Date Palm Scales and Their Management

Date palm (Phoenix dactylifera L.) is one of the oldest fruit crops grown in the arid regions of the Arabian Peninsula, North Africa, and the Middle East [1]. The first domestication of the date palm is believed to have taken place at least 6,000 years ago in Mesopotamia, the lands between the Tigris and Euphrates rivers, in what is today Iraq [2]. With a major proportion of the world’s total date palm production in the Middle East and North Africa, date palms have also been introduced in Australia, India, Mexico, Southern Africa, South America, Pakistan, and the USA [3]. Dates are not only a staple food for local populations in many countries, but their production also contributes significantly to the economy, society, and environment of those countries [1,4]. The date is one of the most valuable domesticated fruit trees because of its ritual significance in human societies, health benefits, productive capacity in harsh semiarid and arid environments, and the range of subsistence products from its fruits and other parts of the large palm [2].

Date palm (Phoenix dactylifera L.) is a perennial plant, the pillar of Oasis’s ecosystem, and a target for pest attack [5]. Among these insects, there is the white scale. Parlatoria blanchardi is one of the main pests of the date palm [5,6], with the highest infestations worldwide observed on the young date palms [7]. Parlatoria blanchardi, is also called the armored scale insect or the white scale. It is widely distributed throughout tropical and subtropical regions where palms grow [8] The date trade over the centuries is among the main causes of the spread of this parasite in India, Central Asia, the Middle East, North Africa and Turkey, and later in Australia and America [9]. It is present in all date palm-growing areas and regions worldwide except in the USA, where heavy infestations have been eradicated completely since 1934 [7]. When Parlatoria blanchardi infests the date fruits, it causes many deformities, which greatly reduce their market value, particularly because this insect species infests the dates in all their ripening stages [7,10]. Parlatoria blanchardi commonly infests the leaf bases, where the insects are hidden by fibers. As populations increase, they infest first the older and then the younger foliage and finally the fruits [11]. It mainly infests the leaves, sucking the sap; if a full leaf is covered with white scales, the leaves dry out. In heavy outbreaks, fruits also attack and fall off before maturity. Nymphs and adults suck the sap from the leaflet, midribs, and fruits [10].

The severity of damage on the Parlatoria scale seems to be variable depending on the locality, date palm cultivar, environmental conditions, and management practices. The state of whether the scale is indigenous or recently introduced into an area plays a role as an important factor in the population control program of this pest [4]. In addition, The invasive date palm scale especially the withe scale caused by Parlatoria blanchardi which is one of the most destructive pests of palms in the world is widely distributed in all continents, a better understanding of the biology and the ecology of this insect and their natural enemies and early detection of infested palms is critical in order to avoid death of palms and is the fundamental to the success of any IPM strategy implemented to reduce this pest [4].

This review summarizes the current knowledge on the distribution, natural history, economic importance and management of the main date palm scales including green scale, red scale, and especially the withe scale.

The main types of scales that affect date palms are green scale, red scale, and parlatoria date scale (white scale). These date palm pests are highly specific to the Arecaceae family (oligophagous) and primarily spotted on the foliage, bunch stalk, and, to a lesser extent, on green fruit, ripening fruits, and shoots of date palm trees [5]. Based on their preferred date palm organ, these arthropod pests are classified into four groups, although some species can infest multiple parts simultaneously. Green and white scales prefer foliage but depending on the severity of the infestation and prevailing weather conditions, they may also attack green or ripening fruits [12]. These infestations lead to weakened date palm trees, predisposing them to attacks by termites and other pests [12].

Palmaspis phoenicis asterolecaniidae known as the green scale insect, it is considered a serious pest of date palms [13], has been recognized as a pest exclusively for date palm (Phoenix dactylifera) [14]. It is found in the Middle East, including Iran, Iraq, Saudi Arabia, Qatar, and Sudan [11,15]. It occurs throughout all date palm growing areas in Israel [16]. It may cause severe damage because it feeds on all parts of the leaves and on the fruits. Infested parts of the pinnae turn yellow and die. Heavily infested fruits are scarred and reduced in value [11].

