Beverly S. Gerdeman

Laboratory and field comparisons of insecticides to reduce infestation of Drosophila suzukii in berry crops.

BACKGROUND The spotted wing Drosophila, Drosophila suzukii (Matsumura, 1931) (Diptera: Drosophilidae), is an invasive pest of small-fruit crops. Unlike most other Drosophila, this insect is able to oviposit into and damage ripe and ripening fruit, making it unmarketable. Because this is a new pest in the United States, it is necessary to identify registered insecticides to manage this insect effectively in conventional and organic production systems. RESULTS The present laboratory bioassays and field trials identified a number of insecticides representing various modes of action that are effective in controlling D. suzukii. Products that performed well in the laboratory bioassay also performed well in the field, indicating that screening of new chemistries in the laboratory is a worthy exercise. Field application of pyrethoids, organophosphates or spinosyns provided 5-14 days of residual control of D. suzukii. The efficacy of the neonicotinoids as adulticides was not satisfactory compared with the other contact-mode-of-action chemistries. Based on the zero tolerance by the small-fruit industry and the individual effects mentioned above, neonicotinoids are not currently recommended for D. suzukii management. CONCLUSIONS There are effective insecticides registered for controlling D. suzukii infestations in susceptible small-fruit crops.

Fine Structure and Functional Morphology of the Spermatodactyl in Males of Heterozerconidae (Gamasida)

Abstract At present, little is known about the biology of Heterozerconidae (Heterozerconina), a very interesting family of gamasid mites. They are podospermic with males having the genital orifice in presternal position and with a sperm transfer process on the chelicerae. This spermatodactyl arises near the basal region of the fixed digit and seems to have a helicoid “duct.” Since they are podospermic, the females show a sperm access system as well. On the other hand, Discozerconidae (also in Heterozerconina) show a slender spermatodactyl arising from the movable digit. Other families among Gamasida have males whose chelicerae are modified as gonopods involved for a direct sperm transfer. Even though behavioral observations support the idea that gonopods are involved in collecting the spermatophores from the male genital opening and transferring them into the female body, still, little is known on the functional morphology and ultrastructure of these gonopods. Here, a preliminary description of the morphology, fine structure and organization of the gonopods in males of Heterozerconidae is reported and the possible functional implications are discussed. Since the position of Heterozerconina has been one of the least understood questions in gamasid systematics, comparing the ultrastructure and organization of the spermatodactyl in Heterozerconidae males with gonopods in other families among gamasid mites (Phytoseiidae and Veigaiidae) might help in better understanding their position in the group.

Heterozerconidae: A comparison between a temperate and a tropical species

A comparative field study was performed between a tropical species and a temperate species of Heterozerconidae (Acari: Mesostigmata). The temperate species, Narceoheterozercon ohioensis Gerdeman and Klompen, is a long-lived mite, which shares an intricate relationship with its host millipede, Narceus annularis(Rafinesque) (Diplopoda: Spirobolida: Spirobolidae). The phenology between these mites and their millipede host shows coinciding periods of oviposition and mating, with both producing a single generation/year. Although the adults appear to feed on the exudates of the millipedes and are rarely separated, the immatures, developing during the summer, have adapted to a free-living, predatory lifestyle within the millipede ‘nest-sites’ of fallen logs. In contrast, the relationship between a Philippine heterozerconid, Allozercon sp., and its host millipede (Diplopoda: Spirobolida: Rhinocricidae) is less constrained. In these tropical species, both the millipedes and their associated heterozerconids produce multiple generations/ year. Millipede mating is no longer a synchronous event and immatures are found throughout the year in localized accumulations of millipede frass, beneath the forest litter.

Ultrastructural and functional adaptations of the female reproductive system in the family Heterozerconidae (Acari, Anactinotrichida, Gamasida, Heterozerconina) and implications for the systematic position of the group.

Heterozerconidae is a poorly known, early derived mite family belonging to Heterozerconina (Monogynaspida, Gamasida (= Mesostigmata)). The systematic position of the family is still controversial and little is known about the biology and anatomy of the taxon. In this paper, the gross anatomy, ultrastructure and functional morphology of the female reproductive system are described comparing genera from different geographic areas. The occurence of podospermy (i.e. the use of a sperm transfer process carried by the fixed digit of the male chelicerae to inseminate females through secondary insemination pores instead of through the oviporus) as insemination mode in this family was documented. Nevertheless, morphological and functional evidence in the reproductive system of the females supports the idea that, in the same family, more than one insemination mode is present: some genera are plesiomorphically tocospemic (i.e. insemination through the oviporus) while others switched to podospermy. Such discovery is of fundamental importance for the determination of the relationship between the family Heterozerconidae and the family Discozerconidae, both belonging tentatively to Heterozerconina and for the phylogenetic position of the Heterozerconina among Gamasida.