Dynamics of Mortality Factors of the Citrus Psyllid in Southern Florida

Proc. Fla. State Hort. Soc. 121:113–117. 2008.

JORGE E. PEÑA*, R.E. DUNCAN, AND JOSEP A. JACAS University of Florida, IFAS, Tropical Research and Education Center, Homestead, FL 33031 and Universitat Jaume I., Castelló de la Plana, Spain

ADDITIONAL INDEX WORDS. Diaphorina citri, Murraya, Citrus, Zelus, Allograpta, Harmonia, Cycloneda, Eriophora, Syrphi- dae, psyllid predators Frequency of parasitoids and predators of Diaphorina citri was recorded during the morning and afternoon hours by observing activity and presence of natural enemies on a D. citri-infested orange jasmine (Murraya paniculata) hedges located in Homestead. The most common natural enemies during these observations were the predators Zelus longipes (Hemiptera: Reduviidae), Allograpta obliqua (Diptera: Syrphidae), Cicloneda sanguinea, Harmonia axyridides (Cole- optera: Coccinellidae), and Eriophora ravilla (Aranea: Araneidae). A survey for predators and parasitoids of D. citri was conducted from Nov. 2005 through May 2006 on limes (Citrus aurantifolia) and on orange jasmine in Homestead, Miami–Dade County. Percentage parasitism from Tamarixia radiata ﬂuctuated between 0.85% and 7.74% for 2nd to 5th instar D. citri. The most common predators were syrphids and coccinellids. A re-validation of predator frequency was conducted from Mar. to Apr. 2007. At this time, reduviids, coccinellids and syrphids were the most common predators observed on M. paniculata. Orange jasmine could be acting as a constant and important surrogate reservoir of D. citri. Our surveys show a pattern of predator interference with parasitoids of D. citri. The role of alternant host plants and the interaction with natural enemies needs to be studied more thoroughly.

The asian citrus psyllid (ACP), Diaphorina citri Kuwayama, Materials and Methods was first found in Florida in 1998 (Halbert et al., 1998). The ACP is considered as one of the most serious pests of citrus if ACTIVITY OF PREDATORS ON M. PANICULATA. An 80-m-long hedge the pathogen that causes huanglongbing disease (HLB, citrus of M. paniculata, located at the University of Florida, Tropical greening), Candidatus Liberobacter is present. Huanglongbing Research and Education Center, Homestead, was selected for was reported in Florida in 2005, making the management of the this study. Predator activity was recorded for 20–30 min by two disease vector more important than ever. First, one of the major observers during the morning (10:30–11:00 AM) and afternoon problems of dispersal of ACP and its population growth is the hours (1:00–2:30 PM) during 4 consecutive weeks between 25 Jan. large number of host plants in Florida. Its host range includes and 16 Feb. 2006. The number of predators was recorded and many citrus relatives, Citrus spp., and other genera within the specimens collected for further identification by insect special- Rutaceae, e.g., Murraya, Amyris, Ptelea, Zanthoxylum, Aegles, ists. To determine infestation levels for ACP, parasitism, and to Atalantia, Severinia and Toddalia (Halbert et al., 2004; Hung observe under the microscope any predator that had escaped from et al., 2000; Koizumi et al., 1996; Tsai and Liu, 2000). Hosts, our visual observations in the field, an additional collection of leaf such as orange jasmine, Murraya paniculata (L.) Jack, might flushes was done after the field visual observations by collecting be contributing more than expected to the population growth of fifteen 10-cm flushes, placing them individually in plastic bags D. citri. For instance, during a study in Broward County during and bringing shoots to the laboratory for further inspection. 1999, Tsai et al. (2002) and Tsai and Liu (2000) concluded that NATURAL ENEMY SURVEY. Two different hedges of M. paniculata continuous shoot flushes produced by orange jasmine could play and one lime grove (Citrus aurantifolia) located in Homestead, an important role in maintaining high populations of this insect FL, were selected for this study. Each M. paniculata hedge was when new shoot flushes were not available in commercial citrus similar in length, 29 and 30 m. Monthly, 20 leaf flushes (≈10 cm groves. The potential importance of orange jasmine cannot be long) were randomly selected from the M. paniculata hedges or overemphasized. This common hedge plant is produced com- from lime trees. The presence of any predator on each flush was mercially and it is commonly planted as a hedge row (in many recorded and the predators were collected and saved for further instances a few meters from citrus trees) in many counties in urban identification. The leaf flush was placed in an individual plastic and suburban landscapes in south Florida, but also in the central, bag and then placed in a cooler and brought to the laboratory for western, and eastern citrus growing areas of Florida (Zones 9, further inspection. All stages of D. citri per flush were recorded 10, 11; Gilman, 1999). as well as the presence of insect mummies and nymphs with the The objectives of this study were to 1) identify predators of parasitoid Tamarixia radiata emergence holes. Insect cadavers of ACP when infesting M. paniculata in southern Florida, and 2) ACP nymphs or adults, still attached to the flush were recorded. determine the dynamics of ACP, its predators, and parasitoids in The stem of each flush, was then placed in a 5-mL glass vial, southern Florida. closed with tissue paper and stored at 23 °C and 70% relative humidity (RH) until parasitoid emergence. No insecticides were applied to any of the sites, during the course of this study. *Corresponding author; phone: (305) 246-7001 x223; email: [email protected]fl.edu VALIDATION OF THE FREQUENCY OF PREDACEOUS SPECIES, 2007.

