AQUEOUS SOLUTIONS OF CHITOSAN: VISCOMETRIC AND FLOCCULATION PROPERTIES

The hydrodynamic and flocculation properties of aqueous solution of chitosan (CS) were investigated at room temperature. The viscometric data of dilute CS solutions were discussed in terms of Wolf method as a function of polymer concentration, salt nature (NaCl, NaNO3, and CaCl2) and concentration. The flocculation properties in emulsions of some commercial pyrethroid insecticides (Fastac 10 EC (F), Decis (Dc) and Karate Zeon (KZ)) were evaluated. The viscosity measurements reveal that the experimental data fit well with the Wolf model and the [η] values decrease in salt aqueous solutions. For the same insecticide concentration (0.02%, v/v), UV-Vis spectroscopy measurements show maximum removal efficiency around 90% for Fastac 10EC and Decis and 80% for Karate Zeon. The residual KZ absorbance decreased with the increase of insecticide concentration in the initial emulsion, from 80% for the lowest concentration (0.02%, v/v) to around 90% for the highest one (0.06%, v/v). The supernatant zeta potential dependence on the chitosan dose pleads for the charge neutralization as the main mechanism for the flocculation of pyrethroid insecticide particles.

Differences in Bifenthrin and Fipronil Susceptibility Among Invasive Latrodectus spp. (Araneae: Theridiidae) and Nontarget Spiders in Japan

Prompt responses to invasive Latrodectus spiders introduced unintentionally are needed worldwide due to their medical and ecological importance. Latrodectus species are chemically controlled using pyrethroid insecticides despite concerns about the ecological impacts of these compounds on biodiversity/ecosystems. Here, the relative sensitivities (acute toxicity: 48-h LC50) of Latrodectus hasseltii Thorell and Latrodectus geometricus C.L. Koch from Japan to the conventional neurotoxic insecticide bifenthrin (pyrethroid) and a new candidate insecticide, fipronil (phenylpyrazole), were examined. Acute residual toxicity tests of these compounds in two nontarget spiders (Parasteatoda tepidariorum C.L. Koch (Araneae: Theridiidae), Badumna insignis L. Koch (Araneae: Desidae)) were conducted for comparison. To test whether bifenthrin and fipronil toxicities differed among the four spiders, corresponding species sensitivity distributions (SSDs) were compared, and hazardous concentrations were determined. Sensitivity (especially in the nontarget species) was two to four orders of magnitude higher for bifenthrin than for fipronil. The SSD patterns of the two insecticides differed significantly, with the spider communities being more sensitive to bifenthrin than to fipronil. The lethal bifenthrin concentration for Latrodectus may reduce spider populations by over 70–90%. If L. hasseltii (established throughout Japan) is targeted for effective population suppression rather than L. geometricus (with a limited distribution range) using the specified insecticide concentration (LC50 value) for fipronil, less than 20% of spider communities will be impacted. Chemical operations aimed at the effective population management and subsequent eradication of invasive Latrodectus spiders while supporting local biodiversity conservation would benefit from considerations of fipronil dosages and target species sensitivities.

Locomotor response of diamondback moth (Plutella xylostella) populations to a neurotoxic insecticide under laboratory conditions

ABSTRACT: The present study aimed to evaluate changes in the locomotor activity of diamondback moth (Plutella xylostella) populations exposed to surfaces treated with the insecticide chlorantraniliprole under laboratory conditions. Diamondback moth populations from municipalities incorrectly using the insecticide [Camocim de São Félix, PE (CSF); Sairé, PE (SR); and Lajedo, PE (LJ)] and two laboratory populations from Recife, PE (RCF), and Viçosa, MG (VÇS) were exposed to dry insecticide residues in increasing concentrations. The following behavioral parameters of the populations were analyzed: walking time (WT), mean walking speed (MWS), and rest time (RT). Regarding RT, the SR and CSF populations demonstrated a behavior of irritability and increased WT with increased exposure concentration. The RCF population presented a contrasting response. The MWS values in the SR and CSF populations showed a decreasing trend with increased exposure concentration. The LJ and RCF populations showed no changes in terms of MWS. The RT values in the SR population decreased with increased insecticide concentration. In general, the SR and CSF populations presented a behavioral pattern different from that of laboratory populations. The changes in locomotor activity observed may result in lower control efficacy of the insecticide due to repellency or escape of insects. Regarding the effect of insecticide concentrations used in the populations, a defined pattern was not observed, and the effect alternated between an increase, a decrease, and an undefined pattern for the variables studied.

Experimental Studies on Locally Produced Insecticide (Ota-piapia)

Introduction: Nigeria, like most countries worldwide find insect pest control a problem, unfortunately, the insecticides available are somewhat costly to the general populace, hence the dependence on the cheaply produced and widely available local insecticide famously called ‘Ota piapia’ literally translating to kill and dry. This study was carried out to determine the safety of ‘Ota piapia’ using Wistar rats as an animal model. Materials and Methods: Fifteen rats were divided into five groups and exposed dermally to 0%, 25%, 50%, 75% and 100% of insecticide concentrations respectively. Evaluation of their behaviour, haematological indices, liver enzyme {alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST)} and gas chromatography mass spectrometry (GC-MS) analysis of the insecticide was used as experimentally indices in evaluating safety limits of the local insecticide. Results: Behaviorally, the rats with higher concentrations of insecticide application showed acute signs of toxicity, with an increase in pack cell volume (PCV%) and lymphocyte and decrease in (total white blood cell count (TWBC) and neutrophils counts hematologically. There was a dose-dependent relationship between insecticide concentration and ALT and ALP activities, while this was not consistent with AST activity. The GC-MS analysis of the insecticide gave 43 components; mainly organic compounds with dichlorvos its main active component, having the highest percentage of 12.74%. Conclusion: Increased PCV%, decreased TWBC and neutrophil counts established in this study and its significant adverse effect on the serum level of liver enzymes implied that the local insecticide ota-pia pia is toxic and must be used with caution.

