Parm Pal Singh

Comparative toxicities of some insecticides to Chrysoperla carnea (Chrysopidae: Neuroptera) and Trichogramma brasiliensis (Trichogrammatidae: Hymenoptera), two arthropod natural enemies of cotton pests

Abstract Relative toxicities of nine insecticides recommended for the control of cotton bollworms were tested against the larvae of Chrysoperla carnea Stephens and adults of Trichogramma brasiliensis Ashmead under laboratory conditions in the Punjab, India. The insecticide concentrations studied were equivalent to those prescribed for field application. When freshly emerged larvae of C. carnea were released on insecticide-treated food (eggs of Corcyra cephalonica Stainton) for 24 h, endosulfan, quinalphos, monocrotophos, phenthoate and fenitrothion caused 74–89% larval mortality over a 72-h period. Phosalone, carbaryl and cypermethrin were moderately toxic (34.1–38.1% mortality), while fenvalerate was the least toxic (19.2% mortality). The surviving larvae in all treatments successfully completed metamorphosis. When T. brasiliensis adults were released on treated host ( C. cephalonica eggs), all these insecticides proved highly toxic (84–100% mortality in 24 h). Phosalone, monocrotophos and fenvalerate inhibited parasitism by 26–64%, but did not affect the emergence of parasitoid adults. The remaining six insecticides severely inhibited parasitism and emergence of parasitoid adults. Thus, phosalone and fenvalerate are relatively safe for the above-mentioned natural enemies and can provide selectivity in an integrated control programme for cotton bollworms.

Regeneration of silica gel in multi-shelf regenerator

In the present paper an investigation on the regeneration of solid desiccant (silica gel) in a modified design of dehumidifier called “Multi-shelf Dehumidifier”, has been reported. A “Packed Bed Dehumidifier” was used as control. Both the dehumidifiers were fabricated and tested simultaneously. The effect of regeneration air temperature, bed-air velocity and number of shelves on regeneration of silica gel was investigated. The range of regeneration air temperature was 42–72°C, while bed-air velocity varied from 0.175-0.55 m/s and number of shelves from 2 to 4. The regeneration time decreased with the increase in regeneration air temperature, bed-air velocity as well as number of shelves. The values of regeneration air temperature and bed-air velocity for minimum energy input were found to be 52°C and 0.175 m/s irrespective of the number of shelves. The effect of the rest period was investigated for these optimum values of regeneration air temperature and air velocity for a number of shelves varying from 2 to 4. The rest periods used were 30, 60 and 180 mins. The regeneration time reduced with increase in rest period for all the values of number of shelves, but the reduction in regeneration time was not appreciable.

Contamination of bovine (buffalo, Bubalus bubalis (L.)) milk from indoor use of DDT and HCH in malaria control programmes

Samples of bovine (Buffalo, Bubalus bubalis (L.)) milk collected from randomly selected houses of Ludhiana and Sangrur districts of Punjab, India, where DDT and HCH, respectively, had been sprayed for the control of malaria, were analysed for insecticide residues between September 1985 and June 1986. The average concentration of DDT residues in samples from the DDT sprayed area were approximately 4-12 times higher than those in the corresponding samples from HCH sprayed areas. Mean levels of HCH residues in samples from the HCH sprayed area were greater than those in samples from DDT sprayed areas by factors of 2-11. Milk samples collected from four rural houses in each district before and after applications of DDT or HCH for mosquito control also showed that indoor use of these insecticides results in a substantial increase in residue levels. About 74% of the samples analysed contained DDT residues above the extraneous residue limit of 0.05 mgkg-1 (whole milk basis). Estimated maximum daily intakes of DDT and beta-HCH through consumption of contaminated milk by 1-3-year-old children exceeded their acceptable daily intakes by nearly three and five times, respectively.

Evaluation of sulphuric acid treatment as the clean-up step for the estimation of BHC and DDT in fatty and non-fatty foods

The potential of sulphuric acid treatment for clean-up of 10 food composites comprising 36 food items of north Indian total diet has been evaluated for the estimation of BHC and DDT residues by gas chromatography with electron-capture detection. In all cases the clean-up was satisfactory without resort to column chromatography. The chromatograms obtained were free from interference by the co-extractives. The method is simple, rapid and economical.