Proc. Fla. State Hort. Soc. 121: 2008. 113 differences of predator species between the morning and afternoon observations (Fig. 2).There were no significant differences between the morning and afternoon observations for Zelus longipes (Heter- optera: Reduviidae) (F = 20.96; df= 4,3). Means of 29.5 and 34.75 Z. longipes were observed during the morning and afternoon, followed by Eriophora spp. (Aranea: Araneidae), Hentzia spp. (Aranea: Salticidae), Camponotus floridanus, Pheidole spp. (Hymenoptera: Formicidae), Cicloneda sanguinea, and Harmonia axyridides (Coleop- tera: Coccinellidae). There were no significant differences between the morning and afternoon observations for the species of coccinellids (t test; F = 1.25; df = 4,3; Pr > F = 0.45). During our visual evaluations of predator activity, Z. longipes FigFig 1. FrequencyFrequency of of different different stages stages of ofasian ACP, citrus level psyllids, of parasitism, level of parasitism, mortality mortalitydue to predation due to predation and was 3 to 4 times more frequent meanand mean number number of predaceous of predaceous syrphid syrphid larvae larvae observed observed under under the the microscope. microscope. than C. floridanus and Pheidole, and approximately 30 times more An orange jasmine hedge of approximately 29 m long located in frequent than C. sanguinea and H. axyridides , Eriophora and Homestead, FL, was selected as the study site. The ACP popula- Hentzia. The highest density of Z. longipes was observed dur- tion was assessed by randomly collecting twenty 10-cm shoots ing the fourth week of the evaluation (F = 26.97; DF =3,1; P per treatment. Weekly counts were made 12 Mar. through 20 Apr. > F 0.01). Surprisingly, during our visual observations, we did 2007. All ACP counts were made under a microscope and the not observe Allograpta obliqua (Diptera: Syrphidae) which number of ACP with parasitoid exit holes or mummies recorded. was recorded later when ACP infestation on leaf flushes was Predators were checked by observing predators on the plants for recorded under the microscope. Eggs and pupae of A. obliqua about 2 min over a 3-d period to total about 10 replications. were observed in close proximity to ACP colonies and larvae were observed feeding on both ACP nymphs and adults. There Results and Discussion were no statistical differences between the different collecting dates for A. obliqua (F = 2.10, df = 3 ; P = 0.55) . Also, there DIURNAL FREQUENCY OF NATURAL ENEMIES OF D. CITRI. The were no significant differences between different collecting relative abundance of predator natural enemies observed on dates for the number of parasitized ACP ( F = 30.76; df = 24, P M. paniculata are presented in Figures 1 and 2 .There were no = 0.16) (Fig. 2). The only emerging parasitoid was Tamarixia radiata. The number of parasitized ACP was not different from the number of predators (A. obliqua) per date (F = 10.53; DF = 8; P = 0.23). In general, during both types of observations, the only two predators observed feeding on ACP nymphs were Z. longipes and A. obliqua. Once, Z. longipes was observed prey- ing on a T. radiata adult, indicating that some predators might be interfering with parasitoid activity. The role of C. floridanus and Pheidole sp. was not clear as we observed them carrying nymphs but no feeding was observed. NATURAL ENEMY SURVEY. With the exception of June 2005, the survey was carried out monthly, from Nov. 2005 to Oct. 2006. We decided to combine the results from the two M. paniculata sites, when no significant differences on ACP densities and differences on predator frequency were found between the two hedges (χ2, DF = 85, value 83.74, P = 0.51; t test; F = 1.43; df = 30, 399; Pr> F = 0.07) . More ACP densities were observed on M. paniculata than on citrus throughout the survey (χ2 = 123.78, DF = 88, P = 0.007). This could be due to the constant production of leaf flushes in M. paniculata, compared to the four leaf Fig. 2. Mean number of different predaceous species observed during flushing periods observed on limes. The range of eggs per shoot Fig. 2. Mean number of different predaceous species observed during morning and afternoonobserved on limes (Table 1) fluctuated between a minimum of hours on amorning M. paniculata and hedge,afternoon Homestead, hours onFL. a M. paniculata hedge, Homestead, FL. zero to a maximum of 74.34 ± 11.41 eggs per flush compared

