CULTIVAR RESISTANCE AND CHEMICAL CONTROL OF TOMATO FRUITWORM, Heliothis Hb. armigera ON TOMATO ( Lycopersicon esculentum Mill. )

Abstract

During present investigation experiments were conducted on the pest phenology on tomato crop for three years (1989-91), at Pes t Peshawar. Institute, Tarnab, Research Agricultural pehnological studies comprised egg, larval population dynamics, spatial distribution analysis and development of larval time sequential sampling plan. On population dynamics, the regression equation for egg and/or larval population development showed feeble negative p values during 1989 and 1991, and positive p values All equations showed poor correlation during the year 1990. coefficient. The sequent ional sampling programme data showed two distinct population configurations i.e. outbreak and endemic. The differences in growth rates between types were small at first. , A total of ca . 6 samples reached to its peak and then declined. (each week) would be adequate to detect type of configuration in any one year. Spatial pattern of H. armigera Hb . egg distribution during the study revealed that index of dispersion (I.D.) values were more than 1 in 1990 and 1991. However, in 1989 the l.D. values oscillated around 1. Moreover, most of the green's index (G.I.) values were positive which confirm the negative binomial The I.D. values of the distribution of Hÿ_ armigera Hb. eggs. spatial pattern of H. armigera Hb. larval distribution were mostly higher than 1. Therefore, larval distribution also fits negative binomial distribution. The results of discriminating doses of potassium fertilizer on egg and larval population, and the fruit infestation showed that there was no significant effect of fertilizer on the uptake of tomato plants, on egg and larval population, and on the infestation of tomato. To compare relative efficacy of nine insecticides, one application was done during the year (1989), and three during each remaining two years of study i.e. 1990 and 1991. All the insecticides were found successful in keeping the larval population below outbreak configuration level upto 15 days after spray. ( viii ) S ! Consolidation of study data over a period of three years revealed that Thiodon was statistically the most effective wiLh 77.88 percent larval mortality, followed by Folidol M (75.96%), Sevin (69.32%), Thuricide (67.12%), Dimilin (66.38%), Edcidin (65.32%) and Atabron (59.85%). Permasect and Azodrin were significantly the mortality larval and 54.66% 58.55% with effective least level). The resulLs also respectively (cdii = 17.03 at 0.05 indicated a tendency in the reduction of effectiveness of Folidol M, Azodrin, Dimilin and Thuricide over a period of three years which might probably be due to enhancement in the degree of tolerance developing in H. armiqera Hb . Cluster analysis on the interactions of eggs and larval per plant, percent fruit damage and yield in Kg per plant of 65 toniaLo cultivars gave five cluster groups. Frequency-wise cluster analysis showed two varieties in group A (3.08%), two in B (3.08%), one in C (1.53%), fifty nine in D (90.78%) and one in E (1.53%). In the regression analysis of correlation between characteristics of 65 varieties and H- armiqera Hb. infestation, step-wise model was fitted, the correlation between infestion gave negative dependence larval infestation (-0.3251) with poor correlation (-0.2558) . Similar coefficient results were obtained for correlation between yield and number of larvae per plant (b=0.4Q04, r=0 . 0893 ) The step-wise model correlation between larval chemical/physical population and parameters gave negative dependence on trichome length (-0.0100) and iron content (-15494E- 04) and positive dependence on zinc (0.0028) and vitamin C (0.0279). Cluster analysis on the interaction of larval duration, pupal duration, adult longevity, duration of life cycle, larval and pupal weight and survival to adult stage also gave five cluster groups . Frequency-wise cluster analysis showed two varieties in group A (3.08%), four in B (6.15%), fifty two in C (84.62%), three in D (4.62%) and one in E (1.53%). Tiny Tim being moderately resistant cultivar, was placed in group E. . The results indicated that integration of resistant cultivar, Tiny Tim and Bacillus thurinqiensis had maximum effect on larval mortality and minimum percent fruit infestation, it was followed by accession 87-11(1) also a resistant line, while the maximum infestation was recorded on the most susceptible cultivar, Big long. The host range and average number of larvae/plant of H. armiqera Hb were recorded on soybean (1.63), gram (4.80), tomato (0.31), tobacco (1.64), maize (0.81), sunflower (0.07), okra (0.67), potato (1.92) and burseem (0.90). Gram was observed to be the most favourable host plant of this pest