Howard, et al. [11] reported that, in southern Iran, 70 % of the palms are infested and, the severity of green scale’s infestations is important where the relative humidity is high occur annually, with a protracted autumn- winter generation and short generations in early summer and autumn. Nymphs are present continuously, but are most abundant in autumn and early summer, at which times control measures may be applied. Green scale may be controlled by spraying with malathion, azinphosmethyl, iazinon, or other materials [17] combined with oil for control of nymphs in spring and late autumn. In cases of severe infestations, a summer spray may be applied to kill first-instar scales before the crawlers settle on the fruit [11].

Phoenicococcus marlatti, or red date scale, is widely distributed wherever date palms are cultivated. While previously considered a significant pest in the United States [19], it is now generally regarded as a minor issue [18]. This scale insect prefers dark, protected areas and is commonly found massed on the white tissue at the bases of leaves and fruit stalks [19]. Under heavy infestations, Phoenicococcus marlatti can contribute to the death of fruit and the premature senescence of some older leaves. The most effective control measures include subjecting infested offshoots to a temperature of 50°C in an insulated room for 65 hours [11].

The red date scale (RDS) frequently infests date palms in its native North Africa and the Middle East, and from there it has spread to Sicily and Spain. In the Western Hemisphere, it was introduced into Argentina on date offshoots and into the southwestern USA on infested date saplings [11,15,20]. In Israel, damages were recorded mainly in the Jordan and Bet She’an Valleys, but RDS is not usually considered a serious pest of date palms [5].

The parlatoria date scale (PDS) is dispersed across most of the date palm growing regions of the world [9,11,15,20].

Date palms are the preferred host of PDS, but its infestations have also been recorded on additional hosts belonging to four plant families: Arecaceae (Palmae), Apocynaceae, Oleaceae, and Rhamnaceae [14]. Infestation levels vary by region, with serious cases reported in Iran, Libya, and Morocco, while lighter infestations have been observed in Afghanistan [18].

The Green Scale may seriously damage the date palms, it infests the pinnae, the rachis, the basal parts of the leaves, and even the fruits. The infested plant parts (mainly the pinnae) turn yellow, and consequently the entire leaf may degenerate. Also, heavy infestation by the scale may kill the palm tree [16]. To control the green scale, the applications of organophosphate insecticides combined with mineral oils were very effective in minimizing the level of GS infestation and damage [21]. In addition, biological control, emergence holes observed in many GS individuals indicate that parasitoids probably exercised efficient control of these pests. This may explain why no further outbreaks of GS since the early 1970s have been recorded in plantations that were not treated with insecticides [5].

Palmapsis phoenicis is an important pest of date palms in Israel. The tests on its control were carried out in the Beit Shean Valley between December 1959 and December 1960. The most effective combinations were 2% of a special formulation of malathion in oil (88 parts malathion and 712 parts white medium oil in 1,500 parts concentrate by weight) and 0.2% wettable diazinon or 0.5 % azinphos-methyl (Gusathion) in 2 % oil emulsion; 0.5-1 % malathion in 2 % oil emulsion was inferior but still satisfactory. The sprays should be applied since the nymphs are more easily controlled than the adult females, during autumn and winter, and they can be supplemented, if necessary, by summer treatment in June or July, during the mass appearance of crawlers, to protect the fruits [21].

With the extensive planting of date palms in Israel, especially in the northern valleys, and with the introduction of high-quality cultivars, the danger posed by the red scale has increased. This pest is likely to retard the development of young palms, and heavy infestations may impair the survival prospects of newly planted young date shoots and may cause dryness and mortality in the infested palms [15]. Table 1 summarizes the main species of scale insects that affect date palms.

Parlatoria blanchardi Targ

Parlatoria blanchardi (Targioni-Tozzetti) is found wherever date palm is grown. It is one of the oldest date palm pests, and it belongs to the family of Diaspididae, characterized by posterior abdominal segment coalescing into a wax-forming structure called pygidium; generally, with lobes and plates or gland spines on the pygidium; legs absent or represented by a small, sclerotized area; and antennae represented by an unsegmented knob [22].

