Thumbnail Image

Theses

Browse

19883
Reset filters
Subject: Agricultural Entomology × Author: KAU × End date: 1988 × Start date: 1988 × Thesis Type: M.Sc ×
Reset filters

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    ThesisItemOpen Access
    Crops loss caused by root-knot nematode infesting coleus parviflours and its control
    (Department of Entomology, College of Agriculture, Vellayani, 1988) Sosamma, P; KAU; Ravindran Nair, K K
    Crop loss caused by the root-knot nematode infesting Coleus parviflorus and its control was studied in a pot culture experiment and a field experiment in the Department of Entomology, College of Agriculture, Vellayani, Trivandrum, during August to December, 1986. The number of leaves, shoot length, fresh shoot weight and weight of tubers obtained were less in inoculated plants than in control. The yield and growth parameters showed an negative correlation with the population of nematodes. A high positive correlation was noticed between the tuber weight and the number of leaves and shoot weight of coleus. The shoot length did not influence the tuber yield significantly. Roots showed profuse galling by the second month. Rotting of roots was observed by the third month, and at harvest, no healthy root was present in infected plants. Tubers when stored developed dark patches on the suface of galls and these spread inwards covering the whole of the internal tissues within nine days, and by the twelfth day the internal contents had turned into a dark brown watery liquid with a bad odour. The peel of the tubers did not show rotting. The nature of rot indicated the involvement of secondary organisms like bacterial and fungi. Histopathological studies showed that the nematodes were lodged in the cortex with head in the stellar region of the root. One month after inoculation, quadrangular giant cells (four in number) were observed in roots. There was cell proliferation in the stellar region of the infected roots. Alternate arrangement of the xylem and phloem was disturbed, though the central cylinder and cortex could be distinguished. Two months after inoculation the giant cells were seen larger and fewer in number. The cytoplasm of giant cells became granular and aggregated towards the head region of the nematode. Stele could not be easily distinguished from the cortex. The cortex was greatly enlarged due to hypertrophy and hyperplasia of cells. The development of medullary rays and secondary xylem noticed in the normal root could not be distinguished in infected roots. Infected roots showed numerous cavities formed by the disintegration of giant cells, egg masses and adult females by end of the fourth month. Necrosis of tissue was also observed. The xylem and phloem elements were not distinguishable. At five months after inoculation the tissues of the roots were completely rotten. In the field experiment application of nematicides one month after planting preceded by the burning of plant material in the field prior to planting was found better than the other treatments. Carbofuran @ 1 kg a.i./ha was more effective than phorate for the control of the nematode. No residue of carbofuran or phorate could be detected in tubers at harvest. The rotting of tubers obtained from different plots when kept in store indicated the inefficacy of the treatments for giving protection from the nematode and the need for a second application of the nematicide at tuber setting. Hot water treatments of the tubers prior to storage did not reduce the damage.
  • Thumbnail Image
    ThesisItemOpen Access
    Biology morphology nature of attack and dispersal of cytobagous salviniae calder and sands (Curculionidae coleoptera)
    (Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1988) Leena, K T; KAU; Joy, P J
    In studies on the biology and morphology of cyrtobagous salviniae calder & sands (curcullionidae: Coloeptera) a very successful agent for the bio control of the menacing weed salyinia molesta Mitchell, the females were found to insert their eggs on leaf base and rhizome scars. The egg period was 7.9 days. There are three instars, the average larva period was 23.5 days. The pupal period extended for 11.3 days. Adults showed a mean life span of 211.9 days. A pre ovipositional period of five to ten days was recorded. The three larval instars differed in respect of the relative size of head capsule and width of mandible. Adult females are slightly larger than the males. The spine like processes towards the distal end of the hind tibia are arranged in a linear manner, while in fore and midlegs these spines are arranged in a circular manner. The hind leg spur does not have a hump. Observations on the nature of damage showed that the adults were capable of arresting the growth of the weed by feeding on the buds and leaves. Occassionally they feed on rhizomes and roots. Larval scraping followed by tunneling resulted in the decay of plant parts. Weed mass showed discolouration about 15 days after initiation of feeding by the weevil and the whole weed became a black mass in about 90 days. The rate of dispersal of adult weevils was found to be very slow.
  • Thumbnail Image
    ThesisItemOpen Access
    Compatibility of insecticide and fungicide used for the control of insect pets and diseases of rice
    (Department of Entomology, College of Agriculture, Vellayani, 1988) Babu, K; KAU; Regunath, P
