Climate Change Effects On Agricultural Pests: The Response of Liriomyza Huidobrensis to Drought-Stressed Potato Plants

Climate change is predicted to bring about major changes in pest and disease incidence, resulting from the effects of global warming and changes in rainfall patterns. While increasing temperatures are expected to influence growth and development, and duration of pest life cycles, changes in precipitation, relative humidity and availability of water can have an effect on pest-host relationships.This study reports the results of one such study conducted in Mauritius andUK, on an important insect pest, Liriomyza huidobrensis, attacking majorcrops such as potato, beans, onion, egg plant, etc. in Mauritius.Drought stress changed the response of L. huidobrensis adults to its potato host. In olfactometer studies, the insects exhibited distinct preference for greener and more succulent potato leaves, irrespective of their intraplant distribution, as opposed to the normal preference of adults to the older leaves of the lower canopy. This was inspite of the fact that biochemical studies of drought stressed and non stressed potato plants showed that the drought stressed plants had a better nutritional profile for the insect larvae than the non-stressed ones.On the other hand, metabolomic studies correlated the changed hostpreference demonstrated by the pest to variations in the metabolite profilesof drought stressed and non-stressed plants, which indicates that adult hostpreference is not always positively related to offspring performance.Keywords: Metabolomics, nutrient levels, insect behaviour, host preference, hostperformance

Study of Various Extracts of Ayapana triplinervis for their Potential in Controlling Three Insect Pests of Horticultural Crops

Chemical groups of Ayapana triplinervis, extracted successively with hexane, petroleum ether, methanol, chloroform: methanol (1:1), and chloroform: methanol (4:1) were studied for their effects on Plutella xylostella, Crocidolomia binotalis and Myzus persicae, three serious pests of horticultural crops in Mauritius. The most bioactive extracts were further fractionated into groups using Thin Layer Chromatography, and seven of those exhibiting strongest activity were tested on each of the three test insects. Results showed that the alkaloids and tannins exhibited greatest feeding deterrence in P. xylostella and C. binotalis, followed by phenols and flavonoids. In the case of M. persicae, A. triplinervis extracts disrupted growth and development of the nymphs, had significant pest control properties, and were good candidates for further study on their potential as botanical pesticides, in the context of an organic farming/ sustainable agriculture system, as an environmentallyfriendly alternative to synthetic insecticides

Investigation on the Use of trapping in the Management of the Banana Weevil, Cosmopolites Sordidus (Germar)(Coleoptera: Curculionidae) in Mauritius

The banana weevil, Cosmopilites sordidus (Germar) is an important pest of banana in Mauritius. At present, control of C.sordidus is achieved by soil treatment with insecticides by growers. No research has been conducted to understand the pest abundance and develop alternative methods to better manage C. Sordidus with minimum use of insecticides. In this 11-month study, the potential of two trap types (pseudostem and pheromone traps) to lure weevils in banana fields was determined at three different ecological sites (Clemencia, Nouvelle France and Rivière du Poste). The effect of treatment of pseudostem trap with insecticides (Imidachloprid, Cyfluthrin and Lambda-Cyhalothrin) was evaluated under field condition. The damage level in fields at Clamencia and Rivière du Poste was also determined. The pseudostem and pheromone traps were effective in luring banana weevils. The average number of weevil caught per week in pseudostem and pheromone traps were 2.03 and 5.92 respectively. Relatively more adults were caught at Nouvelle France. This indicates that weevils were in higher numbers in the super humid site (Nouvelle France) compared to humid Rivière du Poste and dry (Clemencia) sites. Pseudostem treated with Imidachloprid was more effective than the other two insecticides. Damage by C. Sordidus ranged from 15.5% to 31% at Clemencia and Rivière du Poste. Pseudostem and pheromone traps can be used for monitoring and mass trapping of C.Sordidus. A better weevil management can be easily achieved by the use of either pseudostem or pheromone traps and proper timing of soil drenching. This will, no doubt greatly reduce insecticide application in banana field.Keywords: Banana, Cosmopolites sordidus, pseudostem and pheromone traps, insecticides, mass trappin

Crop protection and soil fertility in organic okra cultivation in Mauritius

Okra was grown in organic and conventional systems. The organic plots included an intercrop system, using onion in alternate rows. Well-decomposed manure was used as a soil amendment, and mulching was done with cane straw. A bird net prevented damage by birds to seeds. Neem extract was applied as and when needed based on economic threshold values of important pests. Parameters studied included plant height, leaf area index, soil pH, soil NPK, and yield and quality of harvested okra fruits. Okra was grown in the conventional plots in a monocrop system, fertilised with synthetic NPK fertilisers, and sprayed with synthetic pesticides. Comparison of soil, plant and yield parameters showed that leaf area index, plant height (from week 10) and fruit yield and quality were higher in the organic system compared to the conventional system, while pest damage was equal in the two systems. Soil pH and phosphorus levels were lower in the organic plots, while available nitrogen and potassium were higher in the organic plots