Planthopper Nymphs Research Articles

Wax "Tails" Enable Planthopper Nymphs to Self-Right Midair and Land on Their Feet.

The striking appearance of wax 'tails'-posterior wax projections on planthopper nymphs-has captivated entomologists and naturalists alike. Despite their intriguing presence, the functional roles of these formations remain largely unexplored. This study leverages high-speed imaging to uncover the biomechanical implications of wax structures in the aerial dynamics of planthopper nymphs (Ricania sp.). We quantitatively demonstrate that removing wax tails significantly increases body rotations during jumps. Specifically, nymphs without wax undergo continuous rotations, averaging 4.2 ± 1.8 per jump, in contrast to wax-intact nymphs, who do not complete a full rotation, averaging only 0.7 ± 0.2 per jump. This along with significant reductions in angular and translational velocity from takeoff to landing suggest that aerodynamic drag forces on wax structures effectively counteract rotation. These stark differences in body rotation correlate with landing success: Nymphs with wax intact achieve a near perfect landing rate of 98.5%, while those without wax manage only a 35.5% success rate. Jump trajectory analysis reveals that wax-intact jumps transition from parabolic to asymmetric shapes at higher takeoff velocities and show a significantly greater reduction in velocity from takeoff to landing compared to wax-removed jumps, demonstrating how wax structures help nymphs achieve more stable and controlled descents. Our findings confirm the aerodynamic self-righting functionality of wax tails in stabilizing planthopper nymph landings, advancing our understanding of the complex relationship between wax morphology and aerial maneuverability, with broader implications for wingless insect aerial adaptations and bioinspired robotics.

Rice Brown Planthopper, Nilaparvata lugens (Stål) Feeding Behaviour in Resistant NAGINA22 Rice Mutants

Background: Rice (Oryza sativa L.), is an important staple food and an excellent source of calories in India. Of the different insect pests attacking rice, brown planthopper, BPH, Nilaparvata lugens (Stål) is an important sucking pest causing upto 100% yield losses. Host plant resistance is the most important method in keeping BPH under control and understanding the underlying mechanisms of resistance is necessary to breed the resistant varieties with desirable characters. Methods: Selected EMS mutant lines of Nagina22 (N22) variety, which were previously mass screened under controlled greenhouse conditions were assessed for their antixenosis mechanism to brown planthopper feeding by measuring probing marks and honeydew excretion area by following standard procedures and statistical analysis was done by using Statistix 8.1 software. Result: Both the brown planthopper nymphs and adults probed more in the resistant mutants compared to the susceptible mutants whereas the BPH adults probed more times (24.4) compared to the nymphs (22.2). The recorded honeydew excretion area by the resistant mutants was lower than that of susceptible mutants. In general, the BPH adults fed more and excreted more honeydew (79.5 mm2) compared to the nymphs (59.0 mm2). The damage score has a negative correlation with the probing marks of adults (-0.207) and nymphs (-0.411); and a positive correlation with honeydew excretion of adults (0.547) and nymphs (0.200). In this study, the EMS N22 mutants resistant to BPH, with a greater number of probing marks and less honeydew excretion area can serve as best donors in the breeding programmes to develop brown planthopper resistant varieties.

Application of Riau local entomophatogenic fungi Beauveria bassiana toward brown planthopper pest and production of rice

The decrease in rice production can be caused by pests that can damage the quality and quantity. Pests that always attack rice plants are Brown planthopper. The BPH causes several effects, namely hopperburn, as a virus vector and can cause crop failure. The control of BPHs by farmers to date is by using synthetic pesticides. The use of synthetic pesticides can cause residues, resistance, resurgence, and the destruction of natural enemies. The use of synthetic insecticides can be minimized by using environmentally friendly and sustainable control alternatives, namely by using the local entomopathogenic fungi B. bassiana. This study aims to determine the effect of the application of local Riau B. bassiana on BPH and rice production.The research was conducted at the Laboratory of Plant Pests and Experimental Gardens, Faculty of Agriculture, Riau University from April to July 2020. The research was designed a completely randomized design with five treatments local entomopathogenic fungi concentrations B. bassiana 0 g.l-1 water, 10 g.l-1 water, 20 g.l-1 water, 30 g.l-1 water, 40 g.l-1 water and four replications, in order to obtain 20 experimental units. The results showed that application of Riau local B. bassiana with a concentration of 40 g.l-1 for six days was able to cause the highest mortality of 92.5%. The higher the concentration of Riau local B. bassiana, the lower the attack intensity. The attack of brown planthopper nymphs affects the quality of rice production, but did not affect the quantity of rice production.