The female is protected by an elliptical, convex armor, white gray in color. Its body length is 1–1.5 mm and its width are 0.6–0.8 mm; its body (underneath the armor) is elongate, reddish, and ∼0.8 mm in length. The female is neotenic and lays its eggs underneath the armor. The crawler is reddish, 0.23 mm in length. The male bears flattened and elongate armor, white in color, and its body is ∼0.8 mm in length [5].

From a biological viewpoint, like all Diapsid date palm scale insects, females and males pass through two distinct development types from the second stage onward [23]. The larva in the first stage, after a period of mobile life, settles and begins secreting a white shield. After the first molt, it secretes a second, flattened shield that includes the first-stage shield. A second molt gives rise to the adult female, whose shield retains those of the earlier stages as before [23]. The adults average about 0.7 mm in length; the female is broadly oval, and a bit flattened in all stages [15]. Females stay stationary for life and, after mating, produce numerous eggs. After hatching, the nymphs crawl out from under the female and move about, feeding at various locations until their third molting. These nymphs exhibit pink to red coloring, while adult females are gray [15]. They are about 1.8 mm in length and 0.7 mm in width [24]. Regarding females, a characteristic difference in coloration distinguishes immature females from mature ones; the former are pale pink, while the latter are reddish wine-colored [75]. The duration of the egg stage depends on temperature, ranging from 2 to 11 days, there is nearly continuous overlapping of egg, nymph, and adult stages throughout the year, resulting in generation boundaries that are not clearly defined [15].

Males undergo a different development; under their shield, they form a protonymph (pre-nymph) and a deutonymph (nymph) before maturing and emerging, leaving their empty shield on the leaflet at hatching, male shields have a characteristically elongated shape compared to those of females [23], they are about 1 mm in length and 0.4 mm in width [24]. The male undergoes five nymphal stages and emerges as an adult with well-developed wings [15].

Date palm trees are subjected to attack by several insect pests, especially the white date palm scale, Parlatoria blanchardi (Targioni-Tozzetti) [25]. It infests all parts of the date palm [5] and causes significant damage [23]. At high population densities, infestation covers the fruit bunches and the fruit stalks. Dense populations may impair the development of the palm and cause the fruits to shrink, rendering them unmarketable. In extreme cases, it may cause deterioration of the palm [5]. Laudeho & Benassy [23] reported that in Erfoud (Morocco) a 70 to 80% waste in the date harvest and at El Haroun yield reductions of up to 50 to 60% over three years.

Salman, et al. [26] noted that, most parts of the tree, such as leaflets, leaves, tender shoots, offshoots, twigs, and fruits, are attacked by both immatures and adult females of this diaspidid insect. Adults and nymphs of this insect feed on leaf sap, sucking a great amount of sap that contains macro-elements and microelements. At high levels of infestation with this scale insect, remarkable damage occurs, resulting in early leaf drop and yield reduction. Great damage can be done by this scale insect by sucking the plant sap that gives low rates of photosynthesis and respiration, which leads to curling, yellowing, and dropping of leaves. A characteristic symptom of infestation by P. blanchardi is the appearance and accumulation of its scales on attacked palm parts [5,27].

This insect sucks the sap with its mouth parts and secretes toxic saliva during feeding, causing malformation of leaves and shoots, low photosynthesis, and low respiration rate. All of this leads to curling, yellowing, and dropping of leaves, dwarfing of the plant, and subsequently causes considerable qualitative and quantitative yield losses and eventually affects the marketing value of the fruits. Therefore, the presence of this insect weakens the infested plant itself [28].

In a heavily intestate area by P. blanchardi, it accumulates its scales on the infested part of the tree, secreting toxic saliva [5,28,29] that affects the respiration, transpiration, and photosynthesis processes and thus obstructs the growth process, and several biotic and abiotic factors affect populations of scale insects [30].

