Indicator Plants for Monitoring Pest Population Growth

Four spider species and the predacious mitePhytoseiulus persimilis (Athias-Henriot) were examined in the laboratory for their capacity to feed on the carmine spider mite,Tetranychus cinnabarinus (Boisduval). The adult females ofChiracanthium mildei L. Koch showed the highest capacity for feeding onT. cinnabarinus (27.5 mites/day) and differed significantly from all other spider species, including the immatureC. mildei which consumed an average of 18.9 mites/day — nearly equal to that of the Oxyopidae species (16.8 mites/day). The salticid (10.1 mites/day) and theridiid (9.5 mites/day) spider species had the lowest capacity, which was nearly equal to that of the predacious miteP. persimilis (11.3 mites/day). Results indicate that spiders play an important role as mite predators.

Specialist-feeding phytoseiid mites have a well-documented role in biological control of phytophagous spider mites. However, although there is evidence for the importance of generalist-feeding phytoseiid mites in spider mite suppression, their role is less clear than that of specialists. The effectiveness of generalists as biocontrol agents and their interactions with specialists might be directly influenced by canopy structure or indirectly affected by altering plant microclimate. We manipulated densities of generalist phytoseiid mites and canopy size (large and small) in open-field experiments in an abandoned vineyard. In the first experiment, we increased generalist densities by transferring grapevine foliage housing robust generalist populations, whereas in the second experiment, we lowered generalist densities using the broad-spectrum insecticide chlorpyrifos. In both experiments, we also altered canopy size by tying grapevine shoots. Increasing densities of generalists resulted in lower spider mite densities. Generalists initially decreased densities of specialist phytoseiid mites as well, although specialist densities rebounded as spider mite densities increased later in the experiment. Lowering generalist densities appeared to slightly increase densities of both spider and specialist mites, consistent with the first experiment. However, these effects were not statistically significant, possibly because the reduction in generalist densities through chlorpyrifos application was not as dramatic as our generalist augmentation in the first experiment. Canopy size did not significantly affect pest or predatory mite densities in either experiment. These field experiments demonstrate that generalists can slow spider mite population growth in grapes. In contrast, canopy architecture appeared to have little impact on spider mite biocontrol.

Selenium has shown effectiveness in protecting plants from herbivores. However, some insects have evolved adaptability to selenium. Selenium accumulation in host plants protected them against spider mite feeding. Selenium showed toxic effects on spider mites by reducing growth and interfering with reproduction. After 40 generations on selenium-rich plants, a Tetranychus cinnabarinus strain (Tc-Se) developed adaptability to selenium, with an increased rate of population growth and enhanced ability for selenium metabolism. The high expression of two genes (GSTd07 and SPS1) in the selenium metabolism pathway might be involved in selenium metabolism in spider mites. After GSTd07 and SPS1 were silenced, the selenium adaptability decreased. Recombinant GSTd07 protein promoted the reaction between sodium selenite and glutathione (GSH) and increased the production of sodium selenite metabolites. The results indicated that GSTd07 was involved in the first step of selenium metabolism. Plants can resist spider mite feeding by accumulating selenium. Spider mites subjected to long-term selenium exposure can adapt to selenium by increasing the expression of key genes involved in selenium metabolism. These results elucidate the mechanism of the interaction between mites and host plants mediated by selenium. This study of the interaction between selenium-mediated host plants and spider mites may lead to the development of new and less toxic methods for the prevention and control of spider mites.

The influence of Tetranychus cinnabarinus-induced plant defense responses on Aphis gossypii development

To investigate the relative contributions of bottom-up (plant condition) and top-down (predatory mites) factors on the dynamics of the two-spotted spider mite (Tetranychus urticae), a series of experiments were conducted in which spider mites and predatory mites were released on bean plants. Plants inoculated with 2, 4, 8, 16, and 32 adult female T. urticae were either left untreated or were inoculated with 3 or 5 adult female predators (Phytoseiulus persimilis) one week after the introduction of spider mites. Plant area, densities of T. urticae and P. persimilis, and plant injury were assessed by weekly sampling. Data were analysed by a combination of statistical methods and a tri-trophic mechanistic simulation model partly parameterised from the current experiments and partly from previous data. The results showed a clear effect of predators on the density of spider mites and on the plant injury they cause. Plant injury increased with the initial number of spider mites and decreased with the initial number of predators. Extinction of T. urticae, followed by extinction of P. persimilis, was the most likely outcome for most initial combinations of prey and predators. Eggs constituted a relatively smaller part of the prey population as plant injury increased and of the predator population as prey density decreased. We did not find statistical evidence of P. persimilis having preference for feeding on T. urticae eggs. The simulation model demonstrated that bottom-up and top-down factors interact synergistically to reduce the density of spider mites. This may have important implications for biological control of spider mites by means of predatory mites.

Two species of spider mite, namely the two-spotted spider mite (Tetranychus urticae Koch) and the carmine spider mite (Tetranychus cinnabarinus (Boisduval)), are serious pests of plants grown under glass or polythene. Plants damaged include cucumber, dwarf French bean, pepper, strawberry, tomato, carnation, chrysanthemum and rose; also arum lily, hydrangea, orchids and many pot plants as well as stone fruits and vines.

