Number Of Nymphs Research Articles

Feeding Preference of Lace Bug Stephanitis pyri (F) on Apple Tree

The results showed that the Sharabi cultivar was the most favored of the tested cultivars for infection with the reticulated bug, followed by the Al-Kagdi cultivar, and the least was the Israeli Cultivar, as the average number of adults during its peak in July was 4.46, 1.6, 4.03 insect/leaf for the Sharabi, Israeli and Al-Kagdi cultivars, respectively. While the other stages peaked in the month of August, as the average of number of nymphs reached 8.43, 3.43, and 7.76 insects/leaf for the three cultivars, respectively. As for the insect’s preference for the three plant level and four tree geographical directions, it was noted that the lower level is preferred by the insect, as the average number of infected leaves at the lower level was 5.67, 6.50, 11.83 leaf / tree. Followed by the middle level of 3.92, 5.25, 10.17 adult / leaf and the upper level of 0.00, 0.08, 0.42 adult / leaf for the months of May, June and July, respectively. The results also showed that there were differences in the insect’s preference for one of the four geographical directions, as it recorded a clear preference and significant difference for the eastern and southern directions compared with the northern and western directions. The average number of infected leaves during the month of May was 0.33, 6.00, 6.33, 0.11 leaves, and in June 0.56, 7.44, 7.22, 0.56 leaves, and in July 1.11, 13.00, 13.67, 2.11 leaves for the north, south, east and west directions, respectively.

An Assessment of In-stream Sampling Activity of Macroinvertebrates and Stream Channelization in Dug Run, Allen County, Ohio, USA

Macroinvertebrates are good indicators of stream quality. Changes in populations of sensitive macroinvertebrates help to show stressors to the stream. Student sampling of a section of Dug Run in northwestern Ohio has occurred since 2015. This work has been to identify how changes on the campus including construction, tree removal, and channelization may be impacting stream macroinvertebrates. Student sampling, however, also causes disturbances that may negatively impact macroinvertebrate populations. A break in student sampling—due first to the use of an adjacent off-site location in 2019 and then to COVID-19 beginning in 2020—was expected to impact the number of mayfly nymphs and caddisfly larvae captured, both considered sensitive macroinvertebrates in the stream. To measure the impact of channelization in Dug Run, the study area was split into a channelized reach, an upstream reach, and a downstream reach. Stream habitat was also studied in each reach with macroinvertebrates collected from riffles, undercuts, and pools. After a break in sampling, caddisfly larvae increased initially but have declined in the 2 following years, while mayfly nymphs increased in the last 2 years of the study. No significant differences were found in stream quality monitoring (SQM) index scores between the channelized reach compared to upstream and downstream reaches (H = 4.15; p = 0.126). There was a significant difference in taxa richness among pools, riffles, and undercuts (H = 14.09; p < 0.001). A significant difference was also found in the moderately sensitive macroinvertebrates captured in riffles between the channelized, upstream, and downstream reaches (H = 6.82; p = 0.033). A break in sampling resulted in an initial increase in mayfly nymph and caddisfly larvae samples, but it appears a variety of factors may be responsible for the numbers captured. The channelized reach had higher numbers of scuds and crayfish in riffles among the 3 reaches, which may be the result of a change in their distribution related to lack of undercuts. Both scuds and crayfishwere found in significantly greater abundance in undercuts compared to pools and riffles.

Effect of application equipment to biopesticides for whitefly control (Trialeurodes vaporariorum) in greenhouses

The Greenhouse Whitefly (Hemiptera: Aleyrodidae) is one of the main pests in tomato (Solanum lycopersicum). Pest control with entomopathogenic fungi is an option to reduce the use of agrochemicals. The objective of this work was to evaluate the effect of the application equipment in the control of Trialeurodes vaporariorumthrough the application of the entomopathogenic Isaria javanica. Two trials were carried out (autumn and spring). I. javanica was applied with three pieces of equipment: a hydraulic sprayer with a gun, a pneumatic back-mounted sprayer, and a fixed fogger system. The number of adults and nymphs in different parts of the plant were counted. In both trials the greatest control of adults was observed with the pneumatic sprayer and the control achieved by misting and hydraulic spraying was similar. The control of nymphs was greater with a pneumatic sprayer, but there was also good control with fogger, especially in spring. Consideringthat the number of individuals was below the application threshold, the control was adequate with the three teams. Based on this, if a quick application is sought andthe operator does not enter the greenhouse, the fogger system is a recommended option.