114 Proc. Fla. State Hort. Soc. 121: 2008. Table 1. Mean number of asian citrus psyllid (ACP), parasitism and mortality observed on ﬂushes of citrus, Homestead, FL, 2005–06. There were no mummies and no coccinelids. Mean total Mean total Mean % Mean Mean Mean % Mean Date ACP parasitized parasitized (all) dead mortality mortality syrphids 11-05 3.75 ± 1.51 0 0 0 0 0 0 12-05 0.17 ± 0.09 0 0 0 0 0 0 1-06 9.10 ± 5.87 0.30 ± 0.16 2.4 ± 2.0 0 0.30 ± 0.16 2.4 ± 2.0 0.05 ± 0.05 2-06 3.20 ± 0.85 0 0 0 0 0 0.15 ± 0.11 3-06 8.40 ± 2.89 0 0 0.30 ± 0.16 0.30 ± 0.16 4.2 ± 2.5 0.10 ± 0.10 4-06 22.50 ± 4.86 0 0 0.35 ± 0.19 0.35 ± 0.19 0.5 ± 0.3 0 5-06 15.15 ± 3.47 0 0 0.20 ± 0.16 0.20 ± 0.16 0.4 ± 0.3 0 7-06 0.15 ± 0.11 0 0 0 0 0 0 8-06 0.10 ± 0.07 0 0 0 0 0 0 9-06 0.95 ± 0.49 0 0 0 0 0 0 10-06 0.25 ± 0.20 0.050 ± 0.050 5.0 ± 5.0 0 0.05 ± 0.05 5.0 ± 5.0 0

