	15	150	0	30	30	14
2.4	15	150	30	0	30	9
2.5	15	150	30	30	0	12
2.6	0	150	30	0	0	5
Pheromone						22

In order to try to ascertain which of the minor components contributed to the increased catch, moth catches generated using the standard blend (blend 2.1) were compared with catches using blends in which a single minor component had been removed (Table 2). At the dose tested, removal of limonene appeared to increase catch (blend 2.2), which suggests that it might have an inhibitory effect. The other composition blends displayed similar overall catches.

TABLE 3
Averaged moth catch in lablab bean using traps baited
with the standard floral odour-bait (blend 2.1)
	H. armigera pheromones	Floral odour bait
Male H. armigera	2.8	4.4
Female H. armigera	0	5.2
Maruca vitrata	0	6.6

The standard floral blend (blend 2.1) was found to catch almost twice as many male H. armigera as the standard sex pheromone lure (1 mg dose). Blend 2.1 also caught a significant number of female H. armigera. Interestingly, significant numbers of a related pest species Maruca vitrata (Lepidoptera: Pyralidae) were also trapped, suggesting that the floral blend might be useful for catching a range of pest species.

In Table 4, the results of tests to optimize the effective dose of salicylaldehyde are provided. The tests utilized the standard blend (blend 2.1, in bold), to which differing amounts of salicylaldehyde were added. The averaged trap catch data suggests that, as the quantity of salicylaldehyde is increased, so the total catch of H. armigera increases with no apparent upper limit to catch, even at the highest dose of salicylaldehyde tested (210 μL, blend 4.5). Interestingly, all of the tested blend compositions caught male and female moths in an approximate ratio of 1:3, and all floral blend compositions caught significantly more male moths than the standard sex pheromone.

TABLE 4
Averaged moth catch in a cotton crop using traps
baited with different quantities of salicylaldehyde
in the standard floral odour-bait (blend 2.1)
	Standard blend		H. armigera
Blend	less salicylal-	Salicylaldehyde	Average catch	Ratio
code	dehyde (μl)	(μl)	Male	Female	f/m
4.1	225	0	1.42	3.99	2.80
4.2	225	30	1.59	4.19	2.64
4.3	225	60	1.79	5.29	2.95
4.4	225	150	1.63	5.05	3.10
4.5	225	210	1.87	5.49	2.93
Pheromone			0.42	0

In a similar trial to the one illustrated in Table 4, the standard blend composition (blend 2.1) with phenylacetaldehyde omitted (Table 5), was compared to blend compositions in which different quantities of phenylacetaldehyde were added. Again, the catch of both male and female H. armigera increased with dose of phenylacetaldehyde with no apparent levelling of catch with increased dose. In trial 5, all floral-odour blends tested caught more male H. armigera than were caught by the sex pheromone, with the ratio of male to female moths trapped being typically 1:3.

TABLE 5
Averaged moth catch in a cotton crop using traps baited
with different quantities of phenylacetaldehyde in
the standard floral odour-bait (blend 2.1)
	Standard blend		H. armigera
Blend	less Phenylacet-	Phenylacet-	Average catch	Ratio
code	aldehyde (μl)	aldehyde (μl)	Male	Female	f/m
5.1	105	0	0.61	1.70	2.78
5.2	105	30	0.87	2.69	3.09
5.3	105	60	1.02	3.78	3.72
5.4	105	150	1.38	4.35	3.15
5.5	105	210	1.67	5.45	3.27
Pheromone			0.42	0

Phenylacetaldehyde is generally considered to be attractive to a wide range of Noctuidae and Pyralidae and although, in the above trials, it led to the capture of H. armigera, the numbers were low. A significant number of Hymenoptera were caught in the traps in addition to the moths. Accordingly, in one embodiment of the present invention, suitable deterrent compositions may be added to the attractant compositions, such as peppermint, tea tree oil, cinnamon, bitter almond, lemon oil, vanilla or citronella.

This research has produced an attractant that catches more female moths than the sex pheromone catches male moths, suggesting that the attractant can be used as the basis of a control strategy. Importantly, the attractant was effective at catching male and female H. armigera in a range of crops (cotton, lablab bean and chickpea) in the flowering stage, suggesting that attraction is unaffected by the background crop odour. The attractant also appears to be attractive to a range of other Noctuid pest species in these crops and recent research conducted in the UK has confirmed that the odour bait is attractive to the Silver-Y moth, Autographa gamma, which is an economically important migratory pest species of high-value leafy salads.