Resistance to whitefly mediated by the Mi gene, acylsugars, and zingiberene in tomato

This study aimed to quantify and compare the effects of Mi gene, high leaf levels of acylsugars (AA), and zingiberene (ZGB) individually and in combination, regarding resistance of tomato lines to Bemisia argentifolii. The experiment included 21 genotypes selected simultaneously for high AA and ZGB content, cloned through rooting of axillary shoots with homogeneous sizes, and seven control lines produced from seeds, including 2 genotypes rich in AA (TOM-687 and TOM-688), two genotypes rich in ZGB (TOM-703 and TOM-704), and three lines with low levels of allelochemicals (cv. Santa Clara, TOM-584, and TOM-684), where the TOM-684 line carried the Mi gene. The experiment was conducted in a greenhouse using a randomized complete block design, comprising 28 treatments with 4 replications and 1 plant per plot. The AA and ZGB-rich lines showed higher resistance compared to the other control lines with low levels of allelochemicals, but the TOM-684 control line carrying the Mi gene was more resistant than the non-carriers ('Santa Clara' and TOM-584). The level of resistance conferred by ZGB was similar to that presented by AA. Both ZGB and AA provided higher levels of resistance compared to the Mi gene. The clones selected for both ZGB and AA simultaneously exhibited lower numbers of eggs and nymphs compared to the susceptible controls and were more resistant than the TOM-684 treatment. Overall, the clones even outperformed the lines rich in only one of the allelochemicals, demonstrating a synergistic effect between AA and ZGB for resistance when combined in the same tomato line.

Effects of dominant ant species on ant community structure and ant–hemipteran interactions

Ants often interact aggressively for resources (e.g. nest sites and food) with members of their own or another species. In these competitive interactions, dominant ant species exert a strong influence on ant species coexistence and plant‐associated arthropod community structure. However, few studies have experimentally manipulated the relative abundance of dominant ant species on plants, preventing a mechanistic understanding of the effects of ant competitive interactions on ant community structure as well as on their interactions with other insects, particularly mutualistic hemipterans. In this study, we performed a field experiment in a tropical dry forest in Brazil to investigate the effects of two dominant ant species (Camponotus crassus and Cephalotes pusillus) on the structure ant communities and the abundance of the ant‐tended hemipteran Enchenopa brasiliensis in Solanum lycocarpum plants. For this, we identified and quantified all ant species foraging on plants and estimated the number of egg masses, nymphs and adults of the mutualistic hemipteran before and after experimentally removing nests of both two dominant ant species. Our results showed that removal of C. pusillus nests significantly changed ant community structure, whereas removal of C. crassus nests did not. We also found that nest removal of both dominant ant species had significant effects on hemipteran abundance. In particular, plants generally hosted more hemipteran eggs, nymphs and adults after (vs before) nest removal of both dominant ant species. Overall, this study demonstrates that dominant ant species can play a pivotal role in structuring ant communities and the interactions between ants and honeydew‐producing hemipteran insects.

Patterns of asexual reproduction of the soybean aphid, Aphis glycines (Matsumura), with and without the secondary symbionts Wolbachia and Arsenophonus, on susceptible and resistant soybean genotypes.

Plant breeding is used to develop crops with host resistance to aphids, however, virulent biotypes often develop that overcome host resistance genes. We tested whether the symbionts, Arsenophonus (A) and Wolbachia (W), affect virulence and fecundity in soybean aphid biotypes Bt1 and Bt3 cultured on whole plants and detached leaves of three resistant, Rag1, Rag2 and Rag1 + 2, and one susceptible, W82, soybean genotypes. Whole plants and individual aphid experiments of A. glycines with and without Arsenophonus and Wolbachia did not show differences in overall fecundity. Differences were observed in peak fecundity, first day of deposition, and day of maximum nymph deposition of individual aphids on detached leaves. Bt3 had higher fecundity than Bt1 on detached leaves of all plant genotypes regardless of bacterial profile. Symbionts did not affect peak fecundity of Bt1 but increased it in Bt3 (A+W+) and all Bt3 strains began to deposit nymphs earlier than the Bt1 (A+W-). Arsenophonus in Bt1 delayed the first day of nymph deposition in comparison to aposymbiotic Bt1 except when reared on Rag1 + 2. For the Bt1 and Bt3 strains, symbionts did not result in a significant difference in the day they deposited the maximum number of nymphs nor was there a difference in survival or variability in number of nymphs deposited. Variability of number of aphids deposited was higher in aphids feeding on resistant plant genotypes. The impact of Arsenophonus on soybean aphid patterns of fecundity was dependent on the aphid biotype and plant genotype. Wolbachia alone had no detectable impact but may have contributed to the increased fecundity of Bt3 (A+W+). An individual based model, using data from the detached leaves experiment and with intraspecific competition removed, found patterns similar to those observed in the greenhouse and growth chamber experiments including a significant interaction between soybean genotype and aphid strain. Combining individual data with the individual based model of population growth isolated the impact of fecundity and host resistance from intraspecific competition and host health. Changes to patterns of fecundity, influenced by the composition and concentration of symbionts, may contribute to competitive interactions among aphid genotypes and influence selection on virulent aphid populations.