Table 2. Mean number of asian citrus psyllid, parasitism, and mortality observed on Murraya paniculata hedges (combined data), Homestead, FL, 2005–06. Mean Mean Mean % Mean nymphs Mean nymph Mean parasitized Mean Mean % Mean Mean Date adults total mummies with holes parasitoids (all) dead mortality syrphids coccinellids 11-05 0.316 ± 0.110 3.38 ± 1.00 0.051 ± 0.036 0.077 ± 0.057 0.154 ± 0.130 4.6 ± 3.0 0 4.6 ± 3.0 0 0 12-05 1.125 ± 0.264 24.25 ± 3.97 0.075 ± 0.042 0.025 ± 0.025 0.425 ± 0.179 3.2 ± 1.5 0 3.2 ± 1.5 0 0 1-06 0.725 ± 0.143 12.32 ± 2.77 0.125 ± 0.102 0.225 ± 0.084 0.475 ± 0.172 13.7 ± 5.0 0.300 ± 0.114 18.6 ± 5.4 0 0 2-06 0.667 ± 0.177 22.77 ± 5.00 0.026 ± 0.026 0.051 ± 0.036 0.641 ± 0.342 2.0 ± 0.7 1.692 ± 0.619 9.6 ± 3.2 0.077 ± 0.043 0 3-06 1.273 ± 0.397 25.76 ± 6.42 0.212 ± 0.113 0.182 ± 0.102 1.606 ± 0.481 15.1 ± 4.6 1.000 ± 0.671 19.3 ± 5.0 0.091 ± 0.051 0.030 ± 0.030 4-06 1.375 ± 0.255 16.60 ± 3.28 0 0 0.075 ± 0.055 0.2 ± 0.1 2.125 ± 0.710 5.7 ± 2.6 0.100 ± 0.060 0 5-06 1.500 ± 0.318 30.48 ± 6.57 0.050 ± 0.035 0.025 ± 0.025 0.200 ± 0.073 0.3 ± 0.1 0.300 ± 0.135 1.3 ± 0.6 0.025 ± 0.025 0.025 ± 0.025 6-06 7-06 0.525 ± 0.179 7.38 ± 2.03 0 0 0.150 ± 0.111 2.0 ± 1.7 0 2.0 ± 1.7 0 0 8-06 0.125 ± 0.082 3.62 ± 1.38 0 0.025 ± 0.025 0.050 ± 0.035 2.9 ± 2.5 0 2.9 ± 2.5 0 0 9-06 1.050 ± 0.340 35.45 ± 6.43 0.050 ± 0.035 0 0.200 ± 0.082 2.0 ± 1.0 0.050 ± 0.035 2.0 ± 1.0 0 0 10-06 0.400 ± 0.151 14.75 ± 4.08 0.025 ± 0.025 0 1.150 ± 0.382 13.5 ± 10.0 0.050 ± 0.050 15.1 ± 10.1 0.025 ± 0.025 0

Diaphorina citri - Orange Jasmine to a range of 1.60 ± 0.60 to a maximum of 37.42 ± 6.25 Diaphorina citri - Orange Jasmine eggs per shoot recorded on M. paniculata (Table 2). 40 However, because ACP eggs were always collected on 40 M. paniculata and several times were not found on citrus, Parasitism egg densities were in general signiﬁcantly higher on M. Parasitism χ2 Mortality paniculata than those on limes ( = 178.25, DF = 119; 30 Mortality P = 0.0004). Mean number of psyllids (adults, eggs and 30 nymphs) on M. paniculata was higher (3.51 ± 1.03 to 35.55 ± 6.43) than on lime (0.10 ± 0.07 to 22.50 ± 4.85). With the exception of the months of January and October, 20 when parasitism ranged from 2.4% to 5%, no parasitism 20 P

(mummies or parasitoid emergence) was observed on theP lime shoots compared to a constant parasitism (0.3% to 10 13.7%) observed through the year on the M. paniculata 10 hedges (χ2 = 42.24, DF = 11, P <0.0001). Mortality was defined as the sum of parasitized ACP and the cadavers left on the flushes by predaceous arthropods. Mortal- 0 ity was significantly higher on M. paniculata (Table 2) 0 N D J F M A M J J A S O 2 N D J F M A M J J A S O than on citrus (χ , DF = 15, value = 59.123, P < 0.0001) 2005 2006 (Table 1) (Figs. 3 and 4). A significant relationship was 2005 2006 established between the number of cadavers on flushes and the frequency of predators (F = 23.97; P > F = 0.009, Fig 3. Percent parasitism and mean mortality of the asian citrus psyllid on orange 2 Figjasmine, 3. Percent Homestead, of parasitism FL,and mean2005–06. mortality of the Asian citrus psyllid on orange Jasmine, df 1,9; r = 0.72) for all surveyed sites. Homestead,Fig 3. Percent Fl of2005-2006 parasitism and mean mortality of the Asian citrus psyllid on orange Jasmine, Mostly syrphid predators (0.05 to 0.15/shoot) were observedHomestead, Fl 2005-2006 on the lime grove between Jan. and Mar. 2005 while both syrphid

Proc. Fla. State Hort. Soc. 121: 2008. 115 Diaphorina citri - Citrus Diaphorina citri - Orange Jasmine 6 0.25