Under favorable conditions, Parlatoria date scale can spread over the surfaces of the foliage and fruit of the date palm, covering them with both live and dead insects. The scale feeds on the white succulent tissues at the base of the leafstalk, one of the most protected and inaccessible places on the palm. As the population increases, the insects move from these areas onto the pinnae. Heavy infestations on the pinnae cause them to wither and die. In commercial plantings, date palms are seldom killed by Parlatoria date scale, but feeding by these insects definitely affects the vigor of the palms and decreases yields. Infestations on fruit reduce its commercial value and may render it unfit for human consumption [15].

White scale’s damage is very serious on young palms between two to eight years of age, but even under severe attacks, the palm and its offshoots do not die, Nymphs and adults suck the sap from the leaflet, midribs and dates. Under each scale insect, a discolored area appears on the leaflet. Heavy infestation causes leaflets to turn yellow and contributes to the premature death of the fronds [24,31].

Parlatoria blanchardi infests the date palm leaflets, fronds, midribs, spines, bunches, and fruits where the nymphs and adults feed by sucking the sap from the green parts and the dates most of the year. Then, the color of the infested parts changes from dark green to pale or light green, or to yellow color with the appearance of several spots. These spots start as light green in color and then turn tawny (tan or brownish) in color. Where scales settle and feed, a discolored area of injured tissue develops. The affected areas gradually withered. Severe infestation leads to the death of the leaflets, dry fronds, and premature death by inhibiting transpiration and photosynthesis. All these together cause general weakness in the date palm tree and deterioration in crop production both qualitatively and quantitatively. Particularly because this insect species infests the dates in all their ripening stages, Khalal (Color stage), Rutab (soft ripe stage) and Tamer (full ripe stage) [7] (Table 2).

Distribution and host range

Parlatoria blanchardi (Targioni-Tozzetti) is an insect belonging to the family Diaspididae. This insect is reported in all data producing countries [23]. It’s worldwide and found wherever date palm is grown [4]. It also opts for the areas with high humidity and shaded spots away from the direct sunrays [7]. Parlatoria blanchardi was discovered in 1868 by Blanchard M.E., in an oasis of the Oued-Right, in the Algerian Sahara [31]. It is one of the oldest pests of date palm and is thought to have originated from the oases of Mesopotamia or Iraq [15]. Parlatoria scale was accidentally introduced in the USA, particularly in Arizona, California, and Texas, and it was eradicated in 1914 from Arizona, 1919 from Texas, and in the 1930s from California. Wakil, et al. [4] reported that, due to the international movement and trade in date palm offshoots, the pest is now found in Europe, Central Asia, the Middle East, Africa, the Western Hemisphere, and Oceania.

Date palm (Phoenix dactylifera), is the main host of Parlatoria blanchaardi [23,32]. it is uniquely susceptible to Parlatoria blanchardi due to its extensive cultivation and favorable environmental conditions characterized these grows areas, this relationship underscores the importance of targeted pest management strategies to mitigate the impact of date palm scale on these essential crops [11]. as well as some other Arecaceae. It is also found on Canary Island palm, Phoenix canariensis Chabaud, Washingtonia palm, Washingtonia filifera (Lindl.) H. Wendl., and doum palm, Hyphaene thebaica (L.) Mart [33]. In addition, Wakil et al. [4] reported that the scale has been found on plants belonging to the families Apocynaceae, Oleaceae, and Rhamnaceae. Other hosts of Parlatoria scale included species of the genera Jasminum, Latania, Pritchardia, and Vinca [34]. Additionally, P. blanchardi was found attached to fig leaves, a tree frequently associated with date palms in orchards in southern Morocco [23]. A list of hosts for Parlatoria blanchardi given in Table 3.

