Il olive cotton wool (Euphyllura olivine) is an insect that causes considerable damage to olive groves in the Mediterranean basin. The adult has a 2-3 mm brownish-green body with a well-developed, hunchbacked head, the head bent forward and with a robust appearance, with the wings folded like a roof on the back. It has powerful wings, with a characteristic rib. General color light green, with the front legs tending towards light brown. It is equipped with stinging-sucking mouthparts both in the nymph and adult states. The eggs are 0,35 x 0,14 mm in size. The larvae undergo 4 larval molts, plus the imaginal moult. Their length evolves from 0,4 to 1,5 mm.
The damage to the olive grove
This insect is a flexible species that adapts to various temperatures, although the resistance or sensitivity to the same temperature varies with the individual. He owns a high reproductive potential between 12 and 30 °C, at 32°C ovarian activity is inhibited and at 34-35°C oviposition ceases. The insect is particularly harmful at the nymph stage when it attacks young branches and pinkies.
It feeds on sap through the stylet inserted into the rostrum, altering the normal development of the organs, inducing the sterility of the flowers and the drop of the same and of the fruits. The nymphs secrete a cotton-like mass and honeydew which favors the establishment of the ectoparasitic fungus Capnodium oleaginum, which alters the photosynthesis of the affected plant and decreases its production. The economic damage threshold is around 2.5-3 nymphs per 100 pinkies (IOC, 2007).
Photo 3 – Flower necrosis and presence of filamentous secretion (photo T. Vatrano)
Susceptibility to different olive varieties
Regarding the susceptibility of the CV to cotton wool infestations, in an olive grove cultivated according to the rules of organic farming, with a planting space of 5 x 5 m in theupper Ionian Calabria, on which the cultivars Nocellara messinese, Roggianella, Biancolilla, Coratina are based, emerged from a visual estimate that the variety most susceptible to insect infestations was Biancolilla, followed by Coratina (personal communication).
Counteractions
From the perspective of the use of pesticides with low environmental impact and in the search for solutions that respect the balance in ecosystems, the work of Debo A. et al., 2011 where has she been evaluated the effectiveness of a preparation based on hydroxytyrosol coming from vegetation water, on insect infestations. The preparation was extracted from fresh vegetation water, using a hydrolysis and post-hydrolysis purification process. 42 plants with a high infestation density were selected (122.8 nymphs/m-1 and 80 nymphs/m-1 in April and May 2008; 115.7 nymphs/m-1 and 70.8 nymphs/m-1 in April and May 2009). In chronological order, the preparation was found to be ineffective against eggs, probably due to the highly protective environment in which they are positioned. However, one was observed certain sensitivity of the young nymphs: this phenomenon was attributed to the decrease in production of the filamentous mass, following the treatment carried out in May. The maximum mortality rate was recorded 7 days after treatment, due to the good persistence of the solution on the vegetation.
The preparation provided adequate protection from insect damage, probably due to the stimulation of phenol synthesis. Indeed, it has been suggested that exogenous applications of antioxidant phenols may be able to increase the endogenous phenol content in the plant (Randhir and Shetty, 2003; Yangui et al., 2009).
In an informative section of the ARSAC (Regional Company for the Development of Calabrian Agriculture) it is the use of organic mineral oils is recommended and among the natural antagonists we mention: the endophagous hymenoptera Encyrtuseuphyllurae Silv., the larvae of hoverflies such as Syrphus auricollis Meig. and Orius spp. In integrated pest management you can use the deltamethrin, pyrethroid insecticide that acts on insects by contact and ingestion.
The olive cottonweed, once counted among the secondary insects in the olive grove, appears more and more frequent in the areas of southern Italy, with frequency often associated with climatic events and varietal susceptibility. Gharbi N. et al., 2012 they describe it as a serious problem in Tunisia and which can influence the vegetative development, fertility and reproduction of the olive tree, often associated with weather conditions that facilitate its development and insecticidal treatments, often not very rational, which have destroyed its natural enemies. The objective for the next few years must be to monitor insects such as cotton wool, once little feared but which probably, due to climate changes or precarious balances in ecosystems, could become as dangerous as the key insects already present and develop new eco-friendly methods of control.
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