The odour-bait is composed of compounds found in a range of H. armigera host plants. Preliminary results show that the blend is attractive to both male and female moths and it is therefore assumed to act as a cue identifying a food (nectar) source. However, more female than male moths were caught in baited traps suggesting that the odour-bait may also provide the moths with information about the suitability of the source for oviposition.

The current research has identified a blend of five compounds, including phenylacetaldehyde and salicylaldehyde, which is a particularly effective attractant. Changes in the relative proportions of phenylacetaldehyde and salicylaldehyde appear to have a profound effect on attraction rates. Phenylacetaldehyde is present in current commercial products for trapping Helicoverpa (Magnet®, for example). It is also a minor component of a Helicoverpa attractant, which comprises salicylaldehyde, produced by Li et al. (2005).

In Europe and other temperate regions, the described odour-bait may have three functions: early season monitoring of pest populations, which is particularly important for migratory species such as A. gamma; assessment of the effectiveness of conventional control strategies; and control of pest populations, notably in protected crops, such as tomato, which is protected in Spain. In tropical regions, the odour-bait would have considerable commercial potential for use with field crops, notably chickpea, lablab bean and tomato.

In summary, the field trials of Example 1, conducted with cotton, tomato, chickpea and lablab bean, have generated an effective bait for H. armigera. The bait has also been shown to be attractive to A. gamma in the UK and Maruca vitrata in Bangladesh.

EXAMPLE 2

Field Trials in India and Bangladesh

Table 6 describes the floral bait traps utilised in three series of trials. In addition, five pheromone baited traps (baited with the pheromone of the key Helicoverpa and related spp.) were used as standards for each target species. Lures were changed every two to three weeks.

TABLE 6
2009-10 Floral bait trials composition
				Total traps
	Treatments	Replicates	Traps	per trial
Series 1	Trial 1	9	3	27
Series 1	Trial 2	4	4	16
Series 1	Trial 3	10	3	30	73
Series 2	Trial 4	13	3	39
Series 2	Trial 5	13	3	39	78
Series 3	Trial 6	10	3	30
Series 3	Trial 7	10	3	30	60

The choice of pheromone trap depended on local availability. In India, the preferred trap was the standard Pheromone Chemicals Ltd. plastic funnel trap, while in Bangladesh a plastic water trap was used. Pheromone lures for the trials were provided by NRI. In India and Bangladesh, H. armigera, Maruca vitrata, Earias vittella and Pectinophora gossypiella lures were provided.

The floral baits were provided in sealed lay-flat polyethylene sachets. The sachets were hung inside the traps in the same way as the pheromone lures. Traps were supported at crop height and the height was adjusted periodically to account for crop growth. Yellow-coloured traps were avoided in order to deter pollinators. Preferably, traps should be colourless or green-coloured. Trap covers were opaque. Where necessary, a killing agent was incorporated into each trap—to ensure insects were dead before opening the trap to count catches.

Trial 1 was designed to investigate the effect of altering the relative amount of the two main components, phenylacetaldhyde and salicylaldehyde on catch. The trial was laid out in cotton fields at four locations: Narakoduru and Jammikunta in Andhra Pradesh, India, and Shreepur and Jessore in Bangladesh.

TABLE 7
Relative composition of lures used in Trial 1
	Phenyl-	Salicylal-	Methyl 2-
	acetaldehyde	dehyde	methoxybenzoate	Linalool	Limonene
96/01	0	100	0	0	0
96/02	3	97	0	0	0
96/03	10	90	0	0	0
96/04	30	70	0	0	0
96/05	50	50	0	0	0
96/06	70	30	0	0	0
96/07	90	10	0	0	0
96/08	97	3	0	0	0
96/09	100	0	0	0	0
H. armigera pheromone

Catches of H. armigera in traps with floral baits were low at both locations in India—compared with catches in traps baited with the sex pheromone. However, the opposite trend was found in the Bangladesh trials, where H. armigera catches in both Jessore and Shreepur exceeded those of the sex pheromone baited traps (Table 8).

