M. Shafiq Ansari

Effect of different cole crops on the biological parameters of Pieris brassicae (L.) (Lepidoptera: Pieridae) under laboratory conditions

The effect of different cole crops was studied on biological parameters of Pieris brassicae (L.) in the laboratory at 28 °C, 65% RH, and 12L:12D photoperiod. The results indicated that host plants significantly affected the life history, i.e. survival of developmental stages, oviposition period, and sex ratio of P. brassicae. Comparative study on different host plant revealed that P. brassicae required a maximum of 40 days to complete generation on cabbage, cauliflower, and broccoli. The survivorship and expectation of life declined gradually with the advancement of age; the life expectancy of newly deposited eggs was 23.96 days while it was 8.12 days at the time of adult emergence on cabbage. However, the fluctuations of mortality parameter were seen on all the cole crops. On cabbage, 100% hatching of eggs with low larval mortality were noticed. The highest net reproductive rate (R0) occurred on cauliflower, i.e. 27.1 followed by cabbage 24.89, females per female per generation. Intrinsic rate of increase (rm), was found to be highest (0.09558954) on cauliflower followed by broccoli and cabbage, 0.078886 and 0.077551 females per female per day, respectively. The smallest rm (0.059469 females per female per day) occurred on radish which shows that P. brassicae did not perform well on radish. In addition, P. brassicae may double in 7.2 days on cauliflower, 8.7 days on broccoli, and 8.9 days on cabbage. The sex ratio was computed as 1.5:1, female:male, respectively on cabbage.

Effect of Indian mustard on feeding, larval survival and development of Plutella xylostella at constant temperatures

Feeding behavior of Plutella xylostella under optional to non‐optional conditions was studied at 10°C, 15°C, 20°C, and 25°C on Indian mustard, Brassica juncea. The study reveals that the variety Pusa Bahar was significantly less preferred by the larvae as compared with Pusa Bold and Varuna under optional to non‐optional conditions. Larvae of P. xylostella consumed more food at 25°C than 20°C, 15°C and 10°C. Larval survival was found to be highest on cabbage (control) as compared with Indian mustard and was found to vary with host plants and temperature. The larval survival decreased to 11.29% on Pusa Bahar at 10°C. Increasing the temperature from 10°C to 20°C, larval mortality resulted more on Varuna than Pusa Bahar and Pusa Bold. Developmental period was prolonged on Pusa Bold at 10°C while it was shortest on cabbage at 25°C. A total of 536.47 degree days were required to complete the development by immature stages on Varuna at 25°C and 421.64 degree days on cabbage.

Superparasitism in Cotesia glomerata does not benefit the host plant by reduction of herbivory caused by Pieris brassicae

Superparasitism occurs in Cotesia glomerata L. (Hymenoptera: Braconidae), a gregarious endoparasitoid of Pieris spp. (Lepidoptera: Pieridae). The responses of Pieris brassicae L. larvae to superparasitism were examined in order to elucidate the ecological significance of this behaviour. Models of tritrophic interactions often imply that attraction of herbivore natural enemies by the plant constitutes a defence. Parasitoid attack on herbivores is assumed to result in a reduction in herbivory and or an increase in plant fitness. Coupled with the active involvement of the plant in producing signals, this can be seen as an indirect mediation of wound induced defence. The results show that superparasitism of P. brassicae by the parasitoid C. glomerata reduced survivorship but increased food consumption and weight growth in P. brassicae larvae. The duration of host larval development was found prolonged as the number of oviposition increased and superparasitized larvae (three to five time parasitized) grew slower than unparasitized larvae or larvae parasitized one or two times.

Insecticides: Impact on the Environment and Human Health

Insecticides have saved millions of human and animal lives since the date of their synthesis and use. They have played an important role that brought revolution in the field of agriculture and human health on control of insect pests of crops and vector-borne diseases. More than 80,000 chemical substances are now commercially available in agriculture and industry. About 4.6 million t of pesticides are applied into the environment and insecticides accounted for the largest portion of total use in the world to increase the productivity of food and fibre as well as to prevent the incidence of vector-borne diseases.

