Aeneus Fabricius Research Articles

The effect of insecticide application by dropleg sprayers on pollen beetle parasitism in oilseed rape

Dropleg sprayers apply pesticides below the flower horizon of oilseed rape plants and thus reduce unwanted side effects on pollinating insects. Whether this technique benefits parasitoids of seed and pollen feeding insect pests has not been studied earlier. To answer this question, we first assessed the vertical distribution of pests and parasitoids using a portable aspirator. In addition, parasitism rates of pollen beetle, Brassicogethes aeneus Fabricius (Coleoptera: Nitidulidae), by the larval parasitoid Tersilochus heterocerus Thomson (Hymenoptera: Ichneumonidae) were compared in conventional and dropleg sprayed fields over four years (2016–2019), using the neonicotinoids thiacloprid and acetamiprid. Our results show that seed and pollen feeders were mainly found in the flowering canopy, while the predominant location of parasitoids was species-specific. Among pollen beetle parasitoids, Phradis interstitialis Thomson (Hymenoptera: Ichneumonidae) was more abundant below flowering canopy (63% of total catch), whereas T. heterocerus was mainly caught in the flowering canopy (84% of total catch). In the spraying experiments, average parasitism rates of pollen beetles by T. heterocerus ranged between 55 and 82% in the untreated controls. In the dropleg spray treatments, parasitism rates did not differ significantly from control levels, with the exception of thiacloprid application in 2019. In contrast, conventional spray applications resulted in a reduction of parasitism rates by up to 37% compared to the control for at least one of the insecticides in three out of four years. The impact of conventional application differed between years, which may be explained by the temporal coincidence between spray application and the immigration of parasitoids into the crop. We conclude that dropleg spraying exerts lower non-target effects on the main biological control agent of pollen beetle.

Changes in resistance development in pollen beetle (Brassicogethes aeneus F.) to lambda-cyhalothrin, etofenprox, chlorpyrifos-ethyl, and thiacloprid in the Czech Republic during 2013–2017

Susceptibility of common pollen beetle (Brassicogethes aeneus Fabricius) to four insecticides was monitored at 14 locations in the Czech Republic during 2013–2017 on oilseed rape. Seventy local pollen beetle populations were tested for resistance to lambda-cyhalothrin, etofenprox, chlorpyrifos-ethyl, and thiacloprid. Resistance to lambda-cyhalothrin and etofenprox was determined with the recommended rates of 7.5 g a.i. ha−1 and 40 g a.i. ha−1, respectively. Resistance increased significantly over time only for lambda-cyhalothrin. Chlorpyrifos-ethyl at the recommended rate of 187.5 g a.i. ha−1 exceeded by 4 times the mean 90% lethal dose (LD90) value of 44.4 g a.i. ha−1, and mortality was 100% in all years. Thiacloprid had widely dispersed LD50 and LD90 values, as did lambda-cyhalothrin and etofenprox. Thiacloprid's recommended rate of 72 g a.i. ha−1 was substantially higher than mean LD90 values. Several subpopulations with reduced susceptibility to thiacloprid were, however, found in this study. No cross-resistance among lambda-cyhalothrin, etofenprox, chlorpyrifos, and thiacloprid was determined.

Efficiency of chemical protection of spring rape and mustard from rape blossom beetle

