Comparision of the Efficiency of the Current Oils and Insecticide Compounds in Control of Greenhouse Whitefly, Trialeurodes vaporariorum (Westwood), (Hem.: Aleyrodidae) on Rose and their Interaction

Rose plant (R osa hybrid) is cultivated in nearly all regions of Iran and they are more common in the western areas of Iran. The intensive cultivation of rose often leads to injuries by pathogens or noxious animals and may require the implementation of pest control measures. Among the insect pests of roses, the greenhouse whitefly, Trialeurodes vaporariorum (Westwood) (Hem.: Aleyrodidae), is fairly common pest that it is considered as major pests on roses in Iran. This pest infests the undersides of rose leaves, where the feeding adults and nymphs produce honeydew on which sooty mould grows. Considering the importance of oils in the integrated management program of this pest, in the present survey the possibility of whitefly control on rose plant were carried out to assess mortality rate (MR), synergistic rate (SR) and Lc50 of the oils and common insecticide.
The experiment was conducted in a greenhouse located at the experimental site of National Ornamental Plant Institute, Mahallt, Iran. The plants (Rosa hybrid Apollo) were cut to stimulate rooting and then grown in plot containing a mixture of sand and sheep manure. Nine rose plant cuttings were planted in each plot with 1m2 space and 0.5 m distance each plot. So, each treatment had 9 shrubs of rose. The greenhouse whitefly T. vaporariorum were collected from infested rose plants and reared on rose. Each rose plant with one-year old was infested via 200 different stages of the whitefly. Fourteen days after infesting, compounds were sprayed on the infested plants with electrostatic atomizer backpack sprayer. Before spraying, plots were separated by plastic. Whitefly different stages from behind of three leaflets that separated from 15, 20 and 25 cm tip of plant were counted under a stereomicroscope (10 X) one day before and seven days after treatment. The effect of oils and common insecticide on whitefly mortality rate (MR) was performed in completely randomized block design with 20 treatments, 3 blocks and 4 replications. In addition, the bioassay of neem oil, citowett and volk on nymphal stages (2-4) as well as whiteflies adult were assayed in the greenhouse condition. The bioassay was carried out in clear plastic cages containing a leaf with three leaflets connected to the plant, containing 30 nymphs or 30 adults. Moreover, the bioassay of deltamethrin on adults and buprofezin on the nymphs and also synergistic rate (SR) of three oils including neem oil, citowett and volk on deltamethrin and buprofezin were estimated. The followed formula {SR= (Lc50A ⷎ)/Lc50 (A)} was used for calculating synergistic rate. For bioassay testes, the clear plastic cages containing three leaflets as well as 30 nymphs and also 30 adult whiteflies were used.
Based on the result of the mortality rate of oils and common insecticide, the treatment control, which was neem oil (1 ml/L) mixed with deltamethrin (0.5 ml/L), was caused 91.72 and 90.79 % MR of nymphs and adult whiteflies, respectively. Also the neem oil (0.5 ml/L) and citowett (0.25 ml/L) after water treatment had the lowest effect on the adult and nymphal stages mortality. When the oils separately were used, their LC50 were higher than they used simultaneously with deltamethrin and buprofezin. The results of the bioassay showed the Lc50 of deltamethrin mixed with neem oil, citowett and volk as: 417.55, 290.51 and 639.07 ppm, respectively. The synergistic effect of neem oil, citowett and volk with deltamethrin on the mortality rate of adult whitefly was estimated as 3.62, 5.45 and 2.56, respectively. The highest SR (7.24) of buprofezin for nymphal stage was occurred when it mixed with citowett. In addition, the SR of this pesticide was 4.86 and 3.55 for neem and volk, respectively. Also the Lc50 of buprofezin mixed with neem, citowett and volk were 214.26, 177.32 and 559.56 ppm, respectively.
According to the effect of buprofezin on insect moulting, using of this pesticide mixed with citowett, neem and volk may be helpful for chemical control of nymphal stage of whitefly. In addition, based on our results deltamethrin mixed with same oils is recommended for adult control in integrated pest management programs of this pest. Proper application of pesticides along with oilscan increase synergistic effect of pesticide and reduce their harmful effects.