QQ andand BB biotypesbiotypes–– distribution,distribution, cropcrop--relation,relation, andand theirtheir relevancerelevance toto insecticideinsecticide resistanceresistance

BB QQ

RamiRami Horowitz,Horowitz, SvetlanaSvetlana Kontsedalov,Kontsedalov, VadimVadim KhasdanKhasdan HaggaiHaggai BreslauerBreslauer andand IsaacIsaac IshaayaIshaaya ARO, Dept. of Entomology, Gilat Research Center The Volcani Center, Bet Dagan, Israel biotype B biotype Q

Two biotypes of B. tabaci have been identified in Israel: B - (early 1990’s) Q - (2000) RAPD-PCR products of various Bemisia tabaci strains from Israel

1 2 3 4 5 6 7

Lane 1- DNA ladder; 5- a sample without DNA Lanes 2, 4, 7- samples from Sde-Eliyahu, w-Negev & standard B Lanes 3, 6 – samples from the Carmel Coast & standard Q Q,b Q b Q,B B B Q Q,b B B q Bq

BiotypesBiotypes ofof B.B. tabacitabaci inin Israel,Israel, 20022002--55 CrossingCrossing studies,studies, Q/BQ/B (field(field strains)strains)

Parents Offspring Females Males Females Males Sex ratio 20 40 Female: Male Negev (B) Negev (B) 360 206 1.0 :0.7

Negev (B) Arava (Q) 0 245 0.0:1.0

Arava (Q) Arava (Q) 458 316 1.0:0.7

Arava (Q) Negev (B) 6? 503 0.01:1.0 InIn thethe AravaArava ValleyValley (Israel);(Israel); biotypebiotype surveysurvey waswas conductedconducted duringduring 20042004––55 Organic vs. conventional crops

• In the Arava Valley (Israel); biotype survey was conducted during 2004 – 2005.

• Greenhouse organic peppers, cucumbers and melons – B.B. • Conventional greenhouses – Mostly QQ Proportion of B. tabaci biotype Q and B sampled from sunflower and cotton fields during 2005 cotton season in the Ayalon Valley, Israel 120

Endosulfan 'Polo' Cypermethrin 100

80 Percent Q 60

40 May-3 May-31 June-19 Yuly-18 Aug-24 Date Av-05 Sunflower Cotton Proportion of B. tabaci biotype Q and B sampled from sunflower and cotton fields during 2005 cotton season in the Carmel Coast, Israel 120

Endosulfan Endosulfan 'Polo' 100

80

60

Percent Q 40

20

0 May-31 June-21 July-18 Aug-24 Date

HC-05 Sunflower cotton BiotypeBiotype tolerancetolerance toto insecticidesinsecticides affectsaffects theirtheir fieldfield compositioncomposition

AA BB BB QQ Various populations of Bemisia tabaci collected in Israel, their biotype definition and resistance to pyriproxyfen Strain Collection Location Biotype Resistance date (RR) *S 1987 Tzor’a B 1 Yesha-99 1999 W- Negev B 2 BD-00 2000 Bet Dagan B 4 Negev-00 2000 W- Negev B 0.4 BS-00 2000 Bet She’an B 9 *Pyri-R 1991 GH, W- Negev Q 1,200 HC-00 2000 Carmel Coast Q 637 AV-99 1999 Ayalon Valley Q>b 167 AV-00 2000 Ayalon Valley Q>b 81 W-Gal 2000 W- Galilee Q>b 25 MonitoringMonitoring pyriproxyfenpyriproxyfen resistance,resistance, CarmelCarmel CoastCoast 20022002--33 99

95 90 S

70 B 2002LS 50 Early season Late season 2003ES 30

10 QQ 2003LS Egg mortality (%) Egg mortality 5

1 0.0001 0.001 0.01 0.1 1 10 100 1000 Concentration (ppm) HC-03-tig ResistanceResistance toto PyriproxyfenPyriproxyfen andand biotypebiotype QQ

9 In areas where the use of pyriproxyfen ceased, resistance levels declined to some extent, while… 9 Level of susceptibility was restored completely in the lab (gen. 15-20).

9 Biotype-related resistance? MonitoringMonitoring PyriproxyfenPyriproxyfen Resistance,Resistance, AyalonAyalon Valley,Valley, IsraelIsrael S 99 1996 95 S 90 2001 70 50 2002 30 2003

Egg mortality, % Egg mortality, 10 5 2004

1 2005 0.001 0.01 0.1 1 10 100 1000 Concentration, ppm LabLab assaysassays Susceptibility of B. tabaci strain (AV-02) to pyriproxyfen

Laboratory conditions (15th generations)

99 S 95 90 Unt B 70 B 50 Act Q 30 Msp 10 Egg mortality (%) Egg mortality 5 G0 Q>B 1 0.0001 0.001 0.01 0.1 1 10 100 1000 S=susceptible ;G0 =the original strain; Unt=untreated; Tiger-Sel-02-15gAct=selectionConcentration to Actara (thiamethoxam) (ppm) ; Msp=selection to Mospilan (acetamiprid) Mix of Q&B (1:1, with similar R) maintained for 20 generations; partly pressurized with pyriproxyfen; another part - kept untreated 99

95 90 S- Strain B B 70 1st Gen. 50 B&Q B Untr. 30 Q

10 Pyri- 5 Sel. Egg Mortality, % Egg Mortality,

1 0.001 0.01 0.1 1 10 100

mix-G20 Concentration, ppm Proportion of B. tabaci biotypes throughout the generations

GenerationGeneration untreateduntreated PyriPyri-- selectionselection G-0 1B:1Q 1B:1Q G-4 B 1B:1Q G-8 B Q>B G-12 B Q G-16 B Q G-20 B Q InteractionInteraction ofof B.B. tabacitabaci BiotypeBiotype

1. Both the B and Q biotypes are present in Israel 2. Field populations may consist of a mixture of biotypes 3. Reproductive incompatibility maintains their genetic isolation 4. A possible link exists between B. tabaci biotypes and insecticide resistance 5. Tolerance of Q-type to pyriproxyfen, neonicotinoids and other new insecticides (?) 6. Without exposure to insecticides – higher fitness to “B” (?) 7. Insecticide applications select for Q-type. We can surmise the following scenario

Appearance of Q biotype accompanies resistance to pyriproxyfen and/or neonicotinoids.

Treatments in accordance with IRM programs moderate selection for resistance to those insecticides and concurrently reduce the appearance of the Q-type.

Reuse of the above insecticides against B. tabaci may increase occurrence of the Q-type and development of resistance to one or another group of insecticides.

(Selection to insecticides in B biotype of B. tabaci is feasible, but it is probably slower than in the Q type). Unsolved questions

1. Does B-type have higher fitness than Q-type (is it more competitive)? 2. Why does “B” take over “Q” after several generations under lab conditions? 3. Reproductive barrier: attraction, mating behavior, fertility, symbiont related? B Q