Posts Tagged: spider mite
Detection and reduction of miticide resistance in the twospotted spider mite, Tetranychus urticae
Twospotted spider mite (TSSM) is a global pest infesting a wide variety of crops. TSSM adapts to new hosts very quickly compared to other arthropods and this ability is attributed to the groups or families of genes that detoxify poisonous plant compounds (Grbic et al., 2011). In just nine generations, TSSM was adapted to a resistant cucumber variety (Gould 1978) and this adaptation allowed them to use potato and tobacco as hosts (Gould, 1979) and imparted cross resistance to three organophosphate pesticides (Gould et al., 1982).
Genetic makeup of TSSM also helps to develop resistance to miticides and it has the highest incidence of resistance to pesticides among arthropods (Van Leeuwen et al., 2010; Grbic et al., 2011). Head and Savinelli (2008) reported that TSSM tops the list of arthropods with pesticide resistance by having resistance to 79 active ingredients in 325 cases based on the arthropod resistance database from Michigan State University by Whalon et al. (2006). However, in the current database, the number of resistance cases for TSSM went up to 498 (Table 1).
Multiple factors that contribute to the success of TSSM, rapid development of pesticide resistance, and the ability to feed on a large number of plant species include the following:
i) Short life cycle and high fecundity that lead to multiple generations in a short time.
ii) Haplo-diploid sex determination system, where males develop from unfertilized eggs and females from fertilized eggs. As a results unfavorable recessive alleles will be removed from mite populations.
iii) Spinning of a strong, but very thin webbing that provide protection against natural enemies
iv) Multiple families of detoxification genes that allow digestion, detoxification, and transportation of toxic metabolites.
v) Lateral transfer of genes from bacteria, fungi, and other organisms through lateral gene transfer which facilitated digestion and detoxification of xenobiotics.
vi) Large number (39) of multidrug resistance proteins compared to a smaller number (9-14) in vertebrates or invertebrates.
Since TSSM is a global pest on multiple hosts, the chances of exposure to pesticides is high, which creates a high selection pressure for resistance. Repeated use of effective pesticides renders them ineffective due to resistance development. Gould et al. (1991) reported slower adaptation of TSSM when a lower level of host plant resistance was combined with natural enemies rather than high host plant resistance alone. Monitoring resistance and adopting integrated pest management (IPM) practices is critical in managing TSSM.
General recommendations for managing TSSM:
- Regularly monitor several parts of the field for mite infestations and make appropriate treatment decision depending on the level and distribution of mite populations and environmental conditions.
- Consider an IPM approach by using biological control options (release of predatory mites), modifying cultural practices (avoiding water stress and excessive nitrogen fertilization), and applying botanical (rosemary oil or other similar products), microbial (BotaniGard, Pfr-97, Met 52, Grandevo, and Venerate), or chemical (Table 2) pesticides.
- Provide refuges that support susceptible mite populations to delay resistance development.
- When applying chemicalmiticides rotate those among different mode of action (MoA) groups. Use softer chemicals when predatory mites are used.
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Periodically monitor miticide efficacy and signs of resistance development. If resistance is suspected, conduct a simple bioassay to confirm before field application of the miticide. Collect several leaves samples from different parts of the field with TSSM suspected to have resistance to a particular miticide. Prepare a small quantity of the spray liquid in a container following field application rates. Dip the leaves in the spray liquid and keep them in a covered container (not airtight) in a cool, dry place. Check 48 hours after the exposure to determine the efficacy of or resistance to the miticide based on TSSM mortality.
Bioassay to determine miticide resistance in twospotted spider mites.
Additional information on TSSM and its management in strawberries can be found at:
- Managing spider mites in California strawberries (//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=13943)
- Efficacy of botanical, chemical, and microbial pesticides on twospotted spider mites and their impact on predatory mites (//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=18553)
- Predatory mites for managing spider mites on strawberries (//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=14065)
- Response of predatory mites to chemical, botanical, and microbial miticides in strawberries (//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=14428)
- Spider mite damage causes unique foliar discoloration in Benicia variety (//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=11600)
- Multiple handouts on spider mites in strawberries (http://ucanr.edu/meetinghandouts)
- UC IPM Pest Management Guidelines for spider mites in strawberry (http://ipm.ucanr.edu/PMG/r734400111.html)
References
Gould, F. 1978. Predicting the future rresistance of crop varieties to pest populations: a case study of mites and cucumbers. Environ. Entomol. 7: 622-626.
Gould, F. 1979. Rapid host range evolution in a population of the phytophagous mite Tetranychus urticae Koch. Evolution 33: 791-802.