TABLE 8
Total catches of H. armigera and other Lepidoptera from Trial 1
Location	Narakoduru, Guntur	Jammikunta KVK	Shreepur	Jessore	Jessore
Crop	Cotton	Cotton	Cotton	Cotton	Country bean
		All		All
Code	H. armigera	Lepidoptera	H. armigera	Lepidoptera	H. armigera	H. armigera	H. armigera
96/01	0	8	0	3	1	16	3
96/02	1	28	2	11	6	25	2
96/03	1	37	3	20	8	23	1
96/04	2	56	1	15	25	24	0
96/05	2	75	1	17	19	32	1
96/06	3	86	1	13	35	31	3
96/07	0	75	1	21	27	30	2
96/08	4	100	0	4	26	42	3
96/09	1	94	1	15	20	30	0
HA Pher	701		167		8	33	2

In India, records were taken of all Lepidopterous species caught in the traps. The total Lepidoptera catches reflected the general trends in H. armigera catches. At all locations, blends 96/06 and 96/08 caught the highest number of Lepidoptera. Thus blends containing between 3 and 30 percent salicylaldehyde relative to phenylacetaldehyde were on average the most attractive of the binary blends tested.

In Trial 2, the standard 5-component blend used in Example 1 (96/12) was compared to: Magnet® (96/10), Li et al. (2005) (96/11) and a binary blend of phenylacetaldehyde and salicylaldehyde (96/13).

TABLE 9

Composition (ratio) of lures used in Trial 2 to compare the UoG standard blend with

commercial standards.

Phenyl

Salicyl-

Methyl 2-

Lin-

Limo-

Benzyl

Phenylethyl

alpha

anisyl

butyl

acetaldehyde

aldehyde

methoxybenzoate

alool

nene

Benzaldehyde

alcohol

alcohol

pinene

alcohol

salicylate

cineole

96/10

1

1

1

1

1

1

96/11

3.4

46.1

5.3

24.2

20.9

96/12

54.0

22.0

9.5

9.5

5.0

96/13

70.5

29.5

H. armigera pheromone

In three of the four replicates of Trial 2, the 96/12 blend caught more moths than the 2-component blend and the blend developed by Li et al. (2005), apart from Jessore where catches were comparable. 96/12 caught similar numbers of moths to the commercial Magnet® blend of compounds (Table 10). In Bangladesh (Shreepur, Jessore), the blends caught similar numbers (or higher) of H. armigera as those caught by the female sex pheromone. In India (Narakoduru, Jammikunta), the sex pheromone caught significantly greater numbers of H. armigera—as for Trial 1.

TABLE 10
Total catches of H. armigera and Lepidoptera from Trial 2 comparison of standards
Location	Narakoduru, Guntur	Jammikunta KVK	Shreepur	Jessore
Crop	Cotton	Cotton	Cotton	Cotton
		All		All
Code	H. armigera	Lepidoptera	H. armigera	Lepidoptera	H. armigera	H. armigera
96/010	11	235	4	15	23	25
96/011	4	65	2	6	13	37
96/012	9	221	12	27	54	37
96/013	3	148	5	20	31	42
HA Pher	619		25		25	11.5

In Trial 3, a third component was added to a roughly 70:30 blend of phenylacetaldehyde:salicylaldehyde, to assess whether the additional compound made the binary blend more attractive to nocturnal Lepidoptera. The compositions of the blends tested are shown in Table 11 and the results in Table 12.

TABLE 11
Relative composition of lures used in Trial 3
	Phenyl-	Salicylal-	Methyl 2-
	acetaldehyde	dehyde	methoxybenzoate	Linalool	Limonene
96/14	70.5	29.5	0.0	0.0	0.0
96/15	69.3	27.7	3.0
96/16	64.3	25.7	10.0
96/17	50.0	20.0	30.0
96/18	69.3	27.7		3.0
96/19	64.3	25.7		10.0
96/20	50.0	20.0		30.0
96/21	69.3	27.7			3.0
96/22	64.3	25.7			10.0
96/23	50.0	20.0			30.0
H. armigera pheromone

Methyl 2-methoxybenzoate, linalool and limonene were added to a 70:30 blend of phenylacetadehyde:salicylaldehyde at 3, 10 and 30%. Addition of methyl 2-methoxybenzoate to the binary blend (96/14) increased moth catches at 30% for both H. armigera and other Lepidoptera, at all five locations tested (Table 12). However, there was no apparent increase in catch associated with addition of linalool and limonene at any of the doses tested. At 30%, limonene appeared to act as a repellent (96/23). In Bangladesh (Shreepur, Jessore), similar numbers of H. armigera were caught by the floral blends and by the female sex pheromone, while in India (Narakoduru, Jammikunta), the sex pheromone caught significantly larger numbers of H. armigera—as for Trials 1 and 2.

