A new host and distribution record for the black coccinellid, Stethorus aptus Kapur (Coccinellidae: Coleoptera)

The European red mite, Panonychus ulmi (Koch.), is a very serious pest of temperate fruit crops throughout the world and inflicts heavy losses. The indiscriminate use of broad spectrum pesticides is the main cause for Panonychus ulmi outbreaks by way of development of resistance and suppression of natural enemies (Cross and Berrie 1994). Any long-term commitment to pure chemical approach is unsatisfactory and has necessitated focusing research on other methods, especially biological control (Rather and Bano 2008). The species of the tribe Stethorini Dobzhansky (genera Stethorus Weise and Parastethorus Pang and Mao) are the specialist mite predators in the family Coccinellidae (Biddinger et al. 2009). Earlier, the genus Stethorus and Parastethorus were placed under the tribe Scymnini. But now, it belongs to the monogeneric tribe Stethorini. The Stethorini were unique from all other Scymninae due to their convex anterior margin of the prosternum and truncate clypeus near the antennal bases (Gordon 1985). The genus Stethorus is distributed throughout the world in many different climates ranging from tropical rainforests to temperate deciduous forests and plains to colder northern regions of Europe, Canada, and Russia (Chazeau 1985; Biddinger et al. 2009).

The adults and larvae of Stethorus spp. are specialized predators of spider mites (Tetranychidae) and closely related to false spider mite or flat mites (Tenuipalpididae) (Chazeau 1985). Khajuria (2009) reported that S. punctum LeConte was one of the efficient predators associated with phytophagous mites in India. The European red mite, P. ulmi was found infesting on apple and almond orchards in Kashmir Valley (32.17–36.55° N, 75.32–75.76 °E, 1700 MASL) of Jammu and Kashmir in India. An extensive survey was conducted during March to November 2011, for the collection of natural enemies of P. ulmi, with particular focus on Coccinellids. The collected specimens were sent to the National Bureau of Agriculturally Important Insects, Bangaluru, India, for species identification. After identification, the specimens were deposited in the National Bureau of Agriculturally Important Insects, Bangaluru, India.

Identified species was S. aptus Kapur (1948), which was found feeding on P. ulmi on apple and almond orchards of Kashmir valley in India (Fig. 1d). This is a new host record for S. aptus. This species was reported earlier as a predator on citrus red mite, P. citri (McGregor) in China (Li et al. 1990). The earlier records of Stethorus predators of P. ulmi were S. bifidus Kapur, S. darwini (Brethes), S. gilvifrons (Mulsant), S. puntillum Weise, S. punctum punctum LeConte, and S. vagens (Blackburn) on different host plants (Table 1). Perusal of literature shows that five species of Stethorus have been recorded in India (Table 2). Hence, S. aptus was reported for the first time from India and therefore, a new addition to Stethorus fauna of India was made through this research survey. This species was earlier reported in China (Fujian, Guangdong, Guangxi, Hainan, Zhejiang), Japan (Ryukyu), Malaysia, and Taiwan (Yu 1995). The eggs of S. aptus were light pinkish in color and elongated oval in shape which was laid singly in longitudinal position (Fig. 1a). The larvae were pinkish or pale orange in color in earlier stage and later turn to brown or black (Fig. 1b, e). The pupae were black, covered with numerous white setae, and attached themselves to the posterior side with the leaf surface (Fig. 1c, f). Adults are black, oval to slightly ovate in shape, covered with numerous white setae, and were active flier (Fig. 1g). Both larvae and adults were found feeding on P. ulmi (Fig. 1b, d). The other predatory coccinellid species (or genera) such as Hippodamia convergens Guerin-Meneville, Coleomegilla maculata De Geer, Harmonia axyridis (Pallas), Olla abdominalis (Say), Adalia tetraspilota, Coccinella undecimpunctata, Halyzia sp., Eriopus, Scymnus, and Psyllobora were reported feeding on mites (Rather 1989; Biddinger et al. 2009), but these taxa were not considered to be primary predators of mites (McMurtry et al. 1970; Hodek and Honek 1996).

Life stages of Stethorus aptus feeding on Panonychus ulmi. (a) Egg. (b) Grub feeding on P. ulmi. (c) Pupa on leaf surface. (d) Adults feeding on P. ulmi. (e-g) Magnified picture of grub, pupa and adult beetle

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The attractive characteristics of Stethorus for mite biological control were their prey consumption, longevity, and high reproductive capacity (Biddinger et al. 2009). Hence, there is an immediate need for further studies on biology and ecology, with special preference on their predatory potential and effects of miticides or pesticides. These studies are necessary in order to promote them as a potential biological control agent on mites. There is a need for better knowledge of their requirements, including utilization of alternative foods, refuges for dormancy and from nonselective pesticides, and host-finding mechanisms as stated by Biddinger et al. (2009). These studies would help in integrating pest management strategies with inclusion of S. aptus as one of the biocontrol agent in management of European red mite among temperate fruits crops.