Effect of Temperature on Imago Life Span, Fecundity and Reproduction Rate of Greenhouse Whitefly (T. vaporariorum W.)

Imago life span, fecundity and survival rate of the different developmental stages and average abundance of female offspring of greenhouse whitefly (Trialeurodes vaporariorum) were studied at three constant (18, 22 and 27°C) and one alternating (18/7°C) temperature.Temperature highs are inversely proportionate to imago life span. Temperature increase from 18/7°C to 27°C decreased the whitefly life span 3.3-fold. Under 18°C and 22°C, whitefly laid eggs most abundantly (147 and 126, respectively), while fecundity decreased under lower and higher temperatures. Half the offspring of the investigated whitefly laboratory strain (49.5%) were males, which resulted in lower values of reproduction and growth rates of the whitefly strain.Optimum development of greenhouse whitefly was achieved at 18°C, which is evident from a maximum number of eggs laid and highest average number of potential and actual female offspring (68.2 and 58.3, respectively), compared to the other investigated temperatures.The consequence of a 50.8-day long true generation time is evident from the low values of growth capacity (0.074) and intrinsic rate of increase (0.080). With temperature increasing to 22°C and 27°C, the period of whitefly oviposition showed a tendency to decrease further on. Higher temperatures reduced the total abundance of eggs laid and, consequently, the abundance of potential and actual female offspring, but increased growth rate

Potential Use of Insecticides and Mineral Oils for the Control of Transmission of Major Aphid-Transmitted Potato Viruses

Viruses occurring in Serbia and other countries in the region are a huge problem constrainingseed potato production. At lower altitudes, in lowland and hilly regions, wheretable potato production is widely distributed, more than 50% of healthy plants becomeinfected with potato virus Y during one growing season. Under these conditions, seed potatoproduction is hindered due to a high infection pressure of potato virus Y which spreads farmore rapidly compared to leaf roll virus, virus S and other viruses hosted by this plant species.This study tended to clarify a frequent dilemma regarding the use of insecticides in preventingthe infection of healthy plants with potato virus Y and leaf roll virus, given the oraland written recommendations from pesticide manufacturers, agronomists and scientistsin the field of crop protection arising from a logical conclusion that aphid vector controlresults in virus transmission control.The present findings, which are in agreement with reports of authors from other countries,show that the use of insecticides is ineffective in preventing potato virus Y which isnonpersistently transmitted by aphids from an external source of infection.However, insecticides can exhibit efficacy in preventing potato virus Y transmissionfrom infected plants to healthy plants within a crop, which can have an overall positiveeffect only if seed potato is grown in areas that have no external source of infection.The present results and those of other authors show that insecticides are effective inpreventing the infection of healthy plants with persistently transmitted leaf roll virus.Mineral oils provide effective control of potato virus Y by preventing the infection ofpotato plants with the virus. They can be combined with other management practices toprotect seed potato crops against the virus.Given the fact that the initial first-year infection of healthy potato plants with virus Y inrelation to leaf roll virus is approximately 10-20:1 under conditions in Serbia, and that the useof insecticides fails to ensure protection against PVY, this practice cannot have any positiveeffect on virus control under high infection pressure conditions

Effects of Insecticides on Strawberry Aphid Chaetosiphon fragaefolii (Cockerell) on Resistant and Susceptible Strawberry Genotypes

Strawberry aphid, Chaetosiphon fragaefolii (Cockerell), is the most important vector ofstrawberry virus. Breeding of genotypes resistant to this pest is an important preventivecontrol measure, which can be compatible with rational insecticide application. The aimof the paper was to determine effects of dimethoate and deltamethrin on C. fragaefoliipopulations reared on two strawberry genotypes different in susceptibility: susceptiblestrawberry cultivar Čačanska rana and medium resistant hybrid, zf/1/94/96 (Senga Fructarinax Del Norte). Lower toxicity of deltamethrin was observed (laboratory assay) as well aslower biological efficacy of dimethoate at lower concentrations (field trial) for specimensfrom C. fragaefolii population reared on susceptible strawberry cultivar Čačanska rana