TABLE 12
Total catches of H. armigera and other Lepidoptera from Trial 3
Location	Narakoduru, Guntur	Jammikunta KVK	Shreepur	Jessore	Jessore
Crop	Cotton	Cotton	Cotton	Cotton	Country bean
		All		All
Code	H. armigera	Lepidoptera	H. armigera	Lepidoptera	H. armigera	H. armigera	H. armigera
96/14	2	137	3	25	51	10	4
96/15	5	146	4	26	56	5	6
96/16	9	155	3	19	41	9	3
96/17	4	163	0	17	101	11	10
96/18	4	136	2	14	55	9	0
96/19	5	150	5	14	42	8	4
96/20	7	148	4	28	52	8	8
96/21	3	124	2	19	27	5	3
96/22	2	108	3	21	26	3	10
96/23	3	93	8	15	29	6	12
HA Pher	619		143		46	11.5	7

In Trial 4, two compounds were added to a 70:30 blend of phenylacetaldehyde:salicylaldehyde, to assess whether the additional compounds made the binary blend more attractive to nocturnal Lepidoptera. The compositions of the blends tested are shown in Table 13 and the results in Table 14.

TABLE 13
Relative composition of lures used in Trial 4
	Phenyl-	Salicylal-	Methyl 2-
	acetaldehyde	dehyde	methoxybenzoate	Linalool	Limonene
96/24	70.5	29.5	0.0	0.0	0.0
96/25	69.3	27.7	1.5	1.5
96/26	64.3	25.7	5.0	5.0
96/27	50.0	20.0	15.0	15.0
96/28	69.3	27.7		1.5	1.5
96/29	64.3	25.7		5.0	5.0
96/30	50.0	20.0		15.0	15.0
96/31	69.3	27.7	1.5		1.5
96/32	64.3	25.7	5.0		5.0
96/33	50.0	20.0	15.0		15.0
H. armigera pheromone

Addition of a fourth component to the floral blend had a significant effect on catch of all Lepidoptera (Table 14). In each case, catches were increased compared with the binary blend (96/24) and, in particular, catches of H. armigera in India increased markedly compared to those obtained with the sex pheromone. In Bangladesh, catches of H. armigera with the floral blends exceeded those of the pheromone by a factor of ten. However, from the data, it is not possible to identify any one blend that caught significantly more moths at all locations tested.

TABLE 14
Total catches of H. armigera and other Lepidoptera from Trial 4
Location	Narakoduru, Guntur	Vejendla Guntur	Jammikunta KVK	Shreepur
Crop	Cotton	Tomato	Cotton	Cotton
		All		All		All
Code	H. armigera	Lepidoptera	H. armigera	Lepidoptera	H. armigera	Lepidoptera	H. armigera
96/24	6	20	1	101	3	18	89
96/25	15	27	14	192	13	17	97
96/26	13	26	7	140	10	18	220
96/27	12	29	5	145	9	26	149
96/28	18	28	3	164	18	41	131
96/29	18	30	8	146	15	30	133
96/30	4	21	3	140	1	19	115
96/31	9	21	6	130	8	24	138
96/32	14	20	6	128	6	15	130
96/33	16	27	10	168	9	38	134
HA Pher	49		127		139		12

In Trial 5, the three compounds, methyl 2-methoxybenzoate, linalool and limonene were added to the binary 70:30 blend of phenylacetaldehyde:salicylaldehyde in two ratios, 1:1:1 and 1:1:0.5 at 3, 9, 30 and 90% w/w of the binary blend, to assess whether the additional compounds made the binary blend more attractive to nocturnal Lepidoptera. The compositions of the blends tested are shown in Table 15 and the results in Table 16.

TABLE 15
Relative composition of lures used in Trial 5
	Phenyl-	Salicylal-	Methyl 2-
	acetaldehyde	dehyde	methoxybenzoate	Linalool	Limonene
96/34	70.5	29.5	0.0	0.0	0.0
96/35	69.3	27.7	1.0	1.0	1.0
96/36	65.0	26.0	3.0	3.0	3.0
96/37	50.0	20.0	10.0	10.0	10.0
96/38	7.1	2.9	30.0	30.0	30.0
96/39	69.6	27.9	1.0	1.0	0.5
96/40	66.1	26.4	3.0	3.0	1.5
96/41	53.6	21.4	10.0	10.0	5.0
96/42	17.9	7.1	30.0	30.0	15.0
H. armigera pheromone

In general, the addition of methyl 2-methoxybenzoate, linalool and limonene in either a 1:1:1 or 1:1:0.5 ratio at between 3 and 30% w/w levels increased catch of all Lepidoptera at each of the four locations tested, compared with the binary blend (Table 16). For the first time in India, the floral blends gave a comparable catch to the sex pheromone of H. armigera at one location, Jammikunta, but this may be a reflection of the low population present at the time. The highest catches were obtained with blends 96/37 and 96/41, which contained a 25-30% w/w of the three minor components (methyl 2-methoxybenzoate, linalool and limonene), confirming that the standard blend was indeed the optimal blend of the five compounds both for the target species H. armigera and other Lepidoptera.

