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 AHMED1, NISAR AHMAD AND RASHAD RASOOL KHAN Department of Agricultural Entomology, University of Agriculture, Fasialabad–38040, Pakistan 1Corresponding author’s e-mail: [email protected] 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 2nd 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 (Methamidophos, dimethoate and imidachloprid) were applied @ 500 ml, 300 ml and 250 g/acre, respectively. Among the insects pests, which infest and cause heavy losses to the citrus, citrus psylla Diaphorina citri is the most MATERIALS AND METHODS destructive and consequently the most important of all the insect pests of citrus. Citrus psylla is also a vector of a virus Site. The experiment was conducted at Chak No. 107 (Citrus tristeza colesterovirus), which is responsible for the Northern Branch in Tehsil Sillanwalli, District Sargodha, greening disease of citrus (Su et al., 1991). The population situated at the distance of 15 kilometers on Sillanwalli Road, of citrus psylla fluctuates in relation to the temperature and Sargodha. relative humidity. Citrus psylla peaks twice a year, which Population dynamics. The experiment was conducted on coincides with the periods of citrus flushing in the spring three citrus varieties (Kinnow, Musambi and Feuterell’s and summer (Wang et al., 1996; Sahu & Mandal, 1997). early). One-acre garden of each of the three citrus varieties Chemical control measures like insecticides was selected for conducting the experiment. There were 100 (Dimethoate, monocrotophos, phosphamidon, confidor, plants in area of one acre at 6.6 m distance from row to row decamethrin and fenvalevate), botanicals (neem oil, spray and same distance between plants. The observation on oils (petroleum) and insect growth regulators were tried population dynamics was taken from June 2002 to June against citrus psylla with encouraging results based on 2003. For recording the number of citrus psylla (nymphs which recommendations have been made. Two to three and adults), an area of 13 x 26 m2 was selected at the four sprays of at 10-15 days interval were found to be effective corners and one in the middle on each of three citrus against citrus psylla (Dahiya et al., 1994; Nakano et al., varieties. In this way the each of five selected areas 1999; Shivankar et al., 2000) consisted eight plants. An arrow was thrown in the selected In Pakistan, the studies on population dynamics and area and the nearest plant to the arrow was selected for chemical control of the D. citri have been carried out but counting the number of citrus psylla. From the each selected these studies were not published in scientific literature. The plant four branches were selected randomly form the four information was confined to the annual reports of research sides of the plant. Then the population of citrus psylla both institutes. The present studies were started with the nymph and adult was counted from the terminal 10 cm of following objectives: the each selected branch. For population dynamics the data i. To determine the population dynamic of citrus psyllid was recorded after every 15 days from June 2002 to June in relation to climatic conditions (temperature and relative 2003. The meteorological data was taken form Distt. humidity and rainfall) on different species of citrus Meteorological Department, Sargodha. (Kinnow, Feutrell's early and Musambi) at Sargodha Insecticides trial. For insecticides application two-acre District. garden of the each of three varieties was selected. In each ii. To get the information about the efficacy of three garden 12 plots were made. The size of each plot was 13 x insecticide against citrus psylla. Insecticide 26 m2 feet in three columns and four rows and each plot contain eight plants. There were four treatments including a CITRUS PSYLLA AND ITS CONTROL / Int. J. Agri. Biol., Vol. 6, No. 6, 2004 control and three replication of each treatment following the Table I. Population density of citrus psylla on randomized complete