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The studies were carried out during the period 2018-2021 at the Institute of Agriculture – Kyustendil with the apple Florina cv. grafted on rootstock MM 106. The influence of soil, foliar and combined application of red Californian earthworm organic fertilizers on the productive manifestations of the apple Florina cv. was established through 9 fertilization treatments. Applied fertilization had a positive effect on yield. Treatment with Lumbreco 300 ml/da increased the average fruit weight by 9.8%, and the combined application of organic fertilizer 134 l/da+Lumbreco 200 ml/da – by 17.4% above the standard. Fertilization decreased the dry matter content in fruits by 1.1-4.9%, of sugars – by 0.5-7.6% and of acids by 4.1-20.4%, depending on the variant. [ABSTRACT FROM AUTHOR]

For agriculture, hail is the most unfavourable meteorological phenomenon. An orchard can suffer unwanted and long-term losses from hail. Hail damage predisposes fruit to secondary damage from pests and diseases, so hail protection measures are critical. This review article summarizes the effectiveness of three types of anti-hail nets. Hail netting is crop protection equipment made of strong hail-resistant material such as high- density polyethene. It also provides protection from the harmful effects of UV rays. This hail protection system effectively minimizes damage to observed crops. This net, in addition to protecting the fruit plants, allows enough sunlight to penetrate the plantation. Currently, three colours of anti- hail nets are widely used: transparent, white, and black anti-hail nets. For producers, anti-hail nets directly impacts the colouring of the fruits and their appearance, from there on the realization of the production. Black anti-hail nets provide the best shade, and in some hot areas with strong UV rays, black provides the best protection against fruit sunburn. On the other hand, light-loving fruits that need more sunlight for ripening are suitable colourless and white nets. [ABSTRACT FROM AUTHOR]

Establishing a pest monitoring system through regularly monitoring pest density is a fundamental principle of integrated plant protection. The apple clearwing moth (Synanthedon myopaeformis Bork.), which until the 1960s throughout Europe, was considered one of the secondary pests of apple trees, has become a significant pest in recent years; this may led to changes in apple production technology The creation of intensive plantations, and the introduction of rootstocks with low growth capacity, can lead to the early death of young trees under unfavorable environmental conditions. Damage caused by S. myopaeformis is primarily associated with old, damaged, or otherwise diseased apple trees, as the lack of bark integrity allows the larvae easier access to the inner layers of the trunk and branches. However, the potential to harm even younger healthy apple trees is now recognized. The present study studied the population dynamics of the pest in apple orchards of different ages. In 2022, the beginning of the flight was observed after 03.06.2022, the peak at all three observed orchards was the end of July (18.07.2022), and the end of the flight was established at the beginning of the third ten days of August. The species (Synanthedon myopaeformis Borkh.) was observed annually in apple orchards, and a trend had been observed to move from a minor to a significant apple pest. [ABSTRACT FROM AUTHOR]

The apple (Malus domestica Borkh.) is one of the valuable fruit species grown in Bulgaria, which occupies one of the first places in terms of area and fruit production in the world. The research was conducted from 2018-2021 in a fruitful apple orchard of the Institute of Agriculture – Kyustendil, including apple cultivars Golden Delicious, Granny Smith and Florina in three types of pruning. It was analyzed influence of the applied types of pruning on the yields, fruit quality and economic efficiency of the three apple cultivars. It was found that combination of contour and detail pruning are the most economically efficient method of maintenance trees for cultivar Florina, and for cultivars Golden Delicious and Granny Smith contour pruning is economically effective. [ABSTRACT FROM AUTHOR]

Kyustendil is the oldest and most famous apple growing region in Bulgaria. The aim of the present study is to determine the influence of climatic factors (temperature and air humidity) on honey-bearing productivity of apple cultivars, by determining nectar productivity, pollen productivity and the content of sugars in the nectar. In the older trees, an increase in sugar content of the nectar was observed in Golden Delicious/ММ106 – orchard 2 (created in 2004) was 31.9%, while in Golden Delicious/ММ106 – orchard 1 (created in 2006) is 30.7%. The trees grafted on the M9 rootstock yielded a lower sugar content of the nectar compared to those grafted on MM 106. In orchard 5 of the Florina cultivar grafted on the M9 rootstock, 30.4% sugar content of the nectar was obtained, while those grafted on MM106 - 34.8 %, making them more attractive to insects for pollination. [ABSTRACT FROM AUTHOR]

The influence of the application of soil biofertilizers on the content of sugar, macro, microelements and heavy metals in the fruits of the apple cv. Idared and Red Chief was analysed. In both cultivars, lower values of soluble solids content (SSC), total sugars (TS), inverted sugars (IS), sucrose and higher titratable acidity (TA) were measured, as well as increased absorption of Ca, Mg, Na, P, Cu, Mn. In cv. Idared, in addition to the mentioned elements, the absorption of K and Fe was increased, and the influence of biofertilizers contributed to the reduction of the absorption of Pb, Ni, Cr. The higher Ca content in the treatments enabled a more favorable K/Ca ratio, which contributes to a longer storage of fruits. Biofertilizers with specific consortia of bacteria influenced the utilization of high microbial biodiversity and had a stimulating effect on the uptake of nutrients from the soil and the optimization of their content in apple fruits. [ABSTRACT FROM AUTHOR]

The research was conducted in the period 2018-2021 with six new apple cultivars created at the Institute of Agriculture – Kyustendil. The trees were grafted on MM 106 rootstock and were in full fruiting during the analyzed period. The productive manifestations of the trees and fruit quality (weight, dimensions and chemical composition) were studied. It was found that the cultivars are highly productive and regularly fruiting. Their fruits are large, with a good appearance, have firm flesh, pleasant taste and juiciness. They store better than the control cultivar Golden Delicious. As practically resistant/tolerant to apple scab, they are recommended for wider cultivation to obtain ecologically clean fruit production. [ABSTRACT FROM AUTHOR]