Effectiveness of Azadirachtin (NeemAzal-T/S) in Controlling Pear Psylla (Cacopsylla pyri) and European Red Mite (Panonychus ulmi)

Here we present the results of field trials conducted in Serbia to evaluate the effectiveness of a neem-based product, NeemAzal-T/S (containing azadirachtin-A as its active ingredient in the form of an emulsifiable concentrate) against pear psylla (Cacopsylla pyri) and European red mite (Panonychus ulmi). Efficacy evaluation against C. pyri was carried out in a commercial pear orchard of the Williams pear cultivar, located at Borkovac (Ruma). The insecticides were applied at BBCH 09 pear growth stage, several days before the beginning of hatching of the first generation larvae. The efficacy of azadirachtin was compared to that of mineral oil, abamectin and diflubenzuron. Efficacy evaluation 18 DAT showed total termination of egg laying by C. pyri after treatments with azadirachtin and abamectin, while some new (white) eggs were found after treatment with mineral oil. Diflubenzuron treatment failed to fully stop egg laying, but the number of white eggs was significantly lower than it was in the control. Azadirachtin and abamectin achieved 100% efficacy, while the effectiveness of mineral oil was 97.4%, and that of diflubenzuron a mere 59%. All four insecticides significantly reduced the number of older (yellow) eggs and larvae, the efficacy being 80.5-92.6% (yellow eggs), 69.8-79.3% (larvae I-III instar) and 94.3-100% (larvae IV-V instar). In evaluation 38 DAT, azadirachtin,abamectin and mineral oil achieved 100% efficacy against white and yellow eggs, while diflubenzuron achieved 93% and 86.9% efficacy. All four insecticides were found to demonstrate high efficacy against I-III instar larvae (99.2-100%), but mineral oil treatmentalone achieved high efficacy against IV-V instar larvae (92.4%) as well. Efficacy evaluation against P. ulmi was carried out in a commercial orchard of the Red Chief apple cultivar located at Morović (Šid). Azadirachtin efficacy in controlling a summerpopulation of European red mite was compared to a mineral oil, clofentezine and spirodiclofen.The acaricides were applied when the number of P. ulmi motile forms was below the orientational damage threshold of 3 motile forms per leaf. Azadirachtin reduced significantly the number of motile forms, leaving it well below damage threshold by the end of the trial. Good control efficacy was achieved (77.2-90.4%), the highest level of efficacy being recorded at the end of the trial 38 DAT. In mineral oil treatment 7 DAT, efficacy was 92.4%; 14 DAT and 21 DAT it was 75.2% and 78.9%, and it dropped to below 60% at the end of the trial. The efficacy of clofentezine (39.4-68.2%) was unsatisfactory, which is probably the result of a resistance developing under high selection pressure of these compounds in the Morović locality in preceding years, while the newly introduced acaricide spirodiclofenshowed high and long-lasting efficacy (97.2%, 38 DAT). The results of the trials are discussed in terms of improving management of the populations of European red mite and pear psylla

The Effect of Spiromesifen on the Reproductive Potential of Tetranychus urticae Koch (Acari: Tetranychidae)

