M.M. Davidson

4-Pyridyl carbonyl compounds as thrips lures: effectiveness for Western flower thrips in y-tube bioassays.

In a search for chemical lures to manage the cosmopolitan crop pest western flower thrips (WFT), Frankliniella occidentalis, a Y-tube olfactometer was used to screen 20 compounds, including 18 4-pyridyl compounds. Comparison of Y-tube results for New Zealand flower thrips (NZFT), Thrips obscuratus, with field trapping data for ethyl nicotinate and ethyl isonicotinate, suggested that the minimum attractive dose (MAD) of an odor compound, where significantly ( p < 0.05) more than 50% of thrips walked up the odor-laden arm, provided a measure for selecting compounds to evaluate for potential lure efficacy in the field. Eighteen synthetic 4-pyridyl compounds were tested on female WFT in a Y-tube olfactometer and four 4-pyridyl carbonyl compounds had MADs lower than the known WFT attractants p-anisaldehyde (MAD 10 (-3) microL) and ethyl nicotinate (10 (-2) microL): methyl isonicotinate (10 (-6) microL), ethyl-2-chloropyridine-4-carboxylate (10 (-6) microL), ethyl isonicotinate (10 (-4) microL) and methyl 4-pyridyl ketone (10 (-5) microL). The suitability of MAD for selecting compounds for further evaluation of practical lure efficacy is discussed. Comparisons of activities within homologous series of esters and ketones showed that attractant activity decreased with chain length. 4-Formyl pyridine was an attractant at a dose of 10 (-5) microL, but was repellent at higher doses (10 (-2)-10 degrees microL).

Pyridine Compounds Increase Thrips (Thysanoptera: Thripidae) Trap Capture in an Onion Crop

ABSTRACT The effect of the thrips (Thysanoptera: Thripidae) lures ethyl isonicotinate, methyl isonicotinate, and ethyl nicotinate on numbers of thrips captured in white water traps in an onion (Allium spp.) crop, in New Zealand, was examined. Female onion thrips, Thrips tabaci Lindeman (69.0%), and Thrips obscuratus Crawford (27.8%) (males and females) were the most common species found in traps in the onion crop. Ethyl isonicotinate, methyl isonicotinate, and ethyl nicotinate caught 18,12, and 4× more onion thrips, respectively, than controls (no-lure). In contrast, traps with ethyl isonicotinate set up in a grass field at the same time as the onion crop trial caught 84× more onion thrips than traps without this lure. For T. obscuratus, traps with ethyl isonicotinate, methyl isonicotinate, and ethyl nicotinate caught 10, 13, and 12× more thrips, respectively, than controls in the onion crop.

Methyl isonicotinate induces increased walking and take-off behaviour in western flower thrips, Frankliniella occidentalis

Timely detection of western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is important to help prevent economic damage to crops. Coloured traps are commonly used for thrips monitoring and their efficacy can be markedly improved with the addition of semiochemicals such as methyl isonicotinate (MI). However, the behavioural response of thrips to these compounds is poorly understood. In leaf/petal disc laboratory experiments the effect of MI on adult female WFT was examined with respect to walking and take‐off behaviour. Clean air or air with MI was blown over the leaf/petal discs at an angle of 30° via a glass pipette connected to a wash bottle containing a cotton dental roll with or without a defined amount of MI. At airspeeds of 0.6–1.2 m s−1 and at doses of 1, 10, 50, 100, and 1000 μl (equivalent to indicative concentrations of 1.7, 4.5, 7.3, 8.8, and 14.9 ng MI l−1 air blown over the leaf discs), WFT spent a greater proportion of time walking on chrysanthemum leaf discs in the presence of MI than the non‐attractive thrips compound β‐caryophyllene or clean air. Western flower thrips showed a dose‐dependent take‐off response to the thrips attractant MI, but not to β‐caryophyllene (virtually no take‐off). At 100 μl of MI (8.8 ng l−1 air), WFT spent a greater proportion of time walking on host plant tissue than in clean air, depending on plant disc substrates. Furthermore, WFT took off more often from plant discs exposed to an air current containing MI than from those exposed to clean air. Western flower thrips exposed to MI took off at a similar rate from chrysanthemum leaves, chrysanthemum flower petals, and sweet pepper leaves, but much less readily from bean leaves. The results show that MI stimulates walking and take‐off behaviour for adult female WFT under these experimental conditions and these responses are dose‐dependent and mediated by the host plant. These results are placed in the context of previous research on the behavioural response of thrips to semiochemicals and their implications for thrips pest management are discussed.