Gould, F. Carroll, C. R., and Futuyma, D. J. 1982. Cross-resistance to pesticides and plant defenses: a study of the two-spotted spider mite. Entomol. Exp. Appl. 31:175-180.
Grbic, M., Van Leeuwen, T., Clark, R.M., Rombauts, S., Rouzé, P., Grbic, V., Osborne, E.J., Dermauw, W., Ngoc, P.C.T., Ortego, F. and Hernández-Crespo, P. 2011. The genome of Tetranychus urticae reveals herbivorous pest adaptations. Nature, 479: 487-492. DOI: 10.1038/nature10640
Head, G. and C. Savinelli. 2008. Adapting insect resistance management programs to local needs. In: Onstad, D. W. (Ed.) Insect Resistance Management: Biology, Economics, and Prediction, Academic Press, United Kingdom, pp. 89-106.
Van Leeuwen, T., Vontas, J., Tsagkarakou, A., Dermauw, W. and Tirry, L. 2010. Acaricide resistance mechanisms in the two-spotted spider mite Tetranychus urticae and other important Acari: a review. Insect Biochem. Mol. Biol. 40: 563–572.
Whalon, M. E., Mota-Sanchez, D., Hollingworth, R. M., and Duynslager, L. 2006. Michigan State University Arthropod Resistance Database. http://www.pesticideresistance.org/search.php
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/h4>/h4>Finding Red Colored Mites on Strawberry Plants?
Two spotted spider mite (Fig. 1A) is a major pest of strawberry and caneberries. The spider mites lay 0.14 mm eggs (in diameter) on the undersides of strawberry leaves. Once the eggs hatch and the larvae go through three stages and molt into adult males, and reproductive females. As the name suggests, they are called two spotted spider mite because of one or more dark spots on the bottom half of each side of the body. They are typically dull or yellow colored organism but during the winter months, they undergo diapause (a resting stage) and appear as reddish or orange color (Fig. 1B) which often is confused and misidentified as carmine mite or presumably a new mite never seen before. Carmine spider mite is a bright red colored mite (Fig. 1C) but do not have spots on the either side of the body. They rarely cause economic injury to strawberry. They occurring during the winter and spring months in the Salinas/Watsonville strawberry fields. Predatory mites are also greyish, pale reddish or orange colored in general but they are shiny and moves very fast on the leaves (Video).
For further reading click the Pest Management Guidelines for mites in strawberry (http://www.ipm.ucdavis.edu/PMG/r734400111.html)
Predatory mites for managing spider mites on strawberries
Natural enemies play an important role in managing pest populations. Using predatory mites in strawberries against spider mites is a good example where growers take advantage of the potential of the natural enemies. Multiple species of predatory mites are commercially available and several California strawberry growers use biological control as a complementary tool to chemical control.
Predatory mites belong to four categories – Type I, Type II, Type III, and Type IV.
Type I: These predatory mites are specialists feeding exclusively on spider mites (family Tetranychidae) that produce considerable webbing. They require feeding on spider mites for their survival and reproduction. Type I predators are aggressive and voraciously feed on pest mites. Because of their dependence on spider mites, Type I specialists rapidly decline and cannibalize when pest mite populations decline.
Type II: These are also specialist predators, but they feed on spider mites and other species of mites. They also feed on pollen and in some cases on thrips and other species of predatory mites. Having more food choices for survival and reproduction, Type II specialists continue to be present in the absence of spider mites and are less likely to cannibalize.
Type III: These are generalist predators that feed on multiple species of mites that include spider mites, eriophyid mites, and tarsonemid mites and insects such as thrips and whiteflies. They also feed on pollen, honeydew, and plant juices. Type III generalists are also known to cannibalize and feed on other species of predatory mites in the absence of pest mites or other food sources.
Type IV: These mites primarily feed on pollen and can also feed on pest mites.
There are five species of predatory phytoseiid mites (Acari: Phytoseiidae) that are commercially available for spider mite control.
Phytoseiulus persimilis Athias-Henriot is a Type I specialist that exclusively feeds on spider mites. It is bright orange, teardrop-shaped and moves rapidly. It prefers cooler temperatures and is sensitive to hot and dry conditions. So, it is more effective during earlier parts of the production season before temperatures increase.
Egg and adult of Phytoseiulus persimilis. Egg is slightly oval and larger than twospotted spider mite eggs, which are round. Being able to identify predatory mites and their eggs is important during pest monitoring (Photo by Surendra Dara).
Neoseiulus fallacis (Garman) is a Type II specialist that primarily feeds on spider mites. It is translucent to peach or orange and appears to have a flatter body compared to spider mites or P. persimilis. It is also sensitive to hot and dry conditions.