Induced plant responses to herbivores and pathogens have been found in many systems. We examined intra- and interspecific interactions among three parasites through induced responses in their shared host plant, papaya. Three key parasites attack papaya foliage in Hawaii: the carmine spider mite, Tetranychus cinnabarinus (Boisduval); the papaya rust mite, Calacarus flagelliseta Fletchmann, De Moraes, and Barbosa; and the powdery mildew causal agent, Oidium caricae F. Noack. Under laboratory conditions, papaya seedlings were first exposed to standardized populations of mites and mildew; the parasites were removed, and the clean, previously infested plants were transplanted into the field to be exposed to colonization by natural populations of plant parasites. Population growth of colonizers was monitored for a period of 3 mo. We found no evidence for induced plant resistance. Rather, our results suggest that papaya expresses a weak form of induced susceptibility after injury from papaya rust mites and powdery mildew. Plants exposed to rust mites as young seedlings subsequently supported larger populations of spider mites, and plants exposed early to powdery mildew subsequently supported larger populations of rust mites.

The carmine spider mite, Tetranychus cinnabarinus (Boisduval) and the twospotted spider mite, Tetranychus urticae Koch, are serious pests of strawberries and many other horticultural crops. Control of these pests has been heavily dependent upon chemical acaricides. Objectives of this study were to determine the resistance status of these two pest species to commonly used acaricides on strawberries in a year-round intensive horticultural production region. LC90 of abamectin for adult carmine spider mites was 4% whereas that for adult twospotted spider mites was 24% of the top label rate. LC90s of spiromesifen, etoxazole, hexythiazox and bifenazate were 0.5%, 0.5%, 1.4% and 83% of their respective highest label rates for carmine spider mite eggs, 0.7%, 2.7%, 12.1% and 347% of their respective highest label rates for the nymphs. LC90s of spiromesifen, etoxazole, hexythiazox and bifenazate were 4.6%, 11.1%, 310% and 62% of their respective highest label rates for twospotted spider mite eggs, 3%, 13%, 432,214% and 15% of their respective highest label rates for the nymphs. Our results suggest that T. cinnabarinus have developed resistance to bifenazate and that the T. urticae have developed resistance to hexythiazox. These results strongly emphasize the need to develop resistance management strategies in the region.

Abamectin has been widely used as an insecticide/acaricide for more than 30 years because of its superior bioactivity. Recently, an interesting phenomenon was identified in the carmine spider mite, Tetranychus cinnabarinus, an important pest in agriculture. The gamma aminobutyric acid (GABA) contents in a laboratory abamectin resistant strain of T. cinnabarinus (AbR) were significantly increased. Decreases in activity and mRNA expression of GABA transaminase (GABA-T) were responsible for GABA accumulation in AbR mites. To clarify the mechanism of GABA accumulation mediated abamectin resistance, three artificial approaches were conducted to increase GABA contents in susceptible mites, including feeding of vigabatrin (a specific inhibitor of GABA-T), feeding of exogenous GABA, and inhibition of GABA-T gene expression. The results showed that susceptible mites developed resistance to abamectin when the GABA contents were artificially increased. We also observed that the mites with higher GABA contents moved more slowly, which is consistent with the fact that GABA is an inhibitory neurotransmitter in arthropods. Subsequently, functional response assays revealed that predation rates of predatory mites on GABA accumulated abamectin-resistant mites were much higher than control groups. The tolerance to abamectin, slow crawling speed, and vulnerability to predators were all resulted from GABA accumulation. This relationship between GABA and predation was also confirmed in a field-collected population. Our finding indicates that predatory mites might be used as a tool for biological control to circumvent the development of abamectin resistance in mites.

The stealthiness of predatory mites as spider mite biological control agents

Medical and Veterinary EntomologyVolume 6, Issue 1 p. 90-90 Free Access THE ACARI: REPRODUCTION, DEVELOPMENT AND LIFE HISTORY STRATEGIES. Reinhart Schuster, Reinhart Schuster Chapman & Hall, London, 1991. xxiii + 554 pp. £79. ISBN 0 412 36070 5.Search for more papers by this authorPaul W. Murphy., Paul W. Murphy. Chapman & Hall, London, 1991. xxiii + 554 pp. £79. ISBN 0 412 36070 5.Search for more papers by this authorAlan Walker, Alan Walker Chapman & Hall, London, 1991. xxiii + 554 pp. £79. ISBN 0 412 36070 5.Search for more papers by this author Reinhart Schuster, Reinhart Schuster Chapman & Hall, London, 1991. xxiii + 554 pp. £79. ISBN 0 412 36070 5.Search for more papers by this authorPaul W. Murphy., Paul W. Murphy. Chapman & Hall, London, 1991. xxiii + 554 pp. £79. ISBN 0 412 36070 5.Search for more papers by this authorAlan Walker, Alan Walker Chapman & Hall, London, 1991. xxiii + 554 pp. £79. ISBN 0 412 36070 5.Search for more papers by this author First published: January 1992 https://doi.org/10.1111/j.1365-2915.1992.tb00042.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume6, Issue1January 1992Pages 90-90 RelatedInformation