Factors responsible for stage-specific mortality and sex ratio adjustment in Zygogramma bicolorata Pallister on parthenium in field conditions

Stage specific mortality and sex ratio adjustment in Zygogramma bicolorata Pallister (Coleoptera: chrysomelidae), were evaluated monthly for two consecutive years, 2010 and 2011, in field conditions on Parthenium hysterophorus L. Development of immature stages was considerably affected during the cold seasons of 2010 and 2011, and it was completely arrested in January. Similarly, the mortality survival ratio and indispensable mortality were higher in December, as compared to other months. Generation mortality (K-value) was decreased in May and then further increased from September to December, in both years. A non-significant difference (P < NS) in K-values were evident in July and August 2010, as well as in June and July 2011. Different abiotic and biotic factors may have influenced the mortality of the various immature stages. Greater mortality of eggs was due to their infertility in December. Similarly, mortality of 1st and 2nd instar was significantly high in Feburary, March, October, November and December of 2010 and 2011 due to infection of entomopathogenic fungi Beauveria bassiana. One of the other causes of mortality of 2nd, 3rd and 4th instar was their predation by a pentatomid bug, Perillus bioculatus from 1st week of March to 2nd week of December 2010 and 2011. Pre-pupal mortality was due to lack ofpenetration in soil and pupal mortality was due to malformation. In addition to known factors, some unknown factors may have been responsible for mortality. The least value of sex ratio (proportion of male) showed the greatest number of female emergence. It was also noted that sex ratio was considerably higher in 2010 than in 2011, and that that female population increased gradually year by year. Therefore, the results suggested that Z. bicolorata are continuously adapting to the agro climatic conditions of Aligarh, India. Moreover, the information on the factors responsible for key mortality, can be helpful in devising strategies for its conservation.

Potential of Biopesticides in Sustainable Agriculture

Sustainable agriculture also aims at increasing the yield of food and fiber crops and reducing the incidence of pests and diseases to such a degree that they do not cause extensive damage to crops. With the advent of chemical pesticides in 1940s, this crisis was resolved to a great extent. But the overdependence on chemical pesticides and eventual uninhibited use of them has caused serious health and environmental problems. This concern has encouraged researchers to look for better alternatives to synthetic pesticides. Biopesticides can make important contribution to sustainable agriculture and help reduce reliance on chemical pesticides. microbial insecticide likeBacillus thuringiensis (Bt) produces a proteinic toxin which induces paralysis of the midgut and brings about cessation in feeding after being ingested by insect pests. Other promising candidates areBeauveria bassiana andMetarrhizium anisopliae. The spores penetrate the host cuticle, once inside the body, producing toxic metabolites called beauvericin (B. bassiana) and destruxins(M. anisopliae) responsible for death of the insects. Baculoviruses (Nuclear Polyhedrosis Virus and Granulosis Virus) are safe to human beings and wildlife, their specificity is very narrow. They do not infect beneficial insects and have capacity to persist in the environment, making them very suitable for use in sustainable agriculture. Semiochemicals: attractants and pheromones, and botanicals are important sources of agrochemicals used for the management of insect pests. They degrade rapidly and therefore, are considered safer than chemical pesticides to the environment.

Threats to fruit and vegetable crops: Fruit flies (Tephritidae) - ecology, behaviour, and management

Approximately 4,000 known/described species of fruit flies (Tephritidae) are distributed in tropical, subtropical, and temperate regions of world, out of which 200 species are economically important and damaging/spoiling not only to fruits but also to a number of vegetable crops. Despite their tremendous importance, a limited amount of information is available on the ecology and behaviour of fruit flies especially when compared to fruit fly species complex. It is necessary to understand the ecology and behaviour before the formulation of management strategy. The present review may serves as a baseline data for scientists engaged in fruit fly management programs. Key themes include: (1) demography and population dynamics and, (2) behaviour (e.g. sexual, mating, oviposition, and feeding). The excess of literature on monitoring and management of fruit flies are available, which includes male sterilization and annihilation, mass trapping, chemical baits, mating disruption, and biological control. But few of them are easily adopted by users and give satisfactory control of fruit flies and rest are not easily adopted or if used does not give effective control, because of the lack of knowledge about the ecology and behaviour of fruit flies. If the information on population dynamics, behavior, and the related ecological factors are not jointly gathered, it is almost impossible to carry out an appropriate pest control at the right time and place. We hope that this synthesis will lay the groundwork for future ecological and behavioural studies of fruit fly species, populations, communities, and control.