Contamination of stored food and feed commodities from indoor use of HCH and DDT in malaria control programmes

Samples of wheat grain, straw, flour and green fodder taken from houses sprayed with either HCH or DDT for mosquito control showed the presence of HCH residues at concentrations of up to 91.2, 208.8, 33.1 and 459.0 mg kg-1 and DDT residues up to 11.3, 86.1, 2.2 and 5.4 mg kg-1, respectively. The mean level of HCH residues in samples of wheat grain collected from randomly selected houses in areas sprayed with HCH for the control of malaria was approximately 8 times higher than that for corresponding samples from DDT sprayed areas. In contrast, DDT residues in wheat grain samples from the DDT sprayed area were 3 times higher than the samples from the HCH sprayed area. The results suggest that significant amounts of residues of HCH and DDT become transferred to commodities stored in houses sprayed with these insecticides for mosquito control.

Comparison of sulphuric acid treatment and column chromatographic clean-up procedures for the gas chromatographic determination of organochlorine compounds in some food commodities

Description de deux types de procedes de purification des pesticides organochlores dans toute une serie de produits alimentaires representant une ration alimentaire moyenne

Computer model for performance prediction and optimization of unheated biogas plant

A mathematical model of an unheated biogas plant described in this paper can be used to predict biogas generation at any given geographical location by using laboratory experimental data of methane gas generation at different values of temperature and retention time. So, this model obviates the need for repeating field experiments at different geographical locations. The introduction of new concepts of equivalent temperature and biogas coefficient help to convert laboratory data into field data and minimize the necessity of conducting field experiments. Further, retention time and size of the biogas plant for a given daily requirement of biogas are optimized through life cycle economic analysis. The model has been elaborated by calculating results for biogas generation with cattle dung in a fixed dome type biogas plant located at Ludhiana. Results are presented for various values of daily biogas requirement and cost of feedstock.

Insecticide residues in total diet samples in Punjab, India

Total diet samples, collected every 3 months during a period of 1 year, were analysed for DDT and BHC residues. The food items were purchased from retailers, prepared for eating according to local practices and divided into several food groups. The results show that average dietary exposure to DDT and BHC residues was, respectively, 239 (range: 124-288) and 125 (range: 68-268) micrograms person-1 day-1 for vegetarians, and 225 (range: 138-263) and 134 (range: 63-280) micrograms person-1 day-1 for non-vegetarians. These dietary intake values are much higher than those reported from developed countries. Fatty food groups (milk and milk products, oils and fats, meat and eggs or cheese) were responsible for approximately 85% of the total DDT intake, while BHC residues were distributed more evenly in various food groups. The observed DDT intake is close to its acceptable daily intake (ADI) of 300 micrograms person-1 day-1 for a man weighing 60 kg. No ADI value for BHC residues is available.

DDT and HCH residues in indoor air arising from their use in malaria control programmes

Samples of air from rooms in a residential and rural environment, treated with either DDT or HCH at rates recommended for mosquito control under the National Malaria Eradication Programme of India, i.e. 2 and 3 g m-2, respectively, were analyzed for the residues of these insecticides. During the 8-month sampling period, DDT and HCH levels in indoor air ranged from 1.0 to 14.6 and 0.9 to 2000.1 micrograms m-3, respectively. After an initial fall, residues of DDT showed an increase again and were 5.9 micrograms m-3 in samples collected 240 days after the initial application. In contrast, HCH residues declined at a fast rate in a few days after application and remained low at the time of subsequent samplings. HCH residues were present chiefly in the vapour phase throughout the study. Thirty-four to seventy-eight percent of DDT residues were found in the particulate phase in the samples collected up to 64 days after its application and exclusively in the vapour phase at the time of later samplings. Apart from the contamination of food and feed commodities stored in premises treated for malaria control by absorption of insecticides present in the indoor atmosphere, the residues of these persistent compounds in air are also likely to result in low level pollution of the surrounding and distant environmental media by their dispersion in the global ecosystem.

Abscisic acid is a potent inhibitor of growth and sporidial formation inneovossia indica cultures: Dual mode of actionvia loss of polyamines and cellular turgidity

The inhibition of polyamine biosynthesis inNeovossia indica (Mitra) Mundkur by D,L— α-difluoromethylornithine (DFMO) caused an effective reduction of mycelial growth and sporidial production underin vitro conditions, which was reversed by ornithine application. Abscisic acid proved to be similarly effective, not only in inhibiting mycelial growth and sporidial formation but also the germination of teliospores, which constitute the primary inoculum of the pathogen. ABA-mediated inhibition resulted in decreased polyamine levels and loss of cellular turgidity of mycelial cultures. Scanning electron microscopy of ABA-treated cultures revealed extremely shrunken hyphae, in marked contrast to the turgid controls. It is suggested that the manipulation of ABA levels and/or tissue sensitivity in wheat could be a strategy to combat ‘Karnal’ bunt, the disease caused byN. indica.