Citrus Psyllid Diaphorina Citri Kuwayama Research Articles

Risk of spread of the Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae) in Ghana.

The impact of invasive species on biodiversity, food security and economy is increasingly noticeable in various regions of the globe as a consequence of climate change. Yet, there is limited research on how climate change affects the distribution of the invasive Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera:Liviidae) in Ghana. Using maxnet package to fit the Maxent model in R software, we answered the following questions; (i) what are the main drivers for D. citri distribution, (ii) what are the D. citri-specific habitat requirements and (iii) how well do the risk maps fit with what we know to be correctly based on the available evidence?. We found that temperature seasonality (Bio04), mean temperature of warmest quarter (Bio10), precipitation of driest quarter (Bio17), moderate resolution imaging spectroradiometer land cover and precipitation seasonality (Bio15), were the most important drivers of D. citri distribution. The results follow the known distribution records of the pest with potential expansion of habitat suitability in the future. Because many invasive species, including D. citri, can adapt to the changing climates, our findings can serve as a guide for surveillance, tracking and prevention of D. citri spread in Ghana.

Identification and Distribution of the 'Candidatus Liberibacter asiaticus'-Asian Citrus Psyllid Pathosystem in Saudi Arabia.

Citrus greening disease was first reported in Saudi Arabia during the 1970s when characteristic foliar and fruit symptoms were observed in commercial citrus groves. However, 'Candidatus Liberibacter asiaticus' (CLas) was not detected in symptomatic trees until 1981 to 1984 when CLas-like cells were observed by transmission electron microscopy in leaves collected from symptomatic citrus groves in southwestern Saudi Arabia. Despite the anticipated establishment of the CLas-Asian citrus psyllid (ACP) (Diaphorina citri Kuwayama) pathosystem, CLas presence has not been verified in suspect trees nor have ACP infestations been documented. Given the recent expansion of citrus production in Saudi Arabia, a systematic country-wide survey was carried out to determine the potential CLas distribution in the 13 citrus-growing regions of the country. Citrus trees were surveyed for the presence of CLas-psyllid vector(s) and characteristic disease symptoms in commercial and urban citrus trees. Adult psyllids collected from infested citrus trees were identified as ACP based on morphological characteristics. Real-time quantitative PCR amplification (qPCR) of the CLas β-subunit of the ribonucleotide reductase (RNR) gene from citrus leaf and fruit samples and/or ACP adults revealed that trees were positive for CLas detection in 10 of the 13 survey regions; however, CLas was undetectable in ACP adults. Phylogenetic and single nucleotide polymorphism (SNP) analyses of a PCR-amplified, cloned fragment of the CLas 16S rRNA gene (∼1.1 kbp) indicated Saudi Arabian isolates were most closely related to Florida, U.S.A., isolates. Analysis of climate variables indicated that the distribution of the ACP-CLas pathosystem observed in Saudi Arabia was consistent with published predictions of terrains most likely to support establishment.

The Amino Acid Transporter PtCAT7 and Ammonium Nutrition Enhance the Uptake of Thiamethoxam in Citrus Rootstock Seedlings.

Thiamethoxam (THX), when applied to the soil, can be taken up by citrus roots and subsequently transported to the leaves, providing effective protection of plants against the Asian citrus psyllid (Diaphorina citri Kuwayama). In this study, the field experiments showed that the coapplication of THX and nitrogen fertilizer (AN) did not affect THX uptake in six-year-old citrus plants. However, their coapplication promoted THX uptake in three-year-old Potassium trifoliate rootstocks and relieved the inhibition of AN at a higher level on plant growth characteristics, including biomass and growth of root and stem. RNA-seq analysis found that THX induced upregulation of a cationic amino acid transporter (PtCAT7) in citrus leaves. PtCAT7 facilitated THX uptake in the yeast strain to inhibit its growth, and the PtCAT7 protein was localized on the plasma membrane. Our results demonstrate that THX and N fertilizer can be coapplied and PtCAT7 may be involved in THX uptake in citrus.

Association of Non-host Crop Plants with Mandarin in Host Location and Survival of Diaphorina citri Kuwayama (Hemiptera: Psyllidae).