Can semiochemicals attract both western flower thrips and their anthocorid predators

Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) (western flower thrips, WFT) is a key pest in a range of crops worldwide. Anthocorid species (Hemiptera) are important natural enemies of thrips. Several experiments were undertaken to determine whether a thrips lure, methyl isonicotinate (MI), affected the behaviour of WFT and anthocorids found in outdoor crops. Currently, this volatile compound is used in conjunction with sticky traps for monitoring thrips predominantly in greenhouses in Northern Europe. In the present study, in a nectarine [Prunus persica (L.) (Rosaceae)] orchard and an outdoor capsicum [Capsicum annuum L. (Solanaceae)] crop in Spain, blue sticky and white water traps with MI caught significantly more WFT than traps without MI. The volatile compound also significantly increased both blue sticky and white water trap capture of anthocorids – predominantly Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) – in the capsicum crop. These results indicate that the behaviour of both WFT and O. laevigatus were altered by the presence of the compound and suggest there is potential to develop novel tools based on MI in conjunction with biological control strategies for thrips management.

Field Response of Onion Thrips and New Zealand Flower Thrips to Single and Binary Blends of Thrips Lures

Abstract Tests were performed to determine whether combining two thrips lures, ethyl nicotinate (EN) and ethyl isonicotinate (EI), in the same water trap increased the numbers of New Zealand flower thrips (NZFT), Thrips obscuratus Crawford, and onion thrips, T. tabaci Lindeman (Thysanoptera: Terebrantia: Thripidae), caught in the field relative to traps with a single lure. Traps with both lures (1:1 ratio; mixture or separate adjacent vials) caught 5–9 times more female onion thrips (thelyotokous populations are the most prevalent in New Zealand) than traps with EN only (P < 0.001), but caught similar numbers to traps with EI only. Traps with both lures caught 2–3 times as many male and female NZFT than traps with EI only, but similar numbers to traps with EN only. Thus, a combination of the two lures in one trap could be used to detect and monitor flying onion thrips and NZFT simultaneously.

Trap colour, size, and borders alter catches of Bactericera cockerelli in a potato crop

Visual cues play a key role in host finding in many phytophagous insects, including the tomato potato psyllid (TPP), Bactericera cockerelli (Šulc) (Hemiptera: Triozidae), a serious pest of solanaceous crops. This study evaluated the response of TPP to sticky traps of one of three colours, up to four sizes, and with or without green borders in an organic potato crop in Hawkes Bay, New Zealand. On average, large traps caught a higher density of TPP than small traps (with or without border; 25 and 14 TPP per 100 cm2, respectively). Tomato potato psyllid density on the green border was affected by the colour of the centre trap; a blue centre resulted in substantially fewer TPP on the green border than a yellow centre (9.0 vs. 69.6 TPP per 100 cm2). Trap catches in early summer were male biased, whereas catches of male and female TPP in late summer were approximately equal.

Prey consumption and survival of the predatory mite, Amblydromalus limonicus, on different prey and host plants

ABSTRACT Amblydromalus limonicus consumed fewer first instar Frankliniella occidentalis thrips than Bactericera cockerelli psyllids per day when on the same (1.7 thrips, 3.7 psyllids) or separate (2.9 thrips, 4.4 psyllids) capsicum leaf discs. Mites ate fewer psyllids per day on tomato (1.9) than on capsicum (3.1). Mite survival was similar on both prey and plants.