Ceraeochrysa lineaticornis (Fitch) (Neuroptera: Chrysopidae): Larval Plant Associations and Construction of Debris Packets from Wax of Planthoppers (Hemiptera: Flatidae)

Larvae of the debris-carrying green lacewing Ceraeochrysa lineaticornis (Fitch) (Neuroptera: Chrysopidae) are known to construct their dorsal packets from foliar trichomes of Arizona sycamore (Platanus wrightii S. Watson; Platanaceae) and to prey on nymphs of the lace bug Corythucha confraterna Gibson (Hemiptera: Tingidae). From 2008 to 2018, we observed larvae in a South Carolina botanical garden incorporate plant trichomes, the waxy flocculence and exuviae of flatid planthoppers, and cuticular fragments of assorted arthropods to construct their packets. This represents the first recorded use of planthopper wax by larvae of a debris-carrying chrysopid. Larvae were observed on 61 plant species (31 families), including 30 species of Eurasian ornamentals. Nymphs of the flatids Metcalfa pruinosa (Say) and Ormenoides venusta (Melichar) were present with larvae of C. lineaticornis on all but two of the Eurasian plants. Chrysopid larvae and coccons were found within aggregations of planthopper nymphs on abaxial leaf surfaces of paperplant (Fatsia japonica [Thunb.] Decne. & Planch.; Araliaceae). Larvae preyed on planthopper nymphs in the laboratory. The composition of the larval packets is described, and notes on seasonality of the chrysopid and flatid planthoppers are provided.

CHARACTERISTICS AND TOXICITY OF NANOEMULSION FORMULATION OF PIPER RETROFRACTUM AND TAGETES ERECTA EXTRACT MIXTURES

Characteristics and Toxicity of Nanoemulsion Formulations of Piper retrofractum and Tagetes erecta Extract Mixtures. Nanotechnology has been used in the developing of botanical insecticide formulation for improving its stability and effectiveness. The research was aimed to make nanoemulsion formulations of Piper retrofractum fruits and Tagetes erecta flowers extracts and to evaluate their toxicity against brown planthopper (Nilaparvata lugens [Stål]) nymphs. The development of nanoemulsion formulaions was carried out by using the low energy method with inversion phase emulsification. The toxicity of the four formulations was tested against brown planthopper nymphs using a contact method. Four nanoemulsion formulations were obtained. The study showed that in the developing of the formulations, the type and level of emulsifier materials affected the physical characteristics of formulas, such as stability, surface tension, viscosity, particle size, and particle morphology. The nanoemulsion formulation containing 1% of the mixture of P. retrofractum fruits and T. erecta flowers extracts, 1.75% Triton X-100 emulsifier showed the highest toxic on the brown planthopper nymph, with the LC95 value was 0.15%. The study indicates that nanoemulsion formulation of P. retrofractum and T. erecta extracts are potential to be developed as botanical insecticide to control brown planthopper of rice.

Persistence of Botanical Insecticide Residue of Pyrethrum and Neem in Rice Plant

<em>Brown planthopper is still a major problem in rice. Control using botanical insecticides is considered less effective, since its persistence in rice plantation is short. Research on the persistence of botanical insecticide residues of pyrethrum and neem in rice has been conducted in green house of Entomology, Indonesian Spices and Medicinal Crops Research Institute, Bogor from January to December 2016. The research was aimed to determine the persistence of botanical insecticide residue on rice by testing it to brown planthopper mortality. The study was arranged in complete randomized design with six treatments and four replications. The treatment consisted of two pyrethrum formulas (EC); two neem formulas (EC); positive controls of synthetic insecticides (a.i. carbosulfan) and negative control (water). The method used was Leaf Residue Method, by spraying the formula into one month-old rice plants, then 10 brown planthopper nymphs of forth instar were introduced into each plant in the first, second, third and fourth day after spraying. The planthopper mortality was observed in the first, third, sixth, 24th and 48th hours after introduction. The residuals of all insecticides tested were still affecting the mortality of brown planthopper until the fourth day after spraying, although the effectiveness</em> <em>decreased by the time. The average mortality on the first day introduction after spraying ranged between 53-73 % and in the fourth day after spraying was 18-25 %.</em>

A simple method for obtaining rice black-streaked dwarf virus-infected small brown planthopper nymphs

