Uri Gerson

Mites (Acari) for pest control.

Introduction History and current work the Acari Illustrated keys to ABA families Treatment of individual families Introduction, culture and establishment Sex ratio of ABAs and its effect on mass--rearing, establishment and field performance Influence of host plants and host pests on the efficacy of ABAs Mutual interference between ABAs and natural enemies of ABAs The effect of pesticides on ABAs Acarine biocontrol agents as predators Attributes of efficient ABAs and demonstrating their efficacy Environmental constraints in the use of ABAs Economics and commercial aspects Recommendations for future work References Glossary.

Biology and control of the broad mite,Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae)

The broad mite,Polyphagotarsonemus latus (Acari: Tarsonemidae), is an important, and in some cases recent, pest of diverse crops in tropical and subtropical regions. Infested leaves become bronzed with down-curling margins, buds are aborted and flowers distorted, shoots grow twisted and fruit may be misshapen and russeted. Injuries, presumably due to toxins, occur even after the broad mite is killed by pesticides. There is no evidence thatP. latus transmits plant viruses, but injury may be mistaken for virus or herbicide damage. The mite infests plants referable to ca 55 dicotyledone and two monocotyledone families as well as to the Cupressaceae. Changes in horticultural practices, including control measures, could have caused recent pest outbreaks. The mite may raise a generation in 1 week under optimal conditions (ca 25°C and high relative humidities) and deposit ca. 40 eggs/ female. The usual sex ratio is 1:4 male: female and reproduction is arrhenotokous. Dispersal is effected through male carriage of pharate females as well as by winds, insects (especially whiteflies) and man. Field sampling is facilitated by the pests aggregated distribution. Control options comprise plant resistance, pesticides and biocontrol. Areas for future research include the possible emergence of sibling species or feeding strains, better understanding of the mites reproduction, the effects of host plants on life history parameters, monitoring for pesticide resistance and exploration for additional natural enemies of the broad mite.

Resurgences of spider mites (Acari: Tetranychidae) induced by synthetic pyrethroids

Causes of spider mite (Acari: Tetranychidae) population resurgences consequent upon exposure to synthetic pyrethroid (SP) treatments are reviewed. Resurgences may be seen as soon as 1 week, or even as late as a whole season, post-treatment. Synthetic pyrethroids vary in their adverse effects on spider mites, and also differ in their ability to invoke resurgences of different spidermite species on diverse plants. These pesticides are lethal as well as repellent to phytoseiids and other predators that prey on spider mites, may inhibit fungi which attack the latter, and affect phytophagous competitors. Spider mites are likewise repelled by SPs, thus becoming more evenlydistributed and less web-restricted, with a resultant increase in fecundity. Spider-mite development is shortened due to SPs and the sex ratio becomes more female-biased; onset of winter diapause also seems to be delayed. Synthetic pyrethroids appear to sensitize to spider-mite infestation plants which have not hitherto been attacked. Some SP effects (whether on spider mites, natural enemies or competitors) appear to be direct, whereas others may be mediated through the host plants. The effect of SPs on the other Acari is variable within the Prostigmata and Astigmata. Most Mesostigmata and Metastigmata (ticks) are very sensitive, whilst the Cryptostigmata (Oribatei) appear to be insensitive. Synthetic pyrethroids-induced resurgences of Homoptera are comparatively reviewed, with the conclusion that some of the phenomena may be similar to those observed in spider mites. Various resurgence models are discussed, as well as the three main causes of variation (SPs, spider-mite species, host plants) in the observed phenomena. The need for more rigorous and carefully controlled experimentation is emphasized.

ITS2 sequences as barcodes for identifying and analyzing spider mites (Acari: Tetranychidae)

The use of DNA barcodes, short DNA sequences from a standardized region of the genome, has recently been proposed as a tool to facilitate species identification and discovery. Here we show that second internal transcribed spacer of nuclear ribosomal DNA (rDNA-ITS2) barcodes effectively discriminate among 16 species of spider mites (Acari: Tetranychidae) from Israel. The barcode sequences of each species were unambiguously distinguishable from all other species and formed distinct, nonoverlapping monophyletic groups in the maximum-parsimony tree. Sequence divergences were generally much greater between species than within them. Using a 0.02 (2%) threshold for species diagnosis in our data set, 14 out of 16 species recognized by morphological criteria would be accurately identified. The only exceptions involved the low divergence, 0.011–0.015 (1.1–1.5%), between Tetranychus urticae and Tetranychus turkestani, where speciation may have occurred only recently. Still, these species had fixed alternative rDNA-ITS2 variants, with five diagnostic nucleotide substitutions. As a result, we tentatively conclude that rDNA-ITS2 sequence barcodes may serve as an effective tool for the identification of spider mite species and can be applicable as a diagnostic tool for quarantine and other pest management activities and decision-making. We predict that our work, together with similar efforts, will provide in the future the platform for a uniform, accurate, practical and easy-to-use method of spider mite species identification.

Mites (Acari) as a Factor in Greenhouse Management

This review discusses the economically important pest mites (Acari) of greenhouses, aspects of their biology, and the acarine predators that attack them as well as various insect pests. Greenhouse factors affect pest mites as well as their natural enemy populations and their interactions. Conversely, pest mites affect greenhouse management in terms of the chemical and biological methods required to control their populations. Structure affects heating, cooling, and light, which can be manipulated with suitable screens. Crops often select for pests and their mite enemies. Both groups may be affected in greenhouses by adding pollen and by a CO(2)-enriched atmosphere. These factors impact pest mite populations, the damage they cause, and the methods used to control them. The possibility of incipient evolution occurring in greenhouses, along with the benefits and consequences for pest control, is discussed.

