Scale insect species (Hemiptera: Coccomorpha) and their natural enemies, recorded on agricultural, ornamental and forest plant species in the wider area of Messenian Province (Peloponnese, Greece), 2000 – 2020

Summary The scale insects (Hemiptera: Coccomorpha) recorded on agricultural, ornamental and forest plant species in the wider area of Messenian Province (Peloponnese, Greece) during the years 2000 – 2020 are reviewed. Twenty species were recorded, which belong to four families: Diaspididae: Aonidiella aurantii (Maskell), Chrysomphalus aonidum (L.), Diaspis echinocacti (Bouché), Dynaspidiotus abieticola (Koroneos), D. abietis (Schrank), Lepidosaphes beckii (Newman), L. gloverii (Packard), Lineaspis striata (Newstead), Targionia vitis (Signoret); Coccidae: Ceroplastes rusci (L.), Eulecanium sericeum (Lindinger), Nemolecanium graniformis (Wünn), Parthenolecanium corni (Bouché), P. persicae (Fabricius), Physokermes hemicryphus (Dalman), P. inopinatus Danzig and Kozár, Protopulvinaria pyriformis (Cockerell); Pseudococcidae: Phenacoccus madeirensis Green, Planococcus vovae (Nasonov) and Kermesidae: Kermes echinatus Balachowsky. The biology, phenology and natural enemies in Messenia are discussed for fifteen of these scale species.

Volume Rate Adjustment for Pesticide Applications against Aonidiella aurantii in Citrus: Validation of CitrusVol in the Growers’ Practice

Aonidiella aurantii is one of the most damaging armored scales in citrus crops worldwide. To control this pest, high water volume rates are conventionally used. In order to rationalize the pesticide applications in citrus, IVIA developed CitrusVol, a tool that recommends the optimal volume rate based on the vegetation, the pest or disease and the active ingredient. In this study the objectives were: (i) validate CitrusVol as a tool to adjust the spray volume to control A. aurantii and (ii) quantify its environmental and economical advantages. For this, the spray volume adjusted with CitrusVol was compared with the one conventionally used by farmers in 18 applications in seven orchards during two years. The following parameters were evaluated: (i) spray distribution in the canopy, (ii) A. aurantii males trapped per day, and (iii) number of scales per fruit at harvest. CitrusVol reduced the spray volume and the amount of pesticide by 35% on average. Despite this reduction, a satisfactory spray distribution was achieved, and the volume was found to control the pest in a comparable way to the conventional volume. Moreover, CitrusVol saved per application and on average 31.25 h/100 ha of spray operating time, 241.83 L/100 ha of fuel consumption and consequently, the reduction of emissions of CO2 was 631.18 kg/100 ha. Therefore, CitrusVol allows for efficient, low-input and low-impact pesticide applications.

Morphometric comparison between two populations of Aonidiella aurantii (Maskell) (Homoptera: Diaspididae) from Algeria and Turkey

The size of California red scale Aonidiella aurantii (Maskell, 1879) (Homoptera: Diaspididae) is the most reliable indicator in terms of host quality for Aphytis melinus (DeBach, 1959) (Hymenoptera: Aphelinidae) as well as for the efficiency of its biological control. Our study consisted in comparing the cover and body size of each scale developmental stage belonging to two different populations: one from Algeria and the other one from Turkey. The two scale populations were taken from lemon trees during 3 months. We compared measurements between the two localities and also between the plant organs. The larger individuals were those from Algeria. The same results were confirmed through the plant substrate on which scale was fixed: this size variation observed is mainly explained by climatic variations between the two countries and its repercussions on phenology and metabolism of the host plant. In addition, a higher parasitism rate was noticed in the Algerian scale population compared to that of Turkey.

Evaluation of d-Limonene and β-Ocimene as Attractants of Aphytis melinus (Hymenoptera: Aphelinidae), a Parasitoid of Aonidiella aurantii (Hemiptera: Diaspididae) on Citrus spp.

The volatile organic compounds (VOCs) released from herbivore-infested plants can be used as chemical signals by parasitoids during host location. In this research, we investigated the VOC chemical signals for the parasitoid Aphytis melinus to discriminate between Aonidiella aurantii (California red scale)-infested fruit and non-infested fruit on three different citrus species. First, we identified the chemical stimuli emanating from non-infested and A. aurantii-infested citrus fruits via solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) analyses and identified 34 volatile organic compounds (VOCs). The GC-MS analysis showed qualitative and quantitative differences between VOCs emitted from non-infested and infested citrus fruit. Two VOCs, d-limonene and β-ocimene, were significantly increased in all infested fruit, regardless of the fruit species. The response of the female adult A. melinus to olfactory cues associated with A. aurantii infested fruit was evaluated using a Y-tube olfactometer. In two-choice behavioural assays, A. melinus females preferred infested citrus cues over non-infested fruit. Females showed positive chemotaxis toward these VOCs in all tested combinations involving two dosages of synthetic compounds, d-limonene and β-ocimene, except for d-limonene at a dosage of 10 μL/mL. The application of these VOCs may help to enhance the effectiveness of bio-control programs and parasitoid mass-rearing techniques.