Application Of Dimethoate Research Articles

Seasonal Incidence of Insect Pests and Natural Enemies in Foxtail Amaranthus and Spinach and Efficacy of Dimethoate Against Insect Pests Infesting Leafy Vegetables

An investigation was made to study the efficacy of dimethoate against sucking and defoliator pest-infesting foxtail amaranths and spinach. The efficacy of dimethoate was evaluated at two doses, one at the recommented does of 200 g active ingredient (a.i.) ha-1 and other at double the recommended dose of 400 g a.i. ha-1 along with control and the other at double the recommended dose of 400 g a.i ha-1 along with control. The incidence of leaf webber (Hymenia recurvalis), ear-head bug (Cletus pugnator), Thrips (Thrips tabaci) and leaf miner (Liriomyza trifoli) were observed in foxtail amaranth. In spinach, leaf-eating caterpillars (Spodoptera litura), cutworm (Agrotis ipsilon) and Thrips (Thrips tabaci) were recorded. In spinach at the third leaf stage, nearly 9.20% leaf defoliation, 10.34% leaf damage and a mean thrips population of 3.48/five plants with a mean predator population of 0.32/ five plants were recorded. In the efficacy study, dimethoate was efficient in reducing the infestation of the leaf webber population with pre-mean count of 4.4± 0.87 in control and 1.2± 0.03 in X dose and 0.0± 0.0 in 2X dose after a day after treatment (DAT) in foxtail amaranths. In an efficacy study of dimethoate on thrips in spinach and foxtail amaranth, a complete reduction of thrips population was observed on 3 DAT at X dose and 2X dose with mean thrips population on control was 17.1± 2.12 in spinach and 8.5± 1.24 in foxtail amaranth 3 DAT. These findings indicate that dimethoate application has promising potential as a practical approach for managing insect pests in foxtail amaranth and spinach crops.

The economic efficiency of using protective measures in combating rice pests

In the conducted research in the conditions of the Karatal District of the Zhetysu Region, an analysis of the economic efficiency of rice pest control methods was performed. Among the main pests damaging the crops are the coastal fly, barley miner, and rice midge. The use of the insecticide dimethoate led to a significant reduction in damage from the coastal fly, increasing the biological efficiency to 90.9-94.2%. This, in turn, resulted in an increase in yield by 2.7-3.6 tons/ha compared to the control group. Data analysis also showed that the application of dimethoate is accompanied by a reduction in rice cultivation costs and an increase in net income. The profitability level of using this insecticide was 69.4%, indicating its high effectiveness in terms of agricultural economics. Additionally, the return on additional expenses for protecting rice crops using dimethoate reaches 2.1 times, confirming the economic feasibility of this protection method. Thus, the research results underscore the importance of applying modern rice protection methods and their positive impact on the economic outcome in the region's agriculture. They also justify the need for further research in this area to optimize the rice cultivation process considering economic aspects. Data analysis also showed that the application of dimethoate is accompanied by a reduction in rice cultivation costs and an increase in net income. The profitability level of using this insecticide was 69.4%, indicating its high effectiveness in terms of agricultural economics. Additionally, the return on additional expenses for protecting rice crops using dimethoate reaches 2.1 times, confirming the economic feasibility of this protection method. Thus, the research results underscore the importance of applying modern rice protection methods and their positive impact on the economic outcome in the region's agriculture. They also justify the need for further research in this area to optimize the rice cultivation process considering economic aspects.

Oxidative stress in Arthrospira platensis by two organophosphate pesticides.