Evaluation of release rates of predator, <i>Apertochrysa astur</i> (Banks) (Neuroptera: Chrysopidae) against Rugose Spiraling Whitefly (RSW), <i>Aleurodicus rugioperculatus</i> Martin

Evaluation of release rates of a generalist predator, Apertochrysa astur was carried out against Rugose Spiraling Whitefly (RSW) during 2020-21 and 2021-22 at Dr. YSRHU - SKPP Polytechnic College, Ramachandrapuram and Dr. YSRHU - Horticultural Research Station (HRS), Ambajipeta (100, 200, 300, 400, 500 and 600 eggs per palm). The overall and pooled results during the years 2020-21 and 2021-22, indicated that clipping of A. astur at 600 eggs/palm (T6) recorded the lowest number of RSW spirals, nymphs and pupae, whereas the control palms (T8) recorded with a maximum number of RSW spirals, nymphs and pupae per leaflet.

Tomato Aphid (Aphis gossypii) Secreted Saliva Can Enhance Aphid Resistance by Upregulating Signaling Molecules in Tomato (Solanum lycopersicum).

This study investigated the impact of Aphis gossypii watery saliva on the induction of tomato (Solanum lycopersicum) plant resistance. To examine the role of A. gossypii saliva, we collected watery saliva from A. gossypii after a 48 h feeding period on an artificial diet. SDS-PAGE resolving gel 12% was used to separate the salivary proteins. Relative expression of gene analysis revealed that the intrusion of A. gossypii saliva dripping onto S. lycopersicum leaves triggered robust defense responses mediated by a signaling molecule, i.e., salicylic acid, while the signaling molecule's jasmonic acid-dependent defense responses were moderately activated. Aphid saliva infiltrated S. lycopersicum leaves slowed the intrinsic rate of population growth of A. gossypii and significantly reduced the number of nymphs produced daily, compared to untreated leaves. During a choice test with untreated S. lycopersicum, aphids showed a repellent response towards saliva-infiltrated S. lycopersicum. Moreover, the (EPG) electrical penetration graph analysis demonstrated that the eating pattern of A. gossypii compared to untreated S. lycopersicum, that had been exposed to saliva was negatively impacted. These results provide compelling evidence for the involvement of salivary components of A. gossypii in inducing resistance against aphids in S. lycopersicum plants. Furthermore, the study underscores the crucial role of watery saliva in the intricate interactions between aphids and plants. The activation of pathways was also part of the defensive response (jasmonic acid (JA), salicylic acid (SA) signaling molecules). The findings of this research deliver valuable insights into the potential of watery aphid saliva as a natural defense mechanism against aphid infestations in S. lycopersicum crops.

Seasonal Presence of White Fly Species on Jujube Trees in Nineveh Governorate

The study was conducted in the gardens of Mosul University from September 2019 to September 2020 in order to determine the types of white flies that infest Jujube trees and their seasonal activity. The results showed that Jujube trees, Zizyphus spina Christi, were infected with the following species: Acaudaleyrodes rachipora (Singh), Aleurolobus marlatti (Quan), and Aleuroclava jasmini (Takahashi). The percentage of leaf infection was highest in November, followed by September and August with an average 98.95, 94.85 and 94.63%, respectively. The insect preferred upper surface of the leaf than its lower surface, as the average number of nymphs was 15,11, and 1,39 nymphs/leaf, respectively, and the number of nymphs peaked during the autumn months. Direction had no effect on the rate of leaves infection, and no significant differences appeared between the treatments, while the density of nymphs in the leaves was affected by the direction factor, as the southern direction was significantly superior at a rate of 18.85 nymphs/leaf, and no significant differences were recorded between the other three directions. The results of the weekly catch also showed that the density of adults ranged between (1.28-168) adult /trap, peaking in October, while the adult were absent from the traps during January and February. Some predators were seen preying on the stages of the white fly, Lasiochilus pallidulus (Reuter), Oenepia conglobate (L.), Chrysoperla carnea (Stepheus).

