Applications of Plant Growth Regulators to Container-grown Citrus Trees Affect the Biology and Behavior of the Asian Citrus Psyllid

Abstract

<jats:p>Asian citrus psyllid [ACP (<jats:italic>Diaphorina citri</jats:italic>)] is an important pest of citrus (<jats:italic>Citrus</jats:italic> sp.) in many citrus-growing regions of the world because of its status as the vector of huanglongbing disease [HLB (citrus greening)]. There are currently no HLB-resistant citrus genotypes and no proven treatments for the disease; thus, vector control through the use of frequent prophylactic pesticide applications is key to managing the spread of this disease. However, this practice is unsustainable and other means of altering ACP biology or reducing populations are needed. To this end, six plant growth regulators (PGRs) were tested to determine their effect on citrus tree vegetative growth and the subsequent impact on the biology of ACP. In greenhouse and growth chamber experiments, ACP reared on trees treated with prohexadione calcium and mefluidide exhibited significant reductions in both fecundity and survivorship, whereas uniconazole affected only fecundity and paclobutrazol affected only survivorship. No significant effects of PGRs on adult ACP weight were observed except on uniconazole-treated trees. No eggs were laid on dikegulac sodium-treated trees; however, this was likely the result of severe phytotoxicity rather than a true PGR effect. Oviposition rate was lower on all the PGR-treated trees, except chlormequat chloride under greenhouse conditions, compared with untreated control trees. In general, oviposition was delayed on PGR-treated trees compared with untreated controls. The observed changes in ACP biology and behavior after PGR treatment were not the result of a reduction in the number of suitable oviposition sites (i.e., growth reduction) or toxicity of the PGRs to ACP, suggesting there were PGR-induced plant biochemical changes that altered host plant quality. Leaf nutrient analyses and photosynthesis indicated that there were no correlative changes in plant nutrient status or carbon assimilation that led to the changes in ACP behavior, although it is possible that phloem-specific nutrient or carbohydrate changes could have occurred that were not detected in our whole-leaf analyses. These results support previous studies in which the fitness of various insect species has been affected by PGR applications, but more research is needed to understand the changes in plant chemistry that are responsible.</jats:p>

Quality Matters: Influences of Citrus Flush Physicochemical Characteristics on Population Dynamics of the Asian Citrus Psyllid (Hemiptera: Liviidae)

“…Exogenous application of calcium to developing shoots has been associated with reduced D . citri population and infestation levels [41,42] presumably due to enhanced cell wall thickening and lignification which are unsuitable for egg-laying or feeding. Taken together, D .…”

Effect of plant Growth Regulators onBlissus insularis(Hemiptera: Blissidae)

“…(Ericaceae) because of reduced nutrient availability. Tsagkarakis et al (2012) found that Diaphorina citri Kuwayama (Hemiptera: Liviidae) adults reared on Citrus volkameriana (Rutaceae) trees treated with prohexadione calcium and mefluidide showed significant reductions in both fecundity and survivorship. However, no effect of plant growth regulator use on the suitability of creeping bentgrass against black cutworms, Agrotis ipsilon Hufnagel (Lepidoptera: Noctuidae), and sod webworms (Lepidoptera: Pyralidae) was evident (Rogers et al 2001).…”

Application of Foliar Synthetic Elicitors for the Management of Diaphorina citri (Hemiptera: Liviidae) Populations in Tahiti Lime (Citrus latifolia Tanaka)

“…The life cycle of the ACP is closely related to the presence of new flush shoots in plants. In the tropics, the continuous production of new flush shoots allows ACP populations to remain relatively high at various times of the year, rendering control with systemic or contact insecticides difficult because the new growth cannot be continuously protected by pesticides (Pluke et al, 2008;Tsagkarakis et al, 2012). The strategy of applications of synthetic elicitors can be considered as an effective option in arthropod pest management programs because synthetic elicitors are small molecules that can induce immune responses in plants and produce a positive effect in the management of ACP populations (Pawlowski et al, 2016).…”

“…Elicitors are compounds that stimulate any type of defense in the plant and favor the synthesis of secondary metabolites under conditions of both abiotic and biotic stress and can be applied through foliar sprays. Within these compounds, carbohydrates, lipids, (glyco)peptides, (glyco)proteins, vitamins, and phytohormones can be found (Angelova et al, 2006;Boubakri et al, 2016;Smith et al, 2009;Thakur and Sohal, 2013;Tsagkarakis et al, 2012). Among the compounds studied to activate defense mechanisms in plants against the attack of biotic agents (macro-and microorganisms) are SA, phytohormones, chitosan, and thiamine (vitamin B1) (Ahn et al, 2005;El Hadrami et al, 2010;Thakur and Sohal, 2013).…”

“…Studies on the use of synthetic elicitors have focused mainly on their role in the control of HLB (Canales et al, 2016;Li et al, 2016). However, literature on the use and efficacy of defense activators or growth regulators for population management of the ACP remains limited (Tiwari et al, 2013;Tsagkarakis et al, 2012). Therefore, the objective of the present study was to evaluate the biological efficacy of four different synthetic elicitors (SA, Br, chitosan, and thiamine) on ACP individuals (adults, nymphs, and eggs) under field conditions and also to quantify the effect of these treatments on the physiology and nutritional status of Tahiti lime trees.…”