Effect of potassium fertilization and organic nutrient (Reef Amirich) in the population density of Bemisia tabaci (Genn.) and Thrips tabaci (L.) on cucumber

A field study was conducted at the college of Agriculture, Baghdad UniversityJadiriyah to investigate the effect of adding potassium fertilizer and organic nutrient (Reef Amirich) on the population density of two sucking pests of cucumber, cotton whitefly, Bemisia tabaci and onion thrips, Thrips tabaci during the spring season/2016. Results indicated that potassium sulphate (50, 100 and 150 kg/ha) and organic nutrient (0.8 and 1.6ml/l) reduced both the population density of B. tabaci and T. tabaci nymphs depending on the fertilizer level of the user, the treatment 150 kg/ha for the potassium fertilizer and 1.6 ml/L for organic nutrient was the highest among others when minimized density of nymphs by 1.62 nymphs of B. tabaci/disk leaf and 0.38 nymph of T. tabaci / disk leaf. suggesting a possible increase in cucumber resistance to this pest as a result of the treatments, and the result showed the infestation with B. tabaci was higher in the second half of May, the average number of nymph were 5.35 nymph/ disk leaf, while the highest number of T. tabaci was observed in the first half of May, the average number reached to 2.73 nymph/ disk leaf. The result showed the interaction treatment K150A1.6 was significant superior of percentage of K and increased of content in leaves of Fe, Cu and Zn. *Corresponding Author: Hind Ibrahim AL-Khazraji  Hindaa2007@yahoo.com Journal of Biodiversity and Environmental Sciences (JBES) ISSN: 2220-6663 (Print) 2222-3045 (Online) Vol. 12, No. 2, p. 11-18, 2018 http://www.innspub. net J. Bio. Env. Sci. 2018 12 | AL-Khazraji et al. Introduction The Cucurbitaceae includes about 118 genera and 825 species (Khan et al., 2015). They are among the most widely grown and important vegetable crops in the world. Cucumber (Cucumis sativus L.) one of the most important economic vegetable crops belong to this family. This crop is attacked by a number of insect pests including cotton whitefly Bemisia tabaci (Homoptera: Aleyrodidae). Cotton whitefly is one of important insect pests in many regions of the world, with over 500 host plant species of 74 families (Perring, 2001; Stansly and Naranjo, 2010). Onion thrips (Thrips tabaci L.) (Thysanoptera: Thripidae) is a polyphagous species and a serious pest of a wide range of economically important crops in many parts of the world . Onion thrips is a native to the Mediterranean region, which causes severe damage to various crops in Africa, Asia, Europe, North and South America, and Australasia (Mound, 1997;Boatenget al., 2014). The damage of the whitefly and onion thrips by sucking the sap from leaves and flower buds. Whitefly produces honey dew which facilitates the growth of fungi on leaves and reducing photosynthesis furthermore this pest transmit the virus disease to several crops (Yokomi et al., 1995; Mc Auslane et al., 1996; Larentzaki et al., 2008). There are many important and essential elements nutriticel for plant vegetables, some of these elements required by plants in large amount such as nitrogen and potassium. Potassium plays an important role in physiological activity and plant growth and reproduction. Potassium is one of the essential nutrients of the plant. The plant's need for this element may exceed all other nutrients at some stages of plant growth (Awad, 1987). Potassium has several functions, including the activation of many enzymes, such as Synthetase, Hydrogenase, and Transferase. Potassium is also collected in the guard cells, which act as the driving force of the opening and closing of the stents as this mechanism is related to the content of potassium and sugars (Krauss, 1993). As well as the regulation of the cytosolic voltage of the cells and stimulate the absorption of CO2 by the stents and the formation of ATP (Mengel and Header, 1977, Hsiao and Lauchli, 1986). Organic fertilizer was also used to increase plant productivity one of these nutrients organic nutrient Reef Amirich Adding chemical fertilizers to the soil influences with the survival, development and reproduction of an insect (van Emden, 1966; Auclair, 1976). Pissarek (1983) noted that potassium plays a role in increasing the hardness of the cells of the plant and its tissues are difficult to attack and penetrated by insects and they are resistant to lodging, especially plant of field crops. It was reported that plant damage by insect is comparatively less in K applied plants due to reduced carbohydrate accumulation, elimination of amino acids (Baskaran et al.,1985), higher silica content and increase in the sclerenchymous layer (Dale,1988). Copper caused toxic effects in the insect species, morphological abnormalities, egg sterility and decreased fecundity and when these insect larvae fed on contaminated with cupper (Habustova and Weismann, 2001). Alice et al. (2003) also recorded the low BPH population in plots treated by organic amendments. Due to the economic importance of the sucking insects and the lack of studies related to the effect of fertilizers on insects in the study area so the present study was conducted to assess the effects of Potassium and organic nutrient (Reef Amirich) fertilizer levels in cucumber, on the population density of B. tabaci and Thrips tabaci plant under field conditions. Material and methods Location and experimental design An experiment based on randomized complete block design with 6 treatments and 9 plants for each treatment, each of them replicated three times was carried out in the vegetable field of Horticulture and Landscape Engineering Department, Agriculture College, University of Baghdad. Cucumber (Gazeer hybrid) was planted in area of 450 m2. J. Bio. Env. Sci. 2018 13 | AL-Khazraji et al. Treatments Each block, which has 6 treatments, was a combination of three application rates (50, 100, and 150 kg/ ha) of potassium sulfate fertilizer and two concentrations (0.8 ml/L and 1.6 ml/L) of foliar organic fertilizer (Reef Amirich) and Control check (without fertilization). Reef Amirich