Effect of Wolbachia as biocontrol agent on fecundity and survival of cassava whitefly in northwest Nigeria

Whitefly (Bemisia tabaci Genn.) is known to vectored Cassava mosaic virus (CMV) and Cassava brown streak virus (CBSV), these viruses caused major diseases of cassava in Africa. An experiment was conducted to determine the effect of Wolbachia as biocontrol agent on fecundity and survival of whitefly infesting cassava. Whiteflies infesting cassava were captured and reared using rearing cages. Wolbachia was isolated from infected cassava whiteflies, cultured and used for the inoculations. The experiment was conducted under control conditions using glass cages. Results of this research revealed that number of eggs lay by Bemisia tabaci inoculated with Wolbachia significantly (P = 0.05) reduced weeks after inoculation which significantly differ among the cassava genotypes. Number of eggs lay by B. tabaci free of Wolbachia was significantly higher (964.35) than those inoculated with Wolbachia (46.541) at 4 weeks after inoculation (4WAI). The genotype ‘Dan Aliero’ had the highest number (4WAI 82.33), while, ‘Farin rogo’ had the lowest number of eggs (4WAI 23.33). Number of whitefly nymphs and adults also significantly reduced when B. tabaci was inoculated with Wolbachia. ‘Dan Aliero’ had the highest number of whitefly nymphs and adults (4WAI = 59.00) and (4WAI = 51.00), respectively. ‘Farin rogo’ recorded the lowest number of whitefly nymphs (17.67) and adults (13.00) at 4WAI, respectively. For the first time, Wolbachia were evaluated for whiteflies management. From the finding of this study, Wolbachia can be used as biocontrol agent to suppress whiteflies infestation on cassava and other vegetable crops.

Effect of several reduced-risk insecticides on the population of Bemisia tabaci Genn. and incidence of pepper yellow leaf curl Indonesia virus (PepYLCIV) on chili plants

Tobacco whitefly, Bemisia tabaci Genn. can directly, and indirectly damage chili plants by sucking the plant sap and transmitting Pepper yellow leaf curl Indonesia virus (PepYLCIV), respectively. Farmers control PepYLCIV by using synthetic insecticides with 2-3 applications a week to suppress the vector population. The intensive use of insecticide raises concern about potential detrimental effects on the environment and non-target organisms. An alternative control measure for B. tabaci is the use of reduced-risk insecticides that are effective but safer. Thus, the study aimed to determine the effectiveness of various reduced-risk insecticides in reducing the whitefly population and PepYLCIV incidence. This experiment consisted of 12 treatments using insecticides of abamectin, azadiractin, imidacloprid, deltamethrin, spinosad, and water (control), applied once and twice a week. The results showed that the low-risk insecticides had no significant effect on the numbers of adults and nymphs of B. tabaci and the PepYLCIV incidence. Imidacloprid had significantly lower egg number and PepYLCIV incidence than the control and the other insecticide treatments. Our results also showed that B. tabaci populations were low throughout the season but the incidences of PepYLCIV were relatively high. This indicated a possibility that PepYLCIV is seed-borne.

Population Dynamics and Estimation of Damage of the Spittlebug Aeneolamia varia on Sugarcane in Colombia by Using remote Sensing and Machine Learning Tools

The spittlebug (Aeneolamia varia) is one of the most important sugarcane pests in Colombia, where a recent increase in population and distribution specially in southwestern Colombia have led to the need for new technologies for integrated pest management. The objectives of this study were to determine the spatial distribution of this pest in commercial sugarcane fields and to validate machine learning (ML) tools for indirect injury detection and impact on yield (damage) using satellite images. This study was carried out in fields grown with the CC 01-1940 variety in El Cerrito, Valle del Cauca, Colombia, where systematic sampling of the populations (number of adults and nymphs per stem) was carried out. The spatial aggregation and distribution were determined using Moran’s index and point patterns, sequence observations, and analysis with distance indicators (Sadie). The indirect injury detection and quantification of the impact on production were carried out with a ML approach using satellite image products with 10 m spatial and five days temporal resolutions, obtained from a Sentinel-2 sensor using Google Earth Engine. The results indicated that spittlebug populations had an aggregate spatial behavior and high spatial dependence. In addition, the ML algorithms predicted spittlebug injury, and the effect on production was estimated at 26.4 tons of cane per hectare, which represented a 17% reduction in the expected yield. The use of spatial analysis and remote sensing tools are an alternative for indirect detection of injury and for understanding population dynamics of the pest in sugarcane, so they can become instrumental for decision-making on an integrated pest management program.