Laboratory bioassays were conducted to evaluate the effects of spiromesifen on the fecundity, fertility and population growth of two-spotted spider mite (Tetranychus urticae Koch) after treatment of pre-ovipositing females with five acaricide concentrations: 180mg/l (maximum recommended concentration for use in glasshouses against spider mites), 18 mg/l, 1.8 mg/l and 0.18 mg/l (the last one was discriminative for eggs and immatures in preliminary studies, i.e. produced 100% mortality of those stages) and 0.018 mg/l. After24h exposure, the percentages of females surviving treatment without visible symptoms of poisoning were 50% (180 mg/l), 45% (18 mg/l), 51% (1.8 mg/l), 74% (0.18 mg/l), 96% (0.018 mg/l) and 98% (0 mg/l). Over the first four days after treatment, the females that survived180 mg/l and 18 mg/l laid no eggs. The total number of eggs laid after treatment with these two concentrations was reduced to less than 2% against the control by the end of the trial. The females that survived 1.8 mg/l laid 50% less eggs, compared to the control, while the number of eggs laid by the females treated with 0.18 mg/l and 0.018 mg/l were 19% and 4% lower, respectively. Over the initial four days, egg hatch rates in treatments were 73-87%, and 92-93% in the control. Significant statistical differences between gross fecundity (FCg) and gross fertility (FTg) values in the control and treatments were detected for females surviving 180 mg/l, 18 mg/l and 1.8 mg/l. On the other hand, only the net fertility (FTn) value of females treated with 0.018 mg/l showed no statistically significant difference from the control value. Treatments with 180 mg/l and 18 mg/l significantly reduced the instantaneous rate of increase (ri) 6, 8 and 10 days after treatment, compared to the control. The negative ri values in those treatments indicated a declining population. Sublethal effects of spiromesifen and its impact on T. urticae management are discussed

Effectiveness of Biorational Pesticides for Controlling Some Vegetable Pests in Serbia

Biological effectiveness of three natural products (abamectin, azadirachtin and rapeseed spray oil) and three synthetic products with novel modes of action (acetamiprid, pymetrozine and metaflumizone) against greenhouse whitefly (Trialeurodes vaporariorum), two-spotted spider mite (Tetranychus urticae), green peach aphid (Myzus persicae), cabbage aphid (Brevicoryne brassicae) and cabbage worm (Pieris rapae) was evaluated in glasshouse and field trials at several localities in Serbia in 2004-2008. The effectiveness of these biorational pesticides was compared to several conventional products (alpha-cypermethrin, bifenthrin, dimethoate, diazinon, fenazaquin and pirimiphos-methyl). In glasshouse trials, the efficacy of abamectin against T. vaporariorum in tomato and T. urticae in cucumber was 96.1% and 92.2%, respectively. In controlling T. vaporariorum, pymetrozine achieved 94.1% efficacy, and acetamiprid 94.7%, while the efficacy of rapeseed oil against T. urticae was 84.1-94.6%. In field trials, the efficacy of acetamiprid, pymetrozine and rapeseed oil against M. persicae in pepper was 100%, gt 97% and gt 92%, respectively, and against B. brassicae gt 94%, gt 92% and gt 93%, respectively. In controlling P. rapae, metaflumizone achieved 92.8% and azadirachtin 85.3% efficacy. The conventional pesticides were found to have the same or slightly lower efficacy than biorational ones. The importance of these results for vegetable pest control is discussed

EFFECTIVENESS OF BIORATIONAL PESTICIDES FOR CONTROLLING SOME VEGETABLE PESTS IN SERBIA

Biological effectiveness of three natural products (abamectin, azadirachtin and rapeseed spray oil) and three synthetic products with novel modes of action (acetamiprid, pymetrozine and metaflumizone) against greenhouse whitefly (Trialeurodes vaporariorum), two-spotted spider mite (Tetranychus urticae), green peach aphid (Myzus persicae), cabbage aphid (Brevicoryne brassicae) and cabbage worm (Pieris rapae) was evaluated in glasshouse and field trials at several localities in Serbia in 2004-2008. The effectiveness of these biorational pesticides was compared to several conventional products (alpha-cypermethrin, bifenthrin, dimethoate, diazinon, fenazaquin and pirimiphos-methyl). In glasshouse trials, the efficacy of abamectin against T. vaporariorum in tomato and T. urticae in cucumber was 96.1% and 92.2%, respectively. In controlling T. vaporariorum, pymetrozine achieved 94.1% efficacy, and acetamiprid 94.7%, while the efficacy of rapeseed oil against T. urticae was 84.1-94.6%. In field trials, the efficacy of acetamiprid, pymetrozine and rapeseed oil against M. persicae in pepper was 100%, gt 97% and gt 92%, respectively, and against B. brassicae gt 94%, gt 92% and gt 93%, respectively. In controlling P. rapae, metaflumizone achieved 92.8% and azadirachtin 85.3% efficacy. The conventional pesticides were found to have the same or slightly lower efficacy than biorational ones. The importance of these results for vegetable pest control is discussed