How species-specific is the phoretic relationship between the broad mite, Polyphagotarsonemus latus (Acari: Tarsonemidae), and its insect hosts?

Broad mite, Polyphagotarsonemus latus (Acari: Tarsonemidae), is a serious plant pest in tropical and subtropical regions. Phoretic associations between broad mite and two genera of whiteflies (Insecta: Homoptera: Aleyrodidae), namely Bemisia and Trialeurodes, have been reported from different parts of the world. Our purpose was to determine the specificity of the association between the mite and its phoretic hosts. Two host plants, potatoes and cucumbers, were used to study these relationships in the laboratory. Insects frozen for 24 h were used as potential phoretic hosts in all experiments. Attachment levels were monitored by counting the number of mites attached to each insect. All tests were conducted for 4–6 h, as attachment to Bemisia tabaci on potato shoots leveled off after 4 h, increasing only marginally after 8 h. Attachment levels to thrips (the western flower thrips, Frankliniella occidentalis) and to allate aphids (Myzus persicae) was negligible relative to the attachment to B. tabaci. Broad mite also attached to the whiteflies Dialeurodes citri, Aleyrodes singularis and Trialeurodes lauri, the latter being the least attractive species (including B. tabaci). Washing B. tabaci with pentane greatly reduced attachment. Using cucumbers as hosts did not substantially change the general trend, but attachment levels were lower. The phoretic relationship between broad mite and its insect hosts appears to be specific to whiteflies, with some whiteflies having a higher potential as phoretic hosts.

Acarine pests of citrus: overview and non-chemical control

Abstract The mites that feed on citrus, which belong to the families Tetranychidae, Tenuipalpidae and Eriophyidae, along with a single species in the Tarsonemidae, are listed and ranked according to their injury. All major citrus pests, except the Eriophyidae, are generalists. Analogously, there are only generalists, but no specialists, among the natural enemies that are known, or postulated, to control acarine citrus pests. This suggests that neither the major pest mites nor their natural enemies have evolved on citrus, and that generalist predators thus have a better chance to control the pests. As the introduction of generalist natural enemies is currently restricted by environmental concerns, and as this practice has not led to improved control of the acarine pests of citrus, it is argued that better use should be made of the indigenous predators of citrus mites.

Rearing, release and establishment of imported predatory mites to control citrus rust mite in Israel

Citrus rust mite, Phyllocoptruta oleivora (Ashmead), is a major pest of citrus in Israel. Five species of predatory mites: Amblyseius herbicolus Chant, Euseius victoriensis (Womersley), Euseius elinae (Schicha), Typhlodromus rickeri Chant and Euseius stipulatus (Athias-Henriot), were imported to improve the biological control of the pest. Mite rearing and sampling methods were developed and improved, and the predators were released. Recovery in some citrus orchards was recorded, but only E. victoriensis became established in the north of Israel.

Antagonistic effects of the endophytic fungus Meira geulakonigii on the citrus rust mite Phyllocoptruta oleivora

Aims:  The fungus Meira geulakonigii has been shown to reduce populations of citrus rust mite (CRM; Phyllocoptruta oleivora) on citrus leaves and fruits, in both the field and laboratory. However, attempts to isolate the fungus from leaves and fruits have been unsuccessful. The aims of this study were therefore to determine whether M. geulakonigii is a citrus endophyte, and to assess possible mechanisms involved in its mite‐antagonist activity.

Comparative Behavioural Studies of Larval and Adult Stages of the Phytoseiids (Acari: Mesostigmata) Typhlodromus Athiasae and Neoseiulus Californicus

We compared the behaviours of the indigenous Typhlodromus athiasae Porath and Swirski and the exotic Neoseiulus californicus (McGregor) (= Amblyseius chilenensis Dosse) relative to their persistence in apple orchards in Israel. We studied (1) larval feeding, walking, intraspecific interactions (cannibalism, touch-avoidance responses and/or touching with palps and tarsi) and tendency to aggregate (when resting), (2) predation and cannibalism on phytoseiid eggs by young females and (3) the effects of starvation for 10 days on young females relative to ambulation speed, longevity, fecundity, progeny survival and sex ratio. Larvae of T. athiasae were almost inert, did not feed and hardly walked or interacted whereas larvae of N. californicus fed, walked and interacted, mainly by touching with palps and tarsi. No cannibalism in the larval stage was observed for either species. The presence of prey increased the larval walking and intraspecific interactions of N. californicus but not of T. athiasae. Egg predation by adult females of both species was substantially higher than cannibalism, implying that both are capable of distinguishing their eggs from those of other species. Soaking eggs for 30 min in deionized water increased cannibalism in both species. During the 10 days of starvation, the ambulation speed of adult female N. californicus ranged from 1.8 to 10.1 times that of T. athiasae. The 50% lethal time value (LT50) of T. athiasae (6.0 days) was significantly lower than that of N. californicus (10.4 days). None of the starved T. athiasae recuperated following the reintroduction of prey, whereas 75% of N. californicus did and oviposited after 2 days. These traits should enable N. californicus to persist when prey is scarce; however the selective predation of N. californicus eggs by T. athiasae could prevent establishment of N. californicus. The degree of specialization of these two predators is discussed.