Although it is known that organophosphate insecticides are harmfull to aquatic ecosystems, oxidative damages caused by Dimethoate and Chlorpyrifos are not studied on Arthrospira platensis Gomont. In this study, various Chlorpyrifos (0-150 µg mL-1) and Dimethoate (0-250 µg mL-1) concentrations were added to the culture medium in laboratory to evaulate growth rate, chlorophyll-a content and antioxidant parameters of A. platensis. Optical Density (OD560) and chlorophyll-a decreased compared to the control for seven days in both pesticide applications. Superoxide dismutase (SOD) activity increased at 50 µg mL-1 Chlorpyrifos concentration but it decreased at all concentrations. Although Ascorbate peroxidase (APX) and glutathione reductase (GR) activities increased with Chlorpyrifos application, they did not change with Dimethoate application. Malondialdehyde (MDA) amount decreased at 150 µg mL-1 Chlorpyrifos concentration but it increased in Dimethoate application. The H2O2 content were increased in both applications. Proline decreased in 50 and 75 µg mL-1 Chlorpyrifos concentrations and increased at 150 µg mL-1 concentration, while it increased at 25 µg mL-1 Dimethoate concentration. The results were tested at 0.05 significance level. These pesticides inhibit A. platensis growth and chlorophyll-a production and cause oxidative stress. The excessive use may affect the phytoplankton and have negative consequences in the aquatic ecosystem.

Simultaneous determination of dimethoate and its metabolite omethoate in curry leaf using LC-MS/MS and risk assessment.

This study presents the method development, validation, and simultaneous determination of dimethoate and its metabolite omethoate in curry leaf. Samples were extracted following modified quick, easy, cheap, effective, rugged, and safe extraction protocol and analyzed using liquid chromatography-tandem mass spectrometry. The limit of quantification in the matrix was 0.005μgg-1 for dimethoate and omethoate. Extraction using acetonitrile recorded the average recoveries in the range of 82.25 to 112.97% for dimethoate and 85.57 to 107.22% for omethoate at 0.005, 0.025 and 0.050μgg-1 fortification levels and relative standard deviation less than 5%. Similarly, the relative standard deviation values for intraday (Repeatability) and interday (Reproducibility) tests were less than 15%. Dissipation kinetics of dimethoate 30% emulsifiable concentrate at 200 and 400ga.ih-1 recorded initial deposits of 5.20 and 10.05μgg-1 and 0.33 and 0.48μgg-1 for dimethoate and omethoate, respectively, and half-life of 3.07 and 3.34days. The estimated hazard index value found more than one at a day after dimethoate application. It is not safe for consumer health to use curry leaves in the initial days after application.

Management of Blue Gum Chalcid (Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae) infestation on different species of Eucalyptus trees in Kalu district, Eastern Amhara, Ethiopia

The recently introduced chalcid pest known as the Blue Gum Chalcid (BGC) (L. invasa) is currently one of the major insect pests of Eucalyptus tree species in Ethiopia. A research was conducted in Kalu district, South Wollo, Eastern Amhara, Ethiopia, the main objective of which was to evaluate the effectiveness of synthetic insecticides, hoeing and water showering options against BGC. Two parallel experiments were conducted in the nursery and in the field. Eucalyptus camaldulensis, E. saligna, E. viminalis, E. citrodora and E. globulus were considered in the nursery at Chorisa. One to three-year old E. camaldulensis plantations were considered at Tikuro plantation site. At the nursery, seven treatments and at the field 10 treatments were tested in a Randomized Complete Block Design (RCBD) with three replications from January to February 2019, where treatments were applied 3 times at 15-day intervals. Results from the 1-year old plantation revealed that application of Dimethoate 40%, Carbofuran 3G and Dimethoate 40% + hoeing followed by Carbofuran 3G + hoeing and Thiamethoxam 25WG were effective in checking the BGC insect pest infestation. In the 3-year old plantation, Carbofuran 3G significantly reduced the infestation followed by Dimethoate 40%. At the nursery, Dimethoate 40% and Carbofuran 3G reduced the infestation followed by Carbofuran 3G + Dimethoate 40% and thiamethoxam 25WG. Water showering and hoeing did not reduce BGC infestation in all cases at the field plantations. Treatments that received synthetic insecticides and hoeing had low infestation, the reason for which was the insecticide rather than the hoeing, because the hoeing alone didn’t differ from the control. Application of Dimethoate 40% and Carbofuran 3G with hoeing and weeding activities were recommended to manage and limit BGC insect pest infestations.