1. Arbuscular mycorrhiza (AM), the association of AM fungi and plant roots, may alter morphological and physiological attributes of aboveground plant parts and thereby influence plant‐associated organisms such as herbivores and their natural enemies, predators and parasitoids.2. The interactions between AM and the players of aboveground tri‐trophic systems have mainly been considered in isolation from each other. The effects of AM on aboveground herbivore–carnivore population dynamics and the consequences to plant fitness are unknown.3. We explored AM‐induced compensatory mechanisms for AM‐promoted proliferation of the herbivorous spider mite, Tetranychus urticae Koch, on whole bean plants, Phaseolus vulgaris L. Vegetative and reproductive plant growth, AM fungal colonisation levels, and mite densities were assessed on spider mite‐infested plants colonised or not by the AM fungus Glomus mosseae Nicol. & Gerd, and harbouring the natural enemy of the spider mites, the predatory mite Phytoseiulus persimilis Anthias‐Henriot or not.4. AM symbiosis modulated the aboveground tri‐trophic system to the fitness benefit of the plant. AM‐increased plant productivity outweighed the fitness decrease due to AM‐promoted herbivory: at similar vegetative growth, mycorrhizal plants produced more seeds than non‐mycorrhizal plants.5. AM‐increased spider mite population levels were compensated for by enhanced population growth of the predators and increased plant tolerance to herbivory.6. AM‐enhanced predator performance looped back to the AM fungus and stabilised its root colonisation levels, providing the first experimental evidence of a mutually beneficial interaction between AM and an aboveground third trophic level natural enemy.

Ethylene emission and the activity of oxidative enzymes were studied in tomato leaves after injury by carmine spider mite (CSM) (Tetranychus cinnabarinus Boisduval) feeding. Based on gas chromatographic data it was found that the feeding of 50 CSM for 3 days on young plants of tomato (Lycopersicon esculentum Mill., cv. Slonka) induced an increase of ethylene production by 40%. Elevated ethylene emission by damaged leaves was accompanied by the enhanced activity of oxidative proteins. Activity of total peroxidase and ascorbate oxidase in damaged leaves was about twice as high as compared to undamaged control leaves. Induction of polyphenol oxidase was less pronounced but highly significant. The results obtained suggest that in injured tomato plant’s early defence responses against CSM are characterized by the action of ethylene on oxidative enzymes.

The goal of this study was to evaluate spider mite control efficacy of two dry-adapted strains of Neoseiulus californicus. Performance of these strains were compared to a commercial strain of Phytoseiulus persimilis on whole cucumber, pepper and strawberry plants infested with Tetranychus urticae at 50 +/- 5% RH. Under these dry conditions predators' performance was very different on each host plant. On cucumber, spider mite suppression was not attained by any of the three predators, plants 'burnt out' within 4 weeks of spider mite infestation. On strawberry, all predators satisfactorily suppressed spider mites yet they differed in short term efficacy and persistence. Phytoseiulus persimilis suppressed the spider mites more rapidly than did the BOKU and SI N. californicus strains. Both N. californicus strains persisted longer than did P. persimilis. The BOKU strain was superior to SI in population density reached, efficacy in spider mite suppression and persistence. On pepper, in the first 2 weeks of the experiment the BOKU strain was similar to P. persimilis and more efficacious in spider mite suppression than strain SI. Four weeks into the experiment the efficacy of P. persimilis dropped dramatically and was inferior to the SI and BOKU strains. Overall, mean predator density was highest on plants harbouring the BOKU strain, lowest on plants with P. persimilis and intermediate on plants with the SI strain. Implications for biocontrol of spider mites using phytoseiid species under dry conditions are discussed.

Fenvalerate applied at a rate of 0.11 kg AI/ha to cotton gave equal control of the boll weevil, Anthonomus grandis grandis Boheman, Heliothis spp., beet armyworm, Spodoptera exigua (Hubner), fall armyworm, S. frugiperda (J. E. Smith), and cabbage looper, Trichoplusia ni (Hubner), whether the nozzles were the conventional type (Conejet TX6), the 8001 low-pressure fan nozzle, or Raindrop®, 33974-(3–23). Control of the carmine spider mite, Tetranychus cinnabarinus (Boisduval), with monocrotophos and American Cyanamid AC–85,258 (nitrilacarb 1:1 complex with zinc chloride) applied with Raindrop 33974 (5–23) nozzles was statistically equal to that obtained with conventional nozzles. AC–85,258 was phytotoxic when applied with Raindrop 33974 (5–23) nozzles. An LD50 dose for the boll weevil was found at various distances downwind in relation to the type of spray nozzle used and height above plants. The only significant difference between the conventional and Raindrop nozzle 33974 (3–23) occurred when these were raised to 107 cm above the cotton plants.