Does the seed disperser matter? The influence of dispersal type on survival of Araucaria angustifolia seeds

Zoochoric dispersion is fundamental for the colonization of habitats by plants with large and heavy seeds such as the Paraná pine (Araucaria angustifolia). This is an endangered conifer from South America whose recruitment is heavily impacted by animals, but the way that different zoochoric dispersal modes and deposition sites can affect its successful establishment is not known yet. Thus, in this study, we aimed to evaluate the effect of dispersal mode (accordingly to the seed disperser), distance from adult conspecifics, and disposition site on long-term recruitment success. The experimental design included two environments (forest and open field) and each of them received 30 micro-habitat sampling stations (simulating deposition sites: 10 under conspecific; 10 far from conspecifics, next to a landmark; and 10 far from conspecifics, without a landmark), and each microhabitat had three levels of dispersal type simulating animal treatment (intact buried seed; intact seed over the ground; partially preyed seed over the ground), each with five seeds, totaling 900 seeds. In the forest environment, an experiment was also conducted to verify the fate of seeds using the spool and line technique. The environment and the micro-habitat alone did not explain seed survival, although the dispersal type given by the animal disperser was significant for survival and the buried seeds were the only ones that survived until the last survey. With the spool and line seed experiment, we attested that most of the Paraná pine seeds were preyed after removal (81.5%), and only buried seeds survived, reinforcing the role of scatter-hoarding animals as important agents in the Paraná pine dispersal. This way, our results showed that Paraná pine seeds suffer a very high predation rate, and that only a few seeds escape from predators and recruiting (only 1.1% of the all seeds used in the two experiments), indicating that the survival of seeds is a critical step in the life cycle of this plant, highlighting the role of dispersal mode in recruiting success.

Minicutting technique and IBA application in vegetational propagation of Schinus terebinthifolia Raddi

Vegetative propagation is an alternative for the production of seedlings of native tree species such as Schinus terebinthifolia that presents a high predation rate on its seeds. In order to develop vegetative propagation technology, different concentrations of indolebutyric acid (IBA) were tested in the rooting of apical and intermediate minicuttings of Schinus terebinthifolia. The 2x4 factorial experimental design involved two types of minicuttings (apical and intermediate) and four dosages of the hormone IBA (0, 1000, 2000, and 4000 mg. L-1). The percentages of survival and rooting were evaluated. The intermediate minicuttings (37% and 35%) showed significantly greater survival than the apical cuttings (22% and 9%) respectively at 30 and 60 days, regardless of the IBA concentration. Among the rooting averages at 60 days obtained in the different concentrations of IBA, the treatment of 4000 mg. L-1 generated the highest results (9% for apical and 35% for intermediate). The vegetative propagation by minicuttings of Schinus terebinthifolia demonstrated the viability of intermediate minicuttings with high rooting associated with the highest concentration of IBA.

First Report Using a Native Lacewing Species to Control Tuta absoluta: From Laboratory Trials to Field Assessment

The South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), a destructive pest on tomato, has invaded most Afro-Eurasian countries. Recently invaded by the pest, most tomato crops in greenhouses and open fields in Tajikistan are currently suffering major damage. While failure in management using chemical insecticide has been frequently observed, alternative options such as biological control is urgently needed. In this study, we evaluated the effectiveness of the common green lacewing Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) against T. absoluta. In controlled laboratory conditions, C. carnea showed high predation rate on both T. absoluta eggs (i.e., 36 ± 2 eggs within 24 h and 72 ± 4 eggs within 48 h) and larvae, especially it can attack the larvae both inside and outside the leaf galleries (i.e., an average of 22% of the larvae was killed inside, and an average of 35% was killed outside). In a cage exclusion experiment, T. absoluta showed relatively low larval density in the cages with pre-fruiting release of C. carnea, whereas the larval density was four to six times higher in the “no release” cages. In the “post-fruiting release” cages, the pest population that had already built up during the pre-fruiting stage eventually crashed. In an open-field experiment, the tomato crops in control plots were fully destroyed, whereas low levels of larvae density and damage were observed in the biocontrol plots. Moreover, the field release of C. carnea resulted in significantly higher tomato yield than those without release, despite no differences between the “pre-fruiting release” and “post-fruiting release” treatments. We conclude that the local commercial biocontrol agent C. carnea could be promising for the management of T. absoluta in Tajikistan. It is also one of the first reports showing the management of T. absoluta using a lacewing species. The effectiveness should be validated by further field trials in larger area of commercial crops and various locations.

Intra-guild vs extra-guild prey: effect on predator fitness and preference of Amblyseius swirskii (Athias-Henriot) and Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae)

The relationships between the predatory mites, Amblyseius swirskii (Athias-Henriot) and Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae), and their prey, western flower thrips (Frankliniella occidentalis Pergande) (Thysanoptera: Thripidae), were investigated to determine the effects of predation on intra-guild or extra-guild prey and predator preference. Life history characteristics of both predatory mites were measured when fed eggs and larvae of the other predator species and compared to data obtained when the predators were fed thrips larvae. In addition, choice tests were conducted to determine if the predators had a preference for different prey or if they were indiscriminate predators. Amblyseius swirskii appears to be an important intra-guild predator of N. cucumeris juveniles because of a high predation rate and a preference for N. cucumeris juveniles over thrips. Neoseiulus cucumeris is also an intra-guild predator of A. swirskii juveniles; however, it has a lower predation rate than A. swirskii. Contrary to intra-guild predation theory, intra-guild prey was an equally good or better food source than thrips (extra-guild prey) for both predators, based on high oviposition rates and fast development times. The results of this study indicate a high potential for negative interactions between A. swirskii and N. cucumeris when used together in biological control of thrips.