Persistence Of Imidacloprid Research Articles

Movement, Toxicity, and Persistence of Imidacloprid in Seedling Tabasco Pepper Infested with Myzus persicae (Hemiptera: Aphididae)

Application of imidacloprid to the soil in which Tabasco pepper, Capsicum frutescens L., seedlings were growing was highly effective against the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae). In just 48 h after the soil drench, aphid numbers on treated plants declined from 292.1 to 33.0 per plant, a reduction of 89%. By 72 and 96 h after the application, the reductions were 97 and 100%, respectively. Reductions in green peach aphid numbers also indicated that imidacloprid readily moved throughout the Tabasco pepper plant. Although, initial green peach aphid reductions at 24 and 48 h after imidacloprid application to soil, were greater on the lower leaves than on the upper leaves, by 72 h toxicity was high throughout the plant. At 48 h, overall green peach aphid reduction on seedlings grown in wet soil was significantly higher than that on plants growing in the drier soil. Regardless of soil moisture or leaf location, no live green peach aphids were detected on treated seedlings after 96 h. After the initial uptake period, toxicity to green peach aphid remained high for 5 wk. Under Tabasco pepper production conditions in Central America, the greatest need for aphid management is just after transplanting. Imidacloprid soil drenches before transplanting should offer the Tabasco pepper producer an extended period of aphid-free production.

Identification of Aldehyde Oxidase as the Neonicotinoid Nitroreductase

Imidacloprid (IMI), the prototypical neonicotinoid insecticide, is used worldwide for crop protection and flea control on pets. It is both oxidatively metabolized by cytochrome P450 enzymes and reduced at the nitroguanidine moiety by a previously unidentified cytosolic "neonicotinoid nitroreductase", the subject of this investigation. Two major metabolites are detected on incubation of IMI with rabbit liver cytosol: the nitrosoguanidine (IMI-NO) and the aminoguanidine (IMI-NH2). Three lines of evidence identify the molybdo-flavoenzyme aldehyde oxidase (AOX, EC 1.2.3.1) as the neonicotinoid nitroreductase. First, classical AOX electron donor substrates (benzaldehyde, 2-hydroxypyrimidine, and N-methylnicotinamide) dramatically increase the rate of formation of IMI metabolites. Allopurinol and diquat are also effective electron donors, while NADPH and xanthine are not. Second, AOX inhibitors (potassium cyanide, menadione, and promethazine) inhibit metabolite formation when N-methylnicotinamide is utilized as an electron donor. Without the addition of an electron donor, rabbit liver cytosol reduces IMI only to IMI-NO at a slow rate. This reduction is also inhibited by potassium cyanide, menadione, and promethazine, as well as by additional AOX inhibitors, cimetidine and chlorpromazine. Finally, IMI nitroreduction by AOX is sensitive to an aerobic atmosphere, but to a much lesser extent than cytochrome P450 2D6. Large species differences are observed in the IMI nitroreductive activity of liver cytosol. While rabbit and monkey (Cynomolgus) give the highest levels of total metabolite formation, human, mouse, cow, and rat also metabolize IMI rapidly. In contrast, dog, cat, and chicken liver cytosols do not reduce IMI at appreciable rates. AOX, as a neonicotinoid nitroreductase, may limit the persistence of IMI, and possibly other neonicotinoids, in mammals.

Persistence of Imidacloprid in/on Cabbage and Cauliflower

Persistence of Imidacloprid in/on Cabbage and Cauliflower

Effect of pH and type of formulation on the persistence of imidacloprid in water.

Imidacloprid [ 1-[(6-Chloro-3 -Pyridinyl) methyl ]- N-nitro -2- Imidazolidinimine] is a newly introduced broad spectrum systemic insecticide in the Indian subcontinent by M/s. Bayer India Ltd.. This new chloronicotinyl compound is fairly soluble in water as compared to other non-polar insecticides (Kagabu 1997). It is effective against sucking insects, soil insects, termites and some species of chewing insects and is used as seed dressing, soil treatments and foliar treatment in different crop (Tomlin 1994). Some information regarding the fate of imidacloprid in soil are available (Cox et al. 1997; Rouchaud et al. 1994; 1996 ). Photolysis of the insecticide in aqueous solution was reported by Moza et al. (1998). But little is known about its persistence behaviour in water. The objective of the present investigation is to evaluate the effect of pH of water as well as the type of formulations on the persistence behaviour of imidacloprid in aqueous solution. MATERIALS AND METHODS Analytical grade imidacloprid (purity 99%) and its two formulations - Confidor 200 SL and Gaucho 70 WS were obtained from Ms. Bayer India Ltd.. The reagents used were of analytical grade and the solvents were HPLC grade. The buffer solutions (Titrisol of pH - 4.0, 7.0 and 9.0, E. Merck India Ltd.) were added @ 50mL/500mL of water (HPLC grade) and are designated as A, B and C respectively. 100 ml of these buffered solutions were taken in amber colored glass bottles. Contidor 200 SL (0.5 g) was dissolved in 1.0 L of water (100 µg/mL a.i.) and suitably diluted to 1.0 µg/mL of imidacloprid in the final solution. From this stock solution, Confidor 200 SL (imidacloprid) was applied @ 0.078 mg/L a.i. (T1) and 0.155 mg/L a.i. (T2) in different batches of water (A, B, C) in three replicate numbers. Seven such sets were prepared for sampling at 0, 7, 15, 20, 30, 45 and 60 d after application of the pesticide. All the bottles were kept under room temperature (30 ± 5°C). Solution of Gaucho 70 WS (0.5 g/L) was also prepared (350 µg / mL a.i.) in the same manner, diluted to 1.0 µg/mL of imidacloprid and was applied to different sets of water as described above.

Response of Bemisia argentifolii (Homoptera: Aleyrodidae) to Imidacloprid Under Greenhouse, Field, and Laboratory Conditions

The systemic insecticide imidacloprid has been used successfully to manage Bemisia argentifolii Bellows & Perring and whitefly-borne geminivirus on tomato in south Florida and elsewhere. We evaluated plant and whitefly responses to imidacloprid in greenhouse grown tomato, Lycopersicon esculentum Miller, transplants and field-grown fresh market staked tomato. Seedlings in transplant trays treated with 1 or 2 mg (AI) per plant applied as a drench were protected from egg deposition for up to 6 wk of exposure to a greenhouse colony of whiteflies. In the field, either 280 or 560 g (AI) ha of imidacloprid applied to the soil at transplanting provided protection from all whitefly stages and was better than or equal to protection obtained with weekly sprays of organophosphate/ pyrethroid insecticide mixtures for up to 9 wk. Movement of geminivirus infection vectored by whitefly adults was suppressed in small plots, indicating that imidacloprid acted rapidly on adults. Treated tomato or eggplant, Solanum melongena L. ‘Black Beauty’, functioned as trap crops by reducing whitefly numbers on adjacent untreated tomato. High application rates and persistence of imidacloprid have combined to increase the likelihood of insecticide resistance and to necessitate the development of an easily reproducible bioassay to facilitate monitoring. A leaf-dip bioassay indicated that the LC50 for 10-d-old whitefly nymphs to imidacloprid was 6.1 mg (AI) /liter and the LC90 32.6 mg (AI) /liter. These results could serve as a baseline for whitefly susceptibility in south Florida, given the lack of any previous exposure to imidacloprid of the tested population.