TABLE 16
Total catches of H. armigera and other Lepidoptera from Trial 5
Location	Narakoduru, Guntur	Vejendla Guntur	Jammikunta KVK	Shreepur
Crop	Cotton	Tomato	Cotton	Cotton
		All		All		All
Code	H. armigera	Lepidoptera	H. armigera	Lepidoptera	H. armigera	Lepidoptera	H. armigera
96/34	3	14	2	120	1	14	44
96/35	12	22	3	118	12	27	95
96/36	7	20	2	125	7	22	92
96/37	24	37	4	138	23	40	89
96/38	22	26	7	96	13	22	60
96/39	9	20	2	139	6	19	75
96/40	15	29	2	130	13	34	99
96/41	14	29	2	140	10	28	69
96/42	9	12	2	115	7	14	79
HA Pher	57		165		8

In Tables 17 to 23 the total catches of selected Lepidoptera, Hymenoptera (Apis mellifera and Bombus spp.) and Diptera are shown.

The highest catches of Lepidoptera, Hymenoptera and Diptera were obtained with binary blends that contained more than 50% phenylacetaldehyde (Table 17). Salicylaldehyde alone (96/01) was unattractive to these species of Lepidoptera, although it was attractive to H. armigera. In contrast, phenylacetaldehyde alone (96/09) was attractive to all species recorded, but the addition of salicylaldehyde had only a modest effect on catch, most notably on D. indica.

TABLE 17
Total catches of non-target Lepidoptera, Hymenoptera and Diptera from Trial 1
Location	Narakoduru, Warangal District, AP, India
Crop	Cotton
	Spodopt.	Diaphania	Autogr.	Parnara	Lampides	Other	Apis	Bombus
Code	litura	indica	gama	guttat.	boeticus	Lepidop.	mellifera	spp.	Diptera
96/01	1	1	0	0	0	6	10	0	1
96/02	1	9	1	1	0	16	5	0	4
96/03	2	8	3	2	0	23	4	0	4
96/04	1	16	3	6	0	34	9	1	6
96/05	2	16	10	5	0	45	15	3	10
96/06	2	23	8	20	1	50	12	2	17
96/07	1	14	4	19	1	56	19	1	9
96/08	4	21	9	12	0	62	20	1	10
96/09	1	13	12	14	1	67	18	1	8

The five-component blend (96/12) caught more moths, Hymenoptera and Diptera than the binary blend (96/13) (Table 18). Diptera appeared to be more attracted to the two- and five-component blends, whereas A. mellifera was more attracted by the five-component blend (96/12) and Magnet® (96/10).

TABLE 18
Total catches of non-target Lepidoptera, Hymenoptera and Diptera from Trial 2
Location	Narakoduru, Warangal District, AP, India
Crop	Cotton
	Spodopt.	Diaphania	Autogr.	Parnara	Lampides	Other	Apis	Bombus
Code	litura	indica	gama	guttat.	boeticus	Lepidopt.	mellifera	spp.	Diptera
96/10	9	129	5	3	0	81	46	0	6
96/11	3	15	8	4	0	35	34	0	3
96/12	11	67	28	38	4	106	47	1	19
96/13	7	46	11	20	2	81	33	4	14

There was no apparent increase in catch for any of the 3-component blends tested in Trial 3 (Table 19), compared with the catch obtained using the 2-component 70:30 blend of phenylacetaldehyde:salicylaldehyde (96/14), except perhaps for the Diptera and ‘other Lepidoptera’ with the addition of methyl 2-methoxybenzoate.

