INTERNATIONAL JOURNAL OF AGRICULTURE & BIOLOGY 1560–8530/2004/06–6–970–973 http://www.ijab.org Studies on Population Dynamics and Chemical Control of Citrus Psylla, Diaphorina Citri SOHAIL AHMED 1 , NISAR AHMAD AND RASHAD RASOOL KHAN Department of Agricultural Entomology, University of Agriculture, Fasialabad–38040, Pakistan 1 Corresponding author’s e-mail: saha786@fsd.paknet.com.pk ABSTRACT The experiments were conducted on three citrus species (Feuterell’s early, Kinnow, Musambi) about the population dynamics and chemical control of citrus psylla at Chak No. 107, Sargodha. Data on the population of citrus psylla showed two peak times in a year, firstly in the month of August and 2 nd time in the month of April. Correlation values showed that environmental factors had almost no effect on the population build up of citrus psylla. Three insecticides, methamidophos, dimethoate and imidacloprid applied, had almost equal effect on the population reduction of citrus psylla on all the three species of the citrus. Key Words: Population; Citrus; Insect pests; Insecticides; Imidacloprid INTRODUCTION Among the insects pests, which infest and cause heavy losses to the citrus, citrus psylla Diaphorina citri is the most destructive and consequently the most important of all the insect pests of citrus. Citrus psylla is also a vector of a virus (Citrus tristeza colesterovirus), which is responsible for the greening disease of citrus (Su et al., 1991). The population of citrus psylla fluctuates in relation to the temperature and relative humidity. Citrus psylla peaks twice a year, which coincides with the periods of citrus flushing in the spring and summer (Wang et al., 1996; Sahu & Mandal, 1997). Chemical control measures like insecticides (Dimethoate, monocrotophos, phosphamidon, confidor, decamethrin and fenvalevate), botanicals (neem oil, spray oils (petroleum) and insect growth regulators were tried against citrus psylla with encouraging results based on which recommendations have been made. Two to three sprays of at 10-15 days interval were found to be effective against citrus psylla (Dahiya et al., 1994; Nakano et al., 1999; Shivankar et al., 2000) In Pakistan, the studies on population dynamics and chemical control of the D. citri have been carried out but these studies were not published in scientific literature. The information was confined to the annual reports of research institutes. The present studies were started with the following objectives: i. To determine the population dynamic of citrus psyllid in relation to climatic conditions (temperature and relative humidity and rainfall) on different species of citrus (Kinnow, Feutrell's early and Musambi) at Sargodha District. ii. To get the information about the efficacy of three insecticide against citrus psylla. Insecticide (Methamidophos, dimethoate and imidachloprid) were applied @ 500 ml, 300 ml and 250 g/acre, respectively. MATERIALS AND METHODS Site. The experiment was conducted at Chak No. 107 Northern Branch in Tehsil Sillanwalli, District Sargodha, situated at the distance of 15 kilometers on Sillanwalli Road, Sargodha. Population dynamics. The experiment was conducted on three citrus varieties (Kinnow, Musambi and Feuterell’s early). One-acre garden of each of the three citrus varieties was selected for conducting the experiment. There were 100 plants in area of one acre at 6.6 m distance from row to row and same distance between plants. The observation on population dynamics was taken from June 2002 to June 2003. For recording the number of citrus psylla (nymphs and adults), an area of 13 x 26 m 2 was selected at the four corners and one in the middle on each of three citrus varieties. In this way the each of five selected areas consisted eight plants. An arrow was thrown in the selected area and the nearest plant to the arrow was selected for counting the number of citrus psylla. From the each selected plant four branches were selected randomly form the four sides of the plant. Then the population of citrus psylla both nymph and adult was counted from the terminal 10 cm of the each selected branch. For population dynamics the data was recorded after every 15 days from June 2002 to June 2003. The meteorological data was taken form Distt. Meteorological Department, Sargodha. Insecticides trial. For insecticides application two-acre garden of the each of three varieties was selected. In each garden 12 plots were made. The size of each plot was 13 x 26 m 2 feet in three columns and four rows and each plot contain eight plants. There were four treatments including a