Resistance in pea (Pisum sativum) genetic resources to the pea aphid,Acyrthosiphon pisum

AbstractThe pea aphid (PA),Acyrthosiphon pisum(Harris) (Hemiptera: Aphididae), can cause significant damage to dry and green peas,Pisum sativumL. (Fabaceae). Identifying pea lines with resistance to PA is important to advance available control measures. This research identified lines and putative genes with resistance to PA in the USDAPisum sativumCollection located in Pullman, WA, USA, consisting of 301 lines collected worldwide. Eight commercial pea cultivars were also evaluated. A cluster analysis based on the mean number of adults, nymphs, and total aphids that developed on lines 10 days after the start of infestation by a single adult aphid per plant identified six clusters. Cluster 2, consisting of 48 lines, had the lowest aphid fecundity of all clusters with 2.1 adults, 7.3 nymphs, and 9.4 total aphids produced on average. ‘Lifter’ was the most resistant line based on low aphid fecundity. Lifter is a white‐flowered green dry pea cultivar that can advance PA resistance in food‐type peas. Genotyping by sequencing based on single‐nucleotide polymorphisms (SNPs) were used in genome‐wide association mapping to locate genes or quantitative trait loci (QTL) linked to PA resistance in which three, nine, and six SNPs were associated with resistance to adult, nymph, and total number of PAs that developed on lines, respectively. Seventeen candidate genes were identified in response to PA resistance. The results can effectively be used in breeding programs to target specific genomic regions with PA resistance and in traditional breeding using resistant lines as parents.

Predatory Capacity and Reproduction of Cyrtorhinus lividipennis (Hemiptera: Miridae) Adults Exposed to Low-Temperature Storage and Fitness of the F1 Generation.

Low-temperature storage (LTS) is a way to adjust natural enemy development to meet field release needs and to protect natural enemies from the odds of long-distance transportation. The mirid bug Cyrtorhinus lividipennis Reuter (Hemiptera: Miridae) is an important predator of planthoppers and leafhoppers in rice fields. In this study, the LTS effects were measured on the predatory capacity and reproduction of the mirid adults (provided with 20% honey solution and stored at 13 °C for 12 days), and the fitness of the F1 generation of these adults. Higher predation of the eggs of the brown planthopper Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) was observed in the post-storage females than in the control females. The functional responses of C. lividipennis adults, either exposed to LTS or not, to planthopper eggs fitted well with Holling type II functional responses. Longevity was not affected by LTS, whereas the number of offspring nymphs was 55.6% lower in the post-storage females than in the control females. The fitness of the offspring generation was not affected by the LTS of parental adults. The findings are discussed with their relevance to biological control.

White-tailed Deer and Eco-friendly Supply Chain

Both humans and deer have the potential to contract the intracellular bacterium that is transmitted by the bite of the Amblyomma americanum tick. This tick is a vector for the illnesses Ehrlichia chaffeensis and Ehrlichosis ewingii. They are intracellular bacteria that are gram-negative and can be discovered as individuals or clusters in the cytoplasm of an infected host cell. These bacteria live in membrane- lined vacuoles within the infected host cell. The effect of deer reduction on blacklegged tick has been done on various areas, and the results illustrated that the number of adults, nymphs, and larvae ticks all decreased as a result of the absence of deer. With community-wide prevention methods being appealing, the deer reduction is, to the best of our knowledge, the only other stated measure that acts at a community level and treats deer topically. The procedure for keeping the zoo's eco-friendly supply chain maintained could stand to benefit from the facts presented in this article.

