Antifeedant Effects and Repellent Activity of Loline Alkaloids from Endophyte-Infected Tall Fescue against Horn Flies, Haematobia irritans (Diptera: Muscidae).

Javier Espinoza,Leonardo Bardehle,Andrés Quiroz,Paul Escobar-Bahamondes,Emilio Ungerfeld,Manuel Chacón-Fuentes

doi:10.3390/molecules26040817

Javier Espinoza, Leonardo Bardehle + Show 4 more

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https://doi.org/10.3390/molecules26040817

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Abstract

Haematobia irritans is an obligate bloodsucking ectoparasite of cattle and is the global major pest of livestock production. Currently, H. irritans management is largely dependent upon broad-spectrum pesticides, which lately has led to the development of insecticide resistance. Thus, alternative control methods are necessary. Endophyte-infected grasses have been studied as an alternative due to their capability to biosynthesize alkaloids associated with anti-insect activities. Thus, the main aim of this study was to evaluate the antifeedant and repellent activity of lolines obtained from endophyte-infected tall fescue against H. irritans adults in laboratory conditions. The alkaloid extract (ALKE) was obtained by acid–base extraction. N-formyl loline (NFL) and N-acetyl loline (NAL) were isolated by preparative thin layer chromatography (pTLC) and column chromatography (CC), and the loline was prepared by acid hydrolysis of a NFL/NAL mixture. Loline identification was performed by gas chromatography coupled to mass spectrometry (GC/MS). Feeding behavior was evaluated by a non-choice test, and olfactory response was evaluated using a Y-tube olfactometer. Accordingly, all samples showed antifeedant activities. NFL was the most antifeedant compound at 0.5 µg/µL and 1.0 µg/µL, and it was statistically equal to NAL but different to loline; however, NAL was not statistically different to loline. NFL and NAL at 0.25 µg/µL were more active than loline. All samples except loline exhibited spatial repellency in the olfactometer. Thus, the little or non-adverse effects for cattle and beneficial activities of those lolines make them suitable candidates for horn fly management.

Highlights

Haematobia irritans irritans (L.) (Diptera: Muscidae), commonly named the horn fly, is an obligate bloodsucking ectoparasite of cattle [1] and it is considered one of the major global pests of livestock production [2]
Two pale-yellow oils corresponding to N-formyl loline (NFL) (4.8 mg) and Nacetyl loline (NAL) (6.9 mg) were obtained from the N-formyl loline/N-acetyl loline mixture (NFL/NAL) mixture by column chromatography, and another pale-yellow oil, corresponding to loline (8.6 mg; 55.8 μmol; 35.3%), was yielded by the acid hydrolysis of the NFL/NAL mixture
Loline alkaloid analysis and identification were performed by comparing retention times and mass spectrums from gas chromatography coupled to mass spectrometry (GC/MS) analysis with those of commercial standards

Summary

Introduction

Haematobia irritans irritans (L.) (Diptera: Muscidae), commonly named the horn fly, is an obligate bloodsucking ectoparasite of cattle [1] and it is considered one of the major global pests of livestock production [2] It is a little dark gray fly of between 2 and 5 mm in length, which makes it the smallest biting fly that attacks beef cattle [3,4]. In Chile, H. irritans is found between the regions of Arica y Parinacota and Aysén and it emerges from November until May, showing a large population from December until March [12] Both H. irritans sexes use their piercing proboscis to feed on cattle 24–38 times per day [5], causing annoyance and alteration of grazing behavior, especially when the animals suffer a massive infestation (>200 horn flies per animal) [13,14,15]. This did not consider the losses produced by the decrease in reproductive efficiency and losses in leather quality [26]

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