FROST Temperatures under -8° to -10° C cause damage to small twigs and young sprouts. From -12° to -15° C, the entire skeleton of the tree may be destroyed. Winter colds are the most fearsome ones, especially when accompanied by frost or followed by a quick defrost. A dry cold is less dangerous than a frost occuring during a period of humidity. Late frosts during springtime may damage the blossoms, but this kind of accident rarely happens. In case of frost, a severe trimming up to where the damage is done is called for. And it may even be necessary to cut back the tree to the stump and to regenerate.
		THE OLIVE FLY (Dacus ole Rossi) It is a dipteran (two winged insect) of the Trypetides family of about 8 mm. long. The Dacus hibernates underground, 5 or 6 cm. deep, in the shape of a pupa. In spring, following temperatures and generally from april till june in the South of France, these pupas give birth to flies with a life span of several weeks. As soon as the olives are well developed, around july, these flies pound in the flesh of the olive one egg per fruit. The larva burrows in the flesh of the fruit, causing the olive to rot and to fall. The larva turns back into a pupa inside the olive and gives birth to a fly of the 2nd generation. All through the summer 4 or 5 generations may succeed one another at 20 day's interval. The speed of the evolution is favoured by a high degree of humidity which explains why the Dacus is more dangerous on the mediterranean coast than inland. Each female lies about 60 eggs, which means that at the 4th or the 5th generation, in spite of mortality rates, the number of flies descending from one single female of the first generation may attain several hundreds of millions. The last generation larvas bury themselves underground in autumn to turn into pupas and to hibernate. The Dacus is the most dangerous parasite of the olive tree. It can destroy up to 60 % of the harvest. Because of its nature, the struggle against Dacus is an extremely difficult one. ORGANIC STRUGGLE : Some insects are natural parasites of the Dacus fly : Opins concolor Szet, Opins dacicila, hymenopterous braconides which can be found in North Africa, EulopLus longulus Thoms and Eupelmus urezonus Dalm, which are to be found in Europe. Luckily these Hymenoptera can limit the multiplication of Dacus, in some regions and in certain years. But up till now, breeding these hyper-parasites has not produced satisfactory results.   DACHICIDAL TREATMENTS : a) POISONOUS BAIT. Tentatives have been made to destroy the Dacus through poisonous bait made of syrup and arsenic. This method only produced irregular resultats, because the fly does not feed on a regular basis. b) SYNTHETIC INSECTICIDES : D.D.T.- H.C.H - S.P.C., etc. In order for these to be efficient, the insecticides have to be boiled with a very high concentration of pure product (500 gr. to 1 kg per hl.) and the treatments have to be repeated several times which makes their use quite costly. The insecticides have the advantage of combatting the last generations of Dacus, at the condition of avoiding those with a persistant odour.   TRAPPING : Trapping gives the best results. The insects are captured in glass flytraps that are baited with a solution of 3 % ammoniac phosphate, preferably di-ammoniac. The fly-traps should be put into place in june, 1 or 2 flytraps per tree, to the south and in the shade to prevent excessive evaporation. The solution has to be renewed regularly, more precisely when it has become too concentrated due to evaporation or each time when too many flies have been captured, on the average every 10 to 12 days. Trapping experiments done at Belgentier since1948, have put into evidence the efficiency of this struggling method which has preserved up to 70 or 80 % of the harvest in the test groves compared to other groves. Trapping can be done everywhere, and the method is all the more interesting in that it reduces the number of hibernating larvas, which in turn diminishes each year the attacks with regard to the preceding year. But its efficiency is only guaranteed if the olive grove is sufficiently large and corresponds to total of at least 10.000 trees equipped with flytraps.
		THE MOTH (Prays olellus F). It's a micro-lepidopteran of the Tineides family with three annual generations. The Moth hibernates inside the leaves as an invisible caterpillar. The caterpillars become active in springtime, just before blossoming, they feed for some days on the parenchyma, come out into the open and attack the buds and the young shoots. After having spun a cocoon, the caterpillars turn into butterflies that will lay their eggs onto the undeveloped flowers. This gives birth to a second generation of caterpillars which devour the flowers. The third generation attacks the young olives, penetrate into the stone, eat up the almond and cause the fruits to drop in august and september. The Moth frequently causes the loss of 20 to 40 % of the harvest. Luckily the rapid multiplication of the insect is slowed down by the Eupelmus urezonus Dalm, a chalcidian hyper-parasite we talked about with realtion to the Dacus fly. All the breedings of the Moth which have been done in France for several years under supervision of the "Services Oléicoles", have been parasitized by Eupelmus, often up to 50 % and sometimes even up to 70 %. There exist two efficient treatments against the Moth. The first consists of spraying the trees, shortly before blossoming time, with a mixture of 1 % of lead arseniate, an insecticide which one can equally add to a "bordelaise" mixture at 3 % in order to combat at the same time the cycloconium (peacock's eye). The second consists of spraying, shortly after the forming of the fruits (june) when the butterflies of the 2nd generation swarm, a wet mixture containing 300 gr. of nicotine sulfate for 100 litres of water. It should also be pointed out that the Moths can be trapped by the flytraps that are used against the Dacus.
