Effects of SmartWater, a fluorescent mark, on the dispersal, behavior, and biocontrol efficacy of Phytoseiulus persimilis.

New marking methods for studying small biocontrol agents (especially predatory mites) are needed because many current techniques are expensive, ineffective or not applicable to small organisms. The objective of this study was to determine whether SmartWater, a liquid and permanent fluorescent dye, can be used to mark Phytoseiulus persimilis for experimentation without any deleterious effects on its dispersal, behavior, reproduction, and biocontrol efficacy. Our results show that there were no significant differences in movement, inter-plant dispersal, feeding behavior, survivability, and reproduction between marked P. persimilis and control individuals sprayed with water. We also found that the SmartWater mark lasted for the duration of the mites' life, indicating strong durability over time. Marking efficacy may be reduced, due to a trade-off between batch marking efficacy and the possibility of drowning study organisms. However, we feel future research could improve liquid marking techniques that would reduce this risk. Overall, this study concludes that SmartWater could be a useful marking tool for predatory mites in both laboratory and field studies.

The effect of UVB-blocking plastics on the efficacy of Beauveria bassiana and a conventional product against Lygus lineolaris on low tunnel strawberry.

BACKGROUND: Effective, safe and practical biocontrol options are greatly needed for combating Lygus lineolaris on protected culture strawberry. This study demonstrated how ultaviolet (UV)-selective plastics can improve the efficacy of the fungal biocontrol agent Beauveria bassiana (Mycotrol) compared to the conventional insecticide acetamiprid (Assail) against L. lineolaris on low tunnel strawberry. RESULTS: We found that UVB-blocking treatments improved B. bassiana spore viability in both in vitro and in vivo laboratory experiments. In the field, survival of Mycotrol-treated sentinel L. lineolaris was lowest under UVB-blocking low tunnels, but this did not translate into significant differences among covering treatments in local L. lineolaris density or fruit damage. In contrast, applying the product Assail resulted in the lowest L. lineolaris density and highest quality yield compared to Mycotrol sprays. This was especially pronounced under low tunnels of any UV-limiting plastic. CONCLUSIONS: This study indicates that growing under low tunnels is a useful tool to improve the efficacy of conventional products and biopesticides containing microbial biocontrol agents. The efficacy of both products was improved under low tunnels, and specifically under UVB-blocking plastics for Mycotrol containing B. bassiana. However, there was little evidence that UVB plastics resulted in lower L. lineolaris densities and proportion of damaged fruit for either product in the field. Therefore we conclude that growing under any plastic covering is likely to benefit growers, but the economic value of growing under UVB tunnels is unclear. © 2022 Society of Chemical Industry.

Summer Development and Survivorship of the Weed Biocontrol Agent, Mecinus janthiniformis (Coleoptera: Curculionidae), Within Stems of Its Host, Dalmatian Toadflax (Lamiales: Plantaginaceae), in Utah.

The summer phenology and survivorship of the stem-mining weevil, Mecinus janthiniformis Tosevski and Caldara, a biocontrol agent of Dalmatian toadflax, Linaria dalmatica (L.) Miller, was studied in 2015-2016 as it developed within host plant stems at a low elevation, open rangeland site in northern Utah. Hatching from eggs in spring and early summer, weevils occurred as larvae within stems in June. Earliest maturing adults occurred in mid-July, and the majority of individuals had completed pupal development by early August. Survivorship within stems was high, with two-thirds or more of individuals surviving from egg hatch to adulthood as assessed in mid-September. Mortality rates within stems were highest during larval development, with parasitism accounting for the majority of deaths. At least three parasitoid species (Chalcidoidea: Pteromalidae and Eupelmidae), including both endoparasitoids and ectoparasitoids, were found attacking weevils within stems. Although most surviving weevils remained as adults within stems to overwinter, some adults were found to have chewed exit holes, and in some cases had exited from stems, beginning in July; the fate of these prematurely exiting adults is unknown. Low summer mortality rates within stems should promote weevil establishment under the hot, dry conditions of northern Utah, but parasitism and premature exiting of adults from host stems merit further investigation concerning their potential to reduce biocontrol efficacy. The results presented here for M. janthiniformis phenology within host stems will contribute to the development of standardized, summer monitoring for this biocontrol agent by stem dissection.

Phenology of the Dalmatian Toadflax Biological Control Agent Mecinus janthiniformis (Coleoptera: Curculionidae) in Utah.

The phenology of the stem-mining weevil Mecinus janthiniformis Tosevski and Caldara (Coleoptera: Curculionidae) as adults attacking Dalmatian toadflax, Linaria dalmatica (L.) Miller (Plantaginaceae), was studied in 2014-2015 at two low elevation sites in northern Utah. The seasonal pattern of adult weevil abundance on the host plant at the two sites was most similar between years when described by degree-day accumulation, versus calendar date. Repeated censusing over the growing season revealed that males appeared first and subsequently peaked in abundance on the host plant earlier than females did, such that the adult population was dominated by males early in the season and by females late in the season. Peak female abundance on the host plant occurred at the time when Dalmatian toadflax stems reached their maximum height and density and when they began flowering widely. Maximum toadflax stem heights and densities, and flowering activity, were markedly reduced in 2015 compared to 2014. In contrast to these host plant parameters that vary between years, degree-day accumulation can be used readily for timing collection and survey efforts for adult weevils and female adult weevils in particular. Use of degree-day accumulation can thereby facilitate implementation of redistribution and monitoring programs for M. janthiniformis as a biological control agent of Dalmatian toadflax.