Effectiveness of Cyantraniliprole for Managing Bemisia tabaci (Hemiptera: Aleyrodidae) and Interfering with Transmission of Tomato Yellow Leaf Curl Virus on Tomato.

Cyantraniliprole is the second xylem-systemic active ingredient in the new anthranilic diamide class. Greenhouse (2006), growth chamber (2007), and field studies (2009-2010) were conducted to determine the efficacy of cyantraniliprole for managing Bemisia tabaci (Gennadius) biotype B and in interfering with transmission of tomato yellow leaf curl virus (TYLCV) by this whitefly. Cyantraniliprole applied as soil treatments (200 SC) or foliar sprays (100 OD) provided excellent adult whitefly control, TYLCV suppression, and reduced oviposition and nymph survival, comparable to current standards. The positive results observed in these greenhouse experiments with a high level of insect pressure (10× the field threshold of one adult per plant) and disease pressure (five adults per plant, with a high level of confidence that TYLCV virulent adults were used), indicate a great potential for cyantraniliprole to be used in a whitefly management program. Field evaluations of soil drench treatments confirmed the suppression of TYLCV transmission demonstrated in the greenhouse studies. Field studies in 2009 and 2010 showed that cyantraniliprole (200 SC) provided TYLCV suppression for 2 wk after a drench application, when using a susceptible (2009) or imidacloprid-tolerant (2010) whitefly population. Cyantraniliprole was demonstrated to be a promising tool for management of TYLCV in tomato production, which is very difficult and expensive, and which has limited options. The integration of cyantraniliprole into a resistance management program will help to ensure the continued sustainability of this and current insecticides used for the management of insect vectors, including whiteflies and the TYLCV they spreads.

Monitoring neonicotinoid resistance in biotype B of Bemisia tabaci in Florida.

BACKGROUND: Biotype B of the sweetpotato whitefly, Bemisia tabaci (Genn.), is a worldwide pest that has developed resistance to many insecticides, including the neonicotinoid class. Florida field populations were monitored for susceptibility to the neonicotinoids imidacloprid and thiamethoxam using a cut leaf petiole bioassay method. RESULTS: Average RR(50) values for imidacloprid increased from 3.7 in 2000 to 12.0 in 2003; decreased to 5.0 and 2.5 in 2004 and 2005, respectively; and then increased to 26.3 and 23.9 in 2006 and 2007, respectively. Populations with RR(50) values of about 50 to 60 during generation one reverted to RR(50) values of < or =4 in six generations, when reared without further exposure to imidacloprid. Average RR(50) values for thiamethoxam increased from 2.0 in 2003 to 24.7 in 2006 and decreased to 10.4 in 2007. Populations with RR(50) values of about 22, 32 and 53 during generation one declined to 8, 5 and 6, respectively, after being reared for five generations without exposure to thiamethoxam. The correlation coefficient from the 26 populations that were bioassayed both with imidacloprid and thiamethoxam showed a significant positive correlation (R(2) = 0.58) between these populations. CONCLUSION: The high level of RR(50) values to imidacloprid and thiamethoxam suggest an unstable decline in the susceptibility of B. tabaci to imidacloprid and thiamethoxam, with possible cross-resistance or predisposition for dual resistance selection.

Repellency of ginger oil to Bemisia argentifolii (Homoptera: Aleyrodidae) on tomato.

The whitefly Bemisia argentifolii Bellows & Perring is an economically important pest of tomatoes, Lycopersicon esculentum Mill., inducing an irregular ripening disorder of fruit and transmitting plant pathogenic viruses. With the goal of investigating ginger oil as a protectant for tomato plants, we tested the effects of concentration of ginger oil and application methods on repellency to whitefly in a vertical still-air olfactometer. In choice and no-choice experiments conducted in a greenhouse, we evaluated whether ginger oil would protect tomato seedlings from whitefly settling and oviposition. Ginger oil repelled whitefly adults in the vertical olfactometer. The repellency of ginger oil was attributed to its odor, effective at the concentrations used over a distance of 1-2 mm. Tomato leaf disks dipped in ginger oil repelled whiteflies at concentrations of 0.5, 0.75, and 1%, but not at concentrations <0.5%, in a dose-response experiment conducted in the olfactometer. Repellency increased with increasing ginger oil concentration when leaf disks were dipped in ginger oil but not when ginger oil was sprayed onto the leaf disks. Higher quantities of monoterpenes and sesquiterpenes were deposited on leaf disks dipped in ginger oil than on sprayed leaf disks according to gas chromatographic quantification. In the greenhouse, both choice and no-choice tests were conducted with tomato seedlings dipped in 0.25% ginger oil solution or 2% Tween 20, as treatment and control, respectively. In the choice test, 35-42% fewer whitefly adults settled and 37% fewer eggs were laid during the 24-h exposure period on tomato plants dipped in ginger oil solution than on plants dipped in 2% Tween 20. In the no-choice test, 10.2-16.7% fewer whiteflies settled on treated plants compared with control plants but no significant differences were detected in the number of eggs laid. Higher concentrations of ginger oil could not be used without causing severe wilting of tomato leaves. Ginger oil has potential as a protectant of tomato seedlings against B. argentifolii, but issues of phytotoxicity and coverage need to be addressed.

Plant Growth-Promoting Rhizobacterial Mediated Protection in Tomato Against Tomato mottle virus.

Tomato plants treated with plant growth-promoting rhizobacteria (PGPR), applied as an industrially formulated seed treatment, a spore preparation mixed with potting medium (referred to as powder), or a combined seed-powder treatment, were evaluated under field conditions for induced resistance to Tomato mottle virus (ToMoV). The PGPR strains used, based on their ability to induce resistance in previous experiments, included Bacillus amyloliquefaciens 937a, B. subtilis 937b, and B. pumilus SE34. Experiments were conducted in the fall of 1997 and the spring and fall of 1998 at the University of Florida's Gulf Coast Research & Education Center, Bradenton. All plants were rated for symptoms and analyzed for the presence of ToMoV DNA at 40 days after transplant (dat). Whitefly densities were determined on individual plants in each trial, and marketable fruit yields were determined at least two times during each trial. The highest level of protection occurred in the fall 1997 trial when, at 40 dat, ToMoV disease severity ratings were significantly less in all PGPR powder-based treatments than in either of the seed or control treatments. Detection of viral DNA using Southern dot blot analyses correlated with symptom severity ratings, as did fruit yields. A reduction in ToMoV symptom severity ratings and incidence of viral DNA were also observed for some PGPR treatments in the spring 1998 trial, although corresponding yield responses were not apparent. Little or no resistance was observed in the fall 1998 trial. No differences in disease severity, detection of ToMoV DNA, or yield occurred among treatments in any of the trials at 80 dat. These data show that up to 40 dat under natural conditions of high levels of vector-virus pressure, some PGPR treatments resulted in reduced ToMoV incidence and disease severity and, in some cases, a corresponding increase in fruit yield. The use of PGPR could become a component of an integrated program for management of this virus in tomato.