Functional Response of Chrysoperla carnea (Neuroptera: Chrysopidae) Larvae on Saissetia oleae (Olivier) (Hemiptera: Coccidae): Implications for Biological Control

Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) is a voracious predator of soft-bodied insects such as juveniles of scale insects and the black scale Saissetia oleae (Olivier) (Hemiptera: Coccidae) is an important pest of several crops, such as the olive tree. However, the predatory efficiency of C. carnea on S. oleae has been unstudied yet. The present work aimed to study the functional response of larvae of C. carnea fed on S. oleae nymphs. In a controlled laboratory environment, increasing densities of S. oleae second and third nymph stages were offered to newly emerged specimens of the three larvae instars of C. carnea. After 24 h, the number of killed S. oleae was recorded and the functional response of C. carnea was assessed. The three larval stages of C. carnea displayed a type-II functional response, i.e., killed prey increased with higher S. oleae densities up to a maximum limited by the handling time. The attack rate did not significantly differ among the three instars while the maximum attack rate was significantly higher for the third instar. The handling time of the first larval instar of C. carnea was higher than that of the third instar. Our results demonstrated that S. oleae could act as a food resource for all larval stages of C. carnea. Furthermore, the third larval stage of the predator was the most efficient in reducing S. oleae densities. These results suggest that C. carnea larvae could contribute to S. oleae control in sustainable agriculture.

Life history and population dynamics of Aspidiotus nerii (Bouche, 1833), Homoptera: Diaspididae, Saissetia oleae (Olivier, 1751), Homoptera: Lecanidae and Pollinia pollini (Costa, 1857), Homoptera: Asterolecanidae on olive trees in the Blida Region (Algeria)

The work consists of a study on the level of infestation of the 3 species of olive-infused mealybugs at the two stations (Soumaa and Guerrouaou) in the Blida région, with particular attention to the évolution of Pollinia pollini (Asterolecanidae), Octaspidiotus nerii (Diaspididae) and Saissetia oleae (Lecanidae). Unlike the Soumaa station, there is a large infestation in the Guerrouaou station by the three (most abundant) species with a high rate. The life cycle monitoring and the bio-ecology of these three pests were carried out through periodic population counts on the leaves and twigs of the tree from 08 August 2016 to 29 May 2017 in the wilaya of Blida. It appears that the study of the biology of P.pollini evolves in 2 annual generations (the first is the spring generation; the second is through the summer. The larval stage remains the most abandoned compared to other developmental stages. The South orientation seems the most affectionate by P.pollini. We can conclude that O .nerii has two generations « spring and automne » depending on climatic factors. The East and West exposure represent the places most sought after by this scale where we found a relative abundance between larvae and adult females. S. oleae develops only one generation per year (automnal génération). Females are the most abundant in Soumaa station and larvae in Guerrouaou station. The eastern orientation and the automne season are the most favourable for the development of the mealybug.

First Record of Cheiloneurus clαviger (Thomson) (Hymenoptera: Encyrtidae) on Corfu Island

During an ongoing research programme on Saissetia oleae (Oliv.) (Homoptera: Coccidae) and its parasites on the island of Corfu, the presence of the hyperparasite Cheiloneurus clαviger (Thomson) (Hymenoptera: Encyrtidae) was recorded, for the first time, in samples of parasitized Saissetia oleae in 1991. The identification of C. clagiver was made by the junior author. The adults of Cheiloneurus clαviger emerged from S. oleae females parasitized by Metaphycus lounsburyi (How.) (Hymenoptera: Encytridae), after they were placed in plastic capsules. Tables 1 and 2 give the number of adults of S. oleae, C. claviger and M. lounsburyi that emerged from S. oleae at two experimental fields. M. lounsburyi is one of the main parasitoids of S. oleae acting as an internal parasite of the fourth larval instar. The numbers of C. claviger emerged were very low compared with the numbers of M. lounsburyi, indicating that at present C. claviger is not a serious limiting factor for the population of M. lounsburyi. The presence of a group of coarse bristles at the apex of the scutellum and the long marginal vein of fore wings are the peculiarities of the genus Cheiloneurus. The incomplete infuscation of the fore wings and the colour of the antennae with only the 5th funicular segment blackish can easily allow the discrimination of C. claviger females from those of congeneric species. Cheiloneurus clαviger is reported as a hyperparasitoid of several coccids of economic impor tance mainly via other encyrtid parasitoids. In Italy, C. claviger has been found to act as a hyperparasite of Kermesidi (genus Kermes) which infest Pinoideae. Previous reports on the entomophagous fauna of S. oleae on Corfu do not include C. claviger and it is assumed that the hyperparasitoid has been introduced rather recently. The actual role oil the parasitic complex of S. oleae and the distribution of this hyperparasite on the island should be further investigated.

