Lecture 4: Asian citrus psyllid EPG waveforms and applications for pest management Michael E. Rogers University of Florida Department of Entomology and Nematology Citrus Research & Educa?on Center Lake Alfred, FL Outline of presentation • Introduc?on to Asian citrus psyllid and citrus greening disease • Psyllid EPG waveforms characterized to date • Techniques for maintaining consistency of psyllid EPG recordings • Current applica?on of psyllid EPG research in citrus pest management programs Asian citrus psyllid • Order: Hemiptera – Suborder: Sternorhyncha • Superfamily: Psylloidea – Family: Psyllidae » Diaphorina citri (Kuwayama) • Vector of the pathogen Candidatus Liberibacter asia?cus which causes citrus greening disease – Circula?ve phloem-‐limited bacterium Modified from Bove 2006 M.E. Rogers EPG Studies of Asian citrus psyllid feeding behaviors • First work on ACP feeding behaviors using EPG was a disserta?on published by Bonani (2009) – Characterized psyllid EPG waveforms – Histological correla?ons were made for some of these waveforms • Like other Sternorhyncha, perform intercellular probing • ACP waveforms are similar to other Sternorhyncha with the excep?on of waveform D Waveform C 1.7h C Modified from Serikawa et al. 2012 Waveform C 10 s • Histologically associated with stylet pathway ac?vi?es (Bonani et al. 2010) • All ac?vi?es that occur during stylet penetra?on through different leaf ?ssues • Frequency of 11.5-‐19.0 Hz Waveform D 1.7h C D Modified from Serikawa et al. 2012 Waveform D 10 s • • • • • Correlated with salivary sheath termini in phloem ?ssue (Bonani et al. 2010) Precise stylet ac?vi?es are unknown Transi?on between pathway and phloem phase No analogous waveform produced by aphids Frequency of 1.0-‐3.5 Hz Waveform D variations in appearance Waveform D is par?cularly variable in appearance • • • “Tines” of comb-‐like early part can go up (A) or down (B) Voltage change at the end can go up (A, C) or down (B) Characteris?cs vary based on posi?ve or nega?ve applied signal, posi?on of baseline Waveform E1 1.7h E1 C D Modified from Serikawa et al. 2012 Waveform E1 10 s • Begins ader a poten?al drop (pd) following waveform D • Hypothesized to correspond to saliva?on into phloem sieve elements (Bonani et al. 2010) – Based on similarity to aphid E1 waveform • Most likely where inocula?on of Las occurs • Frequency of 5.0-‐7.5 Hz Waveform E2 E1 C 1.7h E2 D Waveform E2 • • • • 10 s Always occurs ader E1 Correlated with phloem inges?on (Bonani et al. 2010) Acquisi?on of Las ader E2 for ~1h (Bonani et al. 2010) Frequency of 3.0 – 8.0 Hz Modified from Serikawa et al. 2012 Waveform G From Serikawa et al. 2012 • Histologically correlated with salivary sheath termini in xylem vessels (Bonani et al. 2010) • Hypothesized to indicate xylem inges?on based on aphid waveform G • Frequency of 5.0 – 7.0 Hz Non-probing Waveforms Waveform np From Serikawa et al. 2012 Waveform z From Serikawa et al. 2012 Waveform np – Baseline waveform – Highly irregular and spikey – Visually correlated with insect movement on plant (Serikawa 2011, Youn et al. 2011, Serikawa et al. 2012) Waveform z – Baseline waveform, low voltage – Visually correlated with dead or mo?onless psyllid or psyllid that has moved off the plant (Serikawa 2011, Youn et al. 2011, Serikawa et al. 2012) Methods for EPG Recordings of ACP Feeding Behaviors • Monitor – DC amplifier with Ri of 109 ohms – Gain of 50-‐100x – Substrate voltage of 75-‐150 mV • Can affect the appearance of the waveforms • Gold Wire – 0.0010 in (18.5 um diameter) – Cut to 1.5 cm in length Methods for EPG Recordings of ACP Feeding Behaviors • Plant material – Container grown citrus – Pruned to 30 cm – Recordings made on young leaves produced 4 weeks ader pruning – 35% more psyllids reach phloem on young vs. mature leaves (Bonani 2009) • Age of leaves used should be based on the objec?ve of your research Methods for EPG Recordings of ACP Feeding Behaviors • Psyllid considera?ons – Preferen?ally feed on lower leaf surface – Changes in light intensity can affect feeding behaviors – Human movement in room can affect results Prac?cal Applica?ons of ACP EPG Research • Transmission of Las occurs during the ?me when ACP are performing phloem-‐related feeding behaviors • Can phloem feeding behaviors be disrupted or prevented using insec?cides? • What is the true value of insec?cides for managing HLB spread via vector control? – Direct disrup?on of pathogen transmission vs. popula?on suppression Ability of insecticides to disrupt ACP phloem-feeding behaviors • Summary of results for some of the insec?cides evaluated to-‐date Product evaluated Ac4ve ingredient Applica4on method Dura4on of phloem feeding disrup4on Admire Pro 4.6F Pla4num 75 SG Belay 50 WDG Provado 1.6 F Danitol 2.4 EC Lorsban Advanced Delegate WG Movento MPC imidacloprid thiamethoxam clothianidin imidacloprid fenpropathrin chlorpyrifos spinetoram spirotetramat Soil drench Soil drench Soil drench Foliar applied Foliar applied Foliar applied Foliar applied Foliar applied At least 6 weeks At least 6 weeks At least 6 weeks 3 weeks 2-‐3 weeks 24 hours 24 hours none Modified from Rogers 2012 Effects of imidacloprid on ACP feeding behaviors From Serikawa et al. 2012 ACP EPG research results have led to recently regulatory ac?ons! Funding Importance of soil-‐applied neonico?noids for protec?on of young trees from HLB U.S. Environmental Protec?on Agency Regulatory ac?on Florida Department of Agriculture Expansion of neonico?noid pes?cide labels for use in Florida citrus! Examples of Ongoing ACP EPG Research • Understanding the mechanism of pathogen transmission by ACP • Inves?ga?ons into host-‐plant resistance mechanisms for ACP – More work is first needed to bener understand the behaviors occurring during pathway • Con?nued evalua?ons of the effects of insec?cides of ACP feeding behaviors
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