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Keywords: Natural Sciences
Animals (Zoology)
Issue Date: 2016
Abstract: Aspergillus species registered world-wide for grasshoppers and locusts control. This practice is currently under consideration as a potential alternative to chemical insecticides for grasshopper control in Pakistan. Grasshoppers are major agricultural pests. They destroyed the rice, sugarcane, wheat, maize and fodder crops in everywhere. For control of this pest several pesticides of billion rupees are used indiscriminately in every year. On the other hand, these chemicals are injurious and health hazardous effects on living creature and their environment. So, there should be suitable, beneficial and cheap alternative of these poisonous chemical. For this purpose the biological control is very important therefore, an attempt was made to introduce pathogenic fungi, against the reduction of acridid population in Sindh. During the present study, a total of 2520 specimens pertaining to 06 sub-families of Acrididae were collected from different ecological zones of Sindh. The isolation percentage of entomopathogenic fungi and their association with pest species of grasshopper has been presented in comparative manner. Total No. of isolated percentage of Aspergillus niger was reported 6.77% and 5.64% on Acrida exaltata and A. gigantea respectively, in sub-family Acridinae, 6.21% in Acrotylus humbertianus of Oedipodinae and 5.08% Truxalis exmia exmia contaminated with A. fumigatus and Oxya fuscovittata infected 5.08% with A. flavus. The order of prevalence of grasshopper’s species varying in both selected region. Lethal infection level of entomopathogenic fungi from lower Sindh, site-I indicates that significant highest No. of sporulation was recorded for A. gigantea and A. exaltata i.e 71.42% and 68.42% respectively, while unknown fungal infection was 36.36% followed by 31.57% on Phlaeoba tenebrosa and A. exaltata respectively. It was observed that infestation ratio of entomopathogenic fungi vary species to species in different localities. Beside this, observations taken under Scanning Electron Microscopy (SEM) showed that there is significant difference in coloration and phialides pattern of three Aspergillus species including two unknown fungi. SEM results regarding spectrum acquisition indicate that normal weightage % of Oxygen (O2) was highest i.e 56.19% followed by 42.60% for Carbon (C) and very least ratio i.e 1.21% for Sodium (Na) was observed in A. niger. As far as, chemical composition of A. flavus is concerned the normal weightage % for Carbon (C) was 52.33% followed by Oxygen (O2) i.e 46.84% opposing to this, least percentage was calculated for Sodium (Na) 0.83%. In case of A. fumigatus the greater normal weightage % was found for Oxygen (O2) i.e 54.61% followed by 43.92% for Carbon (C). Food consumption and faecal production by the insects treated with different formulation of the Aspergillus species were analyzed under laboratory conditions. Three replicates i.e A. flavus, A. fumigatus and A. niger excluding control. It seems that greater reduction in faecal production was noticed after the treatment of oil formulation. Reduction in feeding of the infected insects stages (N1 to N3) was started after treatment of 1st to 2nd day. Significant reduction in faecal production was noted from 1st to 4th day after that all immature consists on (N1 to N3) stages were died except few individuals. However, mortality of insects on day first was noted significantly highest i.e [F0.48 = 84.65, P < 0.05] followed by [F0.35 = 61.96, P < 0.05] and [F0.27 = 48.00, P < 0.05] on day 4th and 2nd respectively. Beside this, it was extremely low [F0.17 = 30.54, P < 0.05] on day 3rd. As for as developmental stage of (N4 to N6) are concerned their faecal production was significantly reduce on 2nd day i.e [F0.18 = 32.29, P < 0.05]. The faecal production of Acridid (adults) when treated with conidial concentration in H2O was found maximum on first day. Mortality of Acridid adults suggest that maximum casualties were noted on day 7th i.e [F13.7 = 23.56, P < 0.05] followed by [F12.5 = 21.82, P < 0.05] on 6th day and minimum mortality i.e [F0.44 = 77.67, P < 0.05] was on day 1st followed by [F0.77 = 35.26, P < 0.05] on 3rd day. The results showed that cumulative percent of faecal material of the treated insect with various pathogenic fungi was significantly differ with control whereas other three treatments having significant impact on the food consumption and feeding behaviour, even as the mortality of Acridid when treated with H2O formulation, indicate that maximum mortality of individual was record on day 8th i-e [F1.00 = 02.62, P < 0.05] whilst, it was significantly low i.e [F0.06 = 11.34, P < 0.05] and [F0.02 = 04.36, P < 0.05] on day 1st and 2nd. However, mortality of these adult individual were non-significant from day 3rd to 7th respectively. During the present investigation, it was noted that insect pathogen unlike chemical insecticides don’t have quick response on pest feeding but, after 2 nd day insect gradually reduce its feeding. Sexual reproductive activities of Hieroglyphus oryzivorus were also affected by the infection of Aspergillus. It was noticed that infected insects altered their thermoregulatory response and showed very interesting behavioral changing that include: insect’s feeding stopped completely, poor coordination, jerky movements, excessive grooming, loss of orientation, confuse during mating, short mating , drop egg without searching oviposition site, ecdysis process slow or complete stop, Behavioral fever (body temperature raised) and body fat accumulation was also reduced. Present study recommends that exploration and screening must be conducted to provide additional pathogens for evaluation as potential biological control against grasshoppers and locusts.
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