Egyptian Journal of Biological Pest Control, 25(1), 2015, 57-60
Response of the Predatory Mite, Phytoseiulus persimilis Athias-Henriot to Spider Mite-induced Volatiles from Faba Bean and Lima Bean Leaves Somaye K. Shastani; Malihe Latifi and Mahdi Ziaaddini Fac. of Agric., Dept. of Plant Protection, Vali-e-Asr University of Rafsanjan, Rafsanjan, Iran. Email:
[email protected]. (Received: December 16, 2014 and Accepted: February 4, 2015)
ABSTRACT Attraction of the predatory mite, Phytoseiulus persimilis Athias-Henriot to the volatiles emitted from spider mite, Tetranychus urticae Koch, infested lima bean and faba bean leaves and how previous experience affect works on the predatory mite attraction was studied. The results showed that the predatory mites reared on infested lima bean leaves didn’t show a preference to clean air (18%) and volatiles emitted from infested faba bean leaves (51%). When the predators were reared on infested faba bean leaves for 7 days, they preferred infested faba bean leaves to clean air (72%) and clean lima bean leaves (74%).
Key words: Phytoseiulus persimilis, Tetranychus urticae, Foraging behavior, Olfaction, Plant volatiles. INTRODUCTION Tetranychus urticae Koch is a phytophagous with a vast array of host plants and the blends of herbivoreinduced plant volatiles (HIPV) differ between hosts in qualitative and quantitative respects (Takabayashi et al. 1991 and 1994). Host plants respond to presence and damage of spider mites with the production of volatiles that attract the predatory mite Phytoseiulus persimilis Athias_Henriot (Krips et al. 1999). P. persimilis follows these odors to find its prey. Drukker et al. (2000) demonstrated that some studies showed that HIPV mediate arrestment and attraction of predators toward spider-mite infested plants. Many predatory mites can survive on alternative food source, but P. persimilis feeds almost exclusively on the mites of genus Tetranychus (Sabelis, 1985). The present work aimed to study whether the attraction and preference of the predatory mite P. persimilis are affected by experience in a spider mite patch on lima bean and faba bean leaves. MATERIALS AND METHODS The experiments were conducted under greenhouse conditions (25±2°C, 60±10% R.H. and 16L: 8D h). Lima bean (Phaseolus lunatus) and faba bean (Vicia faba) plants were grown in 2.5 ml pots in greenhouse. Potted bean plants were used to rear T. urticae. Adults of T. urticae were transferred to a Petri dish (9cm diameter), each with either lima bean or faba bean leaves placed on wet cotton. The Petri dishes were used as rearing units. Water was added to the rearing units when necessary to keep the cotton moist. Plants with 4 same aged leaves were used for experiments. Predatory mite, P. persimilis was released on the rearing units and was fed on a mixture of all stages of T. urticae. Cultures were kept in growth chamber at
the above conditions. When over population of the predatory mites observed, predators were transferred to a new rearing unit with all stages of T. urticae. Two day old adults of P. persimilis females were selected as searching predators for the olfactory experiments. Olfactometer experiments The olfactory response of P. persimilis to volatiles emitted from spider mite-infested lima bean and faba bean leaves, were tested in a Y-tube olfactometer with a 14 cm long basal arm and two 10 cm long arms, each with 2 cm inner diameter. Predators were introduced at the starting point of a steel Y-shaped wire that was fixed at the center of the Y-tube. An air pump with a flowmeter (Testo 425 Hot Wire ThermoAnemometer) was used to adjust the airflow approximately at 41 min in each arm. Air cleaned by activated charcoal and humidified by passing it through a 1000 ml Erlenmeyer flask with 500 ml of distilled water. The apparatus was oriented horizontally with arms situated 30 cm below florescent lights. Odor sources were changed after five mites had been tested to remove any unexpected bias. 20 P. persimilis adult females were tested per replicate in a climatic-controlled room (25±2°C, 60±10% R.H. and 16L: 8D h). Five replicates were used per experiment, using new source of odors. Spider mite infested lima bean and faba bean leaves were used as odor sources. The behavioral responses were statically analyzed with χ2 test to determine whether their distribution differed from 50:50 in SAS 9.1. In this study two groups of predators were used: A) predators reared from egg to adulthood on spider mite infested lima bean leaves and then left for seven days on spider mite infested lima bean leaves, and B) predators reared from egg to adulthood on spider mite infested lima bean leaves then reared on spider mite infested faba bean leaves for 7 days.