Sorption-desorption of dimethoate in urban soils and potential environmental impacts.

The environmental fate and impact of dimethoate application in the urban environment were assessed in nine selected soils. The pseudo-second-order kinetics model described the kinetics of dimethoate sorption very well in the urban soils exhibiting two distinct phases, an initial partitioning into clay surfaces and soil organic matter, and eventual diffusion into soil micropores. Dimethoate sorption in the urban soils followed the Freundlich model with an R2 value of 0.94-0.99, suggesting a multi-layered sorption on the heterogeneous surfaces. Sorption of dimethoate in the soils was influenced by clay, silt, organic matter, carboxyl and alkyl groups, and Al and Fe oxides. The undecomposed or incompletely decomposed organic matter present in the soils greatly reduced the sorption and enhanced desorption. The calculated lower values for Freundlich constant (KF) indicate the high mobility of dimethoate in the selected soils. Also, the values of groundwater ubiquity score (GUS), leachability index (LIX), hysteresis index (HI), and coefficient of distribution (Kd) for dimethoate in the soils clearly suggest that the insecticide is prone to leaching out significantly from the soil surface to groundwater. Moreover, the surface runoff from impervious places in the urban environment can be considered as a direct source of groundwater contamination, thereby affecting the quality of potable water besides posing a threat to non-target organisms of ecological importance and food safety. Thus, the present novel study suggests that the application of dimethoate in the urban environment having impervious surfaces must be judicious in order to minimize the potential human and ecological health risks.

The Role of Dimethoate and UV-B on Skin of Wistar Rats

The pesticide dimethoate (O-dimethyl-S- Nmethylcarbamoylmethyl phosphorodithioate) is able to induce severe acute toxicity in living organisms. The aim of this study was to evaluate the effects of ultraviolet radiation, alone or combined with exposure to dimethoate, on the rat skin. A total of 38 Wistar female rats (Rattus norvegicus albinus), were distributed into four groups: A (n=9) control group, B (n=10) exposed to ultraviolet-B radiation (UV-B), C (n=10) exposed to UV-B followed by application of dimethoate (UV-B+AGRO) and group D (n=9) exposed to dimethoate (AGRO). Histological examination of the tissues, as well as immunohistochemistry for cleaved caspase 3, Ki-67 and COX-2 expression were performed to all groups. Animals submitted to UV-B exhibited hyperkeratosis with moderate cell atypia. Regarding exposure to UV-B+AGRO, the animals presented hyperkeratosis and atrophy, whereas in animals exposed to AGRO, only atrophy was noticed. The immunohistochemical results on skin revealed that UVB, AGRO and UVB+AGRO decreased cleaved caspase 3 and Ki-67 expression when compared to the control group (p<0.05). COX-2 expression decreased to UVB or AGRO groups compared to controls (p<0.05). UV-B or AGRO exposure is able to induce histopathological changes and altered expression of cleaved caspase-3 and Ki-67 in rat skin, thus being categorized as a risk condition for skin carcinogenesis.

A Re-Evaluation of Olive Fruit Fly Organophosphate-Resistant Ace Alleles in Iberia, and Field-Testing Population Effects after in-Practice Dimethoate Use.

The management of the olive fruit fly (Bactrocera oleae) is traditionally based upon the use of organophosphate insecticides, mainly dimethoate. In this evolutionary arms race between man and pest, the flies have adapted a pesticide resistance, implying two point-mutations of the Ace gene -I214V and G488S- and a 9bp deletion -Δ3Q. We revisited 11 Iberian locations to evaluate this adaptation of organophosphate (OP)-resistant alleles through amplicon sequencing. Screening for populations where the wild type is prevalent allows an identification of hotspots for targeted mitigation measures; we have hence refined the scale to the region with the lowest OP-resistant alleles frequency 71 locations were sampled and individuals checked using a fast and low-cost allele-specific-primer polymerase chain reaction (ASP-PCR) method]. An increase in Ace gene point-mutations was observed, and the Δ3Q mutation remains undetected. The lowest frequencies of the OP-resistant alleles remain in the west, underlining the hypothesis of an introduction of resistance from eastern Mediterranean areas. A field test was performed by sampling the fly population before and after in-practice dimethoate application. A clear reduction in olive fruit fly numbers was observed, with no relevant changes in the genotypic frequencies of the resistance alleles. The findings are discussed in frame of the type and intensity of the selection pressure that has led to the adaptation to resistance and its consequences from the producer perspective.