Neoseiulus californicus (McGregor) is a Type II specialist that primarily feeds on spider mites, but also has Type III generalist characters. It appears similar to N. fallacis. It can withstand warmer conditions better than P. persimilis and N. fallacis. It can withstand cold temperatures for short periods and tolerates relative humidity range from 40-80%.
Egg and adult of Neoseiulus sp. Similar to the P. persimilis egg, this is also large and oval (Photo by Surendra Dara).
Galendromus occidentalis (Nesbitt) also known as western predatory mite is a Type II specialist that primarily feeds on spider mites. It prefers warm temperatures and tolerates dry conditions as low as below 30% relative humidity. It is sensitive to cooler temperatures.
Egg and adult of Galendromus occidetalis along with spider mite egg in the middle. Photo by Jack Kelly Clark, UC IPM.
Amblyseius andersoni (Chant) is a Type III generalist predator. It can tolerate high temperatures when relative humidity is high.
Among these predatory mites, P. persimilis, N. fallacis, and N. californicus are the most commonly used species in strawberries. Using the right species depending on the environmental conditions is important for the success of biological control. Timing insecticide and acaricide applications in a manner that is least disruptive to the predatory mites is essential. When chemical pesticides are necessary, softer materials should be selected.
In addition to the predatory mites, several species of natural enemies feed on spider mites. They include big-eyed bug (Geocoris spp.), black lady beetle (Stethorus sp.), black rove beetle (Oligota oviformis), brown lacewing (Hemerobius spp.), damsel bug (Nabis spp.), green lacewing (Chrysopa spp.), minute pirate bug (Orius tristicolor), predatory midge (Feltiella acarivora), and the predatory sixspotted thrips (Scolothrips sexmaculatus).
Top row: Big-eyed bug, black lady beetle, black rove beetle, brown (upper), and green lacewing (lower)
Bottom row: Damsel bug, predatory midge larva, minute pirate bug, and sixspotted thrips.
Photos by Jack Kelly Clark, UC IPM.
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References
Croft, B. A., L. N. Monetti, and P. D. Pratt. 1998. Comparative life histories and predation types: are Neoseiulus californicus and N. fallacis (Acari: Phytoseiidae) similar type II selective predators of spider mites? Econ. Entomol. 27: 531-538.
Çakmak, I. A. Janssen, and M. W. Sabelis. 2006. Intraguild interactions between the predatory mites Neoseiulus californicus and Phytoseiulus persimilis. Exp. Appl. Acarol. 38: 33-46.
Rincon-Vitova. 2009. Catalog of beneficials. Rincon-Vitova Insectaries, Inc. (http://www.rinconvitova.com/CATALOG%202009%20screen.pdf)
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Managing spider mites in California strawberries
Strawberry field with spider mite infestation. Plants in the lower part of the photo are stunted due to twospotted spider mite damage (Photo by Surendra Dara)
Multiple species of spider mites infest strawberries in California. Twospotted spider mite (Tetranychus urticae) is a predominant and commonly occurring species in all strawberry growing regions on the Central Coast. Strawberry spider mite (Tetranychus turkestani) can also be found along with twospotted spider mite populations especially in the Santa Maria area during warmer parts of the production season. Another species of spider mite, Lewis mite (Eotetranychus lewisii) appears to occur in the Oxnard area in fields near caneberries. Lewis mites have been known to occur in the Santa Maria area at very low numbers. Carmine spider mite (Tetranychus cinnabarinus) may also be present at low numbers in some areas.
Damage: Spider mites are usually present on the under surface of the leaf and form webbing at high densities. They scrape the leaf surface and feed on the plant juices. Damage appears as yellow mottling on the upper leaf surface initially. As the feeding continues, damage leads to scarring and eventual drying of the tissue. Uncontrolled populations can cause stunted plant growth, yield reduction, or even death of the plant.
In the Santa Maria area, spider mites are reported to occur as early as in December soon after planting in some years. Aggressive management practices including the timely release of predatory mites can keep spider mite populations under control. Warm, dry, and dusty conditions can favor spider mite population buildup.
Yellowing (above), drying of leaves (below) from spider mite damage. Webbing is extensive at high population densities. (Photos by Surendra Dara)
Biology: For twospotted spider mites, eggs are round and almost translucent when deposited. Larvae emerge from eggs and have three pairs of legs. Larvae pass through protonymph and deutonymph stages before becoming adults. Except for the larvae, remaining mobile stages have four pairs of legs. Two dark spots on the either side of their body give these mites their name. Adult males are small and wedge-shaped. Adult females are oval and larger than males. Twospotted spider mites complete their life cycle (from egg to adult stage) in about seven days at 86oF.