TABLE 19
Total catches of non-target Lepidoptera, Hymenoptera and Diptera from Trial 3
Location	Narakoduru, Warangal District, AP, India
Crop	Cotton
	Spodopt.	Diaphania	Autogr.	Parnara	Lampides	Other	Apis	Bombus
Code	litura	indica	gama	guttatus	boeticus	Lepidopt.	mellifera	spp.	Diptera
96/14	4	34	6	14	0	91	18	6	6
96/15	5	25	16	21	4	95	20	3	13
96/16	1	27	6	18	4	112	13	1	16
96/17	6	31	13	12	0	109	10	2	12
96/18	2	20	9	15	1	101	11	3	10
96/19	6	32	11	10	2	96	9	4	6
96/20	4	35	7	10	2	95	18	5	5
96/21	2	24	4	20	1	91	5	3	7
96/22	2	24	6	18	0	74	11	0	9
96/23	3	17	7	8	1	63	3	0	3

Addition of a fourth component to the 70:30 blend of phenylacetaldehyde:salicylaldehyde (96/14) had no effect on catches of ‘other Lepidoptera’, Hymenoptera or Diptera in the trial conducted in Narakoduru (Table 20), although the catches were low. In contrast, at Vejendla, where populations were higher, significant differences were observed in catches between the binary blend (96/24) and four-component blend for the nocturnal moth species, S. Litura, D. indica and A. gama and ‘other Lepidoptera’, but the four-component blend had no effect on catches of Hymenoptera or Diptera (Table 21).

TABLE 20
Total catches of non-target Lepidoptera, Hymenoptera and Diptera from Trial 4
Location	Narakoduru, Warangal District, AP, India
Crop	Tomato
	Spodopt.	Maruca	Cnaphal.	Parnara	Lampides	Other	Apis	Bombus
Code	litura	testulalis	medinalis	guttatus	boeticus	Lepidopt.	mellifera	spp.	Diptera
96/24	2	6	6	0	0	15	6	n/a	n/a
96/25	3	3	6	0	2	12	4	n/a	n/a
96/26	1	7	5	0	2	9	7	n/a	n/a
96/27	3	4	9	0	2	14	3	n/a	n/a
96/28	2	2	6	0	2	22	1	n/a	n/a
96/29	3	5	3	0	1	11	2	n/a	n/a
96/30	6	6	5	0	1	20	5	n/a	n/a
96/31	4	2	6	0	1	10	6	n/a	n/a
96/32	1	0	4	0	1	8	2	n/a	n/a
HA Pher

TABLE 21
Total catches of non-target Lepidoptera, Hymenoptera and Diptera from Trial 4
Location	Vejendla, Guntur District, AP, India
Crop	Tomato
	Spodopt.	Diaphania	Autogr.	Parnara	Lampides	Other	Apis	Bombus
Code	litura	indica	gama	guttatus	boeticus	Lepidopt.	mellifera	spp.	Diptera
96/24	20	3	3	24	0	74	0	2	12
96/25	46	6	1	7	3	125	3	1	6
96/26	34	5	7	7	0	87	2	3	15
96/27	27	8	3	8	1	102	4	4	9
96/28	31	12	4	15	0	114	0	6	10
96/29	32	8	0	13	1	98	1	3	12
96/30	39	2	2	5	0	94	2	3	9
96/31	26	4	2	13	0	92	1	5	3
96/32	31	7	5	13	2	79	1	1	6
HA Pher

As with Trial 4 (Tables 20 and 21), low catches observed at Narakoduru meant that there was no apparent increase in catch caused by the addition of methyl 2-methoxybenzoate, linalool and limonene to the binary 70:30 blend (96/34) for any of the Lepidoptera, Hymenoptera or Diptera species observed. However, in Vejendla, where populations were higher, the catch of S. Litura and D. indica was significantly increased by the addition of the 1:1:1 blend of methyl 2-methoxybenzoate, linalool and limonene while catches of ‘other Lepidoptera’ were increased by the addition of a 1:1:0.5 ratio of the minor components (Table 24).

TABLE 22
Total catches of non-target Lepidoptera, Hymenoptera and Diptera from Trial 5
Location	Narakoduru, Warangal District, AP, India
Crop	Tomato
	Spodopt.	Maruca	Cnaphal.	Parnara	Lampides	Other	Apis	Bombus
Code	litura	testulalis	medinalis	guttatus	boeticus	Lepidopt.	mellifera	spp.	Diptera
96/34	2	7	2	1	7	6	6	n/a	n/a
96/35	2	4	4	2	3	10	4	n/a	n/a
96/36	1	7	5	1	4	13	7	n/a	n/a
96/37	5	4	4	0	0	14	3	n/a	n/a
96/38	2	2	0	0	3	10	1	n/a	n/a
96/39	2	4	5	0	2	15	2	n/a	n/a
96/40	2	6	6	0	2	11	5	n/a	n/a
96/41	3	3	9	1	1	13	6	n/a	n/a
96/42		3	0	0	0	7	2	n/a	n/a
HA Pher