Research efforts have been made to develop novel tactics, such as those targeting behavioral control, for management of the Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae), vector of the causal agent of citrus Huanglongbing. Here, we investigated whether association of "Ponkan" mandarin (Citrus reticulata) with volatiles from non-host crops: avocado, passion fruit or coffee, alters host location by the Asian citrus psyllid; and whether they can be temporary hosts for the Asian citrus psyllid. In wind tunnel assays, we found that the association of mandarin seedling with avocado plant volatiles reduced in 30% the number of psyllids sitting on host plants compared to the mandarin alone. In contrast, passion fruit plant volatiles facilitated host location by psyllids, which found mandarin seedlings faster than when exposed to mandarin alone. The association with coffee volatiles did not alter the attractiveness of mandarin to the Asian citrus psyllid. Survival and half-lethal time (LT50) of D. citri fed on non-host plants were longer than those insects with water only, but shorter than those fed on mandarin. Among the non-host plants, D. citri performed better in coffee, followed by avocado and passion fruit plants. Our results indicate that the association of mandarin with avocado plant can be beneficial for Asian citrus psyllid management.

Evaluation of Artemisia absinthium L. Essential Oil as a Potential Novel Prophylactic against the Asian Citrus Psyllid Diaphorina citri Kuwayama

Interest in developing novel crop protectants has increased in the recent decade due to the harmful effects of synthetic pesticides on humans and the environment. Diaphorina citri threatens the citrus industry worldwide and is the primary vector of phloem-limited bacterium (HLB). However, there is no available cure for HLB. Diaphorina citri management mainly depends on the use of synthetic insecticides, but their massive application leads to resistance in pest populations. Therefore, alternative pest management strategies are needed. Our results indicated that fewer D. citri adults settled on plants treated with AAEO than on control 48 h after release. The psyllids fed on citrus leaves treated with AAEO significantly reduced the honeydew production compared to the control. The AAEO showed potent ovicidal activity against the D. citri eggs with LC50 5.88 mg/mL. Furthermore, we also explored the fitness of D. citri on AAEO-treated and untreated Citrus sinensis by using two-sex life table tools. Our results revealed that the intrinsic rate of increase (r) was higher on untreated seedlings (0.10 d−1) than those treated with an LC20 concentration of AAEO (0.07 d−1). Similarly, the net reproductive rate (R0) was higher for untreated seedlings (14.21 offspring) than those treated (6.405 offspring). Furthermore, the AAEO were safer against Aphis mellifera, with LC50 35.05 mg/mL, which is relatively higher than the LC50 24.40 mg/mL values against D. citri. The results indicate that AAEO exhibits toxic and behavioral effects on D. citri, which can be a potential candidate for managing this pest.

Genetic transformation of 'Hamlin' and 'Valencia' sweet orange plants expressing the cry11A gene of Bacillus thuringiensis as another tool to the management of Diaphorina citri (Hemiptera: Liviidae).

The Asian citrus psyllid (ACP) Diaphorina citri Kuwayama (Hemiptera: Liviidae) is the vector of Candidatus Liberibacter spp., the bacteria associated with huanglongbing (HLB), the most devastating disease of citrus worldwide. HLB management has heavily counted on insecticide applications to control the ACP, although there are efforts towards more sustainable alternatives. In previous work, our group assessed the potential bioactivity of different strains of Bacillus thuringiensis (Eubacteriales: Bacillaceae) (Bt) containing cry/cyt genes as feasible tools to control ACP nymphs. Here, we report an attempt to use the cry11A gene from Bt to produce transgenic sweet orange plants using two promoters. For the genetic transformation, 'Hamlin' and 'Valencia' sweet orange seedlings were used as sources of explants. Transgenic plants were detected by polymerase chain reaction (PCR) with specific primers, and the transgene copy number was confirmed by Southern blot analyses. Transcript expression levels were determined by qPCR. Mortality assays of D. citri nymphs were carried out in a greenhouse, and the effect of the events tested ranged from 22 to 43% at the end of the five-day exposure period. To our knowledge, this is the first manuscript reporting the production of citrus plants expressing the Bt cry11A gene for the management of D. citri nymphs.