Residual degradation and toxicity of insecticides against Bactrocera oleae.

Field and lab trials took place in Crete (July to September 2016), concerning the residual degradation and toxicity of seven active ingredients applied as bait sprays against the olive fruit fly. Highest residues were recorded in olive leaves for dimethoate and phosmet (~60mg/kg) immediately after application (day 1+), while a threefold and fivefold reduction was observed 1week later, respectively. Residues of pyrethroids were determined at lower levels (<10mg/kg) but remained almost stable for a longer period of time. Finally, thiacloprid and spinosad residues were determined at 5.81 and 0.19mg/kg respectively (day 1+), and rapidly decreased below the LOQ. Highest toxicity against the olive fruit fly was observed just right after the application of dimethoate (100%), a-cypermethrin (80%), and L-cyhalothrin (72.92%). Although the toxicity of dimethoate was significantly reduced 1week after the application (80%) and then minimized, toxicity of pyrethroids remained almost stable (>60%) for the first 2weeks and then decreased to 30-40%, which remained stable up to the end of the study (8weeks). Concerning phosmet, its toxicity ranged from 35 to 56% for 3weeks with no significant reduction, while spinosad presented a lower toxicity profile (50% only for 1week). The benefits of these results in the knowledge of insecticide residues and their toxicity against olive fruit fly can be used for improving olive fruit fly control.

Efficacy of sowing dates integrated with insecticides against pea aphid (Acyrthosiphon pisum) on lentil

An experiment was conducted at Enewari research site, Debre-Birhan, Ethiopia during the main cropping seasons of 2010–11 and 2011–12 to determine best combination(s) and/or sole practice(s) of sowing date and insecticide management options against pea aphid Acyrthosiphon pisum using Randomized Complete Block Design with three replications. Before application of foliar dimethoate, the earliest sown lentil irrespective of seed dressing (with “Apron-Star”) harboured maximum aphids followed by August 9th and 20th sowings. The pooled data revealed that July 29th, August 9th and 20th sowings having sprayed with dimethoate gave higher yield of 1882.45, 1927.03 and 1843.80 kg ha−1, respectively compared to all other combinations. This suggests that early planting of lentil combined with single foliar application of dimethoate 40% EC could help avoid economic damage and the best sowing date was August 9th. Highest cost benefit ratio (19.35) was observed with dimethoate 40%EC @ 1.5 l ha−1.

Genotoxic effects of starvation and dimethoate in haemocytes and midgut gland cells of wolf spider Xerolycosa nemoralis (Lycosidae)

The aim of this study was to assess the genotoxic effects of starvation and dimethoate (organophosphate insecticide) in female and male wolf spiders Xerolycosa nemoralis (Lycosidae) exposed to the stressors under laboratory conditions. DNA damage was measured in haemocytes and midgut gland cells using the comet assay. In response to the two stressing factors, both cell types showed %TDNA, tail length (TL) and OTM values higher in males than in females. Level of DNA damage in haemocytes was greater than in midgut gland cells. In both sexes, the strongest genotoxicity was recorded at single application of dimethoate. After five-time exposure to the pesticide, genotoxic effects of a single dose were sustained in males and reduced to the control level in females. Starvation stress was well tolerated by the females, in which neither cell type was affected by DNA damage. However, in male haemocytes food deprivation induced severe DNA damage, what suggests suppression of the defence potential at prolonged starvation periods.

