Seasonal Changes and the Interaction between the Horse Chestnut Leaf Miner Cameraria ohridella and Horse Chestnut Leaf Blotch Disease Caused by Guignardia aesculi

The horse chestnut leaf miner Cameraria ohridella (Lepidoptera: Gracillariidae) is an invasive pest of horse chestnut Aesculus hippocastanum (Sapindales: Sapindaceae) and has spread through Europe since 1985. Horse chestnut leaf blotch is a fungal disease caused by Guignardia aesculi (Botryosphaeriales: Botryosphaeriaceae) that also seriously damages horse chestnut trees in Europe. The interaction between the leaf miner and the fungus has not yet been sufficiently described. Therefore, the aim of the present study was to assess leaf damage inflicted to horse chestnut by both C. ohridella and G. aesculi during the vegetation season and to model their interaction. The damage to leaf area was measured monthly from May to September 2013 in České Budějovice, the Czech Republic using digital image analysis of sampled leaves. A simple phenomenological model describing the expected dynamics of the two species was developed. The study revealed that the damage caused by both the pests and the fungus varied significantly among sampling sites within the city. The overall leaf damage exceeded 50% in no-raking sites in August. The mathematical model indicates that infestation by C. ohridella is more affected by G. aesculi than vice versa. Guignardia aesculi is thus the superior competitor of the two species. Our findings highlight the delicate interplay between insect pests and fungal pathogens and the spatiotemporal dynamics influencing them, calling for more research in this understudied area.

Effect of the outbreak of horse-chestnut leaf miner (Cameraria ohridella Deschka & Dimić) on tree-ring width in common horse-chestnut (Aesculus hippocastanum L.)

Common horse-chestnut is frequently infested by the insect pest horse-chestnut leaf miner [HCLM; Cameraria ohridella (Deschka & Dimić, 1986), Gracillariidae, Lepidoptera]. The larvae, feeding on leaf parenchyma, cause browning and dehydration of leaves, which may be shed as early as in summer. The major aims of this study were: (1) to assess the effect of infestation by HCLM on ring-width dynamics in common horse-chestnut; (2) to determine the date of invasion of the pest; and (3) to compare the growth-climate response in the period before and after the invasion of HCLM. In 2017 in north-western Poland, samples from 30 horse-chestnut trees for the dendrochronological analysis were taken with help of a Pressler increment borer. The ring-width chronology was developed using standard dendrochronological methods. Dendroclimatological analyses were made in 2 periods: before the determined date of HCLM invasion (till the year 1999) and after the invasion (in 20002016). In 2000, in spite of favourable weather conditions, a reduced growth rate was observed in 91% of the analysed trees. The period of strong reductions lasted till 2010. Before the invasion, radial growth rate was dependent on temperature and precipitation in May and June of the current year, whereas after the invasion, the growth-climate response was dependent on temperature and precipitation in the preceding year and the correlation was stronger. Surprisingly, in recent years (2011–2016), in spite of infestation by HCLM every year, the health condition of the analysed trees has improved and tree-ring width has increased.

Seasonal Changes and the Interaction Between the Horse Chestnut Leaf Miner Cameraria ohridella and the Horse Chestnut Leaf Blotch Guignardia aesculi

The horse chestnut leaf miner Cameraria ohridella (Lepidoptera: Gracillariidae) is an invasive pest of horse chestnut and has spread through Europe since 1985. The horse chestnut leaf blotch Guignardia aesculi (Botryosphaeriales: Botryosphaeriaceae) is a fungal disease that also seriously damages horse chestnut trees in Europe. The interaction between the leaf miner and the fungus has not yet been sufficiently described. Therefore, the aim of the present study was to assess leaf damage inflicted to horse chestnut by both C. ohridella and G. aesculi during the vegetation season and to model their interaction. The damage to leaf area was measured monthly from May to September 2013 in České Budějovice, the Czech Republic. A simple phenomenological model describing the expected dynamics of the two species was developed. The study revealed a significant effect of sampling site and sampling period on the damage caused by both the pest and the fungus. The mathematical model indicates that infestation by C. ohridella is more affected by G. aesculi than vice versa. The possible mechanisms affecting the relationship between G. aesculi and C. ohridella are discussed.

Identification and Characterization of Leaf-Inhabiting Fungi from Castanea Plantations in China

Two Castanea plant species, C. henryi and C. mollissima, are cultivated in China to produce chestnut crops. Leaf spot diseases commonly occur in Castanea plantations, however, little is known about the fungal species associated with chestnut leaf spots. In this study, leaf samples of C. henryi and C. mollissima were collected from Beijing, Guizhou, Hunan, Sichuan and Yunnan Provinces, and leaf-inhabiting fungi were identified based on morphology and phylogeny. As a result, twenty-six fungal species were confirmed, including one new family, one new genus, and five new species. The new taxa are Pyrisporaceae fam. nov., Pyrispora gen. nov., Aureobasidium castaneae sp. nov., Discosia castaneae sp. nov., Monochaetia castaneae sp. nov., Neopestalotiopsis sichuanensis sp. nov. and Pyrispora castaneae sp. nov.

Fungi Associated with Horse-Chestnut Leaf Miner Moth Cameraria ohridella Mortality

The total mortality of the leaf-miner horse-chestnut pest, Cameraria ohridella, collected in nature, and the mortality associated with mycoses were assessed under laboratory conditions in stages: for eggs mortality rates of 9.78% and 61.97% were found, respectively; for caterpillars, 45.25% and 5.59%, respectively; and for pupae 21.22% and 100%, respectively. At the egg stage, Cladosporus cladosporioides caused mycosis most often (27% of all mycoses); at the caterpillar stage there was no pronounced predominant fungus species; at the pupal stage both Cordyceps fumosorosea and Beauveria bassiana (32% and 31%, respectively) were most dominant; whereas at the adult stage Lecanicillum aphanocladii (43%) were most dominant. C. ohridella moths remained the most vulnerable during the pupal and caterpillar stages. Maximum diversity of fungi associated with the leaf-miner moth was reached during the period of development inside the chestnut leaf (Shannon–Wiener index—H′ = 2.608 at the caterpillar stage, H′ = 2.619 at the pupal stage), while the minimum was reached in the adult stage (H′ = 1.757). In the caterpillar and pupa stages, saprophytic fungi were most often recorded. Comparative laboratory tests revealed novel properties of the fungus L. aphanocladii, its effectiveness as the leaf-miner moth‘s entomopathogen and its suitability for field application trials while developing environment-friendly methods for horse-chestnut pest control.

Using Chestnut Leaf Litter in Aqueous Media Purification from Diesel Fuel

For wastewater treatment, native and thermally modified samples of leaf chestnut litter (LCL) were used as sorption material. Studies were carried out to determine the static oil capacity of the sorption material (SM) in relation to the diesel fuel (DF) and water adsorption depending on the particle size. It was established that the oil capacity of chestnut litter depends on the particle size of the biosorption material, the conditions of its heat treatment, and the duration of contact of the SM with the sorbate. It was found that the maximum sorption capacity by DF for LCL250 is 7.17 g/g. It was determined that the purification efficiency of over 95% is achieved with a dosage of LCL250 over 1.0 g/dm3 and a diesel fuel concentration of 210 mg/dm3.