Sharpshooter & Whiteflies: What s New in Ornamental Research Rick Redak and Erich Schoeller Department of Entomology University of California, Riverside
Study System: Giant Whitefly (Aleurodicus dugesii) 1 mm Trialeurodes vaporariorum Aluerodicus dugesii
GWF Invasion into the United States San Diego (1992)? (1996)? Comfort (1991)? (1996) Volusia Co. (1996)? Honolulu (2002)
GWF California Invasion
Six life stages. Giant Whitefly Biology Bellows et al. (2002) Characteristic wax spirals with mixed life stages
Host Range Giant whitefly is extremely polyphagous and attacks over > 300 plant species in 47 families. Many hosts are economically important ornamentals and food crops. Hibiscus rosa-sinensis Xylosma sp. Strelitzia reginae
Giant Whitefly Damage Giant Whitefly on Xylosma sp. 2 Months of GWF Infestation
Photo Credits: Siavash Taravati & Mike Rose Parasitoid Community Name: Encarsia noyesi Idioporus affinis Entedononecremnus krauteri Family: Aphelinidae Pteromalidae Eulophidae # per Host: Solitary Solitary Solitary Location: Endoparasitic Endoparasitic Endoparasitic Mating Sys: Deuterotokous Arrhenotokous Arrhenotokous Host Range: Generalist Specialist Specialist Host Use: 2-4 th Instar 2-4 th Instar 4 th Instar
Parasitoid Establishment 1-4 1-5 2, 3, and 4 2 6 3 4 Indonesia Encarisa guadaloupe 4, 5, and 6 1 5
Evidence of Parasitism Parasitized 4 th instar Aleurodicus dugesii by A) Idioporus affinis; B) Encarsia noyesi; and C) Entedononecremnus krauteri. Note the distinct appearance of nymphs parasitized by I. affinis due to their yellow abdomens.
Study1: Abiotic Tolerance: Temperature Effects on Development Differences in Abiotic Tolerance may lead to spatial or temporal refugia from competitors. Study Goals 1) Model Giant Whitefly and parasitoid development under constant temperatures 2) Examine temperature effects on Giant Whitefly and parasitoid phenology and distribution in Southern California.
Methods Hibiscus plants infested with giant whitefly (1 leaf/plant) and density manipulated @ 20 nymphs. Plants held at constant temperatures of either 10, 15, 25, 28, 30, or 35 ± 0.2 C (16L:8D photoperiod, 65±10% RH). Development monitored daily and recorded. Replicated for each wasp species
GWF Nonlinear Dev. Models Lactin-2 Model Best Fit 0.04 0.035 Female Predicted Female Observed Topt= 26.40ºC Development Rate (1/d) 0.03 0.025 0.02 0.015 0.01 Male Predicted Male Observed Topt= 25.95ºC 0.005 0 10 15 20 25 30 35 Temperature (ºC)
Giant Whitefly: Development Time Total Development Time Under Constant Temperature o C Females Males 10 --- --- 15 94.79±0.86 a 89.17±1.72 a 20 45.68±0.91 b 49.14±1.04 b 25 29.19±0.18 c 27.22±0.30 bc 28 36.33±0.93 d 30.47±0.88 c 30 --- ---
Parasitoid Development Time Results for 4 th Instar. Other Instars currently in progress. Total Development Time (Days) Under Constant Temperatures Temp ( C) E. noyesi I. affinis E. krauteri 10 15 53.86 ± 0.13 a 50.20 ± 0.65 a 51.38 ± 0.34 a 20 29.91 ± 0.09 b 22.98 ± 0.57 b 24.75 ± 0.25 b 25 15.16 ± 0.05 c 12.00 ± 0.14 c 12.89 ± 0.11 c 28 12.19 ± 0.08 d 16.44 ± 0.16 d 15.19 ± 0.18 d 30 15.20 ± 0.06 c 18.11 ± 0.19 e 16.70 ± 0.09 e 35 Means in columns followed by same letter are not significantly different by Dunn's Test (p < 0.05)
Study 1: Conclusions Giant whitefly successfully developed from 15 to 28 C. Later stages can develop at 30 C, but under constant temp. die during 1 st Instar. Parasitoids successfully developed from 15 to 30 C. Exhibited differences in thermal tolerances. Ongoing work suggests stage parasitized may also have significant effect on development time.
