Geographical Distribution and Long-Term Monitoring of Physokermes hellenicus (Hemiptera: Coccomorpha: Coccidae) on Abies spp. (Pinales: Pinaceae) in Greece

The scale Physokermes hellenicus (Kozár & Gounari) (Hemiptera: Coccidae) has been recently included in the Greek entomofauna as a beneficial honeydew species. However, there are no adequate data about its geographical distribution and degree of infestation. Therefore, a study was conducted to examine these parameters in fifteen mountains of Greece. Furthermore, the monitoring of P. hellenicus infestation was carried out over a six-year period with regard to natural enemies and honeydew presence at three mountains (i.e., Menalon, Parnis and Tymfristos) that are traditional honeybee foraging areas. An extensive geographical distribution of the scale was negatively correlated with the latitude. Over the period of the study, P. hellenicus infestation exhibited a decreasing trend in the three mountains, which was more obvious at Menalon. The abundance of natural enemies of P. hellenicus, their effectiveness on honeydew excretion and the fecundity of P. hellenicus are discussed. The reduction in the honey produced at the Menalon mountain (a protected designation of origin product) could be attributed to the reduced presence of P. hellenicus in the fir forest. Among the other identified arthropods, Dreyfusia nordmannianae Eckstein (Hemiptera: Adelgidae) is reported for the first time infesting Abies cephalonica (Pinales: Pinaceae) in Greece. Furthermore, this species is reported for the first time as a co-parasite with P. hellenicus on A. cephalonica in Greece. Since D. nordmannianae is a serious pest, additional research is needed to determine its status in Greek fir forest ecosystems.

THE ALIEN PSYLLID MACROHOMOTOMA GLADIATA KUWAYAMA, 1908 (HEMIPTERA PSYLLOIDEA HOMOTOMIDAE): SPREAD AND DAMAGE OF A RECENTLY RECORDED PEST OF FICUS MICROCARPA TREES IN TUNISIA

During an inventory study of Psylloidea species carried out in Tunisia, the alien psyllid, Macrohomotoma gladiata Kuwayama, 1908 (Hemiptera Psylloidea Homotomidae), recently recorded in the country, has been detected on ornamental Ficus microcarpa, in public and private parks and gardens in many locations of the urban areas of the governorates of Tunis and Ariana, showing a fast spread in the area. This psyllid species has been observed causing damages and vegetative disorders to Ficus trees, especially white wax secretion, leaf wrapping and honeydew excretion on leaves and twigs. The number of infested trees increased from our first observations in late 2020 to early 2021. An Anthocoris sp. (Hemiptera Anthocoridae) has been observed to naturally prey on M. gladiata in many investigated locations.

Virulence and SSR Diversity of Brown Planthopper (Nilaparvata lugens) Adapted on Differential Rice Host Varieties

Brown planthopper biotype 1, 2, 3 and a representative field population are required for resistance screening of promising rice lines in Indonesia, but the current biotype stocks has shown deviation in virulence patterns. The objectives of this study were to develop a set of brown planthopper populations with differential virulence and to investigate their genetic variability using SSR marker. Females originated from two field populations were selected on variety Mudgo (carries Bph1 gene) or ASD7 (bph2 gene) using honeydew excretion as the virulence parameter. Selection cycles resulted in population T, M, A, and R, which was raised and adapted on variety TN1 (carries no Bph gene), Mudgo, ASD7, and Rathu Heenathi (Bph3, Bph17), respectively. Population R was the most virulent as expected and can be used to represent a field population, but the remaining populations still showed high virulence level. AMOVA and PCoA results based on analysis with 38 SSR primer pairs revealed partial genetic separation among populations, with population R was the most genetically distant from the remaining populations. The desired virulence character of the remaining populations is expected could be achieved after further selection and prolonged adaptation on their respective hosts.

