Plant Protection News

Micromycetes associated with barley and their significance as pathogens in Russia

2023-12-24T15:07:47+00:00

Despite the great attention paid to the study of barley diseases, inaccuracies in the names of diseases, their practical significance, and incorrect use of the scientific names of causal agents can be commonly found in the scientific literature. This may lead to confusion and misidentification of the pathogens that can affect this crop especially as relates to phytosanitary requirements. This review continues the series started with a publication devoted to wheat diseases. This review includes information about the main barley diseases and pathogenic organisms causing them, as well as the species emerging as a potential threat to barley. The current taxonomic status of fungal species and fungal-like organisms associated with various organs of barley is given, and the breadth of their distribution and degree of impact on the crop are summarized. The micromycetes were divided into two groups according to their phytosanitary importance. The first group is represented by fungi of great importance as the pathogens causing the 29 economically important common barley diseases. The second group consists of fungi causing 20 minor and poorly studied diseases with unconfirmed harmfulness, or potential endophytic fungi. Perceptions of their ability to cause disease remain controversial and the available data require confirmation. This dataset can be used as a reference for a more accurate description of the phytosanitary situation. The review will also be helpful for more targeted studies using molecular techniques to clarify taxonomy and areals of fungi associated with barley and to provide more detailed data on disease damage in this crop.

The toxic effect of α-tomatine on the 28-spotted potato ladybeetle Henosepilachna vigintioctomaculata (Coleoptera: Coccinellidae)

2023-12-24T15:01:28+00:00

Glycoalcoloids of plant origin serve as teratogens, causing various teratoses and abnormalities of insect development. Our previous studies discovered dependence of developmental defects in the 28-spotted potato ladybeetle Henosepilachna vigintioctomaculata upon its feeding on certain potato varieties. The present study was undertaken to study the toxic effect of α-tomatine against the 28-spotted potato ladybeetle. Tomatine was chosen as a model glycoalkaloid. Potato leaves were treated with tomatine solutions in different concentrations. Control leaves were treated with distilled water. Ten first-instar larvae were placed in a Petri dish with treated leaves. The effect of tomatine on H. vigintioctomaculata was assessed by appearance of morphological abnormalities in the adults. As a result, a confident direct correlation between the tomatine concentration and the developmental defect frequency was found. Brachelytry and cystelytry were the main anomaly types. When the stock 6 % solution was used, insect mortality was the highest, reaching 70 %. The highest level of teratoses (60 %) among survived insects and relatively high mortality (27 %) were observed in insects treated with 0.6 % solutions of tomatine. As the tomatine concentration decreased, so did the mortality level and developmental defect frequency. At 0.06 % solution treatement, mortality was 17 % and quote of teratoses – 47 %, at 0.006 % – 16.6 % and 6.8 %; at 0.0006 % – 3.3 % and 3.4 %, respectively. Thus, tomatine can be used as an insecticidal compound for potato cultivation.

Determination of Trichogramma euproctidis efficacy against the key pest, European grapevine moth, Lobesia botrana (Lepidoptera: Tortricidae) in the Aegean region vineyards, Turkey

2023-12-25T16:50:10+00:00

European grapevine moth Lobesia botrana is the most important pest causing crop losses in most of Türkiye’s grape growing regions, feeding mainly on inflorescence and grape berries. This study was carried out to determine the release efficiency and the most efficient dose of the native egg parasitoid, Trichogramma euproctidis against L. botrana in an organic vineyard located in the Menemen district of Izmir, in the Aegean Region, which has the largest grape production area. In this context, two different release doses at 75 000 and 100 000 parasitoids/ha were applied to find the most effective one. The effectiveness of the parasitoid was compared in terms of pest infestation rates in grape bunches from parasitoid-released and non-released plots just prior to harvest. The infestation rates in plots released 100 000 parasitoids/ha (12, 4 and 5 %) and 75 000 parasitoids/ha (7.5, 11 and 1 1 %) were lower than control (25, 33 and 70 %) in 2017, 2018 and 2019, respectively. In 2018 and 2019, the high release dose (100 000 parasitoids/ha) applied five or six times in total was the most promising with the lowest pest infestation rates. In this study, the most effective release dose (100 000 parasitoids/ha) of the native egg parasitoid, T. euproctidis, was determined for the first time in Türkiye. In conclusion, the results obtained from the study will encourage the use of this parasitoid in organic and integrated grape growing programs.

The effect of herbicides on arbuscular mycorrhizal fungi associated with annual invasive Asteroideae weeds

2023-12-24T15:01:30+00:00

Invasive plants Galinsoga parviflora and Erigeron canadensis are common in crops and adjacent territories. One of the factors contributing to their spread is the community of arbuscular mycorrhizal fungi associated with these species. The nature of the symbiotic relationship between the host plant and AMF is determined by their phylogenetic position and place of growth. The aim of this work was to determine the level of mycorrhizal colonization of E. canadensis и G. parviflora growing in arable fields and along them. For plants at the flowering stage, high rates of frequency and intensity of mycorrhization were revealed. It has been shown that the level of mycorrhizal colonization of E. canadensis and G. parviflora is significantly influenced by the range of herbicides applied. The application of 2.4 D slightly reduced the intensity of colonization, but significantly stimulated the formation of arbuscules in plant roots. In turn, metribuzin prevented the formation of mycorrhiza. AMF associated with these plants formed a separate clade. This group, in our opinion, is responsible for more effective symbiosis with invasive plants of the Asteroideae subfamily and requires further closer study.

Susceptibility of Bombyx mori larvae to the microsporidium Nosema bombycis from the silkworm and Nosema sp. from the cotton bollworm

2023-12-24T15:01:34+00:00

Microsporidia are widespread parasites and cause diseases in economically important insects. A microsporidian isolate NspHA22 was discovered in the cotton bollworm Helicoverpa armigera in South-Western Russia. It showed 100 % sequence identity of small subunit rRNA gene to Nosema bombycis, a natural parasite of the silkworm Bombyx mori. However, after feeding second or third instar B. mori larvae with spores of the new isolate, insect mortality didn’t differ from that of the control, and no sporulation was revealed in alive and perished insects. In contrast, feeding N. bombycis spores isolated from B. mori resulted in high levels of host mortality and intense parasite sporulation at all the infection dose and larval instars used. This likely indicates that the isolate NspHA22 belongs to a species different from N. bombycis, in spite of identity of rDNA sequences.