		THE NEIROUN (or Olive Scolyte) (Phlaeotritus scaraboeoïdes Bern.). A beetle of the Scolytides family, which digs his galleries in the softer parts of the bark at the base of the twigs or in the skeleton bringing the mounting of the sap to a halt and causing the death of the branches. The beetle attacks most frequently weakened trees. These damages, caused by the larva as well as the adult beetle, become especially apparent in springtime through the sawdust which can be found on the bark in places where the eggs have been pounded. There exists no real cure. One should severely trim the trees that have been attacked, burn immediately the wood and apply a good nitrate fertilizer.
		THE OLIVE TREE THRIPS (Liothrips oleoe Costa) A tubuliferous thysanopteran which most of the time passes unnoticed. It sometimes attacks young flowers and buds which it stings and causes to abort. But its most important attacks are to be seen on young leaves and sprouts. The stings of the insects cause the leaves to curve up in the shape of a crook, the sprouts deform and stop growing. When heavily attacked, the tree becomes stunted and bushy. The spraying of sulfocalcic mixtures at 32 - 36° B in summer produces excellent results against this parasite, as well as the use of phosphoric esters.
		THE PSYLLE (Euphyllura olivina Costa) A hemipter of the Psyllides family which manifests itself by the presence of very white waxy flakes at the axil of the flower bunches, flakes which gave him the name of "cotton" or "blanquette". The damages caused by the psylle are very limited and of little importance.
		THE COCHINEALS BLACK COCHINEAL (sessetia oleae, Bernard). This hemipter of the Lecanine family, specific of the olive tree, can be found all over the mediterranean basin. Its caracteristics are its brown colour and the presence of an H-shaped protrusion on its back. It often proliferates and the development of its colonies which "extenuate the tree" form crustings over the twigs and the leaves. Moreover, its secretions favour the appearance and the spread of fungoid growth. PARLATORIA (Parlatoria oleae Colvée). The presence of this hemipter of the Diaspine family has been signaled in the Californian groves where it is the most dangerous parasite of the olive tree. Against the cochineals, one gets the best results with mixtures on a basis of white oil "type summer" at 1 % containing besides a contact insecticide (rotenone f D.D.T. f H.C.H. f etC.). In case of a massive invasion, one should do three successive treatments at 15 to 20 days interval before blossoming time in spring.
		THE "ROGNE" (Or bacterial tumor of the olive tree) (Bacillus Stavastatanoï). The "Rogne" manifests itself through the appearance on the small branches and the twigs of gnarled knobs, the size of a hazelnut or, more exceptionally, a walnut. This disease is more frequent in Greece and in North Africa than in the northern regions. It causes the decay of the parasitized trees. The disease is caused by a bacillus "Pseudomonas Stavastanoï" which penetrates the tissues after the bark has been damaged (frost, hailstorm, etc.). It is more frequent in groves where harvesting is done by beating the trees with poles. The "Rogne" is extremely contagious and is transmitted by the trimming tools. Thus, one shouldn't use tools on healthy trees without having disinfected them. Besides, to stop the disease from expanding, one should cut away and burn the sick branches.
		FUNGOID GROWTH (Ou noir de l'olivier) Fungoid growth is a whole of several cryptogamic parasites (Capnodium meridionale Arnaud, Capnodium oleae Arnaud, Ceratocarpia cactorum Rolland, Cladosporium herbarum Link, Aureos Basidium pullulens de Barry, Alternaria tenuis Nees, etc.) whose myceliums develop on the surface of leaves and branches, onto the sweet excretions of the black cochineal and sometimes onto the exsudations of sap. Fungoid growth is frequent on bushy trees and may cause the tree to asphyxiate. Treatment begins with combatting the cochineal. Besides, one can hasten the disappearing of the fungoid growth with a cupric mixture at 3 % of Lead Sulfate, containing 1 % of wet sulpfur. It is equally advised to trim the sick trees severely for ventilation and to burn the wood.
		THE PEACOCK'S EYE (Cycloconium oleaginum Castagne). It is a parasite mushroom which brings about onto adult leaves the appearance of eye-shaped, round, very caracteristic brown spots, turning yellow later on. The sick leaves fall prematurely which weakens the tree. Sometimes the mycelium develops on the peduncle of the fruits causing them to fall. Two treatments in march and august with a "bordelaise" mixture at 3 % of lead sulfate, and one treatment in winter take care of the peacock's eye.