Inhibition and recovery of molecular biomarkers of earthworm Eisenia andrei after exposure to organophosphate dimethoate

Dimethoate is a broad-spectrum organophosphorous insecticide produced and used in many countries against a wide range of pests. Like other pesticides, dimethoate also affects many non-target organisms, including soil organisms. In this study for the first time effects of dimethoate on molecular biomarkers (AChE, CES, CAT and GST activity, concentration of GSH and efflux pump activity) of Eisenia andrei earthworms were evaluated using the artificial OECD soil. Earthworms were exposed to environmentally relevant doses of dimethoate (0.03, 0.1, 0.3, 1 and 3 mg/kg) for 1, 3, 6, 10, 15, 21 and 28 days and besides the time-related responses of biomarkers, the recovery of AChE, CES and CAT activity was also investigated. Results showed that dimethoate caused dose dependent significant changes in measured biomarkers – inhibition of AChE, CES and CAT activity; increase in GST activity and concentration of GSH; and both induction and inhibition of efflux pump activity. Additionally, the selected molecular biomarkers showed slow recovery rate and at the highest applied concentration of dimethoate, the inhibition of enzymes was evident even after 28 days of recovery. The obtained results indicate that application of dimethoate in agriculture could have harmful effects on earthworms since application of environmentally relevant doses, i.e. doses that are applied in agriculture, caused significant changes in measured biomarkers.

Relationship between Tomato Yellow Leaf Curl Viruses and the Whitefly Vector

Tomato Yellow Leaf Curl Virus (TYLCV) and Tomato Leaf Curl Virus (ToLCV) are the currently known begomoviruses in Uganda. The relationship with their whiteflies (Bemisia tabaci) vector and its management were not known in Uganda. A direct relationship was expected between these begomoviruses and whiteflies at Buwama in Mpigi district of Uganda. Farmer practices were expected to have limited efficacy. To investigate this, a completely randomised block design was used for all trials with six treatments replicated three times. Treatments evaluated were farmer whitefly pest management practices. These included both chemical pesticide and non-pesticide applications. Data on whitefly population and tomato yellow leaf curl virus disease incidence was recorded weekly, and analysed using SAS and SPSS statistical programmes for ANOVA, and correlations. Ranked means, coefficients of variation and standard errors were noted. Virus-vector relationship field studies established that virus occurrence varied in space and time, and with management practices, crop development stage, and weather conditions. A negative relationship (R = -0.14, p 0.04) was established between number of plants infected with TYLCV (sensu lato) and percentage marketable tomato yield. Tomato maturity was inversely propotional to whitefly infestation (R = -0.5, p 0.0001). Uprooting and application of dimethoate was most effective of the six treatments. Tomato leaf curl virus diseases and whitefly management options were established in Uganda.

Evaluation of the joint effect of glyphosate and dimethoate using a small-scale terrestrial ecosystem

In the present work a small-scale terrestrial ecosystem (STEM) containing a soil collected from an agricultural field in Central Portugal was used to evaluate the effects of the combination of the herbicide glyphosate and the insecticide dimethoate. Earthworms ( Eisenia andrei), isopods ( Porcellionides pruinosus), turnip seeds ( Brassica rapa), and bait-lamina strips were placed in the STEM. The results showed that the application of the recommended field dose of both pesticides did not cause any effect on the weight variation of earthworms and growth of the plants. The application of the herbicide, even at 5 and 10 times the field dose, increased feeding activity in soil (bait-lamina test), although the application of dimethoate led to a decrease in feeding activity in all concentrations tested. The binary mixtures performed showed that according to the Independent Action model, synergism (higher effect than expected from the single exposures) was observed in both the shoot length and fresh weight of B. rapa at 5 times the field dose, but antagonism was observed at 10 times the field dose. Regarding the germination success, synergism was observed at the field dose, but antagonism was detected at 5 times and 10 times the field dose. There was a decrease on the earthworm's weight in all concentrations tested, although no statistical differences were observed in any of the treatments made. Regarding depth distribution of E. andrei, worms were found in the upper layer more than it was predicted for all concentrations. In the mixtures with the field and 5 times the field dose there was a decrease in the feeding activity (bait-lamina consumption) by the soil fauna. From the four biomarkers assessed on the isopods (Catalase, Acetylcholinesterase, Glutathione- S-transferase, and Lipid peroxidation), only a significant decrease in the Acetylcholinesterase activity upon dimethoate and the binary mixtures exposures performed with the field dose was observed and on Lipid peroxidation at the field doses of single and binary exposures.

