Serge Kreiter

Colonization of Languedoc vineyards by phytoseiid mites (Acari: Phytoseiidae): influence of wind and crop environment

A natural increase of phytoseiid mite populations (Kampimodromus aberrans, Typhlodromus pyri and Phytoseius plumifer) was observed in vineyards in Languedoc, Burgundy and Corsica under integrated pest management strategies. The aim of the present study was to characterize the mechanisms of this colonization in space and time in Languedoc. The abundance of phytoseiid mites in the vegetation close to three grape fields was determined twice a year (May and July). Aerial (funnels with water) and soil (felt strip) traps were placed in and around grape fields, in order to assess the colonization potential provided by aerial dispersal and ambulatory locomotion. The populations of phytoseiid mites in the crops were studied twice a month in order to gain information on the make up of the dispersal populations. The species K. aberrans was found in largest quantities in the traps, in the natural vegetation and in the crops. Predatory mite dispersal occurred essentially by aerial dispersal and was dependent on the wind intensity and wind direction. Identical sex ratios were observed in migrant populations and in populations present in the grape fields, woody areas and hedges. A large proportion of immatures was found to move by aerial dispersal. The colonization potential (rapidity, intensity and regularity) was directly associated with the abundance of the phytoseiids and the proximity of natural vegetation. A deep, dense and tall woody area containing suitable host plants for predatory mites constituted the most stable source of phytoseiid mites. Natural colonization of vineyards provides considerable phytoseiid mite potential that could be managed in an agricultural landscape.

Search for effective natural enemies of Tetranychus evansi in south and southeast Brazil

Tetranychus evansi Baker & Pritchard is an important pest of Solanaceae in several countries. Introduced accidentally to Africa, it presently occurs in many countries of that continent. In some of them, it is considered a key pest. The suspected area of origin of this mite is South America. The objective of the present study was to identify phytoseiid mites on solanaceous plants in association with T. evansi in south and southeast Brazil for introduction in the African continent for use in a classic biological control program. Almost 1,400 predatory mites of the family Phytoseiidae were collected, on 22 solanaceous species. The Amblyseiinae were the most diverse group in this study. Twenty-three of the species found belong to this subfamily, while only three belong to the Typhlodrominae and two to the Phytoseiinae. The most abundant and most frequent phytoseiid species were Phytoseius guianensis De Leon and Galendromus annectens (De Leon) of the Phytoseiinae and Typhlodrominae, respectively. The most frequent and abundant species of Amblyseiinae was Neoseiulus tunus (De Leon). Phytoseius guianensis and N. tunus were never found in association with T. evansi and G. annectens was found only once in association with it. Two factors suggested Phytoseiulus longipes Evans as the most promising predator found in this study. It could walk very well on tomato leaves infested by T. evansi, without being hampered by the profuse webbing produced by the prey and by the trichomes. In addition, several specimens of both sexes including eggs and nymphs of the predator were found associated with T. evansi on three different plant species and in two different periods of the year, when T. evansi was the only arthropod present on the leaves.

Kampimodromus aberrans (Acari: Phytoseiidae) from the USA: morphological and molecular assessment of its density

Morphological measurements and a mitochondrial molecular marker (COI) were used to identity specimens reported as Kampimodromus aberrans on hazelnut in the USA. Several species and populations of this genus were studied to assist with identification. Both data types showed that specimens from the USA differed from K. aberrans from other regions. USA specimens seem to belong to the same species as Kampimodromus specimens from France on hazelnut. These mites were morphologically similar to Kampimodromus coryli and K. corylosus, which according to the original descriptions, are distinguished by the presence or absence of a tooth on the movable digit of the chelicera, with K. coryli having one tooth and K. corylosus none. As chelicerae of Kampimodromus from hazelnut in the USA and France are toothless, they are assigned to the species K. corylosus. Studies showed that morphological characters traditionally used to identify Kampimodromus species, such as setal length, are of less value than other characters that are difficult to observe, such as the numbers of solenostomes and the presence of teeth on the movable digit of the chelicerae. Some synonyms are discussed.

Factors affecting ambulatory dispersal in the predaceous mite Neoseiulus californicus (Acari: Phytoseiidae)

Experiments conducted in the laboratory showed that different biotic and abiotic factors affected the ambulatory dispersal behaviour of Neoseiulus californicus. The experimental set-up comprised dwarf alfalfa (Medicago polymorpha) infested or unifested by Tetranychus urticae. Temperatures were measured with thermocouples. Trials were performed at three temperatures, three prey densities, three light intensities, two relative humidities (RHs) and two vegetative states of alfalfa plants, turgid and withered. Deutonymphs were the most dispersive followed by young ovipositional females. High temperatures (35°C), high light intensities (40 000 lux) and drought-stressed alfalfa increased the dispersal of N. californicus. The availability of food in the environment and high moisture (80% RH) slowed down dispersion. The main factors which seem to elicit dispersal behaviour are the deprivation of food and high temperatures which result in an increase in the walking speed of the mite. In addition, other factors tested either increase or reduce the ambulatory dispersal of N. californicus. According to our results, individuals could move from ground cover into apple trees before spring.