Rice black-streaked dwarf virus (RBSDV), an important rice virus, is transmitted by vector small brown planthopper (SBPH) in a persistent manner, but not transovarial transmission. In order to obtain viruliferous SBPH nymphs for relevant research, a simple and reliable method was developed, through allowing SBPH adults laying eggs on RBSDV-infected rice plants. The results showed the hatching nymphs on diseased plants could early acquire virus, and the virus was detected in 2nd-instar nymphs from the spawning method, which was earlier than insect feed on diseased plant. The average viruliferous rate of SBPH from the spawning method was 32.9%, which was not lower than the feeding diseased plant method. The novel method was very easy to operate and time-saving, facilitating the study on the interaction between RBSDV and SBPH nymphs (especially young 2nd-4th instar nymphs), such as, the effect of RBSDV on nymph development, host plant orientation preference of viruliferous nymph, identification of viral interacting protein in nymph, etc.

Responses by the brown planthopper, Nilaparvata lugens, to conspecific density on resistant and susceptible rice varieties

AbstractThis study examines the nature of intraspecific interactions among Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) planthoppers feeding on resistant and susceptible rice varieties. Planthopper nymphs produced less honeydew and gained less weight when feeding on rice variety IR62 (resistant) compared to susceptible rice varieties. A series of bioassays was conducted that varied N. lugens nymph densities on IR62 and IR22 (susceptible). Increasing nymph density facilitated feeding by conspecifics; however, intraspecific competition increased mortality of nymphs on IR62 (but rarely on IR22). Furthermore, nymph weights declined with increasing conspecific density on IR22, and the effects were weak on IR62. More female nymphs than males survived on IR62 but this was not affected by density. Nitrogenous fertilizer increased competition among N. lugens on young plants of IR22, but not on IR62. Results indicate that nymphs have a low efficiency in accessing resources when feeding on IR62, even where the plants have received fertilizer. Female‐biased survival and biomass compensation for mortality may promote population recovery after development on the resistant plant and accelerate adaptation to the resistant variety.

Low Temperature Storage of Southern Rice Black-Streaked Dwarf Virus-Infected Rice Plants Cannot Sustain Virus Transmission by the Vector.

Southern rice black-streaked dwarf virus (SRBSDV) is a novel virus transmitted by white-backed planthopper Sogatella furcifera (Hováth) (Hemiptera: Delphacidae). Due to low virus transmission efficiency by the planthopper, researchers are frequently confronted with shortage of viruliferous vectors or infected rice plants, especially in winter and the following spring. To find new ways to maintain virus-infected materials, viral rice plants were stored at -80°C for 45 or 140 d and evaluated as virus sources in virus transmission by the vector. SRBSDV virions were not degraded during storage at -80°C as indicated by reverse transcription-polymerase chain reaction and reverse transcription real-time PCR detection. The planthopper nymphs fed on the infected thawed plants for 48 h survived at about 40% and showed positive detection of SRBSDV, but they lost the virus after feeding for another 20 d (the circulative transmission period) on noninfected plants. Transmission electron microscope images indicated broken capsid of virions in infected thawed leaves in contrast to integrity capsid of virions in infected fresh leaves. These results show that low temperature storage of SRBSDV-infected rice plants cannot sustain virus transmission by white-backed planthopper.

Interactive Effects of Southern Rice Black-Streaked Dwarf Virus Infection of Host Plant and Vector on Performance of the Vector, Sogatella furcifera (Homoptera: Delphacidae).

Performance of insect vectors can be influenced by the viruses they transmit, either directly by infection of the vectors or indirectly via infection of the host plants. Southern rice black-streaked dwarf virus (SRBSDV) is a propagative virus transmitted by the white-backed planthopper, Sogatella furcifera (Hovath). To elucidate the influence of SRBSDV on the performance of white-backed planthopper, life parameters of viruliferous and nonviruliferous white-backed planthopper fed rice seedlings infected or noninfected with SRBSDV were measured using a factorial design. Regardless of the infection status of the rice plant host, viruliferous white-backed planthopper nymphs took longer to develop from nymph to adult than did nonviruliferous nymphs. Viruliferous white-backed planthopper females deposited fewer eggs than nonviruliferous females and both viruliferous and nonviruliferous white-backed planthopper females laid fewer eggs on infected than on noninfected plants. Longevity of white-backed planthopper females was also affected by the infection status of the rice plant and white-backed planthopper. Nonviruliferous white-backed planthopper females that fed on infected rice plants lived longer than the other three treatment groups. These results indicate that the performance of white-backed planthopper is affected by SRBSDV either directly (by infection of white-backed planthopper) or indirectly (by infection of rice plant). The extended development of viruliferous nymphs and the prolonged life span of nonviruliferous adults on infected plants may increase their likelihood of transmitting virus, which would increase virus spread.