Tingkat Resistensi Helopeltis antonii (Hemiptera: Miridae) pada Tanaman Kakao terhadap Tiga Golongan Insektisida Sintetis

<em>In Indonesia, </em>Helopeltis antonii<em> Signoret is one damaging pest in cacao plant which may </em><em>cause 60% production loss. Farmers have been using synthetic insecticides to control it. However, insecticides use with inappropriate dose can lead to resistance. The research aimed to determine the resistance level of </em>H. antonii<em> </em><em>against three types of insecticides. The research was conducted at Green House of Indonesian Spice and Medicinal Crops Research Institute, Bogor. Collection of field population and interview of insecticides use was conducted at cacao plantation in Bogor, Ciamis, and Sukabumi, West Java from August 2016 to June 2017. The insect used was 3rd instar which divided into two groups, laboratory and field populations. Insecticides used contained active ingredients of chlorpyrifos (organophosphate), lambda-cyhalothrin (pyrethroid), and thiamethoxam (neonicotinoid). Cucumber was used as feed substitute for the multiplication of </em>H. antonii<em> test. The e</em><em>xperiment was performed using five insecticide concentrations determined by preliminary test result. The relationships between insecticide concentration and insect mortality was analyzed by probit program. The interviews indicated that the insecticides widely used by farmers are pyrethroid type. The result demonstrated that field population of </em>H. antonii<em> </em><em>from Bogor and Ciamis were resistant to lambda-cyhalothrin with resistance ratio (RR) of 4.2 and 10.8, respectively, whereas population from Sukabumi had RR value of 1.2. All field population of </em>H. antonii<em> showed resistance indication against thiamethoxam with RR ranged </em><em>from 1.8 to 3.1. Resistance indication to chlorpyrifos was only shown by population from Bogor (RR 1.5).</em>

Integrated Effects of Host Resistance and Insecticide Concentration on Survival of and Turfgrass Damage by the Fall Armyworm (Lepidoptera: Noctuidae)

The residual activity of six concentrations of chlorpyrifos, spinosad, and halofenozide on fall armyworm, Spodoptera frugiperda (J. E. Smith), as mediated by five warm-season turfgrass cultivars expressing varying levels of genetic resistance was evaluated in greenhouse trials. Similarly, varying concentrations of halofenozide were applied to six turfgrass cultivars in the field; mortality of neonate and third-instar fall armyworms was assessed. Reduced rates of chlorpyrifos resulted in lower fall armyworm survival on resistant zoysiagrass cultivars relative to that on bermudagrass or paspalum. In a separate trial when treated with spinosad, survival on the same zoysiagrasses was equal to or greater than that on more susceptible bermuda or paspalum. Reduced rates of halofenozide in another greenhouse trial resulted in lower survival on resistant zoysiagrasses at some concentrations at 7, but not at 14, days exposure compared to more susceptible grasses. In the field, at the full labeled rate of halofenozide, 100% mortality was observed regardless of turfgrass cultivar. Larval survival on the most susceptible turf, “TifEagle”, was higher than that on the remaining turf cultivars at the intermediate rate applied. Larvae exposed to treated turf as third instars displayed a trend toward greater survival at intermediate rates on the two paspalums, “Sea Isle 1” and 561-79, while a trend toward lower survival was observed on “Palisades” and “Cavalier” zoysiagrasses. Factors potentially contributing to the variation in responses observed in the present study include different modes of action of insecticides, host plant resistance mechanisms, differential foliar consumption rates and insecticide dose in relation to body weight. Development of management guidelines for pest management practitioners must address the complexity of potential interactions and may require “case by case” evaluation.

Temperature dependent effects of insecticides on sugar beet weevil - Bothynoderes punctiventris Germ

The aim of the investigation was the assessment of toxicity of different insecticides to Bothynoderes punctiventris Germ. at different temperature (14, 20 and 25?C) under controlled conditions. B. punctiventris adult were exposed to Monokrotofos 20-WSC (Monocrotophos) at concentration 0.4, 0.2 0.1%, Agrometrin 20-EC (Cypermethrin) at 0.05, 0.025. 0.012% and Cimogal (Monocrotophos + Cypermethrin) at 0.1, 0.05 and 0.025% applied at filter paper and fed with treated sugar beet seedlings. The exposition time varied from l to 28 h and was determined upon insecticides toxicity. The effect was assessed upon mortality percentage. The mortality was found to be dependent on insecticide concentration and temperature conditions. After being exposed 18 h at 14?C to Monocrotophos, dependent on concentration applied the mortality ranged from 35 to 63,8%. At 20?C, the corresponding values ranged from 70.8 to 76.3%, at 25?C - from 46.3 to 100%. Under same conditions exposition to Cypermethrin 4 h at 14?C gave mortality from 66.3 to 100% 28.8-83.8% at 20?C and from 1.3 to 55% at 25?C. After being exposed only 3 h to Monocrotophos+Cypermethrin mortality ranged from 10,0 to 68.8% at 14?C 27.5 to 98.8% at 20?C and 1.3 to 37.0% at 25dC. The highest mortality of B. punctiventris adults was induced by Cypermethrin at 14?C, with Monocrotophos at 25?C and Monocrotophos + Cypermethrin at 20?C. It was concluded that temperature conditions dictate the choice of insecticide for B. punctiventris control. The environmental conditions during applications are of vital importance for successful control.