Identification and virulence of entomopathogenic fungi, Isariajavanica and Purpureocilliumlilacinum isolated from the whitefly, Bemisiatabaci (Gennadius) (Hemiptera: Aleyrodidae) in Malaysia

BackgroundThree of entomopathogenic fungi, identified as Isariajavanica (Cjc-03 and Cjw-01) and Purpureocilliumlilacinum (TS-01) were found naturally infecting the whiteflies, Bemisiatabaci (Gennadius) (Hemiptera: Aleyrodidae) on chili and tomato plants. All the isolates were identified by morphological characterization and molecular identification (ITS region amplification). The virulence of the three isolates was evaluated against nymphs of B.tabaci at three different concentrations (1 × 106, 1 × 107, and 1 × 108 conidia/ml) under laboratory conditions and on adults of B.tabaci at one conidia concentration (1 × 107 conidia/ml) under laboratory and glasshouse conditions.ResultsIsariajavanica showed the highest virulence against B.tabaci nymphs and adults in both laboratory and glasshouse conditions. I.javanica exhibited the highest mortality in the laboratory against B.tabaci, nymphs at the highest concentration (1 × 108 conidia/ml) 8 days post-inoculation. Likewise, in the laboratory bioassay, B.tabaci, adults, Cjc-03 isolate exhibited maximum mortality (80.0%), followed by Cjw-01 isolate (77.5%), and TS-01 isolate (65.0%) at the concentration of 1 × 107 conidia/ml at 7 days post-inoculation. The highest mortality rate (63.45%) was recorded by the Cjc-03 isolate and TS-01 (54.22%) isolate at 3 days post-inoculation in glasshouse bioassay using the concentration of 1 × 107 conidia/ml of each of the 2 isolates (Cjc-03 and TS-01) against B.tabaci adults.ConclusionOverall, the findings showed that both isolates of I.javanica and P.lilacinum reduced the number of eggs, nymphs, and adults’ emergence of B.tabaci, following the application of 1 × 107 conidia/ml on tomato leaves in the glasshouse. The newly isolated strains could be developed as a potential commercial biopesticide for managing B.tabaci.

Efficacy of Some Predators and Lecanicillium lecanii Fungus in Controlling of Aphis gossypii (Glover) and Myzus persicae (Sulzer) in Potato Crop

Lokma, N., A.A.A. Saleh, S.A.M. Amer and M F.M. Zawrah. 2023. Efficacy of Some Predators and Lecanicillium lecanii Fungus in Controlling of Aphis gossypii (Glover) and Myzus persicae (Sulzer) in Potato Crop. Arab Journal of Plant Protection, 41(2): 152-160. https://doi.org/10.22268/AJPP-041.2.152160 This study was conducted to evaluate the efficiency of predators and Lecanicillium lecanii suspension as bicontrol agents against Myzus persicae and Aphis gossypii in potato crop, whereas Aphis gossypii had two peaks in the third week of March and April in 2020 and 2021 seasons. In addition, M. persicae had two peaks for both seasons in the fourth week of March and third week of April in 2020 and in the third week of March during 2021. The common predators observed in potato fields were: Coccinella undecimpunctata L., Chrysoperla carnea Steph., Coccinella septumpunctata, Metasyrphus corollae F. and Cydonia vicina isis (Muls.). Regarding potato predators, one peak was found in the second week of March (60 predators/25 leaves) during the 2020 season, and two peaks were found in the third week of March and second week of April (53 and 38 predators/25 leaves, respectively), in 2021 season. On the 8th day after treatment, the entomopathogenic fungus L. Lecanii produced maximum aphid mortality at highest concentration of 108 conidia/ml and 50% concentration of fungal metabolites for both M. persicae and A. gossypii. Meanwhile, L. lecanii 50% metabolites solution had more latent effect by decreasing the longevity and the number of nymphs than when using the spore suspension of 108 conidial/ml. Keywords: A. gossypii, M. persicae, aphid predators, Lecanicillium lecanii, potato.

Identification of Resistance Traits Against Whiteflies, Bemisia tabaci in Certified Varieties and Promising Strains in Field and Semi-Field Experiments