A new distribution map is provided for Parlatoria blanchardi (Targioni Tozzetti), information is given on the geographical distribution in Europe, France, Italy, Spain, ASIA, Afghanistan, India, Andhra Pradesh, Delhi, Gujarat, Punjab, Rajasthan, Iran, Iraq, Israel, Jordan, Kuwait, Oman, Pakistan, Qatar, Saudi Arabia, Syria, Turkey, Turkmenistan, United Arab Emirates, Yemen, AFRICA, Algeria, Chad, Egypt, Eritrea, Kenya, Libya, Mali, Mauritania, Mauritius, Morocco, Niger, Somalia, Sudan, Tunisia, CENTRAL AMERICA & CARIBBEAN, Jamaica, Montserrat, SOUTH AMERICA, Argentina, Bolivia, Brazil, Pemambuco, Rio de Janeiro, Sao Paulo, OCEANIA, Australia, Queensland [32]. It is an important pest in Algeria, Kuwait, Libya, Mauritania, Morocco, and Tunisia. Iraq, Oman, Saudi Arabia, and Sudan consider this pest a moderate one, while Egypt, Jordan, the UAE, and Yemen consider it a minor pest [24].

In Morocco, the Parlatoria blanchardi first appeared in 1937 in the palm groves of Figuig (in the eastern part of the country), originating from the surrounding Algerian oases. Subsequently, P. blanchardi encountered no barriers to its spread. This dissemination is often facilitated by wind but primarily by human activities. Indeed, the exchange of young plants (palm offshoots) frequently occurs in date cultivation and inevitably serves as an excellent source of contamination between different palm groves. Moreover, the decision to introduce an Algerian variety (Deglet-Nour) into the oases of the Tata region in 1941 also led to the establishment of P. blanchardi in these palm groves, located in the western part of the country, which until then were considered unaffected by the pest [35].

Nomenclature and taxonomy

Parlatoria blanchardi Targ. belongs to the order Homoptera, within the superfamily Coccoidea, the family Diaspididae, the subfamily Diaspidinae, and the tribe Parlatorini, and is classified under the subtribe Parlatorina. It was first discovered by Blanchard in 1890 in an Algerian palm orchard. Targioni-Tozzetti was first described in 1892 under the name Aonidielia blanchardi Targ. A detailed morphological description was carried out by Stickney in 1934 and then by Balachowsky in 1953 [36].

Parlatoria blanchardi has received many local designations, like Djreb, Sem, Elmen in Algeria, Gmel in Tunisia, Rheifiss et K’lefiss in Mauritania, Nakoub, Guemla, Tilichte, Tabkhocht et Tasslacht in Maroc [9].

Olive’s infestation

Olives were classified as infested when bearing stings and healthy olives. The data showed a generally low infestation of total olives harvested, with higher values for NGV and NGG (8%) and lower for PC and NGD2 (2%). These data are compatible with olive oil production, which tolerates values of infestation ≤ 10%; however, a degree of infestation greater than 1% prevents the use of the fruits as table olives [28]. Among the samples tested, NGV>NGG> NGD1 showed the higher infestation, while PC and NGD2 showed the lowest (Table 1). NGV samples were the most affected, with 597 total stings, a maximum number of stings for olives of 47, and 30% with stings ≥ 7. NGV was the only sample showing larvae L2 and L3, accounting for 19 total exit holes. The samples NGG and NGD1 had 572 and 470 total stings, maximum stings, and exit holes of 18 and 10 and 21 and 10, respectively (Table 1).

The percentage of olives with stings ≥ 7 was 32, and 25% for NGG and NGD1, respectively. The samples of NGG showed an old infestation with the absence of larvae or pupae in the pulp but 21 exit holes, while two pupae were detected in the samples NGD1 and NGV. The samples of PC and NGD2 showed the lowest level of olive fly attack with only 297 and 243 total punctures and 6 and 5 exit holes, respectively. The maximum number of stings per olive was 7 and 8, with 2% of olives with stings ≥ 7. No larvae or pupae were detected in PC and NGD2 samples (Table 1).

* NG – Nera di Gonnos
¥ PC – Pitz’e e Carroga

Olive fruit fly adults exhibit, under field conditions, a preference for large fruit [20,29]. Olives of the cv Nera di Gonnos (NG) and Pitz’e Carroga (PC) have similar weights (around 5 g) but different shapes; NG is elliptic, while PC is asymmetric with a sharp tip (Figure 1). PC is susceptible to Bactrocera oleae because of its size and earliness.

