Since antiquity, the olive-mill liquid wastes were known to have herbicide and pesticide properties and amurca is considered a precursor to modern pesticides in the classical period (Smith A.E. and Secox D.M., 1975; Levinson H. and Levinson A., 1998).
Both Cato (XCI) and Varro (I, 51) recommended that threshing floors be made from a mixture of soil and amurca so that weeds would not grow. Columella, Palladius30, and the "Geoponika"31 also made mention of this practice. In this instance, the amurca and soil mixture seems to have dried to a hard plaster-like finish which was thus impervious to weeds. However, Varro specifically noted (I, 51) that amurca was poisonous to weeds, ants, and moles. Varro also observed (I, 55) that where the amurca flowed from the olive presses onto the fields the ground became barren, and he went on to state that amurca was poured around olive tree roots and ''wherever noxious weeds grow in the fields''. This latter use must be one of the earliest references to a specific weed killing preparation. Theophrastus (IV, 16) wrote that pouring olive oil over their roots could kill trees, young trees being more susceptible to this treatment than mature ones.
The treatment of seeds with amurca was considered to be useful against insects and other animal pests. Virgil32 (I, 90) recommended that all seeds be soaked in a mixture of amurca and native soda before planting so that greater yields would be forthcoming. Columella (II, 10) held that this latter treatment was successful also in reducing attack by weevils in the mature seed.
Amurca was also used for insect control. Thus, it is mentioned (Columella, II, 9) that unsalted amurca when applied to the furrows at the outbreak of an infestation would drive away the ''destructive creatures'', while applications of amurca and red earth, possibly sandarach (the red arsenic of Greeks), would keep vines free from beetles and ants (Columella, IV, 26). When mixed with soot, gnats could be driven away, and locusts were dispelled by using amurca containing extracts of cucumber or lupins, while caterpillars on cabbages were killed by an application of amurca and ox urine (Palladius, I, 122, 125, 135, 136). In addition to the above methods fumigation
30Palladius Rutilus Taurus Emilianus, Roman author who lived and wrote around the 4th century A.D. Very little is known about Palladius except that his books On husbondrie and De re rustica obtained some celebrity.
31For the citations to the works of Columella, Palladius, Pliny, Theophrastus, Varro, Virgil, and the "Geoponika" the Latin numeral refers to the book number and the arabic number to the chapter. In the case of the writings of Palladius and Virgil, the arabic numerals are to the stanzas and paragraphs, respectively. The works of Cato are not divided into books; thus the Roman numbers associated with these references are to the numbered sections.
32Virgil or Vergil (Publius Vergilius Maro, 70 B.C-19 B.C.), greatest of Roman poets; born in Andes dist., near Mantua, in Cisalpine Gaul. The poet's boyhood experience of life on his father's farm was an essential part of his education. In 41 B.C. Virgil went to Rome, where he became a part of the literary circle patronized by Maecenas and Augustus and where his Eclogues, or Bucolics, were completed in 37 B.C. In these poems he idealizes rural life in the manner of his Greek predecessor Theocritus. From the Eclogues, Virgil turned to rural poetry of a contrasting kind, realistic and didactic. In his Georgics, completed in 30 B.C., he seeks, as had the Greek Hesiod before him, to interpret the charm of real life and work on the farm. His perfect poetic expression gives him the first place among pastoral poets. For the rest of his life Virgil worked on the Aeneid, a national epic honoring Rome and foretelling prosperity to come.
procedures were carried out. The mixture of amurca, sulfur, and bitumen was heated in a copper vessel and the resulting gluey substance applied to the trunks and branches of vines for control of caterpillars (Cato, XCV; XVII, 47). Both Pliny the Elder (XVII, 47) and Palladius (I, 127) remark that the smoke from the boiling mixture of amurca, bitumen, and sulfur (Cato, XCV) was successful in preventing caterpillars from attacking vines. A remedy for blight (Pliny the Elder, XVIII, 45) was to sprinkle the infected plant (vines) with amurca.
Protection of store grain by amurca has often been recommended by various Roman agriculturists from the 2nd century B.C. until the 4th century A.D., indicating the usefulness of this treatment. Amurca, when incorporated into threshing floors, was also helpful in keeping ants away (Cato, XCI; Varro, I, 51) and, on being made into a paste with straw and applied to granary walls, appeared to be instrumental in keeping the grain free from weevils (Cato, XCII). In his well-known treatise De agri cultura (XCII), Cato stated that granary insects and mice can be prevented from damaging stored grain by applying amurca as follows: ''mix amurca with a small amount of ground straw and clay; knead the mixture until it turns into a viscous paste. Smear this paste on the interior walls, floor, and ceiling of the granary and sprinkle aqueous amurca on the dried coatings. When the latter are dried up, deposit cool grain in the treated store. Granary pests will be incapable of damaging grain kept in such stores''. Moreover, Varro, Pliny the Elder, and Palladius improved the above description by supplementing amurca with ground chalk and an insectistatic crushed foliage of coriander (Coriandrum sativum), fleabane (Inula conyza), or wormwood (Arthemisia absinthium) and recommended distributing those mixtures in the stored grain (Beavis J.C., 1988; Levinson H. and Levinson A., 1998).