Tamarixia radiata global distribution to current and future climate using the climate change experiment (CLIMEX) model

The phloem-limited bacteria, “Candidatus Liberibacter asiaticus” and “Ca. L. americanus”, are the causal pathogens responsible for Huanglongbing (HLB). The Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae) is the principal vector of these “Ca. Liberibacter” species. Though Tamarixia radiata Waterston (Hymenoptera: Eulophidae) has been useful in biological control programmes against D. citri, information on its global distribution remains vague. Using the Climate Change Experiment (CLIMEX) model, the potential global distribution of T. radiata under the 2050s, 2070s, and 2090s for Special Report on Emissions Scenarios A1B and A2 was defined globally. The results showed that habitat suitability for T. radiata covered Africa, Asia, Europe, Oceania, and the Americas. The model predicted climate suitable areas for T. radiata beyond its presently known native and non-native areas. The new locations predicted to have habitat suitability for T. radiata included parts of Europe and Oceania. Under the different climate change scenarios, the model predicted contraction of high habitat suitability (EI > 30) for T. radiata from the 2050s to the 2090s. Nevertheless, the distribution maps created using the CLIMEX model may be helpful in the search for and release of T. radiata in new regions.

First Record of Aspergillus fijiensis as an Entomopathogenic Fungus against Asian Citrus Psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae).

The Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae) is the most widespread and devastating pest species in citrus orchards and is the natural vector of the phloem-limited bacterium that causes Huanglongbing (HLB) disease. Thus, reducing the population of D. citri is an important means to prevent the spread of HLB disease. Due to the long-term use of chemical control, biological control has become the most promising strategy. In this study, a novel highly pathogenic fungal strain was isolated from naturally infected cadavers of adult D. citri. The species was identified as Aspergillus fijiensis using morphological identification and phylogenetic analysis and assigned the strain name GDIZM-1. Tests to detect aflatoxin B1 demonstrated that A. fijiensis GDIZM-1 is a non-aflatoxin B1 producer. The pathogenicity of the strain against D. citri was determined under laboratory and greenhouse conditions. The results of the laboratory study indicated that nymphs from the 1st to 5th instar and adults of D. citri were infected by A. fijiensis GDIZM-1. The mortality of nymphs and adults of D. citri caused by infection with A. fijiensis increased with the concentration of the conidial suspension and exposure time, and the median lethal concentration (LC50) and median lethal time (LT50) values gradually decreased. The mortality of D. citri for all instars was higher than 70%, with high pathogenicity at the 7th day post treatment with 1 × 108 conidia/mL. The results of the greenhouse pathogenicity tests showed that the survival of D. citri adults was 3.33% on the 14th day post-treatment with 1 × 108 conidia/mL, which was significantly lower than that after treatment with the Metarhizium anisopliae GDIZMMa-3 strain and sterile water. The results of the present study revealed that the isolate of A. fijiensis GDIZM-1 was effective against D. citri and it provides a basis for the development of a new microbial pesticide against D. citri after validation of these results in the field.

Citrus Huanglongbing correlated with incidence of Diaphorina citri carrying Candidatus Liberibacter asiaticus and citrus phyllosphere microbiome.

In China, citrus Huanglongbing (HLB) disease is caused by the Candidatus Liberibacter asiaticus bacterium, which is carried by the Asian citrus psyllid Diaphorina citri Kuwayama. It was hypothesized that the epidemic of the HLB may related with the rate of bacterium presence in the insect vector and bacterium content in plant tissues, as well as the phyllosphere microbe communities changes. This study systematically analyzed the presence or absence of Ca. L. asiaticus in citrus tree leaves and in the insect vector D. citri over a 6-year period using real-time PCR. In addition, changes in the number of bacteria carried by D. citri over 12 months were quantified, as well as the relationship between the proportion of D. citri carrying Ca. L. asiaticus and the proportion of plants infected with Ca. L. asiaticus were analyzed. Results showed that the proportion of D. citri carrying bacteria was stable and relatively low from January to September. The bacteria in citrus leaves relatively low in spring and summer, then peaked in December. The proportion of D. citri carrying bacteria gradually declined from 2014 to 2019. The proportion of D. citri carrying Ca. L. asiaticus showed a significant positive correlation with the proportion of diseased citrus. The phyllosphere bacterial and fungal communities on the healthy citrus leaf were significantly different with the disease leaf in April and December. Pathogenic invasions change the citrus phyllosphere microbial community structure. It could be summarized that citrus Huanglongbing correlated with incidence of Diaphorina citri carrying Candidatus Liberibacter asiaticus and citrus phyllosphere microbiome.