A novel association between Aphaenogaster subterranea (Hymenoptera: Formicidae) and the nymphs of Reptalus panzeri (Hemiptera: Cixiidae)

The nymphs of the cixiid planthopper, Reptalus panzeri (Low, 1883), were found cohabiting with the myrmicine ant Aphaenogaster subterranea (Latreille, 1798) in a sub-Mediterranean oak forest in mid-western Hungary. Except for a few cases, nymphs were recorded only in the nests of A. subterranea, or were recorded with foragers of this ant from neighbouring colonies. Adult planthoppers were also found in nests of A. subterranea in the emergence period. Neither field nor laboratory studies revealed direct or unambiguous interactions between this ant and the planthopper nymphs that would indicate a trophobiotic relationship, however the fact that nymphs do not try to escape from the ants, which do not attack the nymphs, indicates some kind of mutualistic relationship between them. The main food plant of R. panzeri nymphs in this habitat is likely to be the roots of manna ash (Fraxinus ornus).

Toxic Effects of Nitenpyram on the Brown Planthopper, Nilaparvata lugens (Stål) (Homoptera: Delphacidae)

Laboratory assays explored the potential of nitenpyram, a novel neonicotinoid insecticide developed by Takeda Chemical Industry Co., Ltd. against the brown planthopper, Nilaparvata lugens (Stål) (Homoptera: Delphacidae). All nymphal instars were sensitive to nitenpyram with the first and second instars being the most susceptible (median lethal concentrations [LC50] of 0.14 mg/L at 72 h after treatment). Fifth-instar nymphs were the least susceptible. Mortality of first - second instars treated with 2 mg/L peaked at 48 h after treatment. The five concentrations of nitenpyram tested (2, 1, 0.5, 0.25, 0.125 mg/L) decreased the weight of brown planthopper nymphs following treatment with the insecticide. These laboratory results indicate that nitenpyram may prove to be an effective alternative for the control of brown planthopper in rice culture.

Vector Transmission of a Plant-Pathogenic Bacterium in the Arsenophonus Clade Sharing Ecological Traits with Facultative Insect Endosymbionts

The planthopper Pentastiridius leporinus (Hemiptera: Cixiidae) is the major vector of a nonculturable plant-pathogenic gamma-3 proteobacterium associated with a disease of sugar beet called syndrome "basses richesses" (SBR). The bacterium, here called SBR bacterium, belongs to the Arsenophonous clade, which includes mostly insect-associated facultative symbionts. Assays using field-collected planthopper nymphs and adults were carried out to investigate the interaction of SBR bacterium with the insect vector and its transmission to sugar beet. Field-collected planthoppers showed a percentage of infection that averaged from 57% for early instar nymphs to near 100% for late instar nymphs and emerging adults. SBR bacterium was persistently transmitted by emerging adults. Root-feeding nymphs were able to inoculate SBR bacterium to sugar beet. The bacterium was transmitted vertically from infected parental females to their respective offspring with an average frequency of 30%. Real-time polymerase chain reaction assays on dissected planthopper internal organs revealed a high concentration of the bacterium within male and female reproductive organs and within female salivary glands. SBR-like bacteria were observed through transmission electron microscopy in the cytoplasm of different insect organs including ovaries, salivary glands, and guts with no evidence for cytological disorders. SBR bacterium seems to share common ecological traits of insect-transmitted plant pathogens and facultative insect endosymbionts suggesting it may have evolved primarily as an insect-associated bacterium.

Expression of BrD1, a plant defensin from Brassica rapa, confers resistance against brown planthopper (Nilaparvata lugens) in transgenic rices.

Plant defensins are small (5-10 kDa) basic peptides thought to be an important component of the defense pathway against fungal and/or bacterial pathogens. To understand the role of plant defensins in protecting plants against the brown planthopper, a type of insect herbivore, we isolated the Brassica rapa Defensin 1 (BrD1) gene and introduced it into rice (Oryza sativa L.) to produce stable transgenic plants. The BrD1 protein is homologous to other plant defensins and contains both an N-terminal endoplasmic reticulum signal sequence and a defensin domain, which are highly conserved in all plant defensins. Based on a phylogenetic analysis of the defensin domain of various plant defensins, we established that BrD1 belongs to a distinct subgroup of plant defensins. Relative to the wild type, transgenic rices expressing BrD1 exhibit strong resistance to brown planthopper nymphs and female adults. These results suggest that BrD1 exhibits insecticidal activity, and might be useful for developing cereal crop plants resistant to sap-sucking insects, such as the brown planthopper.