Resistance of DB1 Transgenic Rice Line and others against Nilaparvata lugens, Brown Planthopper

Nilaparvata lugens (Stål), brown planthopper (BPH) is as a major pest of rice crop. Developing rice resistant to BPH is an economically and environmentally friendly approach. A transgenic rice line with DB1 (Dioscorea batatas tuber lectin 1) transgene has been engineered to overcome the problem. The objective of the experiment was to obtain the level of resistance of a DB1 rice line (DB1-inserted cv. Taichung 65) and some rice genotypes against two colonies of BPH. Resistance study was performed in BPH’s preference, honeydew excretion, crop damage, and population development. The resistant test was carried out using two biotypes BPH i.e., biotype 2 (Sukamandi) and biotype 3 (North Sumatera). The result showed that DB1 transgenic rice was moderately resistant to biotype 2, while to be susceptible when invested to biotype 3, indicating that the DB1 gene increases the resistance level, from susceptible to moderately resistant. All tested genotypes were chosen by biotype 2 for laying eggs, while for biotype 3 preferred five genotypes (DB1 transgenic line, PTB-33, Babawee, IR-64 dan IR-42). Genotype significantly differed on number of BPH and was considerably lower on PTB-33 than the others. Honeydew excretion of genotypes showed equal on biotype 2 and 3, except on biotype 3 of IR 42 (susceptible to BPH) which showing high amount of feces. PTB 33 had lower BPH population as compared to others, indicating high resistance to BPH of biotype 2 and 3 from Indonesia. © 2021 Friends Science Publishers

First report on honeydew excretion by the melon thrips, Thrips palmi karny (Thysanoptera : Thripidae) and its biochemical analysis

Sap sucking insects like thrips, aphids, mealybugs, whiteflies exploit the sugar rich phloem for growth and development. The excess sugar in the phloem sap creates osmotic imbalance leading to loss of water from haemolymph to gut lumen. In order to maintain osmolarity, sap sucking insects have developed structural adaptation (filter chamber) and also excrete excess sugar as honeydew through various orifices. The excreted honeydew is known to play very vital ecological role such as natural enemy calling (attracting parasitoids). In this regard scanty information is available on this important aspect for different sap sucking insects. In this study we are reporting for the first time on the composition of honeydew from the major horticultural thrips, Thrips palmi reared on French bean (Phaseolus vulgaris). LC-MS-MS analysis revealed the presence of 15 different sugars majorly inositol, fructose, maltose, glucose and sorbitol @ (130.9 ±0.47μg); (95.1±0.45μg); (60.7 ±0.28μg); (54.2 ±0.40μg) and (28.1 ±0.35μg), respectively.

Antibiosis Effects of Rice Carrying Bph14 and Bph15 on the Brown Planthopper, Nilaparvata lugens

The brown planthopper(BPH), Nilaparvata lugens, is the most destructive insect pest in rice production worldwide. The development and cultivation of BPH-resistant varieties is the most economical and efficient strategy to overcome the destruction caused by BPH. The modified bulk seedling test method was used to identify the BPH resistance level and host feeding choice of rice lines of Liangyou8676(Bph14/Bph15), Bph68S(Bph14/Bph15), RHT(Bph3), Fuhui676, and TN1 on BPH. In the meantime, the population, survival and emergence rate, developmental duration, honeydew excretion, female ratio and brachypterous ratio of adults were used as indicators to detect the antibiosis effects of the different rice lines. The results showed that the resistance levels of RHT, Bph68S, Liangyou8676, Fuhui676, and TN1 to BPH were HR, R, MR, S and HS, respectively. The host choice implied that BPH was more inclined to feeding on rice plants with a lower resistance. An analysis of the antibiosis activity of rice lines RHT, BPh68S, and Liangyou8676 carrying resistance genes indicated a significant reduction in the population growth rate, survival and emergence rate of BPH nymphs, significant delay in the developmental duration of nymphs, reduced honeydew excretion of females, decreased female ratio, and a decreased brachypterous ratio of females and males, when compared with rice carrying no BPH-resistant genes.

