No abstract

A prototype of an improved automated ground release machine was assessed and found, with further improvements, to have the potential to be a promising tool for the release of quality sterile Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) flies in small‐ and medium‐scale SIT control programmes. The following quality parameters of sterile flies were assessed: (i) flight ability, (ii) physical damage caused by the ground release machine, (iii) survival under stress conditions without food and water and (iv) water condensation on flies, after 0.5 and 2 h under the automatically controlled abiotic conditions of 16 ± 0.8°C and ∼58% relative humidity. A total number of seven different treatments, five involving flies held inside the ground release machine and two control treatments of chilled and non‐chilled flies not held inside the ground release machine, were evaluated to assess sterile male quality. Flight ability was as high as 97% in the control treatment (no ground release), compared with the lowest value of 92.5% when a 1‐m‐long screw‐auger, as part of the ground release machine, was tested. Use of a 1‐m‐long screw‐auger significantly increased the percentage of damaged flies up to 7.2%, compared with ≤1.7% in the control treatments. It is confirmed that the length of the screw‐auger is the most important factor affecting quality of the released flies in the ground release system tested. Also, interaction of duration of time inside the machine, screw‐auger rotation and the effect of the directional discharge blower significantly increases the percentage of damaged flies. Evaluation of sterile fly survival under stress conditions, without food and water, confirms that movement or handling of the flies inside the ground release machine drastically decreases percentage of live insects from ≤ 4.5% after 24 h and 0.0% after 48 h, compared with 18.67–21.67% after 24 h and 3.50–5.83% after 48 h in the control treatments. The most important factors affecting sterile fly quality, such as condensation, compaction and damage, from moving mechanical parts are demonstrated to be minimized or eliminated by making adaptations to the ground release machine construction.

A specific survey for the detection of Drosophila suzukii Matsmura 1931 (Diptera, Drosophilidae) in Dalmatia region of the Republic of Croatia during 2013, confirmed that the pest is present and widespread. Adults were detected in traps suspended in Prunus cerasus L. (sour cherry), Prunus persica L. (peach), Ficus carica L. (fig) and Morus alba L. (mulberry) orchards and individual trees, during the fruit maturation period, in 16 (of the 51 locations) where traps were placed in Dubrova cko-neretvanska, Splitsko-dalmatinska,Sibenskokninska and Zadarska counties. This confirmed the rapid spread of D. suzukii in Croatia and this pest is a great concern for areas that are not yet infested that have favourable conditions for the pests' development. The results of the survey highlight the importance of the development and implementation of long-term sustainable control.

During the last decade anthracnose has become a major disease of Satsuma mandarin, the most important citrus crop in Croatia. The aim of this study was to determine Colletotrichum species associated with different symptoms and to identify the origin of inoculum. From 2013 to 2016, 437 samples of plant material were collected. Colletotrichum spp. was isolated from 93% of dried twigs, 35% of dropped flowers, 89% of leaf spots, all fruit (100%) with anthracnose or calyx-end rot symptoms, 12% of fruit with post-harvest soft rot and from 40% of fruit showing spots remaining on trees after harvest. Out of 258 Colletotrichum isolates, 253 has been morphologically identified as C. gloeosporioides (Penz.) Penz. & Sacc. species complex. Twenty-seven representative isolates were selected for phylogenetic analysis. Sequencing the inter-spacer gene region of ribosomal DNA confirmed the identity of the species. Artificial inoculation of flowers led to more than 2-fold higher young fruit drop compared to control. Pathogenicity tests on green fruit induced typical anthracnose symptoms on 82% of inoculated fruit two months after inoculation. Inoculation of mature fruit caused the appearance of typical anthracnose symptoms on 87% of inoculated fruit. These results showed that C. gloeosporioides species complex is responsible for different disease types on Satsuma mandarin, and that the fungus is present throughout the year on different plant organs.

The hypothesis of this study was that different plant hosts of the medfly Ceratitis capitata may cause variability as a prerequisite for its invasiveness. The main objective was to determine population variability based on medfly wing shape in three favorable medfly host plants (peach, fig and mandarin) from different agroecological growing areas with different pest management practices, and to evaluate phenotypic plasticity as a basis for future expansion into new areas and new hosts. Using geometric morphometric methods across 14 specific landmarks on the medfly wings, 10 populations were tested from infested peach, fig and mandarin fruits, as well as laboratory-grown sterile populations. The studies led to the following main findings: (1) all of the medfly populations that were studied exhibited sexual dimorphism in wing shape; (2) the hosts in which the medfly develops influence wing shape and condition its variability; (3) there is significant variability between laboratory mass-reared sterile and wild individuals in male and female populations; (4) a high phenotypic plasticity of medfly populations was observed along the study sites. Even the low but clearly detected variability between different agroecological conditions and localized variability indicate genotypic stability and high phenotypic plasticity, which can be considered as a prerequisite for medfly invasiveness and dispersal to new areas.

Sterile insect technique (SIT) control method is integrated in many ongoing area-wide programs for Ceratitis capitata W. control management who largely depends on the sterile male competitiveness. The use of semiochemical supplements originated from host and non-host plant materials to better manage the physical conditions and handling of sterile C. capitata males in fly emergence and release facilities improve the cost-effectiveness of the SIT worldwide. Since C. capitata adults are regularly captured in groves of nonhost olive, Olea europaea L. in the Mediterranean region, the aims of this research were to asses: (1) attraction of sterile males by olive fruit of different maturity stages; (2) attraction to olive fruits surface (egzocarp) and mesocarp and (3) attraction to three different olive cultivars. The results provide clear evidence that sterile males show strong attraction to volatile compounds from the surface and mesocarp of immature and semi matured olive fruits with no significant difference between fruits treated and nontreated with artificial cuts in mesocarp. The response of sterile C. capitata males to fully matured fruits were significantly the weakest. Sexually mature sterile males were attracted to green immature olive fruits stronger than sexually immature sterile males, while both categories showed strong attraction to semi matured olive fruits without significant difference between both categories.