The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is the most important pest of citrus worldwide because it serves as a vector of "Candidatus Liberibacter" species (Alphaproteobacteria) that cause huanglongbing (citrus greening disease). All commercially cultivated citrus is susceptible and varieties tolerant to disease expression are not yet available. Onset of disease occurs following a long latent period after inoculation, and thus the pathogen can spread widely prior to detection. Detection of the pathogen in Brazil in 2004 and Florida in 2005 catalyzed a significant increase in research on D. citri biology. Chemical control is the primary management strategy currently employed, but recently documented decreases in susceptibility of D. citri to several insecticides illustrate the need for more sustainable tools. Herein, we discuss recent advances in the understanding of D. citri biology and behavior, pathogen transmission biology, biological control, and chemical control with respect to "Candidatus Liberibacter asiaticus." Our goal is to point toward integrated and biologically relevant management of this pathosystem.

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Biology and management of Asian citrus psyllid, vector of the huanglongbing pathogens.

Predicting the effects of climate change on natural enemies of agricultural pests

By 2014, huanglongbing (HLB), the most destructive disease of citrus, and its insect vector, the Asian citrus psyllid (ACP), Diaphorina citri (Kuwayama), became established in all major citrus-growing regions of the world, including the United States, with the exception of California. At present, application of insecticides is the most widely followed option for reducing ACP populations, while application of antibiotics for suppressing HLB disease/symptoms is being practiced in some citrus-growing regions. Application of insecticides during the dormant winter season, along with cultivation of HLB-free seedlings and early detection and removal of symptomatic and asymptomatic trees, has been very effective in managing ACP. Area-wide management of ACP by application of insecticides at low volume in large areas of citrus cultivation has been shown to be effective in managing HLB and reducing management costs. As insecticide resistance is a major problem in sustainable management of ACP, rotation/alternation of insecticides with different chemistries and modes of action needs to be followed. Besides control of the insect vector, use of antibiotics has temporarily suppressed the symptoms of HLB in diseased trees. Recent efforts to discover and screen existing as well as new compounds for their antibiotic and antimicrobial activities have identified some promising molecules for HLB control. There is an urgent need to find a sustainable solution to the HLB menace through chemical control of ACP populations and within HLB-infected trees through the judicious use of labeled insecticides (existing and novel chemistries) and antibiotics in area-wide management programs with due consideration to the insecticide resistance problem. © 2014 Society of Chemical Industry

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Chemical control of the Asian citrus psyllid and of huanglongbing disease in citrus.

Action of insect growth regulator insecticides and spinosad on life history parameters and absorption in third-instar larvae of the endoparasitoid Hyposoter didymator

A major challenge of agriculture is to increase food production to meet the needs of the growing world population, without damaging the environment. In current agricultural practices, the control of pests is often accomplished by means of the excessive use of agrochemicals, which can result in environmental pollution and the development of resistant pests. In this context, biopesticides can offer a better alternative to synthetic pesticides, enabling safer control of pest populations. However, limitations of biopesticides, including short shelf life, photosensitivity, and volatilization, make it difficult to use them on a large scale. Here, we review the potential use of neem oil in crop protection, considering the gaps and obstacles associated with the development of sustainable agriculture in the not too distant future.

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Neem Oil and Crop Protection: From Now to the Future.

The biological effects of a commercially available neem seed extract (Neemix. 4.5, 4.5% azadirachtin, AZ) were assessed on the brown citrus aphid, Toxoptera citricida (Kirklady), a recently introduced insect pest of citrus in the United States and its parasitoid, Lysiphlebus testaceipes. When small citrus seedlings were dipped with the neem extract at 11–180 ppm AZ, 0–8% of nymphs and 0–17.5% of adults survived 7 d after the treatment while 95% of nymphs and 42.5% of adults in the control survived for the same period. The extract drastically reduced longevity of both adults and nymphs, adult fecundity, and molting of nymphs at all tested concentrations. Spraying neem extract (11–180 ppm AZ) onto potted citrus plants in the greenhouse also significantly reduced aphids by 20–100%, while control aphid populations increased by 950% 7 d after treatment. Application of the extract had little impact on the survival of adult parasitoids and developing parasitoids within aphids because parasite emergences...

https://bioone.org/journals/Environmental-Entomology/volume-31/issue-1/0046-225X-31.1.172/Effect-of-Neem-Seed-Extract-on-the-Brown-Citrus-Aphid/10.1603/0046-225X-31.1.172.pdf

Effect of Neem Seed Extract on the Brown Citrus Aphid (Homoptera: Aphididae) and its Parasitoid Lysiphlebus testaceipes (Hymenoptera: Aphidiidae)

The biological effects of a neem-based biopesticide, containing 4.5% azadirachtin, were assessed against the Asian citrus psyllid, Diaphorina citri Kuwayama, a recently introduced insect pest and potential disease vector of citrus in the United States. Over the concentration range 11-180 ppm azadirachtin, no mortality of adult psyllids was observed when exposed to treated plants. Adult psyllids demonstrated a small but significant repellent effect from treated plants in a choice experiment, but showed no preference to oviposit on treated or untreated plants. Psyllid nymphs were susceptible to azadirachtin at very low concentrations and activity perhaps was due to developmental inhibition. At a concentration of 22.5 ppm azadirachtin, ecdysis was not observed past 4 days after treatment and all nymphs were dead within 7 days. The densities of psyllid nymphs on treated plants exposed to a greenhouse population were significantly reduced by concentrations as low as 10 ppm azadirachtin. Over the range of concentrations used in these experiments, the product caused no phytotoxicity to tender foliage of either citrus or orange jasmine plants. Field trials are warranted to determine suitability of neem-based biopesticides for inclusion in citrus integrated pest management programs.

