C. carinatus is a mite native to Asia. It is now also present in Africa, Europe, the USA and Australia. It usually attacks camellias and can reduce tea leaf production. In Kenya, C. carinatus has resulted in loss of capital due t...
C. carinatus is a mite native to Asia. It is now also present in Africa, Europe, the USA and Australia. It usually attacks camellias and can reduce tea leaf production. In Kenya, C. carinatus has resulted in loss of capital due to the reduction in tea leaf production.
The genus Calacarus is a distinctive group of mites, as the females usually have a purplish body and three or five longitudinal wax-bearing ridges on the opisthosoma (Lindquist et al., 1996; Anon., 2014). Wax may also occur on the dorsal shield, following the dorsal shield lines (Lindquist et al., 1996). The rostrum of the female is relatively large and curves downwards (Huang, 2014). The coverflap of the female mite is 32.2 to 36 µ wide and 19.8 to 21.3 µ long, with many faint, short lines (Huang, 2014).
C. carinatus is smaller than two-spotted spider mites, and individuals are referred to as ‘rust mites’ due to the bronzing caused on infested leaves (Anon., 2014) (see Symptoms).
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
C. carinatus usually attacks camellias, but has also been found attacking Spathiphyllum plants in Florida greenhouses (Anon., 2014). It is said to have an unusually wide host range compared to other members of the genus, apart from Calacarus citrifolii (Lindquist et al., 1996). In addition to attacking Camellia sinensis, it has also been reported from Camellia japonica and ‘two hosts in two other dicot families’ (Lindquist et al., 1996). Other hosts include: leaves of Viburnum opulus in California, USA; Capsicum annum in Mauritius (Moutia, 1958); and Camellia kissi and Camellia caudate in Assam, India (Das and Sengupta, 1962).
C. carinatus causes a bronzing or purple discolouration of infested leaves, hence the common name ‘rust mite’ (Mamikonyan, 1935; Anon., 2014). This is more apparent on the leaf margins (Shiao, 1976). Infested leaves also have a ‘dusty’ appearance due to the cast skins of the mites and the residue of ‘mite wax’ on the leaf surface (Anon., 2014). Leaves attacked by the mites turn completely brown and dry up, and defoliation occurs in heavy infestations (Shiao, 1976; Vazquez, 1991). The mites usually attack older leaves and show a preference for the upper surface, especially along the midrib and margins (Light, 1927).
The eggs are usually laid along leaf veins (Anon., 2014) and singly (Lindquist et al., 1996). The eggs hatch in approximately 6-8 days, and the total development time from egg to adult is approximately 10-12 days (Anon., 2014), although this is dependent on temperature; 13-14 days have been recorded in January (Anon., 2014), 9 days in March and 7 days in July or August in tea plantations in the USA (Jeppson et al., 1975).
There are two nymphal instars and the females begin ovipositing on the third day after the final moult (Oliver and Cancienne, 1980). According to Oliver and Cancienne (1980) an average of 7.5 eggs are laid in 8 days; King (1937) reported that females laid up to 13 eggs at a rate of 1-2 a day. King (1937) also reported that C. carinatus exhibits arrhenotokous parthenogenesis (where unfertilized eggs develop into males).
Shiao (1976) reported that a generation lasted 20 and 50 days at 28.5 and 16.5 degrees centigrade, respectively.
Populations of mites usually build up during dry periods in tea plantations and significantly decline during rainy periods (Anon., 2014). In local greenhouses, numbers of mites decline when plants are frequently watered with over-head irrigation (Anon., 2014).
The purple tea mite usually occurs with the pink tea mite (Acaphylla theae) in India (Lindquist et al., 1996) and was reported as ‘generally associated’ with A. theae in the USA (in Los Angeles and ‘two other counties’) on Camellia (Armitage, 1946).
Muraleedharan and Chandrasekharan (1981) reported peak numbers of mites in January, April, May and November in tea plantations in south India. In Japan, Shiao (1976) reported that population size increased gradually from June to October, but was adversely affected by rainfall. High temperature and high relative humidity, as well as heavy rainfall, were reported to significantly reduce mite numbers in Munnar, Kerala, India (Muraleedharan et al., 1994). Low temperatures are also reported to have an adverse effect on mite populations (Muraleedharan and Chandrasekharan, 1981). In addition, Danthanarayana and Ranaweera (1972) also suggested that mite numbers could be influenced by certain biochemical processes in tea leaves. C. carinatus were reported to prefer shaded tea, except in August, in Tripura, India (Pande and Nandi, 1983).
When vertical distribution of the purple tea mite was studied on Camellia sinensis in India, it was found that mites showed a preference for bottom leaves (Muraleedharan et al., 1994). Leaves at the top and in the middle of the plants contained significantly fewer numbers of mites. Bushes that were pruned three and four years previously harboured greater densities of C. carinatus than bushes in the first half of the pruning cycle.
Harris (1982) reported that C. carinatus is the preferred prey of the cecidomyiid Lestodiplosis oomeni in West Java, Indonesia. However, it was also noted that the efficiency of the predator would probably be compromised by a ceraphronid parasite that frequently attacked it.
Sharma and Kashyap (2002) reported that Syrphus sp., Coccinella septempunctata, Oxyopes sp. and the parasitoid Diaeretiella sp. are the most important natural enemies in tea orchards in general (i.e. not specific to C. carinatus) in Himachal Pradesh, India.