Al-Issa, Z., M.N. Salti, M. Nabahan and A. Khalifa. 2023. Identification of Resistance Traits Against Whiteflies, Bemisia tabaci in Certified Varieties and Promising Strains in Field and Semi-Field Experiments. Arab Journal of Plant Protection, 41(2): 173-182. https://doi.org/10.22268/AJPP-41.2.173182 Plants have developed defense systems to cope with pests’ challenge, especially insects to reduce their damage. In this study, some resistance traits in 30 cotton (Gossypium hirsutum) genotypes against cotton’s whitefly, Bemisia tabaci (Genn.) were evaluated through semifield experiments, where antixenosis of certified varieties and promising strains to the insect where studied by designing adhesive cage placed on leaves of the plant third upper, insect development from egg to adult were regularly observed and rates of development and survival, lifespan, sex ratio, and total emergence of adults were monitored. Preference test was conducted through recording numbers of different insect stages in 1cm2 area. Field experiments were carried out by planting cotton genotype for two successive seasons (2018, 2019). Insect density was evaluated by measuring whiteflies density every 15 days until the end of the growing season. During the 2020 season, trichome density in 1cm2 area was determined and their length and diameter were also determined at the 8 th node of cotton genotypes. The results showed that no significant differences among cotton genotype in relation to insect survival rate, lifespan, sex ratio, and emergence rate of adult. This study revealed that there were significant differences in trichome density in 1 cm2 of leaf area ranged between 86.33 to 160.7/cm2 . The correlation was significantly negative between egg and trichome density (R= -0.984). However, no significant correlation between length and diameter of trichome with nymph and egg density. The egg density varied from 32 to 54 egg/cm2 , whereas nymph’s density varied between 3.8 to 6.1 181 Arab J. Pl. Prot. Vol. 41, No. 2 (2023) nymphs/cm2 , and the variety Raqqa 5 had the highest density of whitefly nymphs and eggs during the two seasons. Whiteflies density peak was around mid-September and started to decline until mid-October. The results obtained suggested that there is a role for trichome density in resistance to whiteflies and there aren’t antixenosis between studied cotton’s genotypes. There is a need to investigate cotton genotypes from different cotton species such as G. arboreum, G. barbadens, G. thuberi for the presence of insect resistance traits. Incorporation of such resistance in cotton cultivars is a key for sustainable pest management. Keywords: cotton’s whiteflies, egg number, nymph number, resistance traits, preference, trichome

Predatory capacity and intraguild interaction between aphidophagous predators in the control of rose bush aphids

Chrysoperla externa (Hagen) and Hippodamia convergens (Guérin-Meneville) are voracious generalist predators, and important aphid control agents. In an environment containing a complex of species, the occurrence of intraguild interactions can interfere in the predator behavior and consumption. The aim of this work was to know the number of nymphs of Rhodobium porosum (Sanderson) and Macrosiphum rosae (Linnaeus) consumed by larvae of C. externa and H. convergens, and the interaction between these predators when confined together. First, second and third instar nymphs of R. porosum and M. rosae were provided in Petri dishes containing rose leaflets and second instar larvae of the predators. Intraguild interaction was studied in Petri dishes containing first instar nymphs of both aphid species and a second instar larva of C. externa plus one of H. convergens. A third treatment consisted of dishes containing a second instar larva of both predators maintained in the absence of prey. The evaluations took place throughout the entire instar of the predators. C. externa consumed a greater number of R. porosum nymphs and H. convergens a greater number of M. rosae nymphs. For both species of prey, the highest consumption was verified on the last day of evaluation. There was a positive interaction when the predator’s larvae were confined in the presence of aphid nymphs, with no mortality observed for any of them. In the absence of prey, there was 70% mortality of H. convergens larvae due to intraguild predation.

Mathematical modelling and optimal control of production losses caused by Miridae

Cocoa mirid, Sahlbergella singulars, is the major pest of cocoa (Theobroma cacao) responsible of several damage in plots in West Africa and particularly in Cameroon. Occasional damage accounts for 30 40% of pod losses. However, when miridae affect the foliage, gradual wilting occurs and eventually, tree death. A few studies have focused on describing the time evolution of Miridae in the plot in Cameroon, yet numerous questions remain. The aim of this paper is to estimate and control the losses of production caused by the bites of miridea. To do this, we will formulate and study a mathematical model for the dynamics of pods that takes into account the feeding and egg-laying of adults miridae on pods. We present the theoretical analysis of the model. More precisely, we compute equilibria and derive a threshold parameter that determines the presence or not of miridae in the plot. Throughout numerical simulations, we found that miridae can cause approximately 39.21% of production losses (which represents approximatively USD 1276.8 revenue losses) when initially, one has 1200 plants in the plot. After, we aim to increase cocoa production through optimal control. Optimal control consists in reducing density the number of nymphs and adults miridae in the plot. We studied the controlled model and we found that losses with control shrink to 20.58% which corresponds to USD670.32 income revenue.