Phylogenetic and biogeographic analysis of the genus Phytoseiulus (Acari: Phytoseiidae)

Kanouh, M., Tixier, M.‐S., Okassa, M. & Kreiter, S. (2010). Phylogenetic and biogeographic analysis of the genus Phytoseiulus (Acari: Phytoseiidae) —Zoologica Scripta, 39, 450–461.

Morphometric variation between populations of Kampimodromus aberrans (Oudemans) (Acari : Phytoseiidae): implications for the taxonomy of the genus

This study reports variation between populations of the phytoseiid mite Kampimodromus aberrans (Oudemans). The influence of seasons (summer and winter), different host plants, and localities on morphological variation was investigated to determine the reliability of the parameters usually used to distinguish species in the genus Kampimodromus. This study was conducted in southern France. The specimens examined consisted of three summer and three winter populations each collected from Celtis australis L., Quercus pubescens Willdenow (referred as Q. pubescens no. 1 in the text) and Corylus avellanae L., and three additional summer populations collected from each of Q. pubescens (referred as Q. pubescens no. 2 in the text), Vitis vinifera cv. Carignan and Vitis vinifera cv. Cabernet-Sauvignon. Significant differences were observed between the winter and summer populations. Females of summer populations had longer setae than females of winter populations. However, these differences are usually very small. Greatest differences were observed within the population collected in summer on Q. pubescens no. 1 from which two distinct groups of specimens were distinguished. To determine if more than one species of Kampimodromus were present on this plant, measurements of other closely related species were also included in the analysis. It was concluded that all the females studied belong to K. aberrans. However, the setal variations observed raised the following questions. (i) What is the validity of other closely related species whose setal lengths differ only slightly from those of K. aberrans? (ii) Are setal lengths useful characters to distinguish between closely related species in the genus Kampimodromus?

Phytoseiid Mites (Acari: Phytoseiidae) from Guadeloupe and Martinique

Nine species of mites of the family Phytoseiidae are reported for the first time from Guadeloupe and Martinique. Measurements of the specimens of each species collected are given.

Morphological variation in the biological control agent Neoseiulus californicus (McGregor) (Acari : Phytoseiidae): consequences for diagnostic reliability and synonymies

The extent intraspecific variation among 42 morphological characters within Neoseiulus californicus (McGregor) (Acariu2009:u2009Phytoseiidae) is examined. Neoseiulus californicus is an important biological control agent used commercially worldwide to control pest mites in many crops. The correct diagnosis of this species is thus of prime importance for successful biological control and agricultural development. Incorrect interpretation of intraspecific variation could lead to misidentification and potentially to the description of new species that may be invalid. Three hundred female N. californicus representing ten populations collected from all over the world were measured and compared with the types of two morphologically close species: Neoseiulus marinus (Willmann) and Neoseiulus ornatus (Athias-Henriot). Significant differences between the populations were observed for almost all of the characters considered. However, these differences were small and low within-population standard errors in measurement data were observed. The mites collected in Chile were very different from the specimens of the other populations of N. californicus considered. The level of intraspecific morphological variation found within N. californicus indicates that caution must be applied to correctly determine species boundaries within this genus and morphological variation needs to be considered more in species’ descriptions. Based on our morphological analysis we conclude that N. ornatus, N. marinus and N. californicus are valid species. Redescriptions of these three species are given in this paper.

Resistance to fenazaquin and tebufenpyrad in Panonychus ulmi Koch (Acari: Tetranychidae) populations from South of France apple orchards

Abstract Following failures to control the European Red Mite ( Panonychus ulmi ) using METI-acaricides in some apple orchards in the south of France, resistance to fenazaquin and tebufenpyrad was studied under laboratory conditions. Resistance ratios ranged from 19.8 to 28.8 and from 16.8 to 39.8, respectively, for fenazaquin and tebufenpyrad when compared to the most susceptible of the 2 reference populations. An examination of bioassays responses showed that resistance was higher with tebufenpyrad than with fenazaquin. The recommended field rates for these compounds corresponded only to the LC 95 for fenazaquin and the LC 70 for tebufenpyrad. These results confirm resistance development to METI-acaricides in ERM field populations and suggest it could be responsible for reduced persistence of mite control and in some cases for control failure in apple orchards.

Search for effective natural enemies of Tetranychus evansi (Acari: Tetranychidae) in northwest Argentina

The mite Tetranychus evansi Baker & Pritchard (Tetranychidae) probably originated in South America. Because of its importance as a tomato pest in Africa, an extensive project has been conducted to detect potentially effective natural enemies in South America for the classical biological control of the pest in Africa. A search for the natural enemies of T.xa0evansi was conducted in the Province of Tucumán, northwestern Argentina, in December 2004, and this report describes the results. One hundred predatory mites of the family Phytoseiidae referring to 11 species were collected on 11 examined species of solanaceous plants. The most abundant phytoseiid species collected were Neoseiulus californicus (McGregor) and Euseius concordis (Chant). Adults and immatures of those species, as well as of Neoseiulus idaeus Denmark & Muma, Phytoseiulus fragariae Denmark & Schicha and Proprioseiopsis cannaensis (Muma) were found in association with T.xa0evansi, suggesting that they were developing on the pest. However, because of the possible biological differences between populations of a given species, biological studies evaluating T.xa0evansi as a prey for those predators seem desirable.