One of the most dangerous pests of cabbage crops which can damage plants in the budding and flowering phases in all areas of their cultivation is a rape blossom beetle (Meligethes aeneus Fabricius, 1775). The pest is widespread throughout Ukraine; it causes significant damage to the crops every year and reduces the seed yields. It should be noted that the rape blossom beetle is not new to our country and as a pest of rape and other crops from the cabbage family has been mentioned since 1845, and a detailed description of its morphology, biology and ecology can be found in the works of the nineteenth century. It is established that in the Eastern Forest-Steppe of Ukraine the first individuals of the rape blossom beetle appear on the flowering wild growing plants (first of all on dandelion and buttercup) when the average daily temperature exceeds 8 °C, it is the middle of the first decade of April and the beginning of the third decade of April. The mass emergence of the rape blossom beetles takes place when the daily average temperatures are at the range of 9–13 °C and the sum of the effective temperatures above 5 °C is at the range of 100–113 °C, it is the middle of the second decade of April and the end of the third decade of April. The females of the rape blossom beetle usually lay 2–3 eggs into one bud of spring rape or mustard. When protecting the crops from the rape blossom beetle the highest technical efficiency was noted when applying the binary mixture of the microbiological preparation Actophyte, 0.25 % of emulsion concentrate in the dose of 4.8 L/ha and systemic insecticide Biscaya, 24 % of oily dispersion (0.25 L/ha) and in 14 days after spraying it was 76.6 % on white mustard, 74.3 % on Chinese mustard and 76.2 % on spring rape. The highest growth increase in the yield capacity was observed in the same variant; for white mustard it was 0.431 t/ha, for Chinese mustard it was 0.265 t/ha and for spring rape the growth increase amounted to 0.277 t/ha. As a result of the researches it is established that the weight of 1000 healthy seeds is 2,6996 g, and the weight of the seeds damaged by the larvae of the rape blossom beetle is 0.4213 g, so it is reduced by 84.4 %. The filling of the damaged seeds is 6.8 times more, which indicates that they are smaller in diameter and frail. The undamaged seeds of spring rape contain 35.92 % of fat, and the damaged seeds contain only 17.48 %, which is 2.05 times less. The protein content in the undamaged seeds was 30.97 % and in the damaged ones it was 32.23 %, that is 1.04 times more. The germination rate of the undamaged seeds of spring rape under the laboratory conditions on the eighth day was 90.0 %, and the germination rate of the damaged ones amounted to 58.0 % and was lower by 32.0 %.

Trap Crops and Insectary Plants in the Order Brassicales

Abstract This paper reviews the most important cases of trap crops and insectary plants in the order Brassicales. Most trap crops in the order Brassicales target insects that are specialist in plants belonging to this order, such as the diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), the pollen beetle, Meligethes aeneus Fabricius (Coleoptera: Nitidulidae), and flea beetles in the genera Phyllotreta and Psylliodes (Coleoptera: Chrysomelidae). In most cases, the mode of action of these trap crops is the preferential attraction of the insect pest for the trap crop located next to the main crop. With one exception, these trap crops in the order Brassicales have been used with brassicaceous crops. Insectary plants in the order Brassicales attract a wide variety of natural enemies, but most studies focus on their effect on aphidofagous hoverflies and parasitoids. The parasitoids benefiting from insectary plants in the order Brassicales target insects pests ranging from specialists, such as P. xylostella, to highly polyfagous, such as the stink bugs Euschistus conspersus Uhler and Thyanta pallidovirens Stål (Hemiptera: Pentatomidae). In the order Brassicales, the three most common trap crops are Indian mustard, Brassica juncea (L.) Czern, Chinese cabbage, Brassica rapa L., and yellow rocket, Barbarea vulgaris R. Br., while the three most common insectary plants are sweet alyssum, Lobularia maritima (L.) Desv., white mustard, Sinapis alba L, and B. vulgaris. Except for Tropaeolum majus L. (Tropaeolaceae) and Capparis decidua (Forssk.) Edgew. (Capparaceae), the tested trap crops and insectary plants in the order Brassicales belong to the family Brassicaceae.