Plant jasmonic acid mediated contrasting effects of two citrus aphid species on Diaphorina citri Kuwayama.

Herbivores may influence each other directly and through plant mediated inter-specific interactions. The Asian citrus psyllid (Diaphorina citri Kuwayama) and citrus aphids are key pests that can co-exist on citrus, but their plant-mediated interaction between them is unknown. Here we investigated plant-mediated effect of two citrus aphid species, the polyphagous Aphis spiraecola Patch and the oligophagous Aphis (Toxoptera) citricidus (Kirkaldy) on the feeding behavior and reproduction of Diaphorina citri, and explored the underlying mechanisms. In comparison with those on aphid free plants, Diaphorina citri had decreased reproduction and reduced phloem feeding on Aphis spiraecola pre-infested plants, while the reproduction and feeding efficiency were increased on Aphis citricidus pre-infested plants. Jasmonic acid (JA) dependent defense was significantly activated by Diaphorina citri feeding on Aphis spiraecola pre-infested plants, but was suppressed by Diaphorina citri feeding on Aphis citricidus pre-infested plants compared with that on aphid free plant. By contrast, only one tested marker gene in salicylic acid (SA) signaling was activated by Diaphorina citri feeding on Aphis spiraecola pre-infested plants. Furthermore, exogenous application of methyl jasmonate, but not SA, conferred resistance against Diaphorina citri in our citrus trials. Our results indicate that pre-infestation by two citrus aphid species differentially altered Diaphorina citri induced citrus JA dependent defense, which resulted in different effect on subsequent Diaphorina citri performance. © 2022 Society of Chemical Industry.

Influence of daily temperature maximums on the development and short-distance movement of the Asian citrus psyllid

Temperature is a key factor in insect biology and ecology. Climate change is driving insect exposure to temperature extremes and understanding the effect of extreme temperatures on the biology of invasive agricultural pests will be key to predicting the effect of temperature increases. Here, we simulated diurnal cycles with different lengths of exposure times to maximum temperatures experienced in summer in different locations of California on the survivorship and development of the Asian citrus psyllid (ACP) (Diaphorina citri Kuwayama). ACP is the invasive vector of Huanglongbing disease (HLB), a lethal bacterial pathogen of citrus which is currently spreading in the Los Angeles, California basin. We also tested the effect of high or low humidity at high temperatures on ACP survival and development and the effect of high temperatures on short-distance dispersal. ACP were able to complete their life cycle in all temperature treatments (28–43 °C) except in daily cycles when 43 °C was maintained for 6 h. Temperature and exposure time significantly decreased adult emergence above 40 °C. High temperatures significantly increased development time with longer development as exposure times to high temperatures increased. The interaction between low humidity and high temperature increased the number of emerging adults and decreased developmental times. ACP short-distance dispersal increased over time but was not affected by temperature. These results indicate that ACP are capable to develop in temperatures higher than previously reported, suggesting that increasing temperatures may reduce the invasive capacity of ACP in regions where maximum daily temperatures are increasing along with the duration of such temperatures throughout the day.