Study 1: Future Directions SC Phenology study ongoing monitoring giant whitefly and parasitoid populations. GP WS HS FA QC MM Examining temperature effects on population dynamics and parasitism rates. MC J A 20 km
Study 2: Host Preference and the Influence of GWF Wax No Choice Tests 60 b 50 Percent Parasitism 40 30 20 a c a a a a 4th Instar 3rd Instar 2nd Instar 1st Instar 10 0 d b b b b E. noyesi I. affinis E. krauteri Parasitoid Species Bars marked with different letters within species indicate significant differences (p 0.05).
Giant Whitefly Wax Wax Production varies considerably for each nymphal stage. 3 rd Instar with little wax 4 th Instar with prolific wax
Study 2: Effects of Host Wax on Parasitoid Efficacy Many situations these waxes appear to serve as a defense against natural enemy attack. (Sensu Edmunds, 1974). Primary (offers pre-emptive protection). Visual camouflage against natural enemy detection. Physical inhibition of natural enemy searching behavior Secondary (protection during detection/attack). Physical prevention of feeding. Physical barrier against natural enemy attack. Chemical repellency. Prevention of aggression via chemical mimicry of non-prey.
Methods: Wax Effects Single Hibiscus leaves infested with A. dugesii. 4 th instars manipulated to 20/leaf. Wax blown away or left intact (n=15 species/treat). Single female introduced into the arena. Females observed for 1 hr. Host identity and # parasitized recorded. Experimental design for parasitism rate analysis.
Methods: Wax Effects
Methods: Behavioral Analysis For each trial the frequency, duration, and sequence of each behavioral event was recorded. 1) Walking 2) Searching * 3) Resting 4) Feeding 5) Grooming * 6) Host Encounter * 7) Drumming 8) Ovipositing 9)Disengagement Female Encarsia noyesi exhibiting characteristic oviposition stance on 4 th instar Aleurodicus dugesii. Note the erect posture and downturned antennae. *Asterisks indicate behaviors used for hypothesis testing
Results: Parasitism Rates There was a significant interaction effect of species and wax on observed parasitism rates (Neg. Binomial GLM: Χ 2 = 64.43, p-value < 0.0001).
Results: Foraging Behavior ns p=0.1072 p=0.1318 ns Asterisks indicate p<0.001 Species x Wax interaction on searching and grooming behavior (Two-Way MANOVA: (F = 5.85, p-value = 0.005). Mean host interaction time did not differ by species (F = 5.06, p = 0.105) or wax treatment (F = 1.22, p = 0.276).
Study 2: Conclusions Wax production by A. dugesii caused a significant reduction in I. affinis and E. noyesi parasitism rates. The magnitude of the wax effects varied by species with I. affinis experiencing greater negative effects of wax than E. noyesi. This may be due to its poor ability to clean off wax particles Idioporus affinis with an accumulation of wax particles.
Study 2: Conclusions Cont. Results from this study highlight the importance of prey wax in mediating predatorprey interactions. It is important to consider the defensive potential of these waxes when selecting natural enemies to release for biological control.
Study 2: Future Directions Examine effects of wax on E. krauteri. Parasitizes through upper leaf, so expect no wax effect. Specializes on 4 th Instar, may be evolved behavior for wax avoidance.
Sharpshooter Insecticide Resistance with Brad White & Frank Byrne Are glassy-winged sharpshooters developing resistance to neonicotinoid, pyrethroid, or carbamate insecticides? Materials used to manage insect populations in citrus and grapes (as well as a variety of other crops/species as needed). Materials used to achieve pest-free status for shipment of nursery material.
Sharpshooter Insecticide Resistance The following populations are being sampled and the genetic bases for resistance are being searched for. Central Valley: citrus, grapes, untreated vegetation Temecula Valley: citrus, grapes, untreated vegetation Orange & L.A. County: commercial nurseries, untreated urban areas.
Sharpshooter Insecticide Resistance Just now completed genetically sequencing a portion of the genome responsible for one of the protein sub-units that are altered with insecticide resistance.