Parasitism Syrphids 5 0.20 Mortality Coccinelids

4 0.15

3 0.10 P b M 2 0.05

1 0.00 N D J F M A M J J A S O 0 2006 N D J F M A M J J A S O 2005 2005 2006 Fig. 6. Most common predators observed on orange jasmine, Homestead, Fig. 4. Percent parasitism and mortality caused by predators on flushes FL, 2005–06. of citrus infested with asian citrus psyllids, Homestead, FL, 2005–06. Fig. 6 Most common predators observed on orange jasmine, Homestead, 2005-2006 Fig 4. Percent parasitism and mortality caused by predators on flushes of citrus infested withspecies of coccinellids and Allograpta obliqua. These results ACP, Homestead, FL 2005-2006. were similar to those recorded during our first survey during Diaphorina citri - Citrus 2006 (Table 3). 0.16 This research corroborates the report from Tsai et al. (2000) 0.14 Syrphids that hedges of orange jasmine can support a large range of psyl- Coccinelids lids during winter months when citrus are not producing leaf 0.12 flushes. Therefore, orange jasmine, could be acting as a constant 0.10 and important surrogate reservoir of ACP densities. At the same time, these host plants serve as reservoirs for parasitoids and 0.08 predators. Therefore, the role of alternant host plants and the 0.06 interaction with natural enemies needs to be studied more thor- b M oughly. Secondly, populations of the ACP are fed upon by many 0.04 generalist arthropod predators, with the highest frequency by coccinellids (Michaud, 2004) but other species such as spiders, 0.02 lacewings, hover flies or syrphids and minute pirate bugs prey 0.00 on D. citri in central Florida. Pluke et al. (2005) reported only N D J F M A M J J A S O coccinellid species feeding on D. citri on citrus in Puerto Rico. 2005 2006 Our surveys show a different pattern of predators. For instance, reduviid assassin bugs appear to be the most frequent predators Fig. 5. Most frequent predators found on citrus, Homestead, FL, followed by syrphid and then coccinellids. Although this could 2005–06. Fig 5. Most frequent predators found on citrus , Homestead, FL, 2005-2006 be a matter of location, i.e., assassin bugs are more common in southern Florida than in central Florida, the low levels of parasit- (0.03 to 0.10) and coccinellids (0.02 to 0.03) were observed from ism observed in southern Florida in Murraya are similar to those February through May (Fig. 5). Only syrphids were observed observed by Michaud (2004). Therefore, interference of predators as predators during Oct. 2006 in the M. paniculata hedge (Fig. with the parasitoid could be suspected. For instance, during our 6). diurnal observations, Zelus spp. was observed once attacking RE-EVALUATION OF PREDATOR FREQUENCY, 2007. The preda- an adult of T. radiata, suggesting possible interference with the tor with highest frequency was Z. longipes followed by two exotic parasitoid. The use of conservation biological control

Table 3. Psyllids: Mean number of asian citrus psyllid/ﬂush and mean number of different species of predators observed during 2007. Parameter Day 0 Day 5 Day 11 Day 18 Day 27 Day 34 Adults/rep 0.15 ± 0.1 2.00 ± 4.95 ± 1.1 1.25 ± 0.2 1.10 ± 0.2 0.75 ± 0.4 Eggs/ﬂush 4.45 ± 1.3 5.55 ± 27.75 ± 4.2 60.40 ± 5.0 13.20 ± 2.2 41.20 ± 4.8 Nymphs 26.60 ± 4.0 18.5 ± 12.00 ± 1.5 21.05 ± 3.8 44.65 ± 3.3 19.55 ± 4.1 Mean no. of psyllids/rep 31.20 ± 4.6 26.05 ± 44.70 ± 6.0 82.70 ± 6.0 58.95 ± 4.9 61.50 ± 6.1 Mean no. of parasitized nymphs 0.0 ± 0.0 0.0 ± 0.0 0.0 ± 0.0 0.0 ± 0.0 0.1 ± 0.1 0.0 ± 0.0 Zelus longipes 7.82 ± 1.0 18.50 ± 3.5 15.20 ± 2.8 24.30 ± 3.3 19.11 ± 8.7 8.91 ± 3.0 Coccinellidae 0.18 ± 0.1 0.10 ± 0.1 0.06 ± 0.1 0.10 ± 0.1 0.11 ± 0.1 0.09 ± 0.1 Spiders 0.0 ± 0.0 0.0 ± 0.0 0.0 ± 0.0 0.0 ± 0.0 0.10 ± 0.1 0.0 ± 0.0 Allograpta 0.0 ± 0.0 0 ± 0.0 0.0 ± 0.0 0.0 ± 0.0 3.77 ± 3.7 0.0 ± 0.0