Asian Citrus Psyllid Diaphorina citri (Kuwayama) (Hemiptera: Liviidae) and its Detection Survey in Citrus Orchards of Sindhuli, Nepal

Citrus greening, also known as Huanglongbing (HLB), is one of the world's most devastating citrus diseases. In Asia, including Nepal, the disease is vectored by Asian citrus psyllid (Diaphorina citri (Kuwayama)) that transmits the pathogen Candidatus Liberibacter asiaticus, which is a fastidious, phloem-limited bacterium. Recently, the Sindhuli district of Nepal, well-known for sweet orange production, has been suspected of this destructive disease. Therefore, a detection survey on the vector was conducted by Plant Quarantine and Pesticide Management Centre, Lalitpur, in coordination with Prime Minister Agriculture Modernization Project, Project Implementation Unit, Sindhuli, during the second week of April 2021. The survey carried out on six major citrus growing pockets in the Sindhuli district revealed the presence of D. citri in the citrus orchards of Golanjor rural municipality ward no. 3, Sindhuli. Also, it was found that 2.96 percent and 20 percent of the surveyed citrus orchards of Sindhuli and Golanjor-3 were infested by D. citri, respectively. The existence of the vector in the orchards has increased the chances of citrus greening occurrence; however, tests like Polymerase Chain Reaction (PCR) can be helpful for the further confirmation of the disease in the region. In addition, the government should organize campaigns to make the citrus growers familiar with its vector insect-citrus psyllid, HLB, and its preventive and curative management measures as soon as possible to minimize the losses from the disease.

Genetic diversity of Diaphorina citri (Hemiptera: Liviidae) unravels phylogeographic structure and invasion history of eastern African populations.

The Asian citrus psyllid (Diaphorina citri Kuwayama) is a key pest of Citrus sp. worldwide, as it acts as a vector for Candidatus Liberibacter asiaticus, the bacterial pathogen that causes citrus Huanglongbing. Diaphorina citri has been reported in Kenya, Tanzania, and more recently in Ethiopia. This study assessed the genetic diversity and phylogeographic structure of the pest to gain insights into the potential sources of its introduction into Africa. Population structure and differentiation of D. citri populations from China, Ethiopia, Kenya, Tanzania, and the USA were assessed using 10 microsatellite loci. Additionally, five new complete mitogenomes of D. citri collected in China, Ethiopia, Kenya, Tanzania, and the USA were analyzed in the context of publicly available sequences. Genotype data grouped the D. citri populations from Kenya and Tanzania in one cluster, and those from Ethiopia formed a separate cluster. The two genetic clusters inferred from genotype data were congruent with mitochondrial sequence data. The mitogenomes from Kenya/Tanzania/China had 99.0% similarity, and the Ethiopia/USA had 99.9% similarity. In conclusion, D. citri populations in eastern Africa have different sources, as the Kenyan and Tanzanian populations probably originated from southeastern Asia, while the Ethiopian population most probably originated from the Americas.

Insight into Biological Control Potential of Hirsutella citriformis against Asian Citrus Psyllid as a Vector of Citrus Huanglongbing Disease in America.

Studies on Hirsutella citriformis Speare are scarce. Among these, some reports have focused on phenotypic identification, based on its morphological structure and morphometric characteristics. This fungus is known to control economically important citrus crop pests. In recent years, H. citriformis has received increased attention as a control agent for the Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae), which causes the Huanglongbing (HLB) disease. Unfortunately, formal H. citriformis strains characterization is marginal, which mainly involves the role of biologically active exudates (metabolites) produced during their growth. Information regarding their mode of action and biocontrol potential is limited. However, epizootics reports of this fungus, under suitable environmental conditions for its development (25 °C to 28 °C and ~80% relative humidity), have demonstrated its parasitization efficacy. Therefore, it becomes challenging to determine whether H. citriformis strains may be developed as commercial products. In this review, we showed relevant information on isolation and bioassay strategies of H. citriformis to evaluate potential biocontrol strains under laboratory and field conditions in America.

Climate-induced range shifts of invasive species (Diaphorina citri Kuwayama).

