Plant Protection News

Through twilight to the light: a new sight of variability in codling moth behavioral reactions

2024-10-14T10:22:21+00:00

The codling moth, Cydia pomonella (L.) is the most dangerous pest of orchard crops in the world. The aim of the paper is to evaluate the attractiveness of low-power UV LEDs for the codling moth, including their interactions with the synthetic sex pheromone bait, under a highly variable level of natural illumination during the season at dusk in St. Petersburg as compared to the south of Russia. Traps of two designs (adhesive Delta and container funnel-shaped Unitrap) were placed in orchards located in town Pavlovsk (St. Petersburg) and farmstead Slobodka (Krasnodar Area). The LED efficiency was significantly different in these two locations: in the former, the moths were not attracted by UV, whereas in the latter, light trapping was quite active. A positive phototaxic reaction of moths in St. Petersburg was absent both during the White Nights and in the subsequent period, i.e. independently of illumination level at dusk. In both locations, no increase in the catch of codling moth adults with pheromone traps was recorded after they were supplemented with UV LEDs. Moreover, when Delta traps were used in Slobodka, a highly reliable antagonism of light vs pheromone bait was observed. The results are discussed using extensive literature data on insect phototaxis, codling moth behavior, its ecological plasticity and the ability to adapt to local habitats, which allows assessing the prospects for further research. In addition, an original algorithm is demonstrated for calculating the beginning and end of White Nights period for entomological objects which is of interest in terms of conducting research with insects at high latitudes.

Effect of temperature and density of Macrolophus pygmaeus (Heteroptera, Miridae) nymphs on their viability during mass rearing

2024-10-14T10:22:21+00:00

When Macrolophus pygmaeus nymphs were kept in large numbers while fed ad libitum on S. cerealella eggs in the presence of water and plant leaves, their survival was significantly lower at 20–22 °C, in comparison to 24–25 °C and 27–28 °C at all insect densities tested. Development was significantly longer at 20–22 °C. The yield of adults was significantly higher at 20–22 °C as well. The weight of the adults is defined by the sex and wasn’t dependent on temperature or nymph density. We associate the decrease in survival at 20–22 °C with cannibalism due to impaired water and food consumption, a decrease in daily weight gain (1.3 times in the case of water supply and 1.5 times in the case of both water and feed supply) and desynchronization of the physiological age of the nymphs. As a result of this desynchronization, the older individuals consumed those lagging behind in development. This resulted in equalized age composition, allowing for simultaneous emergence of adults, but decreased their number. Nymphal density reliably affected their survival at temperatures of 20–22 °C and 24–25 °C. However, despite the differences between the nymphal survival scores at the higher and lower densities were statistically significant, they were quite small. During mass breeding, they can be neglected in favor of a higher density of larvae, which allows for intensification of the production of the M. pygmaeus.

Polymorphism in wild South American potato Solanum chacoense for resistance to Colorado potato beetle Leptinotarsa decemlineata

2024-10-14T10:22:22+00:00

*corresponding author, e-mail: erogozina@vir.nw.ru
The Colorado potato beetle (CPB) – Leptonotarsa decemlineata is a dangerous potato pest in Russia. The creation of resistant varieties represents the most reliable method for protecting potatoes from this phytophage. A reliable phenotypic assessment of accessions stored in gene banks as seed collections is necessary before using wild potatoes as sources of resistance traits. Plants of nine accessions of S. chacoense (55 genotypes) from collection of the N.I. Vavilov All-Russian Institute of Plant Genetic Resources (VIR) were grown for three years on the experimental plot of VIR branch (Tambov region), where the environment is favorable for CPB. Annually seven parameters were recorded: the number of overwintered beetles per plant, the population of egg per plant, the number of older larvae per plant, the proportion of plants with more than 20 older larvae, the score of haulm damage, the proportion of plants with a high damage score and the number of second generation beetles. The origin of S. chacoense plants belonging to different accessions (“families”) in the VIR collection reliably affects their infestation and damaging by CPB. The influence of the “family” factor is 12–46 % depending on the assessed parameter. Solanum chacoense plants k-21854 are highly resistant and those of k-7394 are vulnerable to CPB. Plants in accessions k-2732, 2861, 3060, 19769, and 21848 were infested by the pest at different levels and varied in their individual damage parameters. Solanum chacoense genotypes k-19769 (542-3) and k-21854 (546-3) showed a high resistance to CPB during all three years of study.

Features of the arbuscular mycorrhizal fungal community associated with annual ragweed

2024-10-14T10:22:20+00:00

Ambrosia artemisiifolia is a highly harmful invasive plant of North American origin, belonging to the tribe Heliantheae of the subfamily Asteroideae. One of the factors influencing the competitive ability of invasive Asteraceae species includes mutualistic relationships with arbuscular mycorrhizal (AM) fungi. There is a hypothesis that the effectiveness of this symbiosis is influenced by the phylogenetic position and the origin of species. The aim of our work was to identify the characteristics of the AM-fungi community associated with annual ragweed. It was shown that the community is less diverse than closely related species from the tribe Astereae. The major difference is that the AM-community contains only widespread species of the order Glomerales, such as Glomus spp. and Funneliformis mosseae. It is possible that other factors have a greater influence on the A. artemisiifolia competition.

Feeding behavior of predatory bug Nabis ferus (Heteroptera: Nabidae) toward aphids

2024-10-14T10:22:19+00:00

This study investigated the feeding behavior of the generalist predator Nabis ferus (Heteroptera: Nabidae) toward various Aphididae species as prey in a laboratory setting. Data were obtained on the predatory behavior of N. ferus, including a ranking of the most preferred species for feed. Eight representatives of the Aphididae family were used as prey: Schizaphis graminum, Rhopalosiphum padi, Aphis fabae, Megoura viciae, Brevicoryne brassicae, Aphis pomi, Myzus cerasi and Aphis urticata. The average number of prey ranged from 11.2±1.18 in the case of bird cherry-oat aphid to 13.7±0.38 in case of the apple aphid. The consumption of M. viciae individuals was significantly lower, averaging 6.6±1.03 aphids per predator. These studies have implications for the biological control of phytophagous pests in agriculture. These findings highlight the potential of N. ferus as a sustainable and effective control agent to organic farming.