Life History Traits and Population Growth of Greenhouse Whitefly (Trialeurodes vaporariorum Westwood) on Different Tomato Genotypes

The effects of five tomato genotypes (cv. Narvik and hybrids NS-6, Tamaris, Alliance and Marko) on the survival, reproduction, development and population growth of the greenhouse whitefly Trialeurodes vaporariorum were examined. A laboratory population of T. vaporariorum had been reared on tobacco plants for three years before the study. Females that laid eggs on the genotype Marko lived significantly longer and their offspring needed significantly shorter periods to develop than females on the genotype Narvik. The highest gross and net fecundity rates were found in females on the genotype Marko (36.74 eggs/ female and 27.93 eggs/female, respectively) and they differed significantly from the corresponding rates of females living on the genotype NS-6 (18.55 eggs/female and 15.33 eggs/ female), who had the lowest fecundity rates. The highest gross and net fertility rates were also found in females on the genotype Marko (31.24 adults/female and 23.73 adults/female), and they were significantly higher than those of females living on NS-6 (14.85 adults/female and 12.53 adults/female). Besides, net fertility rate of the females living on the genotype Narvik (13.80 adults/female) was also significantly lower than the rate of females on Marko. The instantaneous rates of increase showed no significant difference over a 10-day interval following the start of oviposition, while the increase rate was significantly higher on the genotype Marko after 12, 14 and 16 days, compared to the genotype NS-6. Eighteen, 20 and 22 days after the beginning of oviposition, the instantaneous rate of increase on the genotype Marko was significantly higher than it was on NS-6 and Narvik. Our data provide a basis for further research aiming to improve programs of integrated management of greenhouse whitefly

Efectiveness of Spirodiclofen in the Control of European Red Mite (Panonychus ulmi) on Apple and Pear Psylla (Cacopsylla pyri)

The effectiveness of spirodiclofen, an acaricide and insecticide with a novel mode of action, in protecting apple from the European red mite (Panonychus ulmi) and pear from pear psylla (Cacopsylla pyri) was tested in field trials in four sites in Serbia in 2004, 2005 and2007. The efficacy of P. ulmi control was investigated at Morović(Šid), where the effects of spirodiclofen were compared with those of fenazaquin, clofentezine, fenpyroximate and bifenthrin. Applied in 2004 at a rate of 0.096 g a.i. L-1 against the overwintering eggs ofP. ulmi, spirodiclofen achieved 86% efficacy, while the efficacies of fenazaquin and clofentezine (25 days after treatment) were 84.4% and 27.8%, respectively. In the same season, spirodiclofen displayed high and prolonged efficacy against a summer population of P. ulmi: the efficacy of this acaricide applied at concentrations of 0.096 and 0.144 g a.i. L-1 was 98% and 96.9%, respectively, while fenpyroximate, clofentezine and bifenthrin achieved 43%, 59.5% and 62% efficacy, respectively (45 days after treatment). This effect of spirodiclofen against the summer population was confirmed in the same site in 2005, when 94.9-95.7% efficacy was achieved (47 days after treatment). The efficacy of spirodiclofen, amitraz and abamectin against eggs and larvae of the first generation of C. pyri was examined at a Bela Crkva site in 2004, and in sites at Mandjelos (Sremska Mitrovica) and Bela Crkva in 2005. Applied at a concentration of 0.144 g a.i. L-1 at the beginning of hatching, spirodiclofen was found to achieve 83.2-95% efficacy, abamectin 93.5-94.9% and amitraz 78.9-95.6% efficacy (14 days after treatment). Applied in a site at Borkovac (Ruma) in 2007 at a rate of 0.096 g a.i.L-1 before hatching of the first generation larvae, spirodiclofen reduced the number of eggs and larvae of C. pyri by 72%, 82% and 89% in evaluations 18, 25 and 38 days after treatment, while abamectin and diflubenzuron achieved reductions of 92%, 95% and 91%, and 78%,71% and 86%, respectively