The Asian citrus psyllid (ACP) Diaphorina citri Kuwayama (Hemiptera: Liviidae) is a destructive, invasive species that poses a serious threat to the citrus industry wherever it occurs. The psyllid vectors the phloem-limited bacteria 'Candidatus Liberibacter americanus' and 'Ca. L. asiaticus', causal agents of the incurable citrus greening disease or huanglongbing (HLB). It is essential to understand which regions and areas are suitable for colonization by ACP to formulate appropriate policy and preventive measures. Considering its biology and ecology, we used a machine learning algorithm based on the MaxEnt (Maximum Entropy) principle, to predict the potential global distribution of ACP using bioclimatic variables and elevation. The model predictions are consistent with the known distribution of ACP and also highlight the potential occurrence outside its current ecological range, that is, primarily in Africa, Asia and the Americas. The most important abiotic variables driving the global distribution of ACP were annual mean temperature, seasonality of temperature and annual precipitation. Our findings highlight the need for international collaboration in slowing the spread of invasive pests like D. citri. © 2022 Society of Chemical Industry.

Biology of the Asian citrus psyllid Diaphorina citri (Hemiptera: Psyllidae) on Curry Leaf, Murraya koenigii

Biology of the Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae) was evaluated on curry leaf Murraya koenigii. The study revealed that D. citri is an important pest of ‘curry leaf’ in homestead gardens, farmer’s fields and forest areas in Saharanpur, Uttar Pradesh, India. The hatching percentage of the eggs was 80.25±3.47%, while the viability of the nymphal instars was 65.2±2.49%. The total nymphal period was 13.40±1.23 days. Adults emerged after 4-5 (4.4±0.50) days from fifth instar nymphs that took 35-40 minutes to emerge. The males lived for 24.94±0.65 days, with a total developmental period of 37.058±2.20 days, whereas the females survived for 39.81±0.53 days, having a total developmental period of 42.94±3.21 days. Pre-oviposition, oviposition and post-oviposition periods lasted for 2.75 ± 0.71, 22.6 ±5.18 and 3.35±1.03 days, respectively. Female fecundity was recorded to be 550-800 (692.90 ± 99.34) eggs per female.

Screening commercial entomopathogenic fungi for the management of Diaphorina citri populations in the Lower Rio Grande Valley, Texas, USA

Ten strains of entomopathogenic ascomycete fungi, sourced from commercial formulations of blastopore or conidiospore formulations, were tested in 14 different formulations in a primary acquisition/direct spray bioassay against adult Asian citrus psyllid (Diaphorina citri Kuwayama (Hemiptera: Liviidae)). The Cordyceps (Isaria) javanica Apopka 97-C (conidia) strain was used as the standard. A statistical ranking system was established in which top performing pathogenic strains were selected for further screening and eventual field trials. Modified Potter-type spray towers were utilized to deliver a range of doses of viable spores to adult D. citri in an aqueous spray consistent with the rate of spores per hectare often used in real-world spray applications. Mortality was assessed after a seven-day incubation period under controlled climate conditions reflecting those in the Lower Rio Grande Valley (LRGV) of Texas, USA. Of the 14 preparations, the strains Metarhizium anisopliae E9, C. fumosorosea Ifr9901, Beauveria bassiana ATCC 74040 and ANT-03, M. anisopliae ESALQ1037, and M. robertsii DWR2009, showed greater levels of mortality than the standard, Apopka 97-C, in the laboratory setting. Of those six, two (Ifr9901 and ANT-03) were selected for further evaluation based on efficacy, commercial availability, geographical registration, and market outlook on production.

'Candidatus Liberibacter' Pathosystems at the Forefront of Agricultural and Biological Research Challenges.

'Candidatus Liberibacter' Pathosystems at the Forefront of Agricultural and Biological Research Challenges.

Crude Extracts and Alkaloids Derived from Ipomoea-Periglandula Symbiotic Association Cause Mortality of Asian Citrus Psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae).

