Comparison Ability of Three Plant Pesticides, Two Chemical Acaricides and Conventional Mineral Oil against Citrus Red Mite Panonychus citri (McGregor) (Acarina: Tetranychidae)

The harmful plant mites not only feed on crops, but also have irreversible damage to humans. The synthetic pesticides can be replaced with natural products for pest control. The agricultural products, health and hygienic of humans can be treated with harmful caused by the mites (Wooley, 1988). The citrus red mite (CRM) Panonychus citri (McGregor) (Acarina: Tetranychidae) is one of the most important herbivorous pests in citrus growth area. For the first time, this pest was reported from Mazandaran province in 1940. The nymph and adult of these pests create identified small, silver and gray spot on leaves and fruits. As a result of feeding, contamination can cause necrosis of leaves, loses of young leaves and reduce the plant freshness. The synthetic of pesticides has been used for controlling of this pest for a long time. The application of non-normative methods for control of the mites can cause pest outbreaks and destroy the natural enemies of the pest. This pest has been resistant to a wide range of pesticides such as; Dicofol, Hexythiazox, Abamectin and Pyrothroids in field conditions. In recent decays, the organic agriculture has been grown dramatically. Lio (2003) has reported that at least 30 countries produce organic citrus fruit. So, for growing organic citrus in Iran, it also suggested to use the low impact pesticides to the environment and the human health. In this research, the comparison toxicity of three botanical pesticides Tondexir (red pepper extract), Sirinol (garlic extract), Palizin (eucalyptus extract) with two common chemical pesticides (Hexythiazox and Fenpyroximate) and common mineral oil has been investigated against adult and protonymph of citrus red mite P.citri.
The citrus red mite (CRM) has been collected from infected trees from citrus orchard and brought into the lab; after that, the adult and nymphs were separated. The citrus red mite has been reared on citrus leaves in growth chambers with constant condition (25 ±2oC, 16:8 L/D and 60% RH conditions). The primary test has been done to identify the maximum and minimum concentration. For bioassay experiments, the citrus leaves were washed and cleaned with distilled water and prepared in 20 mm diameter leaf disc. The bioassay was carried out using leaf dip methods with different concentration of the following pesticides after primary experiment: Mineral oils (2000, 2828, 4000, 5657 and 8000 ppm), Tondexir (1000, 1368, 1871, 2559 and 3500 ppm), Sirinol (750, 1102, 1620, 2381 and 3500 ppm), Palizin (2000, 2378, 2828, 3364 and 4000 ppm), Hexythiazox (250, 370, 548, 811 and 1200 ppm) and Fenpyroximate (500, 679, 922, 1252 and 1700 ppm). The mortality was recorded at 24, 48 and 72 h after-treatments. All experiments were conducted with three replications. The statistical analyses were performed by SPSS version16.0 software.
The Probit analysis was shown that the LC50 value of the mineral oils on protunymph and adult of citrus red mite were 1743.6 and 1898 ppm, the LC50 value of the Tondexir were1305.9 and 1549 ppm, the LC50 value of the Sirinol were 666.1 and 693.9 ppm, the LC50 value of the Palizin were 2206 and 1969.2 ppm and the LC50 value of the Hexythiazox were 223.6 and 227.3 ppm at 72 h post-treatments, respectively consequently and the probit analysis was revealed that the LC50 value of the Fenpyroximate on protonymph and adult of citrus red mite were 480 and 439.3 ppm at 72 h post-treatments, respectively. Consistent with our result, the acaricide, Hexythiazox had higher toxicity on adult and protonymph of CRM in comparison to the other pesticides. Among three botanical pesticides, Sirinol has the highest toxicity. Due to the low risk of three botanical pesticides, they should be considered in IPM program.
The data analysis of this research was shown that among different compounds, the highest and lowest toxicity on adult and protonymph were obtained with Hexythiazox and Plazin consequently respectively. By comparison the LC50 values, the protonymph was more susceptible than adult. With regards of being low risk and natural products of the botanical pesticides and mineral oils for humans, it is better to use these products to control red mites.