Vitex agnus-castus is a Preferred Host Plant for Hyalesthes obsoletus

Hyalesthes obsoletus Signoret (Homoptera: Cixiidae) is a polyphagous planthopper that transmits stolbur phytoplasma (a causative agent of "yellows" disease) to various weeds, members of the Solanaceae, and wine grapes (Vitis vinifera L.) in Europe and the Middle East. Planthoppers were collected by hand vacuuming eight native plant species. Vitex agnus-castus L., a shrub in the Verbenaceae, hosted the largest number of H. obsoletus, although Olea europaea L. also served as a host for adults. Using a Y-olfactometer, we compared the planthoppers relative preference for V. agnus-castus, Convolvulus arvensis, and V. vinifera. V. agnus-castus was more attractive to both male and female H. obsoletus than the other plants. H. obsoletus antennal response was stronger to volatiles collected from V. agnuscastus than from Cabernet Sauvignon variety of V. vinifera. To determine if V. agnus-castus would serve as a reservoir for the pathogen, H. obsoletus were collected from leaf and stem samples of native V. agnus-castus, and were tested by polymerase chain reaction (PCR) for the presence of phytoplasma DNA. While 14% and 25% (2003 and 2004, respectively) of the insects tested positive for phytoplasma DNA, none of the plant samples tested positive. To determine if V. agnus-castus could serve as a host plant for the development of the planthopper, we placed emergence cages beneath field shrubs and enclosed wild-caught H. obsoletus in a cage with a potted young shrub. We found adult H. obsoletus in the emergence cases and planthopper nymphs in the soil of the potted plant. We concluded that V. agnus-castus is attractive to H. obsoletus, which seems to be refractory to phytoplasma infections and warrants further testing as a trap plant near vineyards.

In situ localization of proteinase inhibitor mRNA in rice plant challenged by brown planthopper

Proteinase inhibitor (PI) mRNA was localized byin situ hybridization in tissue sections of root, stem and leaf of the resistant rice (B5) plant fed by brown planthopper nymphs. In the rice material without BPH feeding, PI gene was expressed in the root, stem and leaf, while the abundance of PI mRNA was low. In the rice material fed by BPH, PI gene was expressed substantially in the parenchyma of rice stem and leaf, but weakly in the root. The results indicated that the PI gene was up-regulated in the rice plant challenged by brown planthopper. For the first time, we reported the expression changes of proteinase inhibitor gene in plant which was infested by a piercing/sucking insect.

Effects of Selected Chemical Pesticides on Agamermis unka (Nematoda: Mermithidae), a Parasite of the Brown Plant Hopper, Nilaparvata lugens

Selected commercial and technical grade pesticides were tested against the egg, preparasite and adult stages of Agamermis unka , a nematode parasite of the brown planthopper, Nilaparvata lugens . The commercial insecticide, diazinon (LC = 0.37 ppm), was most toxic to the 50 preparasites, followed by phenthoate (LC = 0.43 ppm), BPMC (LC = 0.44 ppm), IBP 50 50 (LC = 0.46 ppm), cartap hydrochloride (LC = 0.82 ppm) and buprofezin + isoprocarb 50 50 (LC = 1.11 ppm). The least toxic commercial pesticide tested was the fungicide, pencycuron 50 (LC = 2.19 ppm). Out of 12 technical grade insecticides tested, phenthoate, monocrotophos, 50 diazinon and carbofuran (LC = 0.37-0.46 ppm) were highly toxic to the preparasites, followed by 50 buprofezin, BPMC and fenitrothion (LC = 0.74-0.86 ppm). Fenthion, etofenprox, chlorpyrifos, 50 imidacloprid and MIPC (LC = 1.11-2.19 ppm) were the technical grade insecticides least toxic 50 to the preparasites. Most preparasites survived for up to 24 h at the low insecticide concentrations (0.63 and 0.31 ppm). Preparasites that were exposed to BPMC for 24 h at concentrations as high as 5.0 ppm and survived the treatments infected brown planthopper nymphs. Four selected insecticides-chlorpyrifos, BPMC, imidacloprid and carbofuran-had significant adverse effects on A. unka egg hatching. Eggs that were in the insecticide solution for 168 h fared poorly with imidacloprid having the best survival ( > 2% of the eggs hatching at 0.04 ppm). No eggs hatched from the other insecticide treatments. Three selected insecticides, BPMC, imidacloprid and chlorpyrifos, tested against adult A. unka showed that most adults survived the exposure to the insecticides between 0.31 and 2.5 ppm. At 5.0 ppm of BPMC or chlorpyrifos none of the adults survived, whereas with imidacloprid 70% of the adults survived. Egg deposition by the surviving adults was greatly reduced in those treated with the insecticides compared with those in the controls. Imidacloprid had some negative impact on the preparasites' ability to infect BPH nymphs, but it had the least detrimental effect of the insecticides tested on preparasite survival and on the eggs and adults of A. unka .