Simple SummaryFungi in the genus Periglandula (Clavicipitaceae) are endosymbionts of plants in the Convolvulaceae family (morning glories and relatives) where they may help protect plants from herbivory by production of bioactive compounds known as ergot alkaloids. We investigated mortality and behavior of nymphs and adults of Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae) exposed to crude extracts from morning glories and to synthetic ergot alkaloids known to be produced in Convolvulaceae-Periglandula symbioses. We monitored effects of extracts or synthetic compounds on survival, host settling, and feeding. Several ergot alkaloids reduced survival of D. citri on treated surfaces. Crude extracts and synthetic ergot alkaloids reduced D. citri adult settling on treated host plants compared with water controls. We observed an antifeedant effect of the crude extracts at concentrations which otherwise caused minimal adult mortality. Our results indicate that ergot alkaloids produce both toxic and sub-lethal effects on D. citri that could be useful for management of this pest.Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is an important economic pest of citrus crops because it vectors the causal pathogen of huanglongbing (HLB; aka citrus greening). Population suppression of D. citri with insecticides has been disproportionally relied on for HLB management and a greater diversity of more sustainable tools is needed. Periglandula spp. is a fungal endosymbiont (family Clavicipitaceae) that forms a mutualistic relationship with members of plants in family Convolvulaceae. This association results in the production of ergot alkaloids that were previously documented as having psyllicidal properties. We investigated the mortality and behavior of D. citri exposed to crude extracts from morning glories in the plant family Convolvulaceae, as well as synthetic ergot alkaloids. Nymphs and adults were exposed to the crude plant extracts from Periglandula positive species of Convolvulaceae, as well as five synthetic ergot alkaloids. Treatments were prepared by exposing clippings of citrus to 100 ng/µL of crude extract from Periglandula-positive species of Ipomoea (I. imperati, I. leptophylla, I. pandurata and I. tricolor), and Turbina corymbosa, and from one Periglandula-negative species (I. alba) (100 ng/µL). Mortality of adult and nymphal D. citri was significantly higher than the control after exposure to extracts from I. tricolor and I. imperati. The synthetic ergot alkaloids, lysergol (10–100 ng/µL), ergonovine maleate (100 ng/µL), agroclavine (10–100 ng/µL), and ergosine (10–100 ng/µL) increased mortality of D. citri nymphs, while ergosine (100 ng/µL) and agroclavine (100 ng/µL) increased mortality of adults compared to water controls. Fewer D. citri adults settled on plants treated with crude extracts or synthetic ergot alkaloids than on water controls at 48 h after release. D. citri that fed on citrus leaves treated with 10 ng/μL solution of crude extract from the Periglandula-positive species Ipomoea (I. imperati, I. leptophylla, I. pandurata, I. tricolor), and Turbina corymbosa excreted significantly less honeydew compared with a negative water control and extract from Periglandula-negative species (I. alba). Our results indicate that crude extracts and ergot alkaloids exhibit toxic and sub-lethal effects on D. citri that could be useful for management of this pest.

Pengaruh pengelolaan agroekosistem terhadap kelimpahan kutu loncat jeruk Diaphorina citri Kuwayama (Hemiptera: Liviidae)

Asian citrus psyllid (ACP) Diaphorina citri Kuwayama is a serious problem in citrus because it transmits huanglongbing (HLB) disease. Agricultural practices without paying attention to the agroecosystem complexity often cause the agroecosystem more suitable for insect pests proliferation and less friendly to natural enemies. The research aims to study the effectiveness of agroecosystem management compared to conventional farming in the ACP control. The effects of both treatments on the diversity and abundance of ACP’s natural enemies as well as the incidence and severity of HLB were also studied. Agroecosystem management consists of preventive and responsive actions. Preventive action was carried out through a polyculture system, planting refugia and legume cover crop, providing beetle banks, applying lime, applying organic and inorganic fertilizers, citrus pruning intensively, maintaining drainage ditches, and mechanical weed control. Responsive action is short-term control when the abundance of ACP reaches the action threshold. Responsive action was carried out through biological or chemical control. Meanwhile, conventional farming is a series of conventional farming and pest control techniques commonly applied by farmers. Each treatment was applied in three orchards of Siam Orange cv. Pontianak Citrus nobilis Lour var. microcarpa Hassk. The results showed that agroecosystem management was more effective in controlling the ACP population so that its abundance was lower and less fluctuated than conventional farming. ACP’s natural enemies in agroecosystem management were also more diverse than conventional farming. The abundance of ACP’s natural enemies and the incidence and severity of HLB in the two treatments were not significantly different.