Colour choice behaviour in the pollen beetle Meligethes aeneus (Coleoptera: Nitidulidae)

The pollen beetle Meligethes aeneus Fabricius (Coleoptera, Nitidulidae), a pest of oilseed rape (Brassica napus), is known to respond to coloured stimuli; however, current understanding of the underlying mechanisms of colour choice in this species is limited. In the present study, physiological and behavioural experiments are conducted to determine the response of the pollen beetle to colours in the field. Spectral sensitivity is measured in 10 animals using the electroretinogram technique. Light flashes (100 ms) at varied wavelengths (340–650 nm, 10‐nm steps) and at different light intensities are applied to the eye after dark adaptation. In behavioural experiments in the field, 100 water traps of varying colours (from yellow to green to blue with varying amounts of white and black added, and with known spectral reflectance) are set out on a bare soil field in May 2008. The mean spectral sensitivity curve of M. aeneus peaks at 520 nm; however, a model template fitted to the long wavelength tail of the observed curve reveals a peak at approximately 540 nm (green). A secondary sensitivity peak is observed in the ultraviolet (UV) range (370 nm). A total of 2482 pollen beetles are captured in the coloured traps. The results show that the pollen beetles' preference for yellow over other colours can be modelled as a colour opponent mechanism (green versus blue); however, further experiments are needed to specify responses to colours with higher UV reflectance. These findings may be used to optimize trap colours for monitoring to help develop integrated pest management strategies for pollen beetle control.

The spatial dynamics of pollen beetles in relation to inflorescence growth stage of oilseed rape: implications for trap crop strategies

AbstractSemi‐field‐scale arrays of oilseed rape (Brassica napus L.) (Brassicaceae) plants were used to observe the development of distributions of pollen beetles (Meligethes aeneus Fabricius) (Coleoptera: Nitidulidae) in a simulated trap crop system where inflorescence growth stage alone was used to manipulate the pest. Over two successive years, pairs of 1 m spaced square arrays of 100 glasshouse‐grown plants were placed 40 m apart in the field in May, and were subject to natural infestation by pollen beetles. The test plot of each pair had a simulated trap crop, with an outer row of plants at early flowering stage intended to protect more susceptible inner plants at late bud stage, and the control plot had all plants at the late‐bud stage, simulating a standard crop situation. Pollen beetles were counted daily on each plant for 10–13 days. The spatio‐temporal development of plot infestation was analysed in relation to the distribution of racemes in bud and raceme in flowers using Spatial Analysis by Distance IndicEs (SADIE), and tests of edge and centre distribution. Inflorescence growth stage characteristics were shown to be important in determining the spatial distributions of pollen beetles. In control plots, the numbers of racemes in bud and in flower were never edge or centre distributed. In test plots, racemes in flower were always edge distributed, and racemes in bud began edge distributed and became centre distributed. Pollen beetle numbers were usually spatially associated with the abundance of racemes in bud and/or in flower. In control plots, pollen beetles were neither edge nor centre distributed, but in test plots they maintained a significant edge distribution for 7–10 days. At the end of the experiments, females were more centre distributed in the test plots than males, and were more closely associated with racemes with buds, whereas males were more associated with racemes with flowers. In early flowering stage plants, the number of racemes in flowers were a good indicator of the abundance of racemes in buds, but this relationship was lost as flowering progressed. Although flowering racemes provide strong cues for immigrating pollen beetles, the abundance of buds may be a more important determinant of residence time, particularly for females, and is therefore a critical determinant of trap crop effectiveness.

Occurrence and dynamics of <i>Nosema meligethi</i> (Microsporida) in populations of <i>Meligethes aeneus</i> (Coleoptera, Nitidulidae) in Finland

A total of 221 samples of the beetle Meligethes aeneus Fabricius were collected from southern and central Finland in 1989-90, and 10 152 beetles were individually examined to determine the occurrence of the microsporidian disease Nosema meligethi Issi & Raditsheva. The dynamics of this disease was followed at seven sites throughout the season, and its ecological aspects were studied at one locality, Hartola. The level of N. meligethi infection steadily increased in M. aeneus populations during the season, with horizontal transmission appearing to take place in flowerheads, where the beetles aggregate to feed. Infected beetles migrated to overwintering sites earlier than did healthy beetles, and just prior to overwintering, infected beetles were lighter in weight than healthy ones. This fact may drastically affect the overwintering survival of infected beetles.