The samples of NGD2 and PC belonged to the same orchard and were subjected to the same field management. The plants followed a meticulous protocol of treatments with plant protection products, which decreased the population of Bactrocera oleae and, consequently, fly attack in these samples. The resulting low level of damage on the olives confirms this behavior.

Thirteen fatty acids were detected and subsequently identified by GC-MS. No qualitative differences were observed among healthy and infested olives, neither among different samples of the same cultivar nor from cultivars.

Concerning data, little differences were observed in the quantitative composition of fatty acid among olive samples from healthy or infested cultivars. Oleic acid was the most concentrated methyl ester in all samples, with average values of 56.84 ± 3.33% and 56.38 ± 4.99 in healthy and infested, respectively, followed by linoleic acid (15.14 ± 11.27% healthy and 14.52 ± 27.06% infested), palmitic acid (18.30 ± 4.49% healthy, and 18.58 ± 3.64 infested), all other fatty acids accounted for less than 4% (Table 2).

However, comparing healthy and infested samples from each orchard, we identified two patterns: NGD1, NGG, NGV, and PC and NGD2 (Table 2).

The former had higher levels of oleic acid and lower palmitic and linoleic acid in healthy olives, whereas the second had higher palmitoleic and linoleic and lower oleic acid in healthy olives related to infested. All samples showed higher levels of cis 13, 16 docosadienoic acid in healthy vs infested. Montedoro et al. [30] reported that fatty acid composition could be influenced by various factors such as environmental factors, infestation, and agronomic techniques; on the contrary, Mraicha et al. [31] observed that also very severe infestation did not cause essential changes in the fatty acid composition. More recently, Valencic et al. [32] reported that olive oils affected by damaging infestation had lower amounts of oleic acid and higher amounts of myristic, linoleic, and linolenic acids. Our data confirmed the slight differences in the fatty acid composition among healthy and infested olives; however, the results showed a reversed behavior compared to the literature data.

The rate of oleic/linoleic acid showed higher values in the most damaged olives (NGV, NGG, and NGD1) than in the less infested (NGD2 and PC) (Table 2).

Grouping fatty acid for the level of unsaturation evidenced MUFA as the main fraction in all samples, followed by SFA and PUFA. NGD1, NGG, and NGV had average values in infested olives, slightly higher for saturated (SFA) and polyunsaturated (PUFA) and lower values for monounsaturated (MUFA) compared to healthy.

On the contrary, in healthy olives, NGD2 and PC showed lower SFA and PUFA values and higher MUFA values (Table 2) than infested ones (Figure 3). Moreover, the oleic/linoleic acid ratio was almost even in all samples of NG, while it was higher in the infested samples from PC and NGD2.

Fatty acid data were analyzed using multivariate statistical analysis (Figure 4). A PCA model was created using all samples. Healthy samples were identified by the letter “a” while infested by the “b”. The scores plot of the principal component 1 versus the principal component 2 confirmed the similarity among the samples (Figure 4A). However, PC samples were well separated from NG samples. NGVb samples were probably distinguished from the others for a higher infestation level.

The PLS-DA model, created to evaluate the significance of the difference between healthy and infested olives, showed poorly differentiated classes. Only NGVb, the most affected by olive fly, was separated from the other samples (Figure 4B).

The importance of the variables in distinguishing the two groups was ranked according to their VIP scores in the PLS-DA model. The results indicated that oleic acid (variable 8) had the highest correlation with the grouping of the infested olives, followed by palmitoleic (variable 3) and linolenic acid (variable 11).

Squalene showed uneven amounts among the different samples. The trend was similar, with lower amounts in infested vs. healthy in NGD2 and PC, while NGD1, NGG, and NGV samples showed an even amount between healthy and infested. PC showed values notably higher, accounting for 32.07 ± 9.85 and 20.71 ± 8.32 in healthy and infested, respectively (Table 2).

