Browsing by Author "Nalina Kumari, T"

Now showing 1 - 3 of 3

Degradation of mancozeb residues in pepper and the effect of processing on the removal of residues
(Kerala Agricultural University, 1997) Naseema Beevi, S; Thomas Biju Mathew; Visalakshi, A; Nalina Kumari, T
Impact of botanicals on pests and defenders in rice ecosystem
(Department of Entomology, College of Agriculture, Vellayani, 2000) Ajaya Kumar, C; Nalina Kumari, T
The magnitude and intensity of insect pest and their defenders at different growth stages of rice were assessed in a survey during the virippu season of 1998, adopting random sampling technique, in three taluks of Thiruvananthapuram district. The survey revealed that the occurrence and distribution of the population of pests and defenders were same in the various locations, where the tolerant variety Jyothi was cultivated. The total population of pests and defenders observed at different growth stages of the crop followed a definite pattern in the three locations. Different concentrations of the leaf extracts of A. indica, and C. infortunatum and nimbecidine were evaluated in the laboratory for their antifeedant and deterrent activity and contact toxicity against important pests of rice and their defenders. Based on the percentage of leaf protection, the plant products tested were superior to control against C. medinalis. The same effect was noticed with N. depunctalis, only with the highest dose of leaf extracts of A. indica and nimbecidine. Seventy five per cent deterrent effect was observed to N. lugens at the highest dose of the plant products. None of the plant products showed any deterrent action against L. acuta or exhibited contact toxicity to L. acuta, C. medinalis. N. depunctalis andN. lugens. Both the defenders tested CL. pseudoannulata and O. nigrofasciatay; were safe with the plant products. 2 Replicated experiment was conducted on rice to evaluate the efficacy of plant products in suppressing the pests as well as in augmenting the defenders under field conditions. The leaf extract of C. infortunatum was found to be efficient in suppressing the population of C. medinalis. The effect was same as that with insecticides. The population of N. depunctalis was reduced by the leaf extracts of A. indica and C. infortunatum as observed in treatment with carbaryl. The suppressing effect observed on N. lugens was same with both the leaf extracts and insecticides, whereas, none of the treatments showed reduction in the population of L. acuta. The total population of the pests in general, showed a varying effect of plant products at different growth stages of the crop. Leaf extracts of C. infortunatum resulted in an immediate suppression of the total population of the pest at 20 DAT, whereas, A. indica gave significant reduction at 40 DAT. The treatments didnot show any effect on the total pest population at 60 DAT. The effect of plant products on spider population revealed that they were found to be safe. The leaf extract of A. indica increased the spider population at 20 DAT and C. infortunatum at 60 DAT, whereas, insecticides showed harmful effect up to three days after application. Adverse effect with plant products on the population of 0. nigrofasciata was not observed in any of the treatments. An increase in the population of the predator was observed with leaf extracts of A. indica at 20 DAT and with C. infortunatum at 40 and 60 DAT. Significant reduction in the population of Agriocnemis spp. was recorded in treatment with leaf extract of C. infortunatum, whereas, significantly higher population was observed in treatment with leaf extract of A. indica. The population of M crocea was reduced due to the application of plant products and the effect was retained up to three days after application. 3 The influence of plant products on the total population of defenders has clearly indicated that the leaf extracts of A. indica and C. infortunatum were safe to the defenders. Based on the P:D ratio, these products were found to have the best effect in augmenting the population of defenders and suppressing the population of pests. Significant differences in the grain and straw yield was not recorded either in treatments with plant products or with insecticides when compared with control. Overall assessment of the results obtained revealed that A. indica and C. infortunatum can be effectively and safely used for the management of important pests of rice with out much adverse effect on non target organisms in the rice ecosystem. Just like A. indica, C. infortunatum could also be utilised for developing effective plant protection chemicals for replacing undesirable synthetic insecticides in integrated pest management.
Studies on the extent of damages caused by pests of stored copra and controle of the important pests
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1989) Nalina Kumari, T; Mammen, K V
The magnitude and intensity of insect pest attack in stored copra, in the Southern Districts of Kerala, were assessed in an elaborate survey, adopting a random sampling technique for two years. The survey revealed that insects cause significant damage even in well preserved good quality copra stocked for more than five months. N. rufipes, O. surinamensis, A. advena and L. serricorne were the major pests recorded. The immature stages of N. rufipes, adults and immature stages of the other pests were seen inside the tunnels made between the endosperm and testa. N. rufipes and O. surinamensis were distributed widely, while the predominant insects observed at Nedumangad were A. advena and L. serricorne. All the insects were found breeding on copra from June to October. A positive correlation between moisture content of copra and the insect incidence was observed in the studies. The influence of A. flavus on the extent of damage caused by these pests showed that the presence of the mould was not a predisposing factor for insect attack. The extent of damage in copra due to the infestation by N. rufipes was 12.2 per cent at the end of sixth month whereas O. surinamensis caused only three per cent damage. When combind with fungus, the damage caused by N. rufipes was reduced by 50 per cent. This effect was not observed on O. surinamensis. The infection by the fungus adversely affected the oil content of copra and this effect was not altered by the preceeding or succeeding infestation of the insect. The insect attack alone caused significant reduction in oil yield of copra during the sixth month after exposure only. The quality of oil was adversely affected when infested by insects and fungus independently. The infestation of insects preceeding or succeeding fungal infection did not alter the adverse effect caused by them independently. The quantitative loss caused by the attack of N. rufipes and O. surinamensis to copra obtained from different varieties of coconut did not show significant variations. Among the different varieties tested LM and LO were more favourable to N. rufipes and DxT and TxD to O. surinamensis. Two to six fold increase in the longevity of the adults of N. rufipes was observed when they were provided with immature stages in addition to copra for feeding. N. rufipes and O. surinamensis caused significantly greater damage to copra under eight per cent and six per cent moisture levels respectively. The development of N. rufipes was totally arrested in copra with four per cent moisture content. The development of immature stages and adult population of N. rufipes were higher in copra containing eight per cent moisture level and those of O. surinamensis in copra containing six per cent moisture. The response to moisture fluctuations was more conspicuously seen in O. surinamensis than in N. rufipes. Though the population of insects were found to be high in reused gunny bag followed by heap storage, the extent of damage was higher in heap storage than in reused gunny bags. High populations of N. rufipes and O. surinamensis were recorded from heap and reused gunny bags respectively. Low populations of insects were recorded in copra stocked in polythene/alkathene lined gunny bags and netted polythene bags. But the oil extracted from copra stored in these types of bags gave significantly higher acid values. In the trials done to find out a safe prophylactic method of control against pests of copra, malathion and phoxim proved more toxic to N. rufipes and malathion and fenitrothion to O. surinamensis. When these insecticides were evaluated for their persistence on gunny bags, malathion 0.4 per cent gave protection up to five months and fenitrothion 0.8 per cent up to six months. The residues of malathion and fenitrothion came below tolerance limits, 15 and 60 days after treatment respectively . For complete control of the major pests of copra 4.5 g/m (2.5 g ai/m ) of aluminium phosphate with one day exposure period was found adequate. The residue of phosphine in the copra fumigated as above was below tolerance limit.