Genetics of Field Resistance of Rice to Brown Planthopper1

The brown planthopper [Nilaparvata lugens (Stal)] is one of the most serious insect pests of rice (Oryza sativa L.) in South and Southeast Asia. Because cultivars with vertical resistance to brown planthopper have “broken down” due to brown planthopper biotype selection, field resistant cultivars with horizontal resistance are being evaluated. The inheritance of field resistance to brown planthopper in two traditional rice cultivars, ‘Utri Rajapan’ and ‘Triveni’, was investigated. Twenty‐day old seedlings were infested with second and third‐instar brown planthopper nymphs. Reactions of F1, F2, and F3 populations from the crosses of resistant cultivars with the susceptible parent ‘TN1’ revealed that two independently segregating recessive genes govern resistance in both cultivars. Allelism tests revealed that the two cultivars have the same genes for resistance.

A New Dominant Gene for Resistance to Whitebacked Planthopper in Rice1

The mode of inheritance and allelic relationships of genes for resistance to whitebacked planthopper, Sogatella furcifera (Hbrvath), in 15 resistant cultivars of rice, Oryza sativa L., were studied. One‐leaf stage seedlings were artificially infested with second‐ and third‐instar whitebacked planthopper nymphs. Reactions of the seedlings were recorded when the susceptible check, ‘Taichung Native 1’, (TN1) was completely killed. The reactions of F1, F2, and F3 progenies from the crosses of test cultivars with TN1 revealed that single dominant genes confer resistance in ‘Boegi Boera’, ‘DD4’, PI 184675‐6, ‘Siam Garden’, ‘Rening’, ‘N'Diang Marie’, ‘Manggar’, ‘Oha’, ‘Gokhue Saier’, ‘Tjempo Tolo’, and ‘Nemai‘. Two independent dominant genes govern resistance in ‘ARC5752’, ‘Chaia Anaser’, ‘Katuyhar Dhan’, and ‘Dhera Dun Basmati’. Tests for allelism revealed that the single dominant genes in Boegi Boera, DD4, PI 184675‐6, Siam Garden, Rening, Oha, Gokhue Saier, Tjempo Tolo, and Nemai, and one of the two independent dominant genes in ARC5752, Chaia Anaser, Katuyhar Dhan, and Dhera Dun Basmati are allelic to Wbph 1, and that the second gene in ARC5752 is allelic to Wbph 2. The second gene in Chaia Anaser, Katuyhar Dhan, and Dhera Dun Basmati was allelic to Wbph 3. The single dominant genes of N'Diang Marie and Manggar segregated independently of Wbph 1, Wbph 2, and Wbph 3. The dominant gene of N'Diang Marie was designated an Wbph 5. The allelic relationships of the dominant gene from Manggar to Wbph 5 are not known.

Efficiency of Sticky Boards for Population Estimation of the Brown Planthopper, Nilaparvata lugens (STAL)(Hemiptera : Delphasidae) on Rice Hills

A simple sampling method using a sticky board of 18×25 cm for estimationg the population of brown planthopper nymphs on rice hills was developed and the efficiency of this method was studied.When a rice hill was struck by hand three times successively, about 90% of the total catch was caught by the initial two beatings. Approximately 40% of the total nymphs which fell around the rice hill were caught by a sticky board in the standard position. A significant correlation was obtained between the catch on the sticky board and the total number of fallen nymphs. Highly significant correlation coefficients were also obtained between the partial counts in the medial 1/2∼1/4 area of a sticky board and the whole board counts, suggesting that the partial count can be substituted for the whole board count.