Making the Shift from Research to Commercial Orchards: A Case Study in Aphid–Peach Tree Interactions as Affected by Nitrogen and Water Supplies

Peach orchards are intensively sprayed crops, and alternative methods must be found to replace pesticides. We intend here to evaluate if limiting water and nitrogen (N) supply could be effective in controlling aphid infestation in commercial orchards. N and water supply were therefore either unrestricted or restricted by 30% only for water, or for both water and N, in 2018 and 2019 on trees of two contrasting varieties. Natural infestations (green peach aphid, mealy plum aphid, leaf curl aphid) were monitored regularly at tree and shoot level. Infested and control shoots were compared for their development during the infestation period, their apex concentrations of total N, amino acids, non-structural carbohydrates, and polyphenols at infestation peak. At tree level, limiting both water and N supplies decreased the proportion of infested shoots by 30%, and the number of trees hosting the most harmful specie by 20 to 50%. Limiting only N supplies had almost no effect on infestation severity. At shoot level, the apex N concentration of infested shoots was stable (around 3.2% dry weight) and was found to be independent of treatment, variety, and year. The remaining biochemical variables were not affected by infestation status but by variety and year. Shoot development was only slightly affected by treatment. Aphids colonized the most vigorous shoots, being those with longer apical ramifications in 2018 and higher growth rates in 2019, in comparison with the controls. The differences were, respectively, 40 and 55%. It was concluded that a double restriction in water and N could limit, but not control, aphid infestations in commercial orchards.

Population and harmfulness of phytophages in peach orchards in the conditions of the Southern Steppe of Ukraine

Goal. To determine the number and harmfulness of the main phytophages on peach cultivars of different ripening terms in order to plan measures to protect the crop from pest damage. Methods. Laboratory-field. The research was carried out in peach orchards of the Scientific and Production Site «Naukova» of Melitopol Fruit Growing Research Station named after M.F. Sydorenka of Institute of Horticulture of NAAS according to generally accepted methods. Monitoring of the number of phytophages was performed on peach cultivars of different ripening terms: Iiun`s`kyi rannii, Melіtopol’s’kyi iasnyi, Charivnyk, Zlatodar, Vireneia, Redhaven, Spokusa, Zolotystii, Mriia and Yuvileinyi Sydorenka during bud swelling, inflorescence opening (pink tip), flowering, growth and maturations of the fruits. Results. Entomoacarocenosis of peach plantations has 15 species of insects pests and 2 species of mites. During the flowering period, the main harmful species was Epicometis hirta Poda., the number of imagoes in different cultivars was 0.3—5.8 specimens/100 flowers. Population intensity of peach trees with green peach aphids (Myzodes persicae Sulz.) for certain cultivars reached the level of 1.9 points, mealy plum aphid (Hyalopterus pruni Geoffr.) — did not exceed 0.8 points. Density of mites, Thrips fuscipennis Haliche and Typhlocyba rosae L. varied in the range of 0.4—2.5; 0.8—2.4; 0.5—1.6 specimen/leaf, respectively. The main fruit-damaging pests in peach orchards were oriental fruit moth (Grapholitha molesta Busck.) and peach twig borer (Anarsia lineatella Zell.). The degree of fruit damage by Lepidoptera pest oriental fruit moth on early-ripening peach cultivars was 3.0—4.0%, increased on medium- and late-ripening cultivars to 6.8% and 11.7%, respectively. The level of fruit damage by peach twig borer compared to the eastern fruit moth was 2.8—10.7 times lower, depending on the cultivar. Conclusions. In the conditions of the South of Ukraine, 15 insect pests and 2 species of mites were recorded in peach orchards. During the growing season, the number of most species of phytophagous, including weevils, leafroller moths, mites, thrips, Typhlocyba rosae on different peach cultivars did not exceed the economic threshold of harmfulness. During the flowering period, Epicometis hirta was the threat to peach orchards. In the summer of 2019, the harmful effects of sucking phytophages, in particular aphids, led to delayed growth and development of shoots, deformation of leaves. The main species of pests that reduced the yield and fruit quality were oriental fruit moth and peach twig borer.

Aphids (Hemiptera: Aphididae) on Plum and Cherry Plum in Bulgaria

The species complex and infestations of aphids on plum (Prunus persica) and cherry plum (Prunus cerasifera) in Bulgaria were investigated during the period 2013–2018. Nine species from the family Aphididae were found: Brachycaudus helichrysi Kaltenbach (leaf-curling plum aphid), Hyalopterus pruni Geoffroy (mealy plum aphid), Phorodon humuli Schrank (hop aphid), Brachycaudus prunicola Kaltenbach (brown plum aphid), Brachycaudus cardui Linnaeus (thistle aphid), Brachycaudus persicae Passerini (black peach aphid), Rhopalosiphum nymphaeae Linnaeus (waterlily aphid), Aphis spiraecola Patch (spiraea aphid) and Pterochloroides persicae Cholodkovsky (peach trunk aphid). The dominant species on plum are Hyalopterus pruni and Brachycaudus helichrysi. The first species is more widespread and of significantly higher density. The dominant species on cherry plum are Phorodon humuli and B. helichrysi. The species Brachycaudus prunicola is widespread both on plum and cherry plum in Bulgaria. It was found only on twigs, and therefore cannot be considered as a dangerous pest on fruit-bearing plum trees. The other species, some of them described as dangerous pests on plum, are today fairly rare and occur in low density, thus posing no danger to orchards.