Population dynamics of Saissetia oleae. Ι. Assessments of ροpulation and mortality

The population dynamics of Saisselia oleae (Oliv.) (Homoptera: Coccidae) was studied in Corfu during five successive yearly generations (1981-1986). Successive estimates of the population of S. oleae were obtained within each of the five yearly generations and survivorship curves were constructed showing the progressive re­duction of the living population within each generation and population changes from generation to generation. The calculated mortality rates indicate that the population of S. oleae suffers heavy mortality. The major mortality factors were high temperatures during summer, the action of predators, particularly during spring, and mortality of crawlers during summer. Overall survival rate was very low and corresponded to total generation mortality that ranged from 99.693% to 99.987%. It is assumed that variation in the action of mortality factors cause considerable I’l Uctuations of the S. oleae population.

Flight period of some parasitoids and a predator of the olive black scale (Saissetia oleae Olivier) on Corfu island

The time of year the adults (flight period) of the parasitoids of S. oleae: Μetaphycus helvolus, Μetaphycus lounsburyi, Scutelista cyanea and Moranila californica and the predator Chilocorus bipustulatus are present, was determined in three areas of Corfu island: Lima, Kontocali and Avliotes. M. helvolus apparently has two flight periods: the first is from A­pril till July and the second from November till December. All the other natural enemies have only one flight period per year. The flight period of M. lounsburyi is from April till August, while S. cyanea flies from August till the end of September or the first days of Oc­tober, and M. californica adults are present from July till the middle of December. Adults of C. bipustulatus appeared from July till December or the middle of January.

Preliminary information on parasitization rates and larval survival of Metaphycus helvolus Comp. and Metaphycus lounsburyi How., parasites of Saissetia oleae Olivier, under laboratory conditions

Parasitization rates and larval mortality of M. helvolus and M. lounsburyi parasites of S. oleae were studied under laboratory conditions. Mean life duration of M. helvolus, under temperature 23±1oC and relative humidity 65-70%, was found to be 8.4 days. Only a relatively small proportion of the individuals of S. oleae was parasitized, but the greater proportion of the larvae of the parasite was successfully developed to the adult stage. Mean life duration of M. lounsburyi, under temperature 19±1oC and relative humidity 65-70%, was found to be 10.2 days. Oviposition of M. lounsburyi occurred at a much higher rate but the fact that several eggs were usually laid per S. oleae individual greatly reduced the proportion of the parasitic larvae which developed to the adult stage.

Preliminary results for the eνaluation of the action of Saissetia oleae parasites in Corfu.

The action of parasites of Saissetia οleae (OIiv.) (Homoptera-Cοccidae) is studied in Corfu from 1980 in the framework of an ongoing project on the population dynamics of Saissetia οleae. Results obtained during the period 1980-1983 from 17 experimental sites indicate the following: a) the population of S. οleae increased in 1981 but from 1982 it declined to very low levels; following the overall decline of the host population, parasitization rates of third instar larvae (mainly by Μetaphycus helνolus Comp.) were relatively low and ranged from 2.1% to 6.7% for the autumn period and from 14.6% to 29.4% for the spring period; this does not minimize the possibility that Μetaphycus helνolus plays an important role on the regulation οf S. οleae populations; b) a considerable proportion of females of S. οleae is attacked during summer by Μetaphycus lounsburyi How. (an internal parasite on preovipositing females), Μoranila californica How. and Scutellista cyanea Μοtsch. (egg predators), but their significance upon the population system of S. οleae is not expected to be great. The action of Μetaphycus lounsburyi in spring, when the peak of the suitable stage occurs (i.e. fourth instar larvae), appears to be very low, at least for these three years. Its action is delayed and most of the specimens of this parasite emerge from ovipositing females in early summer. Among the species attacking S. οleae females, Μ. californica (recently introduced in Corfu) was the most abundant and it might be worthy to be introduced to other parts of Greece too.