block design (RCBD). Three different citru spp insecticides dimethoate, imidachloprid and methamidophos were applied with the help spray gun on a knapsack sprayer. Dates Feuterell's Early Kinnow Musambi Statistical analysis. For the analysis of population 01-06-2002 0.60±0.04 0.35±0.15 1.10±0.27 15-06-2002 0.00±0.00 0.10±0.06 0.20±0.10 dynamics the data was subjected to regression and 01-07-2002 0.15±0.11 0.05±0.05 0.50±0.17 correlation with meteorological data. The efficacy of 15-07-2002 2.65±0.59 2.40±0.41 2.95±0.71 insecticides was analyzed by One Way ANOVA and means 01-08-2002 9.25±2.21 9.45±1.66 11.45±2.2 were compared by LSD. 15-08-2002 0.30±0.13 0.10±0.07 0.90±0.23 01-09-2002 4.85±1.14 3.75±0.82 6.60±1.52 15-09-2002 10.1±2.14 10.40±2.2 11.80±2.3 RESULTS 01-10-2002 2.15±0.64 2.10±0.64 2.95±0.62 01-11-2002 3.4±0.96 1.40±0.37 1.90±0.55 Population dynamics of citrus psylla on three citrus 01-12-2002 1.25±0.35 0.00±0.00 0.00±0.00 15-12-2002 0.45±0.19 0.00±0.00 0.00±0.00 species. Data of mean number of citrus psylla on Feuterell’s 01-01-2003 0.00±0.00 0.00±0.00 0.00±0.00 early per shoot are given in the Table I. The maximum 15-01-2003 0.00±0.00 0.00±0.00 0.00±0.00 number of citrus psylla on Feuterell's early was recorded on 01-02-2003 0.00±0.00 0.00±0.00 0.00±0.00 1-8-2002 (9.25), 15-9-2002 (10.10), 1-04-2003 (11.15) and 15-02-2003 0.00±0.00 0.00±.00 0.00±0.00 01-03-2003 0.50±0.17 0.00±0.52 0.8±0.24 15-04-2003 (12.15). The minimum and maximum number 15-03-2003 2.35±0.36 0.00±1.48 2.70±0.44 of citrus psylla per shoot in the data were zero and 24, 01-04-2003 11.15±0.18 2.00±3.10 11.30±0.89 respectively, (data not shown). Analysis of the variance of 15-04-2003 12.15±0.81 8.50±3.14 12.75±0.83 the mean number of citrus psylla at fortnight interval 01-05-2003 3.95±0.87 10.50±2.2 4.35±0.66 15-05-2003 1.85±0.36 2.00±1.17 2.75±0.47 showed highly significant variation among the number of P-value 0.00** 0.00** 0.00** citrus psylla at various fortnights. Data of the mean number of citrus psylla per shoot on relative humidity, rainfall and date-rainfall showed a Kinnow are given in the Table I. The maximum no, of citrus positive regression coefficient value. In the equation for the psylla on Kinnow was recorded at 1-8-2002 (9.45), 15-9- effect of minimum and maximum temperature on the 2002 (10.40), 1-4-2002 (8.50) and 15-4-2003 (10.50). No population, R2 values were very low. The maximum R2 citrus psylla was seen from 1-12-2003 to 15-2-2003. The (19.42) value was observed in multivariate equation of the minimum and maximum no. of citrus psylla in the data were effect of above-mentioned environmental factors on the zero and 25, respectively, (data not shown. Analysis of population variance of mean number of citrus psylla at fortnight The effect of minimum and maximum temperature, interval showed highly significant variation among the relative humidity and rainfall on the population dynamics of number of citrus psylla at various fortnights. citrus psylla on kinnow is given in Table II. The correlation Data of mean number of citrus psylla per shoot on values obtained by the Pearson's analysis (MiniTab11) Musambi are given in Table I. The maximum number of showed that the relative humidity, rainfall and date-rainfall citrus psylla on Musambi was recorded on 15-7-2002 were negatively correlated with the population. The effect of (11.45), 15-9-2002 (11.80) and 15-04-2003 (12.75). No rainfall and date-rainfall was non-significant as correlation citrus psylla was seen from 1-12-2002 to 15-2-2003. The values were less than 0.1. The minimum and maximum minimum and maximum number of citrus psylla per shoot temperature was positively correlated with the population. in the data were zero 0 and 27, respectively, (data not The simple regression equations of the effect of minimum shown. Analysis of variance of mean number of citrus and maximum temperature, relative humidity, rainfall and psylla at fortnight interval showed highly significant date-rainfall showed a positive regression coefficient value.