In Kenya, C. carinatus has resulted in loss of capital due to the reduction in tea leaf production (IPPC Secretariat, 2005). Due to the damage it causes to tea and ornamental plants of economic importance in other parts of the world, such as Taiwan (e.g. Huang, 1974) and India (e.g. Shanker et al., 2002), it follows that economic losses due to mite infestations will be suffered there also. Radhakrishnan and Prabhakaran (2012) stated that severe infestations result in 8-10% crop loss in tea ecosystems. Homburg (1955) suggested that a resurgence in the economic importance of mites in Indonesia was probably largely due to a result of change in cultural practices used after blister blight.
In addition to a reduction in economic return caused by mite damage, there are also costs associated with inputs. Othieno et al. (1981) published a paper on the economics of fertilizer application to smallholder tea farms in Kenya, and reported that bushes not receiving fertilizer were heavily infested with C. carinatus compared to fertilized bushes, where no mites were found.
C. carinatus is a pest of aesthetically-important plant species (e.g. Oliver and Cancienne 1980), and so where these species are used in a biodiversity-rich setting, there is risk that that the biodiversity will be compromised with presence of this pest species.
Calacarus carinatus is a pest of Camellia japonica, which is a flowering tree/shrub and valued for its aesthetics. Oliver and Cancienne (1980) stated that this mite and Acaphylla steinwedeni infest Camellia japonica throughout the state of Louisiana, USA. Large populations of the mites cause foliar discolouration and scabbing, which results in loss of aesthetic value and economic losses. The interaction between trees and people is often highly regarded, as outlined by Evans (2007), and so any pest that compromises this relationship will be regarded as having a negative social impact.
C. carinatus causes a bronzing or purple discolouration of infested leaves (Mamikonyan, 1935; Anon., 2014). Infested leaves also have a ‘dusty’ appearance due to the cast skins of the mites and the residue of ‘mite wax’ on the leaf surface (Anon., 2014). The white skins and wax on the upper leaf surface can be seen using a hand lens (Anon., 2014). Leaves attacked by the mites turn completely brown and dry up, and defoliation occurs in heavy infestations (Shiao, 1976; Vazquez, 1991).
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
Early Warning Systems
Due to the fact that mites (especially the eggs) can be cryptic on plant parts and therefore pose a risk of accidental introduction in the plant trade, it is important to have measures in place to counteract accidental introduction. For example, in Kenya, the importation of any plant material is subject to strict specified conditions. Procedures include having suitable available information on the plant material to evaluate the pest risk of potential invasives. Regulations ensure that plant materials are imported and exported with appropriate permits and phytosanitary certificates. The authority is in place to treat of destroy infested plants or plant products (IPPC Secretariat, 2005).
In Kenya, inspections are carried out at international airports, sea ports and borders. Most border control points are located in the south and west, given the considerable trade in plant material with Uganda and Tanzania (IPPC Secretariat, 2005).
C. carinatus was introduced into Kenya in the 1976 and caused a reduction in tea leaf production (IPPC Secretariat, 2005). Public awareness of has been raised by, for example: publishing procedures on plant import requirements in the print media; holding public seminars at entry points; and preparing and distributing pamphlets, brochures and annual reports (IPPC Secretariat, 2005).
Cultural Control and Sanitary Measures
Rau (1965) stressed the importance of providing shade, carrying out late pruning with cleaning out, avoiding disturbing soil in cold weather and ensuring good drainage as actions to control mites in tea plantations. However, this does partly contradict findings by Pande and Nandi (1983) who reported that C. carinatus actually prefers shaded tea, except in August, in Tripura, India.
Care should be taken when moving infested plants within economically important tea plantations, and between countries in the import/export plant trade. By introducing border control checks, such as those in place in Kenya (IPPC Secretariat, 2005), and by considering that mites can be carried on the clothing of personnel working amongst infested plants, measures to mitigate movement of the pest can be set in place.
Sharma and Kashyap (2002) reported that Syrphus sp., Coccinella septempunctata, Oxyopes sp. and the parasitoid Diaeretiella sp. are the most important natural enemies in tea orchards in general in Himachal Pradesh, India, where C. carinatus is one of the most important pests attacking tea bushes. The authors investigated the effect of pesticides on pests and natural enemies and found that deltamethrin, cypermethrin and ethion were highly toxic to Syrphis sp. and C. septempunctata. Conversely, applications of 1500 ppm azadirachtin or a combination of neem, triterpenoids and azadirachtin, or Bacillus thuringiensis were found to be safe to natural enemies.
Sulphur compounds have been used against various eriophyoid mites on tea for many years (e.g. Mamikonyan, 1935; Das, 1965), but if insufficient time is left after treatment and before harvest, this method of control can cause tainting problems (Cranham et al., 1962; Lindquist et al., 1996).
In Tamil Nadu, India, dicofol, sulfur, ethion, phosalone and quinalphos have been used to control various pests of tea, including C. carinatus (Muraleedharan and Varathatajan, 1988).
Due to the fact that few of the several pesticides available for mite control are suitable in organic fields, more recent control methods have evaluated plant extracts against C. carinatus (e.g. Radhakrishnan and Prabhakaran, 2012). Radhakrishnan and Prabhakaran (2012) evaluated aqueous, methanol and chloroform extracts of Lantana camara, Bidens pilosa, Ageratum conyzoides, Equisetum arvense, Tithonia diversifolia and Capsicum annum. B. pilosa, E. arvense, A. conzyzoides and C. annum were acaricidal 96 hours after spraying at higher concentrations. Methanol extracts were found to be more efficient that aqueous and chloroform extracts, and aqueous extracts of C. annum and T. diversifolia showed ovicidal effects at 5% concentration.