Field efficacy of wintertime insecticide applications against greenbugs, Schizaphis graminum (Rondani) (Hemiptera: Aphididae) on winter wheat ( Triticumaestivum L.)

Winter wheat producers in Oklahoma often combine an insecticide with a top-dress application of nitrogen during late fall and winter to control existing greenbug populations. We evaluated the efficacy of three classes of insecticides applied in cold weather field conditions ranging from −13.3 to 28.9 °C from 2002 to 2004 for greenbug control in winter wheat in replicated small plots. Insecticides provided control ranging from 0% to 98%, but generally responded similarly to temperature. Percent control of greenbugs resulting from applications of dimethoate, chlorpyrifos and λ-cyhalothrin was correlated with maximum, minimum and average daily temperatures that occurred two days post-treatment. While percent control was unique for each insecticide, a combined regression of percent control against average daily temperature predicted that a 95% level of control would be achieved when post-treatment temperatures exceeded 13.6 °C. Rainfall that occurred post-treatment affected the efficacy of dimethoate but did not affect the other insecticides. Insecticide persistence was extended under cooler temperatures, allowing acceptable control 14 days post-treatment if temperatures warmed. The decision to apply insecticides should be made based on existing treatment thresholds for greenbug, but if treatment with an insecticide is warranted, winter wheat producers can expect reasonable control of greenbugs from insecticides applied during the winter, as long as post-treatment temperatures exceed 13 °C within the following 14 days.

Development of Tolerance of Egg Plant (Solanum melangena L.) to Field Application of Dimethoate

Dimethoate, at field concentration (1.419 mg g(-1) fr wt), caused inhibition of photosynthesis, transpiration and stomatal conductance of Solanum melangena L. on first treatment but subsequent treatments caused adaptation and recovery of these parameters. The variable fluorescence (F(v)), dissipation (DI(0)/RC), 2 ms relative variable fluorescence (V(j)), net rate of PS II closure (M(0)), and maximum trapping rate of active PS II (TR(0)/RC) increased initially but reduced to the control value with repetition of treatment. However, fluorescence yield (TR(0)/Abs), electron transport probability (ET(0)/TR(0)) and activity of RC (ET(0)/RC) increased with each treatment. With each subsequent treatment there was enhancement of activities of esterases and decrease of insecticide content of leaves.

Response of coccinellid community to the dimethoate application in olive groves in Northeastern Portugal

In this work we assessed the effects of the application of dimethoate on the coccinellid community. The field work was carried out on a weekly basis, in two different olive groves, from April to November of 2002 and 2003 and captured coccinellids were identified to species level. Principal response curves (PRC) method was used to analyse the effect of the dimethoate application on the abundance of coccinellid species. A total of 23 species were identified from the two olive groves. Nine species occurred in both olive groves and in the two years of the study. Scymnus interruptus was the dominant species in the control grove with 46.4% of the total Coccinellidae recovered while in the grove treated with dimethoate, Rhyzobius chrysomeloides represented 35.7% of the total number captured. PCR showed that the main effect of the treatment was a significant reduction of the abundance of the most common species of the coccinellid community (S. interruptus and Chilocorus bipustulatus) in the treated grove. This can also have implications on the preservation of ecological functions associated with coccinellids, namely their role as control agents of olive pests.

