Guava is an important fruit crop and getting an important commercial fruit in Bangladesh. There are a lot of problems in guava cultivation in Bangladesh among which the guava spiraling white fly (Aleurodicus dispersusu Russel) has become a serious problem to guava cultivation in Bangladesh. In the recent time, it has been a common and major pest of Kazi Piara, a high yielding guava variety released by Bangladesh Agricultural Research Institute (BARI). Severe infestation of this pest may result in defoliation of the whole plant causing serious yield reduction of the fruit crop. Indirectly, the white fly causes reduction of yield by transmitting viral pathogens and through secretion of wax and honey dew, reduces the photosynthetic areas of the plant (Alam et al., 1998). Heavy colonization of white fly may cause a serious indirect damage to the crop due to honeydew excretion on the leaves or on fruit surfaces which encourages growth of the sooty mould by a fungus, Capnodium citri and in turn affects the yield both in quantitative and qualitative way (Byrnee et al., 1990, Kajita and Alam, 1996). Among 46 species, 3 species, Aleurodicus nubilans (Buckton), A. spiniferus (Quaintance) and A. woglumi (Ashby) were reported to be the pest of guava in Bangladesh including Aleurodicus dispersus Russel (Alam, 1962). From a two time study at the Germplasm Centre of Fruit Tree Improvement Project (FTIP) showed that the incidence and abundant of white fly from August to May (Rahim and Rahman, 2001).
To control white fly, use of chemicals is common in Bangladesh, which causes hazards to health through residual effect of chemical insecticides. It also creates natural imbalance through killing the beneficial insects. Moreover, sometimes it was for the chemicals, do not control white fly completely. So, to save the environment for the better health of the human being and making a friendly environment for the beneficial insect, an attempt was undertaken to control the spiraling white fly of guava by spraying wheel powder, a common, cheap and readily available detergent of Bangladesh.
Materials and Methods
The experiment was conducted in the Guava Orchard of Germplasm Centre of Fruit Tree Improvement Project, Department of Horticulture, Bangladesh Agricultural University, Mymensingh during October-January 2000 and 2001. Different levels of concentrations, viz., 1.0, 2.5, 5.0, 7.5, 10.0, 15.0, 20.0, 30.0 and 40.0 g litre-1 detergent (wheel powder) were mixed with tube well water and were sprayed 3, 10 and 20 days after the 1st spray. The total population of the insect was counted before 1st spray, 3 days after 1st spray but before 2nd spray, 10 days after 10 1st spray but before 3rd spray and 21 days after 1st spray but before 4th spray as 2nd, 3rd and 4th spray was done 3, 10 and 21 days after 1st spray respectively. Knapsack sprayer was used to spray the detergent. It was sprayed during 10-12 am. The two-factors experiment was laid out in randomized complete block design (RCBD) with 4 replications having 3-unit plant per replication.
Results and Discussion
Spraying with 10 g litre-1 of detergent was found most effective after 4th spray having no white fly in guava leaves without any leaf burning followed by 15 g litre-1 after 3rd spray having no white fly in the leaves with little burning of the leaves (Table 1). Sprayed with detergent @ 20 g litre-1 of water was effective in white fly control causing little, medium and serious leaf burning after 2nd, 3rd and 4th spaying respectively.
|| Effect of different concentration of detergent (wheel powder)
on the control of guava white fly
|DAFS= Days after first spray ** = P<0.01
|| Effect of frequency of spraying of detergent on the control
of guava white fly
|| Effect of different concentrations of detergent (wheel powder)
and frequency of spraying on the control of guava white fly
|DAFS= Days after first spray **: P<0.01
Sprayed with detergent @ 30 and 40 g litre-1 of water was also found effective in controlling white fly with serious leaf burning followed by total leaf dropping.
The effect of different time intervals of spraying of the detergent (wheel powder) on the control of the guava white fly showed that most effective control was recorded at 4th spray spraying 21 days after the first spray followed by 10 days after the 1st spray (Table 2). The mean number of guava white flies alive after each time intervals of the spray was significantly varied among the treatments.
Detergent (wheel powder) spraying @ 10 g litre-1 of water at 4th spray (21 days after the 1st spray) was found the most effective to control the guava white fly successfully followed by 15 g litre-1 at second spray 10 days after 1st spray with out any leaf burning (Table 3). A little leaf burning was found while spraying the detergent @ 15 g litre-1 of water after the 2nd spray. Spraying of the detergent @ 40 g litre-1 of water was found to cause serious leaf burning followed by leaf dropping.
In conclusion, the cheap and readily available detergent, wheel powder was found most effective to control white fly. Spraying of the wheel powder @ 10 g litre-1 of water at 4th spray (21 after 1st spray) was found most effective to control the white fly without any burning of the guava leaves. The 2nd spray was done 3 days after the 1st spray, 3rd spray was done 10 days after the 1st spray and the 4th spray was done 21 days after the 1st spray.
Spray of the detergent @ 15 g litre-1 of water was also found most effective if it was sprayed two times with out any leaf burning.