Antibiosis effects of rice carrying Bph14 and Bph15 on the brown planthopper, Nilaparvata lugens

The brown planthopper (BPH), Nilaparvata lugens, is the most destructive insect pest in rice production worldwide. The development and cultivation of BPH-resistant varieties is the most economical and efficient strategy to overcome the destruction caused by BPH. In this study, the modified bulk seedling test method was used to identify the BPH resistance level and host feeding choice of rice lines of Liangyou8676 (Bph14/Bph15), Bph68S (Bph14/Bph15), RHT (Bph3), Fuhui676, and TN1 on BPH. Meanwhile, the population, survival and emergence rate, developmental duration, honeydew excretion, female ratio and brachyptery ratio of adults were used as indicators to detect the antibiosis effects of the different rice lines. The results showed that the resistance levels of Rathu Heenati (RHT), Bph68S, Liangyou8676, Fuhui676, and TN1 to BPH were HR, R, MR, S and HS, respectively. The host choice implied that BPH was more inclined to feeding on rice plants with a lower resistance. An analysis of the antibiosis activity of rice lines RHT, BPh68S, and Liangyou8676 carrying resistance genes indicated a significant reduction in the population growth rate, survival and emergence rate of BPH nymphs, significant delay in the developmental duration of nymphs, reduced honeydew excretion of females, decreased female ratio, and a decreased brachyptery ratio of females and males, when compared with rice carrying no BPH-resistant genes.

Antibiosis effects of rice carrying Bph14 and Bph15 on the brown planthopper, Nilaparvata lugens

The brown planthopper (BPH), Nilaparvata lugens, is the most destructive insect pest in rice production worldwide. The development and cultivation of BPH-resistant varieties is the most economical and efficient strategy to overcome the destruction caused by BPH. In this study, the modified bulk seedling test method was used to identify the BPH resistance level and host feeding choice of rice lines of Liangyou8676 (Bph14/Bph15), Bph68S (Bph14/Bph15), RHT (Bph3), Fuhui676, and TN1 on BPH. Meanwhile, the population, survival and emergence rate, developmental duration, honeydew excretion, female ratio and brachyptery ratio of adults were used as indicators to detect the antibiosis effects of the different rice lines. The results showed that the resistance levels of Rathu Heenati (RHT), Bph68S, Liangyou8676, Fuhui676, and TN1 to BPH were HR, R, MR, S and HS, respectively. The host choice implied that BPH was more inclined to feeding on rice plants with a lower resistance. An analysis of the antibiosis activity of rice lines RHT, BPh68S, and Liangyou8676 carrying resistance genes indicated a significant reduction in the population growth rate, survival and emergence rate of BPH nymphs, significant delay in the developmental duration of nymphs, reduced honeydew excretion of females, decreased female ratio, and a decreased brachyptery ratio of females and males, when compared with rice carrying no BPH-resistant genes.

Quantification of antibiosis levels in nine different rice genotypes against Nilaparvata lugens (Homoptera: Delphacidae)

Studies on different parameters of antibiosis to simultaneously compare diverse genotypes with different resistance levels are lacking. Such studies are necessary to identify the genetic variability among resistant genotypes, which, ultimately, can lead to the identification of resistance genes with diverse mechanisms. The current study was undertaken to quantify antibiosis levels in nine rice genotypes against the brown planthopper (BPH), Nilaparvata lugens (Stål), under glasshouse conditions using nine parameters. Among these genotypes, RP2068-18-3-5 and Ptb33 displayed significantly better performance as compared to other genotypes in most of the parameters studied and did not differ from each other. Rathu Heenati was the best in unfertilised eggs laid and similar to the above two genotypes regarding percent of nymphal survival. All the test genotypes performed significantly better than the susceptible check TN1, though INRC3021 did not differentiate from the former in some tests. The overall damage score was positively and significantly correlated with the amount of honeydew excretion, percent nymphal survival and emergence, the proportion of brachypterous females, female population, and growth index, and were negatively and significantly correlated with percent unfertilised eggs laid and nymphal development period. Regression analysis revealed a significant linear relationship between damage score and nymphal emergence, nymphal survival percentage, and proportion of brachypterous females. RP2068-18-3-5 is the new source of BPH resistance identified through this study, which breeders can further use in resistance breeding.