Microbial Insecticides: Food Security and Human Health

Sustainable agricultural systems must be adopted to increase the food and fiber production keeping in view of human health and increase in population; the number of undernourished has increased to almost 20% (The state of food insecurity in the world economic crises – impacts and lessons learned. In Food and Agriculture Organization of the United Nations, Rome). Insect pests have been causing serious damage in the fields and stored grains and their products. Interventions is required to limit the losses, therefore, synthetic insecticides have played a significant role in their management for more than 60 years. Indiscriminate use of insecticides have left undesirable residues in the environment, which are toxic to human beings and non target organisms as well as insects have developed resistance against them and resurgence of pests that lead to find a suitable, sustainable and efficient method of management. Microorganisms: bacteria, viruses, fungi and protozoa form the most abundant and diverse groups, which offer a vast resource for exploitation to use in the management program. Bacillus thuringiensis is a gram positive, occurs in soil and ubiquitous in distribution. It produces parasporal crystalline body which contains one or more cry proteins that can be toxic to a number of insects. cry proteins are encoded by cry genes and 200 of them are identified. Similarly, a number of insect pests are also vulnerable to viral diseases. Nuclear Polyhedrosis and Granulosis Viruses are commonly used against the Lepidoptera. They are highly species specific and safer to human beings. Fungi, often act as important natural control agents that limit the insect population. Promising results are obtained by Beauveria bassiana and Metarhizium anisopliae against many insect pests. B. bassiana grows naturally in soil throughout the world and causes white muscardine disease. Therefore, intensive work is required to improve the efficacy of microbial insecticides through molecular biology and genetic engineering to enhance their role in the insect management for better food security.

Insecticidal effect on a population of Spilarctia obliqua (Lepidoptera: Arctiidae)

Survivors of Spilarctia obliqua derived from 3rd instars that had ingested LC50 of imidacloprid (0.025%), dichlorvos (0.014%) and endosulfan (0.012%) were studied through the life table method. Survivorship was reduced in insecticide exposed populations as compared to 45‐day in the control groups. Egg hatching was significantly decreased for the insecticide treated populations. Total larval mortality was the highest for endosulfan (36.76%) as compared to the individuals that died among control groups (14.29%). Life expectancy (ex) was decreased gradually over time and stage of development for insecticides tested and the control groups. Dichlorvos (0.014%) has caused a significant reduction in the potential fecundity i.e. 315 females/female/generation, while 415 in the unexposed cohorts. Net reproductive rate (Ro) was the lowest in endosulfan (118.47 females/female/generation) treatment followed by dichlorvos (141.97), imidacloprid (144.49) and the control groups (272.42). Similarly, the intrinsic rate of increase (rm) was substantially decreased after exposure with endosulfan (0.124 females/female/day) as compared to 0.135 in the unexposed cohort. The finite rate of increase (λ) was not significantly different among the insecticide treatments and control groups. Mean generation time was significantly reduced after exposure to dichlorvos (37.19 days). However, 41.34 days were required to complete one generation by S. obliqua in the absence of insecticides. Based on these results, population of S. obliqua would double in 5.19 days under the influence of dichlorvos while requiring 5.13 days for unexposed cohorts.

RETRACTED ARTICLE: Foraging of Host-Habitat and Superparasitism in Cotesia glomerata : A Gregarious Parasitoid of Pieris brassicae

The study investigates differences in the oviposition pattern of a braconid parasitoid, Cotesia glomerata (Linn.) in Pieris brassicae (Linn.) in relation to their use of different cruciferous food plants. The response of P. brassicae to superparasitism and consequences for the parasitoid were examined in order to elucidate the ecological significance of this behaviour. Female parasitoid located various crucifers and searched for host more frequently almost on all the host plants tested i.e. cabbage, cauliflower, Chinese cabbage, broccoli and radish. According to the estimated relative number of female locating hosts, cabbage was the most attractive plant for C. glomerata and total number of eggs laid in host larvae feeding on it was higher than in larvae feeding on other plants. Laboratory experiments demonstrated that superparasitism reduced survivorship of P. brassicae larvae. Superparasitism lengthened parasitoid development and prolonged the feeding period of host larvae. Sex ratio and the body weight of emergent wasps correlated negatively with brood size. Despite a trade-off between maximising brood size and optimising the fitness of individual offspring, two or three ovipositions on P. brassicae larvae resulted in a greater female dry mass than did a single oviposition on the host. Thus, superparasitism might be of adaptive significance under certain circumstances, especially when host density is low and unparasitized hosts are rare in a habitat.