Seasonal Abundance and Spatial Pattern of Distribution of Liriomyza trifolii (Diptera: Agromyzidae) and Its Parasitoid on Bean and Squash in South Florida

American serpentine leafminer, Liriomyza trifolii, is a polyphagous insect pest that feeds on a wide range of vegetable and ornamental plants around the world. To develop an effective IPM program, information on the seasonal field distribution and population dynamics of leafminer and its parasitoids is very important. Therefore, seasonal abundances and spatial distributions of, L. trifolii on snap bean and squash were studied during four crop growing periods between 2013 to 2015 in Homestead, Florida. The mean numbers of mines, larvae, pupae, emerged adults, and parasitoids on snap bean were highest at 2 weeks after planting during all four growing periods. Whereas, the mean numbers of mines, larvae, pupae, emerged adults, and parasitoids on squash were highest at 3 weeks after planting during all four growing periods. L. trifolii distributions tended to be aggregated on snap bean at 2 weeks after planting during most of growing periods but had uniform distributions on squash at 2 weeks after planting during most of growing periods. Similar results were seen on the distribution of leafminer parasitoids on both bean and squash.

Silica nanoparticles as pesticide against insects of different feeding types and their non-target attraction of predators

The agricultural use of silica (SiO2) nanoparticles (NPs) has the potential to control insect pests while the safety and tritrophic effects on plants and beneficial natural enemies remains unknown. Here, we evaluate the effects of silica NPs on insect pests with different feeding niches, natural enemies, and a plant. Silica NPs were applied at different concentrations (75–425 mg/L) on field-cultivated faba bean and soybean for two growing seasons. The faba bean pests, the cowpea aphid Aphis craccivora and the American serpentine leafminer Liriomyza trifolii, and the soybean pest, the cotton leafworm Spodoptera littoralis, were monitored along with their associated predators. Additional laboratory experiments were performed to test the effects of silica NPs on the growth of faba bean seedlings and to determine whether the rove beetle Paederus fuscipes is attracted to cotton leafworm-infested soybean treated with silica NPs. In the field experiments, silica NPs reduced the populations of all three insect pests and their associated predators, including rove beetles, as the concentration of silica NPs increased. In soybean fields, however, the total number of predators initially increased after applying the lowest concentration. An olfactometer-based choice test found that rove beetles were more likely to move towards an herbivore-infested plant treated with silica NPs than to a water-treated control, suggesting that silica NPs enhance the attraction of natural enemies via herbivore-induced plant volatiles. In the laboratory, while silica NPs inhibited the development of faba bean roots at 400 mg/L, they did not affect germination percentage, germination time, shoot length, or vigor index compared to the control.

Seasonal Abundance and Spatial Pattern of Distribution of Liriomyza trifolii (Diptera: Agromyzidae) and Its Parasitoid on Bean and Squash in South Florida

ABSTRACTAmerican serpentine leafminer, Liriomyza trifolii, is a polyphagous insect pest that feeds on a wide range of vegetable and ornamental plants around the world. To develop an effective IPM program, information on the seasonal field distribution and population dynamics of leafminer and its parasitoids is very important. Therefore, seasonal abundances and spatial distributions of, L. trifolii on snap bean and squash were studied during four crop growing periods between 2013 to 2015 in Homestead, Florida. The mean numbers of mines, larvae, pupae, emerged adults, and parasitoids on snap bean were highest at 2 weeks after planting during all four growing periods. Whereas, the mean numbers of mines, larvae, pupae, emerged adults, and parasitoids on squash were highest at 3 weeks after planting during all four growing periods. L. trifolii distributions tended to be aggregated (1 < b/β) on snap bean at 2 weeks after planting during all four growing periods but had uniform (1 > b/β) distributions on squash at 2 weeks after planting during all four growing periods. Similar results were seen on the distribution of leafminer parasitoids on both bean and squash.

Leafminer attack induces plant-mediated facilitation of conspecific pupae in the soil

Plants and herbivores are engaged in intimate antagonistic interactions, with plants trying to mount effective defense responses and herbivores attempting to manipulate plants for their own benefit. Here we report on a new mechanism by which herbivores can facilitate their own development. We show that tomato (Solanum lycopersicum) leaf attack by the American serpentine leafminer Lyriomiza trifolii accelerates the development of conspecific pupae in the soil adjacent to the plant. This pattern was reversed in the jasmonate-signaling deficient tomato mutant def-1. Chemical analyses revealed that L. trifolii leaf attack changes the production of root volatiles in a def-1 dependent manner. Thus, leaf-feeding herbivores can interact with their soil-dwelling pupae, and jasmonates and root volatiles likely play relevant roles in this phenomenon. This study expands the repertoire of plant-herbivore interactions to herbivory-induced modulation of metamorphosis.