58 Assessment of the effect of new experience of plant-prey Response of predators belonged to group A were tested on 1. Spider mite infested lima bean leaves versus clean faba bean leaves, 2. Spider mite infested lima bean leaves versus clean air, and 3. Spider mite infested faba bean leaves versus clean air. The response of predators belonged to group B were tested to 1. Spider mite infested faba bean leaves versus clean lima bean leaves, 2. Spider mite infested faba bean leaves versus clean air, and 3. Spider mite infested lima bean leaves versus clean air. Assessment of the effect of experience on predator’s preference Response of predators belonged to groups A and B were tested to spider mite infested lima bean leaves versus spider mite infested faba bean leaves. RESULTS AND DISCUSSION Assessment of the effect of new experience of plant-prey Predators belonged to group A showed a significant preference to spider mite infested lima bean leaves over clean faba bean leaves (71%) (χ2= 22.0417, df= 1, p=0.0391) and clean air (80%) (χ2= 39.2245, df= 1, p˂0.0001) but these predators didn’t prefer volatiles from clean faba bean leaves (51%) than to clean air (45%) (χ2= 0.375, df= 1, p˂0.05) (Fig. 1). Predators belonged to group B showed a significant preference to spider mite infested faba bean leaves over clean lima bean leaves (74%) (χ2= 29.5684, df= 1, p˂0.0001) and clean air (72%) (χ2= 24.000, df= 1, p˂0.0001), but these predators didn’t prefer volatiles from infested lima bean leaves (37%) to clean air (57%) (χ2= 4.2553, df= 1, p=0.0391) (Fig. 2). These results showed that preference of predator to infested lima bean leaves
changed to infested faba bean leaves, during 7 days in which the predators were reared on infested faba bean leaves. Krips et al. (1999) showed also that the predators, reared on gerbera with spider mites, had a stronger response towards the gerbera volatiles than the predators, reared on bean with spider mites. They demonstrated that experience with spider miteinfested gerbera leaves greatly increases the response of the predators to spider mite-induced gerbera volatiles. In contrast, the predators that were kept for six days on spider mite-infested bean leaves didn’t show preference for volatiles from gerbera leaves with spider mite damage. Six days of experience in a spider mite patch on lima bean leaves greatly enhanced the response of P. persimilis (Krips et al., 1999). They demonstrated that this is most likely caused by a change in behavior of individual predators rather than a selection for the bestresponding individuals. Takabayashi et al. (1994) showed that the response of P. persimilis was affected by experience. The predator’s response to infested cucumber leaves increased gradually during seven days that it was reared on this plant. Dick et al. (1990) found that P. persimilis reared on T. urticae-infested lima bean preferred the odor from T. urticae-infested lima bean over the odor from T. urticae-infested cucumber. This preference changed gradually to a preference for T. urticaeinfested cucumber during a period of 7 days when the predators were reared on T. urticae-infested cucumber. They suggested that the predators learned to respond to cucumber odors by sensitization that is by prolonged exposure the predators got used to cucumber odors and responded to them in the same way as they previously responded to lima bean odors (Drukker et al., 2000). Papaj and Prokopy (1989) defined sensitization as a gradual increase in response to a stimulus with repeated exposure to that stimulus.
Figure (1): In the Y-tube olfactometer, response of predators reared from egg to adulthood and then for seven days on spider mite infested lima bean leaves to a: Spider mite infested faba bean leaves versus clean air b: Spider mite infested lima bean leaves versus clean air c: Spider mite infested lima bean leaves versus clean faba bean leaves. (χ2 test: ***p