Life stages of the twospotted spider mite. Eggs (round and translucent), larva (three pairs of legs), protonymph, deutonymph, adult male (wedge-shaped), and adult female. (Photo by Surendra Dara)
Read more about spider mites and their damage in my previous articles at //ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=5771 and //ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=11600.
Monitoring: Regularly monitor fall-planted strawberry crop during the first four months for spider mite infestations. Collect 10 mid-tier leaflets/acre from a small field (5 leaflets/acre if the field is large) and count the number of mites using a hand lens or using the mite brushing machine. Economic threshold is 5 mites/mid-tier leaflet. For summer-planted strawberry crop, the threshold is 10 mites/mid-tier leaflet during the first few months. After harvesting commences, thresholds are higher and range between 15-20 mites/mid-tier leaflet.
Management options
- Thorough and regular monitoring is important to make treatment decisions.
- Promote vigorous plant growth through adequate chilling, water and nutrition management.
- Avoid excessive nitrogen as it may increase mite infestations.
- Use low fences, drive slowly and water roadways to prevent dusty conditions.
- Avoid practices that disrupt natural enemy populations and use miticides that are safe to natural enemies.
- Alternate chemicals with different modes of action to reduce the risk of resistance development where strawberries are continuously grown.
- If you suspect mite resistance to a particular chemical, do a simple test before spraying. Prepare a small quantity of the chemical to be sprayed at a concentration equal to the field application rate. Dip a mite-infested leaf in the liquid, let it dry and then keep it in a container or a bag. For comparison, dip another mite-infested leaf in plain water and keep it separately. Observe the leaves one and two days after the treatment. Depending on how many mites are dead on treated leaf compared to the control (water treatment), the effectiveness of the chemical can be determined.
- Conserve or release natural enemies like predatory mites. Phytoseiulus persimilis is a specialist predator and is effective early in the season. Neoseiulus californicus, which tolerates warmer temperatures and a wide range of humidities, is a generalist predator and a predominant species later in the season. Studies indicate that P. persimilis is not an option for controlling Lewis mite. There are several other natural enemies like minute pirate bug (Orius tristicolor), a small, black lady beetle (Stethorus spp.), a small, black rove beetle (Oligota oviformis), big-eyed bugs (Geocoris spp.), brown lacewings (Hemerobius spp.), green lacewings (Chrysopa spp.), six-spotted thrips (Scolothrips sexmaculatus), damsel bugs (Nabis spp.), a cecidomyiid fly maggot (Feltiella acarivora), and a predaceous midge.
Predatory mite (Neoseiulus sp.) and its larger and oblong egg (top right corner) along with small round spider mite eggs (bottom). (Photo by Surendra Dara)
Female twospotted spider mite and its eggs along with adult predatory mite, Phytoseiulus persimilis. (Photo by Jack Kelly Clark)
Spider mite damage causes unique foliar discoloration in Benicia variety
New UC short-day variety Benicia (Photo by Surendra Dara)
Different species of spider mites attack strawberry plants. Spider mites feed on the underside of the leaves, scrape the tissue, and suck the plant juices. As a result, corresponding area on the upper leaf surface initially shows yellow spots. As the damage advances, these spots expand and gradually turn into brownish, dry patches of dead plant tissue.
Twospotted spider mite infestation and damage on the lower side of the leaves causes yellow discoloration on the upper side (above) in Albion. Stippling of yellow spots on an infested foliage (below). (Photos by Surendra Dara)
As the damaged tissue dies, brown, dry patches develop on the upper leaf surface in Albion. (Photo by Surendra Dara)
Spider mite damage symptom in Benicia, the new short-day (June-bearing) cultivar from University of California, seems to be different compared to other varieties. While the upper leaf surface corresponding to the damaged lower surface shows initial yellow discoloration even at high mite densities in varieties such as Albion or San Andreas, it turns dark purple in Benicia even at low to moderate mite densities. Physiological response of Benicia to mite damage probably contributes to this unique symptom. Such a discoloration can be useful for early and easy detection of spider mite infestations.
Twospotted spider mite infestation on the lower side of the leaf (above) causes dark purple discoloration of the corresponding upper side (below) in Benicia.
(Photos by Surendra Dara)
Foliar damage symptoms in Benicia by twospotted spider mites.
(Photo by Surendra Dara)
Benicia is adapted for early planting and produces larger fruits with excellent flavor compared to some other short-day varieties.
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