TABLE 23
Total catches of non-target Lepidoptera, Hymenoptera and Diptera Trial 5
Location	Vejendla, Guntur District, AP, India
Crop	Tomato
	Spodopt.	Diaphania	Autogr.	Parnara	Lampides	Other	Apis	Bombus
Code	litura	indica	gama	guttatus	boeticus	Lepidop.	mellifera	spp.	Diptera
96/34	23	5	1	14	2	89	1	2	3
96/35	15	18	1	12	1	81	3	0	5
96/36	27	15	2	3	1	79	0	2	6
96/37	34	20	2	16	1	78	1	1	3
96/38	14	12	2	0	1	61	0	0	4
96/39	29	6	4	6	0	98	4	3	8
96/40	15	7	7	8	0	99	1	2	4
96/41	36	6	3	11	1	93	0	4	6
96/42	19	10	2	2	2	82	0	5	9
HA Pher

In summary, the field trials conducted in India and Bangladesh with cotton, tomato and country bean suggest that a 50:20:10:10:10 blend of phenylacetaldehyde, salicylaldehyde, methyl 2-methoxybenzoate, linalool and limonene is a particularly-attractive blend. However, any blends of phenylacetaldehyde and salicylaldehyde with at least two of the three minor components methyl 2-methoxybenzoate, linalool and limonene in ratios of between 3 and 30% had similar levels of attraction.

The influence of dose was not tested in these trials. However, it is not anticipated that the optimal blend will change with dose, as the current blends were tested over at least four-week periods, during which time there were no apparent variations in overall catch levels. The general trends in relative catch of H. armigera were mirrored in the total catch of Lepidoptera suggesting that the floral attractant would be useful at trapping pests in a crop which had a species complex.

In India, in addition to H. armigera, significant numbers of other pest species were also caught with the floral-baited traps notably Spodoptera litura (armyworm), Earias vittella (spotted bollworm), Diaphania indica (cucumber moth), Autographa gama (silver-Y), Maruca testulalis (legume pod borer), Cnaphalocrocis medinalis (rice leafroller), and low numbers of minor pests such as Parnara guttatus (paddy skipper), and Lampides boeticus (long-tailed pea-blue). The catches of S. Litura and E. Vittella were perhaps not too surprising given that they are cotton pests but the other species were unexpected. D. indica is a major pest of cucurbits in export crops such as gherkins. M. testulalis is a major pest of legumes. L. boeticus is a minor pest of legumes. P. guttatus and C. medinalis are pests of rice. A. gama is a polyphagous pest, not recognised by farmers in India, which is increasingly important in Europe.

REFERENCES

• Bruce, T. J. & Cork, A. (2001) Electrophysiological and behavioural responses of female Helicoverpa armigera to compounds identified in flowers of African Marigold, Tagetes erecta. Journal of Chemical Ecology, 27, 1119-1131.
• Bünning, E. (1956). Endogenous rhythms in plants. Annual Review of Plant Physiology, 7, 71-90.
• Chamberlain D. J., Brown N. J., Jones O. T. & Casagrande E. (2000) Field evaluation of a slow release pheromone formulation to control the American bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae) in Pakistan. Bulletin of Entomological Research, 90, 183-190.
• Dobson, H. E. M. (1994) Floral volatiles in insect biology, pp. 47-81, in E A. Bernay (ed.). Insect-plant Interactions, Vol. V, CRC Press, Boca Raton, Fla.
• Gabel, B., Thiéry, D., Suchy, V., Marion-Poll, F., Hradsky, P. and Farkas, P. (1992) Floral volatiles of Tancetum vulgare L. attractive to Lobesia botrana Den. Et Schiff. Females. Journal of Chemical Ecology, 18, 693-701.
• Heath, R. R., Landolt, P. J., Dueben, B. & Lenczewski, B. (1992) Identification of floral compounds of night-blooming jessamine to cabbage looper moths. Environmental Entomology, 21, 854-859.
• Hess, D. (1983) Die Blüte. Ulmer, Stuttgart.
• Honda, K., Omura, H. & Hayshi. (1998). Identification of floral volatiles from Ligustrum japonicum that stimulate flower-visiting by cabbage butterfly, Pieris rapae. Journal of Chemical Ecology, 24, 2167-2180.
• Ilse, D. (1928). Über den Farbensinn der Tagfalter. Z. Vergl Physiology, 8, 658-692.
• Li, W.-Z., Yuan, G.-H., Sheng, C.-F., & Guo, X.-R. (2005) Active compounds in Populus nigra L. Wilted leaves responsible for attracting Helicoverpa armigera (Hübner) (Lep., Noctuidae) and new agaropectin formulation. Journal of Applied Entomology, 129, 557-562.
• Matile, P. & Altenburger, R. (1988) Rhythms of fragrance emission in flowers. Planta, 174, 242-247.
• Miyakawa, M. (1976). Flower-visiting behaviour of the small white butterfly, Pieris rapae crucivora Boisduval, Annotationes Zoologicae Japonenses, 49, 261-273.
• Naumann, C. M., Ockenfell, P., Schmitz, J. & Francke, W. (1991). Reaction of Zygaena moths to volatile compounds of Knautia arvensis (Lepidoptera: Zygaenidae). Entomologia Generalis, 15, 255-264.
• Pawar, C S Srivastava, C P & Reed, W. 1993 Phenylacetaldehyde: an attractant for Heliothis armigera. International Chickpea Newsletter, 8, 27-28
• Scherer, C. and Kolb, G. (1987a). Behavioral experiments on the visual processing of color stimuli in Pieris brassicae L. (Lepidoptera). Journal of Comparative Physiology, A, 160, 645-656.
• Wiesenborn, W. D. & Baker, T. C. (1990). Upwind flight to cotton flowers by Pectinophora gossypiella (Lepidoptera: Gelechiidae). Environmental Entomology, 19, 490-493.
• Witzgall, P., Kirsch, P. & Cork, A. (2010). Sex pheromones and their impact on pest management, Journal of Chemical Ecology, 36, 80-100.
• Zhu, Y., Keaster, A. J. & Gehardt, K. O. (1993). Field observations on attractiveness of selected blooming plants to noctuid moths and electroantennogram responses of black cutworm (Lepidoptera: Noctuidae) moths to flower volatiles. Environmental Entomology, 22, 162-16

