Citrus limonoids and their semisynthetic derivatives as antifeedant agents against Spodoptera frugiperda larvae. A structure-activity relationship study

The antifeedant activity of Citrus-derived limonoids limonin (1), nomilin (2), and obacunone (3) and their semisynthetic derivatives 4-26 was evaluated against a commercially important pest, Spodoptera frugiperda. Simple chemical conversions were carried out on the natural limonoids obtained from seeds of Citrus limon. These conversions focused on functional groups considered to be important for the biological activity, namely the C-7 carbonyl and the furan ring. In particular, reduction at C-7 afforded the related alcohols, and from these their acetates, oximes, and methoximes were prepared. Hydrogenation of the furan ring was also performed on limonin and obacunone. The known antifeedant properties of the Citrus limonoids are confirmed. Comparison with previously reported data shows that insect species vary in their behavioral responses to these structural modifications. Highly significant antifeedant activity (P < 0.01) for two natural (1 and 3) and three semisynthetic limonoids (4, 8, and 10) was observed against S. frugiperda.     

Encapsulation rates of the parasitoid <Emphasis Type="BoldItalic">Anagyrus</Emphasis> sp. nr. <Emphasis Type="BoldItalic">pseudococci</Emphasis>, by three mealybug species (Hemiptera: Pseudococcidae)

Laboratory studies assessing the degree of suitability of the mealybugs Planococcus ficus (Signoret), Planococcus citri (Risso) and Pseudococcus calceolariae (Maskell), towards the Sicilian ecotype of the encyrtid parasitoid Anagyrus sp. nr. pseudococci were carried out. All three species of mealybugs were shown to encapsulate the eggs of the encyrtid; however, significant differences were revealed among them in rates of encapsulation and/or superparasitism. The level of aggregate encapsulation and effective encapsulation of the parasitoid eggs by P. citri (74.95 ± 0.87 and 60.19 ± 1.70, respectively) was significantly higher than that recorded for P. ficus (aggregate encapsulation = 58.43 ± 0.83 and effective encapsulation = 31.31 ± 1.55) and significantly lower than the values found in Ps. calceolariae (93.99 ± 0.97 and 88.61 ± 2.03, respectively). As such, rates of parasitism were significantly lower for P. ficus compared with both P. citri and Ps. calceolariae. The two latter species of mealybugs showed similar rates of parasitism by A. sp. nr. pseudococci. Moreover, a significantly higher rate of superparasitism was found for Ps. calceolariae compared with both P. citri and P. ficus, whereas no significant differences were found between the two species of Planococcus for this parameter.     

Evaluating side effects of newer insecticides on the vine mealybug parasitoid <Emphasis Type="Italic">Anagyrus</Emphasis> sp. near <Emphasis Type="Italic">pseudococci</Emphasis>, with implications for integrated pest management in vineyards

Control of the invasive vine mealybug Planococcus ficus (Signoret) can be achieved through integration of different management strategies such as the application of chemical treatments and biological control. However, compatibility between these control methods is considered crucial when adopting integrated pest management (IPM) programs against this insect pest. The recently used insecticides Prev-Am®, a contact biopesticide, and spirotetramat, a systemic tetramic acid insecticide, were assessed in laboratory conditions for their side effects on the vine mealybug parasitoid Anagyrus sp. near pseudococci with reference to chlorpyriphos-methyl, an organophosphate insecticide conventionally used for mealybug control in vineyards. Regarding contact toxicity, chlorpyriphos-methyl caused 100% parasitoid mortality 24 h after treatment, but parasitoid mortality from Prev-Am® or spirotetramat was almost absent. Neither the total parasitoid offspring/female nor the sex ratio of the progeny was negatively affected by Prev-Am® or spirotetramat relative to the untreated control. According to the IOBC classification for laboratory trials, both Prev-Am® and spirotetramat were rated harmless (IOBC category 1), whereas chlorpyriphos-methyl was categorized as harmful (IOBC category 4) to A. sp. near pseudococci. None of the insecticides adversely affected the development of the parasitoid pupal stage inside mealybug mummies or the survival of the emerged parasitoids. The practical implications of the results for implementing mealybug IPM programs in vineyards are emphasized and discussed.     

Polyphenols distribution in juices from Citrus allotetraploid somatic hybrids and their sexual hybrids

The polyphenol profile of an interspecific allotetraploid somatic hybrid, achieved by protoplast fusion, the 'Valencia' sweet orange ( Citrus sinensis L. Osbeck) + 'Femminello' lemon ( Citrus limon L. Burm), and three sexual hybrids obtained by backcrosses between Femminello lemon and the allotetraploid somatic hybrid ('Valencia' + 'Femminello') was studied by liquid chromatography-ultraviolet-diode array detector-mass spectrometry (LC-UV-DAD-MS). The aim of the work was to evaluate whether superior traits and improved performance can be observed in these new genotypes. Ten flavonoids (TF), comprising seven flavanones and three flavones, and four hydroxycinnamic acids (HCA) have been characterized and quantified in all hybrids and compared with those of the respective parents. The 'Valencia' + 'Femminello' somatic hybrid shows an intermediate polyphenol composition with respect to those of the parents, with a slight prevalence of lemon influence. The three sexual hybrids show, instead, different and more complex chromatographic profiles.     

Melanaspis corticosa: a new insect pest of olive trees in Europe

The presence of the South African Obscure Scale, Melanaspis corticosa (Brain) (Hemiptera, Diaspididae), was detected infesting olive trees, in Portugal. The identity of the scale insect was confirmed based on both morphological and molecular studies. Until now, this species was only known in a few African countries, including Guinea, Mozambique, South Africa and Zimbabwe. This is the first record of this species in Europe and in the Palearctic region. The scale was observed in 15 different locations, in the Algarve, since its first detection at the end of 2016. Samples were collected between 21 December 2016 and 10 March 2022, covering all seasonal periods. Most of the sampling sites resulted from private requests from farmers and proprietaries received by the Plant Protection Division of the Regional Directorate of Agriculture. Although it is considered a polyphagous species, it was not observed in other plant species, besides olive trees. The actual dispersion in the region suggests that M. corticosa became established and has been expanded its distribution since its arrival. This scale insect is a potential injurious pest of olive trees and needs to be studied to clarify its pest status and develop effective pest management strategies.