116 Proc. Fla. State Hort. Soc. 121: 2008. (CBC) is a component of integrated pest management and it is Proc. 12th Conf. of the Intl. Org. of Citrus Virologists, University of increasing in importance and popularity (Barbosa, 1998). CBC California, Riverside. research is focused on improving reliability by strengthening the Gilman, E.F. 1999. Murraya paniculata. University of Florida, Coop. natural enemy community in terms of population density and Ext. Serv., Inst. Food Agr. Serv., Fact Sheet FPS-416. species diversity (Cardinale et al., 2003). Studies on interference Halbert, S. and K. Manjunath. 2005. Asian citrus psyllids (Sternorrhyn- cha: Psyllidae) and greening disease of citrus: A literature review and of predators on activity of exotic parasitoids of this important assessment of risk in Florida. Fla. Entomol. 87:330-353. pest are warranted. Lim, W.H., O. Shamudin, and W. Ko. 1990. Citrus greening disease in Malaysia:pp. 100-105. In: B. Aubert, S. Tontyaporn, and D. Buangsu- Literature Cited won (eds.). Rehabilitation of citrus industry in the Asia Pacific region. Proc. Asia Pacific Intl. Conf. on Citriculture, Chiang Mai, Thailand, Aubert, B. 1990a. Integrated activities for the control of hunaglung- 4–10 Feb. 1990. UNDP-FAO, Rome. bin-greening and its vector Diaphorina citri Kuwayama in Asia, p. Michaud, J.P. 2004. Natural mortality of Asian citrus psyllid, Diapho- 133–144. In: B. Aubert, S. Tontyaporn, and D. Buangsuwon (eds.). rina citri (Homoptera: Psyllidae) in central Florida. Biol. Control Rehabilitation of citrus industry in the Asia Pacific Region. Proc. Asia 29:260–269. Pacific Intl. Conf. on Citriculture, Chiang Mai, Thailand, 4–10 Feb. Pluke, R.W., A. Escribano, J. Michaud, and P. Stansly. 2005. Potential 1990. UNDP-FAO, Rome. impact of lady beetles on Diaphorina citri (Homoptera:Psyllidae) in Chavan, V.M. and A.S. Summanwar. 1993. Population dynamics and Puerto Rico. Florida Entomol. 88:123–128. aspects of the biology of citrus psylla, Diaphorina citri Kuw., in Ma- Tsai, J., J-J. Wang, and Ying-Hong Liu. 2000. Seasonal abundance of harashtra, p. 286–290. In: P. Moreno, J.V. da Graca, and L.W. Timmer the asian citrus psyllid, Diaphorina citri (Homoptera: Psyllidae) in (eds.). Proc. 12th Conf. of the Intl. Org. of Citrus Virologists, University southern Florida. Florida Entomol. 85:446–451. of California, Riverside. Tsai, J.H. and Y.H. Liu. 2000. Biology of Diaphorina citri (Homoptera: Gao, S., M. Garnier, and J.M. Bové. 1993. Production of monoclonal Psyllidae) on four host plants. J. Econ. Entomol. 93:1721–1725. antibodies recognizing most Asian strains of the greening BLO by Viraktamath, C. and B. Bhumannavar. 2002. Biology and ecology and vitro immunization with an antigenic protein purified from the BLO, management of Diaphorina citri Kuwayama (Hemiptera: Psyllidae). p. 244–249. In P. Moreno, J.V. da Graca, and L.W. Timmer (eds.). Pest Mgt. in Hort. Ecosystems 7:1–27.

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