Claims

1. An attractant composition for attracting insects of the moth families Noctuidae and Pyralidae or the species Diaphania indica insects, the composition comprising phenylacetaldehyde, salicylaldehyde and at least one of methyl-2-methoxybenzoate, linalool and limonene, wherein phenylacetaldehyde comprises between 40 and 90% of the total weight of the composition, and salicylaldehyde comprises between 3 and 60% of the total weight of the composition.

2. An attractant composition as claimed in claim 1 comprising at least two of: methyl-2-methoxybenzoate, linalool and limonene.

3. An attractant composition as claimed in claim 2 wherein at least two of: methyl-2-methoxybenzoate, linalool and limonene, each comprise between 3 and 30% of the total weight of the composition.

4. An attractant composition as claimed in claim 1 comprising phenylacetaldehyde, salicylaldehyde, methyl-2-methoxybenzoate, linalool and limonene.

5. An attractant composition as claimed in claim 4 wherein the ratio of phenylacetaldehyde:salicylaldehyde:methyl-2-methoxybenzoate:linalool:limonene is approximately 50:20:10:10:10.

6. An attractant composition as claimed in claim 1 further comprising at least one compound selected from the group comprising: benzaldehyde, benzyl alcohol, phenylethyl alcohol, anisyl alcohol, α-pinene, butyl salicylate (Z)-jasmone, methyl salicylate, diacetone (4-hydroxy-4-methyl-2-pentanone), (E)-myroxide, (Z)-b-ocimene, and (R)-(−)-piperitone.

7. An attractant composition as claimed in claim 1 wherein the composition further comprises an antioxidant.

8. An attractant composition as claimed in claim 7 wherein the antioxidant is at least one of: α-tocopherol, α-, β-, γ-, or δ-tocotrienol, and butylated hydroxytoluene.

9. An attractant composition as claimed in claim 7 wherein the antioxidant comprises between 10 and 100% w/w, based on the amount of phenylacetaldehyde.

10. An attractant composition as claimed in claim 1 further comprising at least one of: a UV screener and a UV absorber.

11. An attractant composition as claimed in claim 10 wherein the composition comprises carbon black as UV screener.

12. An attractant composition as claimed in claim 10 wherein the composition comprises a UV absorber selected from at least one of: o-hydroxybenzophenones and benzotriazoles.

13. An attractant composition as claimed in claim 1 further comprising at least one carotenoid.

14. An attractant composition as claimed in claim 13, wherein at least one carotenoid is vitamin A.

15. A method of attracting insects of the moth families Noctuidae and Pyralidae or the species Diaphania indica insects comprising providing an attractant composition as claimed in claim 1.