Phenolic fraction composition

The analysis of HPLC-DAD chromatograms at 280 and 360 nm allowed us to identify 11 main phenols: hydroxytyrosol, tyrosol, vanillic acid, vanillin, p-cumaric acid, luteolin 7-glucoside, verbascoside, 3-OH-cinnamic acid, oleuropein, luteolin, methyl-luteolin (Figure 5). All cultivars belonging to Nera di Gonnos (NG) had overlapped chromatographic profiles (Figure 5A), while PC showed a specific profile at 360 nm with the presence of three undefined peaks and the absence of the peak at 16.35 (Figure 5B).

PC samples showed notably less amounts of Oleuropina glycoside. The 280 nm and 360 nm analyses showed minor differences between healthy and infested samples.

Hydroxytyrosol, tyrosol, luteolin, and CH3-luteolin had lower values in healthy olives samples, while oleuropein, oleuropein glucoside, and luteolin-7-glucoside had higher values in healthy samples (Table 3).

NGV, NGD1, and NGG showed the most remarkable differences between healthy and infested samples (Table 3). At the same time, NGD2 and PC had almost overlapping values except for oleuropein glucoside, luteolin, and methyl-luteolin. The data of total phenols corresponded to the number of stings, with NGD2 and PC almost overlapping (Figure 6). Spectrophotometric analysis of total phenols showed a reversed amount in NGD2 and PC, with less significant differences compared to HPLC DAD analysis.

The two analyses are performed at different wavelengths, and the analytical responses cannot be compared.

Hydroxytyrosol and tyrosol derive from oleuropein and ligstroside hydrolysis, and each process that may cause hydrolysis of oleuropein and ligstroside can increase these two metabolites.

Literature data reported that the infestation of olives by Bactrocera oleae can cause extensive damage to the tissue and the cells of the olive pulp, affecting the phenol fraction and the aromatic profile [17,19,32-34].

The data reported in this paper confirmed the general decrease of phenol fraction; a significant decrease of oleuropein and oleuropein glucoside can be noted, with a resulting increase of OHtyrosol and tyrosol.

The damage related to the infestation against the cells increases the release of enzymes, which leads to the degradation of the secoiridoids compounds, growing the amount of the smaller phenols. This condition can be characterized in the samples NGV, NGG, and NGD1, most affected by the parasite (Table 3). A decrease in the total content represents the trend of the bisphenols; however, each single phenol follows a proper dissipation rate.

The rates were well related to the level of infestation; NGD2 and PC showed the lowest differences among the reported phenols.

It has been reported that olive infestation could affect olives and olive oil quality. In this paper, we examined the changes in some olive quality parameters concerning Bactrocera oleae infestation. The samples analyzed showed a level of infestation ranging from 10 to 2% and were above the level accepted (1%) for the technological processing of table olives. However, the biochemical analysis showed beneficial characteristics, with only minor differences from healthy olives. The olives most affected by infestation, both for the number of stings and the total level of infestation, were represented by the samples of NGV, NGG, and NGD1. Infestation influenced only slightly the fatty acids fraction; however, it was possible to distinguish two sets of data, constituted by NGG, NGD1, and NGV, which showed higher levels of SFA and PUFA and lower MUFA in healthy vs infested olives. In comparison, NGD2 and PC showed higher MUFA levels and lower SFA and PUFA. The oleic/linoleic acid rate confirmed the presence of two distinguished patterns, which were well separated by multivariate analysis. This fact may indicate a degradative process of MUFA to load in two opposite directions, the increase of unsaturation and the saturation of individuals’ double bonds. Single phenols showed higher amounts of oleuropein and luteolin precursors in healthy than infested olives, data confirmed by the analysis of total phenols, which had higher values in healthy vs infested. The differences among single and total phenols (as the sum of single phenols) were positively correlated with the total number of stings, decreasing in the samples most infected (Figure 6). The data demonstrates that new studies are needed to understand better the biochemical reaction at the base of phenols and fatty acid modifications in response to pest attacks.

None.

No conflict of interest.

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