Methyl isonicotinate - A non-pheromone thrips semiochemical - And its potential for pest management

Methyl isonicotinate is one of several patented 4-pyridyl carbonyl compounds being investigated for a variety of uses in thrips pest management. It is probably the most extensively studied thrips non-pheromone semiochemical, with field and glasshouse trapping experiments, and wind tunnel and Y-tube olfactometer studies in several countries demonstrating a behavioural response that results in increased trap capture of at least 12 thrips species, including the cosmopolitan virus vectors such as western flower thrips and onion thrips. Methyl isonicotinate has several of the characteristics that are required for an effective semiochemical tool and is being mainly used as a lure in combination with coloured sticky traps for enhanced monitoring of thrips in greenhouses. Research indicates that this non-pheromone semiochemical has the potential to be used for other thrips management strategies such as mass trapping, lure and kill, lure and infect, and as a behavioural synergist in conjunction with insecticides, in a range of indoor and outdoor crops.

The effect of background plant odours on the behavioural responses of Frankliniella occidentalis to attractive or repellent compounds in a Y-tube olfactometer

The western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), causes major losses in agricultural and horticultural crops worldwide. The volatile compounds methyl isonicotinate, p‐anisaldehyde, eugenol, and linalool are known as olfactory attractants, and salicylaldehyde is known as a repellent for F. occidentalis under clean‐air conditions in laboratory experiments. In the present study we assessed the responses of F. occidentalis to these compounds when presented alone, in combination, and in the presence of background odours emanating from cucumber (Cucumis sativus L., Cucurbitaceae), capsicum (Capiscum anuum L., Solanaceae), chrysanthemum (Chrysanthemum morifolium Ramat., Asteraceae), clove basil (Ocimum gratissimum L.), and lavender (Lavandula angustifolia L., both Lamiaceae) plants in a Y‐tube olfactometer. In the presence of any background plant odour, the attractiveness of pure methyl isonicotinate to F. occidentalis proved to be consistently significant. Compared to clean‐air conditions, a slightly lower percentage of thrips chose the Y‐tube arm loaded with 10% p‐anisaldehyde in the presence of cucumber leaf odour. With non‐flowering clove basil plants in the background, F. occidentalis responses to 1% eugenol, a constituent of clove basil essential oil, were neutral, and the same applied to responses to pure linalool, a constituent of lavender essential oil, in the presence of flowering lavender plants. Also, thrips responses to pure or diluted salicylaldehyde were clearly influenced by plant background odours. We simulated a push‐pull situation and found a trend indicating that the percentage of F. occidentalis choosing the airflow loaded with the attractant methyl isonicotinate was higher when the airflow in the other arm of the Y‐tube was loaded with the repellent salicylaldehyde compared to clean air, and vice versa. We showed interactions between attractive or repellent volatile compounds and the environmental odours in the chemical ecology of F. occidentalis and the potential of a combined use of these compounds in thrips pest management.

Host plant influences establishment and performance of Amblydromalus limonicus, a predator for Bactericera cockerelli : Host plant influences Amblydromalus limonicus performance

BACKGROUND Management of tomato potato psyllid (TPP; Bactericera cockerelli (Šulc)) predominantly relies on insecticides. However, biological control agents (BCAs) could provide viable alternatives to suppress TPP populations. In this laboratory experiment, we assessed the predatory mite Amblydromalus limonicus (Garman & McGregor) as a BCA of TPP on whole plants of two tomato and two pepper cultivars over a 5-week period. RESULTS Plant species and cultivar had a significant effect on the ability of A. limonicus to suppress populations of TPP. Numbers of TPP were suppressed by A. limonicus on four pepper treatments, but on only one tomato treatment. Amblydromalus limonicus could survive and reproduce on pepper and tomato, but more were found on pepper at the end of the 5-week period. CONCLUSION Amblydromalus limonicus has the potential to suppress TPP populations on pepper but not tomato cultivars, based on the present study. Possible reasons for these results include the difference in leaf morphology between species, and higher predator:prey ratios on pepper than tomato because of the longer TPP generation time on pepper.