Effect of a neem biopesticide on repellency, mortality, oviposition, and development of diaphorina citri (homoptera: psyllidae)

Lysiphlebus testaceipes (Cresson) is a solitary endoparasitoid of aphids and is the primary parasitoid attacking cereal aphids in the Great Plains, especially Schizaphis graminum (Rondani). In a previous study, it was found that a Lincoln, NE, isolate of L. testaceipes had a much higher survivorship at cold temperatures than isolates from Stillwater, OK, and Corpus Christi, TX. This suggested that the Nebraska isolate was locally adapted to the northern environment and perhaps genetically divergent from southern populations. We tested for genetic differentiation of the above isolates by sequencing portions of the COI and 16S mtDNA genes. We also examined a Florida isolate reared from Toxoptera citricida (Kirkaldy) and L. fabarum Marshall as an outgroup. The Great Plains isolates (Nebraska, Oklahoma, and Texas) were homogeneous with 0% and 0–0.2% sequence divergence in the COI and 16S gene fragments, respectively. The Florida isolate differed from the Great Plains isolates in nucleotide sequence b...

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Genetic Similarities Among Geographic Isolates of Lysiphlebus testaceipes (Hymenoptera: Aphidiidae) Differing in Cold Temperature Tolerances

A collection of Bacillus thuringiensis isolates plausibly active against coleopteran insects was obtained from the Agricultural Research Service Culture Collection. Each isolate was cultured, spores and δ-endotoxin crystals were pelleted by centrifugation and lyophilized, and the resulting product was incorporated in insect diet for testing against Diaprepes abbreviatus neonates. A bioassay method was developed that utilized small amounts of insect diet and B. thuringiensis spores and δ-endotoxin to treat single neonates confined to 0.2-mL clear polymerase chain reaction (PCR) tubes. The method was less expensive in terms of labor and materials as compared to previous methods and reduced control losses due to burrowing and aggressive behaviors of D. abbreviatus larvae confined together. Of 19 B. thuringiensis isolates screened for activity against D. abbreviatus with a discriminating dose of 250 ppm spores and δ-endotoxin on diet, 5 were selected for further evaluation in dose-response experiment...

https://bioone.org/journals/Florida-Entomologist/volume-89/issue-4/0015-4040(2006)89[441:AOBTIA]2.0.CO;2/ACTIVITY-OF-BACILLUS-THURINGIENSIS-ISOLATES-AGAINST-DIAPREPES-ABBREVIATUS-COLEOPTERA/10.1653/0015-4040(2006)89[441:AOBTIA]2.0.CO;2.pdf

Activity of bacillus thuringiensis isolates against diaprepes abbreviatus (coleoptera: curculionidae)

A commercial preparation of the microbial entomopathogen, Bacillus thuringiensis subsp. tenebrionis (Btt) was evaluated for biological activity against the Diaprepes root weevil, Diaprepes abbreviatus (L.). A reduction in survival was observed for neonatal larvae exposed to insect diet incorporated with Btt and in potted citrus treated with a Btt soil application. A treatment-induced, weight gain reduction for neonates was indicated only in the diet assay. Larvae exposed at 5 weeks old to diet treated with Btt demonstrated a dose-dependent mortality response. The mean ages for larval death ranged from 111 to 128 days among treatments. The LC50 for larvae in this age group was 6.2 ppm [AI] and the slope of the probit line was 2.29. The mortality response of larvae exposed at 12 weeks old also was dose dependent and the mean ages for larval death ranged from 130 to 141 days among treatments. The LC50 for larvae in this age group was 25.4 ppm [AI] and the slope of the probit line was 2.75. The delayed patterns of mortality that we observed among larvae treated at 5 and 12 weeks old indicates that disease is slow to develop in older larvae but that death occurs before maturation is completed.

https://www.jstor.org/stable/pdfplus/3496885.pdf

A. A. Weathersbee

Papers

Effect of Neem Seed Extract on the Brown Citrus Aphid (Homoptera: Aphididae) and its Parasitoid Lysiphlebus testaceipes (Hymenoptera: Aphidiidae)

Effect of a neem biopesticide on repellency, mortality, oviposition, and development of diaphorina citri (homoptera: psyllidae)

Genetic Similarities Among Geographic Isolates of Lysiphlebus testaceipes (Hymenoptera: Aphidiidae) Differing in Cold Temperature Tolerances

Activity of bacillus thuringiensis isolates against diaprepes abbreviatus (coleoptera: curculionidae)

Susceptibility of diaprepes abbreviatus (coleoptera: curculionidae) to a commercial preparation of bacillus thuringiensis subsp. tenebrionis