    Experiments were conducted in the laboratory, pots and field during 1986-88 to ascertain the compatibility of insecticides and fungicides commonly used for the control of insect pests and diseases of rice. Standard bioassay technique and poisoned food technique were adopted in the laboratory studies using N. lugens and R. solani as test organisms. Based on these, concentrations to give 25, 50 and 75 per cent mortality of insect and 50, 75 and 100 per cent inhibition of the fungus were selected. The interaction of the insecticides and fungicides when mixed in the above doses, in all possible combinations, was studied with reference to their fungicidal and insecticidal effect assayed with the above test organisms. Pot culture experiments were conducted for the assessment of effect of (i) combining insecticides and fungicides on the control of sheath blight and BPH, (ii) applying fungicides and insecticides in sequence and in combination on the control of sheath blight and N. Lugens and (iii) spraying fungicide – insecticide in combinations at different intervals after preparing the mixture, on the control of sheath blight and N. lugens. A field trial was also laid out for assessing the efficacy of fungicide – insecticide combinations for the control of sheath blight. The insecticidal effect of monocrotophos on N. lugens was not significantly altered when used in combination with captafol, ediphenphos or carbendazim in widely varying proportions. A synergistic effect was observed when quinalphos was combind with captafol or ediphenphos. Enhancement of action of lower dose of quinalphos when combind with captafol and ediphenphos was observed in pot culture study also. Enhancement in the insecticidal activity of quinalphos in the laboratory in combination with carbendazim (at 1 ppm, 2.5 ppm and 5 ppm) was limited to lower doses of the insecticide. With higher dose of the insecticide there was no significant synergism. This favorable ratio of insecticide fungicide combination is not possible in the field since the dose of fungicide required in the field for the control of R. solani ranges from 500 – 1000 ppm. Laboratory studies showed that the insecticidal effect of HCH 0.2% was significantly reduced when combined with captafol. But at 0.071 and 0.026% the combinations showed no antagonistic effect. In the pot culture experiment the insecticide and its combinations with two doses of captafol came on par. The lower dose of HCH and ediphenphos combinations were superior to the treatment with insecticide alone. The same result was obtained when HCH was combined with carbendazim in the laboratory. In pot culture studies the combinations did not show any difference with the use of HCH alone for the control of N. lugens. Laboratory studies showed feirly high fungicidal effect for monocrotophos. Monocrotophos used in combination with fungicides showed antagonistic effect at higher levels of captafol, ediphenphos and carbendazim. But with lower concentrations there was an enhancement of fungicidal effect. In the laboratory the fungicidal effect of quinalphos was observed to be high. While no antagonistic effect was observed when it was used in combination with higher levels of captafol and carbendazim, the combinations with lower levels of all the three fungicides showed synergistic effect. In the case of ediphenphos, combination of quinalphos with the higher level of fungicide showed antagonistic effect. The fungicidal effect of HCH was very high in the laboratory at all the three doses tried. The three doses of HCH in combination with varying doses of fungicides gave 100% inhibition of the fungus in the laboratory. In the pot culture experiment among the treatments, captafol 1500 ppm and monocrotophos 0.05% alone was found to be better in fungicidal action compared to the treatments with fungicides alone. Antagonistic alone was found to be better in fungicidal action compared to the treatments with fungicides alone. Antagonistic effect in disease control was observed where HCH 0.2% was combined with carbendazim 1000 ppm and ediphenphos 1000 ppm. In the field experiment, higher control of the disease was obtained in combinations of monocrotophos 0.05% with captafol 3000 ppm, or 1500 ppm, ediphenphos 500 ppm and quinalphos combined with captafol 3000 ppm and ediphenphos 500 ppm. Combination of HCH with captafol did not show any antagonistic effect, but antagonistic action was observed in combination with ediphenphos and carbendazim. Overall assessment of the data obtained from the laboratory, pot culture and field experiments showed that monocrotophos and quinalphos could be combined with captafol and ediphenphos without any antagonistic effect or even with synergistic effect. With carbendazim, monocrotophos alone is compatible. The synergism will be more in combinations in which higher proportion of insecticides were used. The possibility of lowering the quantity of fungicide in treatments when compatible insecticides and fungicides were used in combination for the control of diseases also was indicated in the experiment. When the application of fungicides and insecticides in sequence (fungicide followed by insecticide and vice-versa) was compared to the combined application, it was found that in general the treatments were all on par. It was further seen that keeping of mixtures up to 24 hours after formulation did not affect the insecticidal and fungicidal properties of the mixtures and hence they can be kept for the required length of time after preparation to finish the spraying operation in the field without any adverse effect on toxicity.