It is likely the above blends of amurca to have acted by clogging the wall crevices and cracks, which could have otherwise served as hiding and oviposition niches for pest species, as well as by suppressing substances which are capable of repelling and suppressing pest populations. A revived interest in pest-averting procedures practiced in antiquity may be worthwhile in view of the destructive side-effects of certain pesticides on the environment as well as the alarming increase and spread of pesticide resistance in storage insect species (Levinson H. and Levinson A., 1998).
Amurca was also used as a means of protecting clothes from moths and as a preservative for dried fruits (Cato, XCVIII, XCVIX).
The role of amurca is difficult to assess though it does seem to have been a universal remedy against insects, weeds, and plant diseases. The composition of amurca is unfortunately difficult to deduce. Pliny the Elder mentioned (XV, 4) that amurca was a bitter, watery liquid and this bitterness is now known to be chiefly due to the easily hydrolysable glycoside oleuropein (Fernandez-Diez M.J., 1971) whose structure has been elucidated (Inouye H. et al., 1970). It is not known whether this glycoside possesses any pesticidal properties. The amurca would also have contained traces of phytocidal, insecticidal, and fungicidal glyceride oils as well as oleic acid. Salt was sometimes added to the olives prior to pressing which may have resulted in additional phytotoxic properties (Columella, XII, 52; Palladius, XI, 16). Thus, it is impossible to state whether the ancient amurca was effective against some weeds, or the salt associated with it was the control agent. A further and complicating factor was that during the preparation of amurca, as described by Varro (I, 64), the liquid was boiled to about two-thirds of its original volume in a copper vessel. In this way not only would the amurca become contaminated with traces of copper, but also a number of extra products could be formed by hydrolytic processes. As copper salts are now known to be extremely effective against certain fungal diseases, it is possible that the amurca prepared in this manner contained fungicidally active amounts of the metal.
Capasso R. et al. (1994b) investigated the possible utilization of OMWW and its bioactive polyphenols in protection of olives against Bactrocera oleae (Insecta: Diptera: Tephritidae). Among the main polyphenols occurring in OMWW, catechol showed the most deterrent action on the oviposition of B. oleae; 4-methylcatechol was less active, whereas hydroxytyrosol and tyrosol were inactive. In contrast, synthetic o-quinone was found to be stimulant at 7.5 x 10_2M. Two other synthetic derivatives of catechol, diacetylcatechol, and guaiacol (2-methoxyphenol), were also deterrent, suggesting these compounds undergo a biochemical transformation into catechol by means of the bacterial symbionts of B. oleae. OMWW and their phenolic extracts showed deterrence only when highly concentrated, while natural olive juice was strongly deterrent. Experiments carried out to evaluate the effect of olive juice and catechol on the fecundity of B. oleae showed that they strongly reduce this function.
Capasso R. et al. (1995) investigated also the possibility of using OMWW as a pesticide to protect the olive plant against the knot disease caused by Pseudomonas syringae pv. savastanoi and the tomato plant against the serious disease caused by Corynebacterium michiganese (Gram-positive). Among the main polyphenols present in OMWW, 4-methylcatechol proved to be the most toxic to P. syringae pv. savastanoi at 10_4mol/l, and also demonstrated bactericidal activity, while on C. michiganese was only slightly active; catechol and hydroxytyrosol were less active on P. syringae pv. savastanoi, but inactive on C. michiganese; tyrosol was completely inactive on both bacteria — see Chapter 2: "Characterization of olive processing waste'', section: "Antimicrobial activity of OMWW'' and Chapter 3: "Environmental effects'', section: "Effects on soil biological properties".
In the light of the obtained results, it is recommended that the use of raw OMWW should be avoided, since it causes leaf and fruit abscission (Fiume F. and Vita G., 1977) and is highly toxic on Hep2 human cells. Therefore, one can conclude that OMWW needs to be fractionated in order to separate and isolate the antibacterial catechol, 4-methylcatechol, and hydroxytyrosol. However, catechol and 4-methyl-catechol could not be used because they are toxic on Hep2 and phytotoxic (Bartolini S. et al., 1994). As a matter of fact, hydroxytyrosol is the only promising OMWW polyphenol, which could be used in agriculture on P. syringae pv. savastanoi, since it is not phytotoxic (Bartolini S. et al., 1994) and not toxic on Hep2 human cells.
Table 10.1. Liquid foliar fertilizer based on OMWW (ES2139505, 2000)
Nitrogen Hydrogen Oxygen Sulfur
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