INTEGRATED MANAGEMENT OF PAPAYA RING SPOT VIRUS (PRSV) IN AGRO ECOLOGICAL CONDITIONS OF BIHAR

Over the last decade Papaya ring spot virus (PRSV) has been identified as a major threat of papaya production resulting in heavy reduction in area under this crop. In an attempt to combat the disease, a field trial was conducted to manage PRSV through integrated approach. Seven treatments viz. 1. Raising of papaya seedlings under Nylon net (40-60 mesh) and spraying of Dimethoate (1.05%) 3 days before planting; 2. Use of two rows of maize as a border crop (Maize sown 15 days ahead of planting); 3. Application of neem seed kernel extract (2%) at 15 days interval (30 days after planting); 4. Application of Dimethoate (1.05%); 5. Application of neem oil 1% + Dimethoate (1.05%); 6. Two rows of maize as a border crop + application of Zn (0.5%) and B (0.1%); and 7. Control without any treatment was evaluated in randomised block design (RBD) with 12 plants/treatment with spacing of 1.8×1.8 m/plant during 2005-2006 and 2006-07. All the treatments were replicated thrice. Observation on PRSV incidence was recorded starting from 60 to 210 days after planting (DAP) at monthly interval. Initially at 60 to 150 DAP there were significant differences among various treatments in relation to their effect on the incidence of PRSV. The most effective treatment was application of neem oil 1 % + Dimethoate 1.05% with least disease incidence (6.66%) and 41.66% respectively at 60 and 150 DAP. This was followed by application of Dimethoate 1.05% with 16.33 and 56.66% PRSV incidence while the untreated (control) plants registered 68.33 and 90% incidence respectively at 60 and 150 DAP. But after 210 days all the treatments were at par in relation to their effect on disease. However the treatment comprising of neem oil 1 % + Dimethoate 1.05% showed the minimum disease incidence (76.66%) as compared to the control showing 100% incidence at 210 DAP. Growth and yield characters of papaya i.e. plant height at first flowering, plant height at first harvest, stem girth at harvest and number of fruits were significantly affected by the treatments while mean fruit weight was not affected markedly. Likewise some quality parameters of fruits i.e. TSS and central cavity diameter did not show notable difference due to the treatments although other quality parameters like average fruit weight, fruit length, fruit diameter and hundred seeds weight were appreciably affected by the treatments.

Photosynthetic and fluorescence responses of Solanum melangena L. to field application of dimethoate

The organophosphorus insecticide dimethoate, at field concentration (1.419±0.086 mg a.i. g −1 fr.wt. of leaf tissue) did not cause any significant degradation of chlorophylls and carotenoids in Solanum melangena L. On the other hand, there was significant reduction of photosynthesis, transpiration and stomatal conductance during 6 h after spray application of the insecticide. Distinct change of OJIP fluorescence transient with increase of J and I rise and corresponding decrease in P rise was observed during 6 h after insecticide application. The fluorescence parameters, viz., relative variable fluorescence at J level ( V j), net rate of PS II closure ( M 0), energy dissipation (DI 0/RC) and maximum trapping rate of active PS II (TR 0/RC), during the same treatment period, showed significant increase but variable fluorescence ( F v), fluorescence yield (TR 0/Abs), electron transport probability (ET 0/TR 0), and activity of RC (ET 0/RC) showed significant decrease. All physiological and fluorescence parameters, and the OJIP fluorescence transient recovered steadily to the control level during 48 h after insecticide application. There was continuous reduction in the insecticide content of the leaf tissue during the observation period.

EVALUATION OF AN IPM MODULE AGAINST THE LEAFHOPPER, AMRASCA DEVASTANS (DISTANT) IN COTTON

To develop an IPM module against cotton leafhopper different tactics like, leafhopper resistant cultivar (KC 2) were integrated in different combinations and were evaluated. When the susceptible LRA 5166 was raised from imidacloprid treated seed with cluster bean intercrop and need based application of dimethoate 0.03 % leafhopper population was reduced by 79.01 per cent and seed cotton yield increased by 31.76 %. The pest reduction was 57.08 % with mere introduction of resistant cultivar viz., KC 2; the yield increase was 58.82 %. The yield increase was 125.88 % when the resistant cultivar KC 2 was raised from imidacloprid treated seeds, grown with cluster bean intercrop and applied with dimethoate on need basis.