Michael P. Parrella

Insecticide Resistance in Western Flower Thrips

Leaf dip bioassays were used to determine the breadth of tolerance of three pesticides for western flower thrips (WFT) populations collected from greenhouses with minimal (’sD’ strain) and intensive insecticide use (’sB’ strain), and from a susceptible colony where no pesticides were applied for 1 yr prior to the study (‘UC’ strain). Additionally, five doses of three pesticides were applied topically. In the bioassays insecticide treatments were more efficacious against the ‘UC’strain than the field-collected strains; topical applications showed increased resistance levels in the’ sB’ strain.

IPM — Approaches and Prospects

Thrips continue to increase as pests of agricultural and greenhouse crops. While there has been a dramatic increase in crop damage by a number of species with disparate life cycles (Heliothrips haemorroidalis, Taeniothrips inconsequens, Thrips palmi, etc.), the greatest problem worldwide on the largest number of crops is caused by the western flower thrips (WFT). Knowledge of the general biology and ecology of thrips, especially of WFT, has expanded rapidly over the past ten years. However, effective management programs for control are still unproven for many major crops attacked by this pest. Reliable programs do not exist for greenhouse cultivation of floricultural crops where WFT is the most serious threat to producing unblemished material capable of satisfying export quarantine requirements. Using WFT on floriculture crops as an example, various management options available to growers under the tenets of integrated pest management are explored. The realities and limitations of each are discussed and areas of future research identified.

IPM of western flower thrips

Several management strategies have been developed for control of WFT based on the biology and behavior of the pest. The following IPM strategies are described for control of WFT: physical exclusion and screening considerations; cultural controls such as weed control around greenhouses, avoidance of continuous cropping, and disposal of plant residues; monitoring; and chemical control.

Symposium: Advances in Integrated Pest Management Programs for Ornamental Plants: Advances in Sampling in Ornamentals

The traditional viewpoint that there is a zero tolerance level for pests or their damage on ornamental plants has hindered the development of statistically accurate sampling plans. Monitoring procedures determining initial presence, peak flight times, etc. have been developed, but actual methods to estimate pest populations on plants are lacking. This is changing coincidentally with grower perceptions that some pests or damage can be tolerated. This attitude change is most common in crops where a considerable portion of early growth is not marketed, where pesticide resistance renders even weekly insecticide applications less than satisfactory, or where restrictions on pesticide use has forced growers to be more judicious about pesticide applications. Recent developments in sampling for adults and larvae of the leafminer, Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) using yellow traps and/or leaf samples in chrysanthemums, marigolds and gypsophila are reviewed. In addition, the utility of using yellow traps to monitor adult whitelifes, Trialeurodes vaporariorum (Westwood) and Bemisia tabaci (Gennadius) (Homoptera; Aleyrodidae) on poinsettias, is discussed.

Two New Natural Enemies of Western Flower Thrips in California

An entomophilic nematode, Thripinema nicklewoodii (Tylenchida: Allantonematidae) and an endoparasitic wasp, Ceranisus sp. (Hymenoptera: Eulophidae) were recently recovered from western flower thrips (WFT) in California. Observations suggest nematode transmission into WFT occurs while the thrips feed on the plant. Females parasitized by the nematode appear to be reproductively sterile. The parasitic wasp was collected in samples of thrips-infested alfalfa and garden roses. Under laboratory conditions it predominantly oviposited into first instars, resulting in WFT death at the pre-pupal stage. Host-feeding was common. Identification of the wasp to the species level remains undetermined.

Polyandry and Reproduction in the Serpentine Leaf Miner Liriomyza trifolii (Diptera: Agromyzidae)

We investigated the hypotheses that Liriomyza trifolii is a polyandrous species and that multiple mating is required to maximize female fecundity. In addition, the hypothesis that male copulating frequency reduces female fecundity was examined. Using sterile and fertile males, we found that L. trifolii females mate more than once during their life span, and that multiple mating is required to maximize female fecundity. A similar amount of sperm was transferred during five successive male copulations with an equal insemination probability. However, the probability of reproduction failure was strongly correlated with the male copulating sequence. Moreover, the failure rate of sperm transfer was found to be 6.8%. In light of these results, possible selection pressures driving for polyandry in L. trifolii are discussed.

The Effect of Leaf‐Mining by Liriomyza Trifolii on Seed Set in Greenhouse Marigolds

The effect of foliage feeding by the serpentine leafminer, Liriomyza trifolii (Burgess), on seed production and germination by male-sterile marigolds (Tagetes erecta L.) was examined over two cropping seasons in commercial production greenhouses. Five components of T. erecta relative fitness (the number of flowers, ovules, and germinations per plant, seed mass, and plant height) were compared in plants grown under four different control strategies representing three different intensities of L. trifolii herbivory: no control (high herbivory), biological or chemical control (intermediate herbivory), and insect-free (low herbivory). In both years of the study, significant between-treatment differences in number of viable seeds per plant were detected but no significant differences were found in the other four relative fitness measures. The number of viable seeds was highest with high herbivory (no-control treatments) and lowest with comparatively low herbivory (chemical and insect-free treatments). L. trifolii damage may reduce photosynthate availability, which may slow seed development and increase the length of time in which ovule physiological and morphological conditions are suitable for successful fertilization. Because all plants within each year received an equal number of pollinations occurring at the same time relative to plant growth, ovules within plants in the high-damage treatments may have had a greater probability of being fertilized, resulting in an increase in production of viable seeds.

A Do-It-Yourself Cartridge Aspirator

An aspirator is a tool used to collect small specimens through the use of suction. The specimen is then deposited in some type of collecting vessel, where it can be confined. The container can then be removed and a new one can be placed in the system. In the case of the beloved “pooter,” the specimen can be blown back out of the aspirator into a collecting container. Suction can be provided using a mechanical pump or mouth suction. Current commercially available aspirators lack the ability to maintain suction on the collecting vessel once the cap has been opened to change out the collecting vessel, which is a problem when working with highly mobile specimens that can readily escape. There are a few …