ABSTRACT One of the most effective and cost-efficient methods to manage plant parasitic nematodes is to use resistant cultivars. However, little information on the resistance of commercial okra cultivars grown in the country was available. Therefore, nine okra cultivars were evaluated for their comparative resistance against Meloidogyne incognita, the most damaging root-knot nematode. None of the tested okra cultivars showed high level of resistance. However, three cultivars viz. Pusa Swami, PB Selection and Green Star appeared as moderately resistant. Sabz Pari, Neelum and Tulsi were found moderately susceptible to the nematode. Two cultivars i.e. Ikra-1 and Ikra-2 were susceptible and Arka Anamika was highly susceptible. The okra cultivars differed significantly in their growth parameters depending on their response to M. incognita. Moderately resistant cultivars sustained little damage as compared to moderately susceptible or susceptible cultivars while the highly susceptible cultivar suffered the maximum damage by the nematode. Significant differences in the numbers of galls, eggmasses and reproductive factors of M. incognita on the nine okra cultivars were also observed. The highest numbers were found on Arka Anamika, followed by Ikra-1 and Ikra-2. The lowest numbers were found on the moderately resistant cultivars, followed by the moderately susceptible ones. High and positive correlations between the number of galls and eggmasses and the decreases in growth metrics were found using linear and non-linear regression analysis.

Abstract Brown planthopper (BPH), Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) is an economically important insect pest of rice crop worldwide including Pakistan. The use of chemicals insecticides to control the BPH population has been considered an effective strategy. However, long-term and intensive use of insecticides has resulted in resistance against this pest. In this study, six recommended insecticides were tested against BPH over the period of 2015-2019 to determine the susceptibility level. From 2015-19, susceptibility of BPH was reduced to all tested insecticides. Increasing trend of LC50 values was recorded in fipronil (18.23-35.11 mg/L), imidacloprid (64.22-128.8 mg/L), buprofezin (185.01-315.0 mg/L), chlorantranilipyrole (199.2-263.3 mg/L), pymetrozine (248.2-315.5 mg/L), and nitenpyram (21.07-34.3 mg/L) respectively from 2015 to 2019. Correlation coefficient values indicated a significant relation (P < 0.05) between fipronil, imidacloprid, and buprofezin. The study will be helpful for resistance management strategies to prevent the resistance development in BPH against insecticides.

Resumen El saltamontes marrón (BPH), Nilaparvata lugens (Stål) (Hemiptera: Delphacidae), es una plaga de insectos económicamente importante del cultivo de arroz en todo el mundo, incluido Pakistán. El uso de insecticidas químicos para controlarla ha constituido una estrategia eficaz; sin embargo, utilizarlos de forma prolongada e intensiva ha ocasionado que la plaga se vuelva resistente a dichos pesticidas. En este estudio se probaron seis insecticidas recomendados contra la BPH durante el periodo 2015-2019 para determinar el nivel de susceptibilidad. De 2015 a 2019, la susceptibilidad a la BPH se redujo a todos los insecticidas probados. Se registró una tendencia creciente de los valores de LC50 en fipronil (18.23-35.11 mg/l), imidacloprid (64.22-128.8 mg/l), buprofezina (185.01-315.0 mg/l), clorantranilipirol (199.2-263.3 mg/l), pimetrozina (248.2-315.5 mg/l) y nitenpiram (21.07-34.3 mg/l) respectivamente de 2015 a 2019. Los valores del coeficiente de correlación indicaron una relación significativa (P < 0.05) entre fipronil, imidacloprid y buprofezin. El estudio será útil tanto para llevar a cabo estrategias de manejo de la resistencia como para prevenir el desarrollo dicha resistencia de la BPH hacia los insecticidas.