Min B. Rayamajhi

Pseudophilothrips ichini (Hood) (Thysanoptera: Phlaeothripidae) is native to Brazil and was selected as a biological control agent of Brazilian peppertree, Schinus terebinthifolia Raddi (Anacardiaceae), in Florida (Habeck et al. 1994; Cuda et al. 2004; Wheeler et al. 2016a; Wheeler et al. 2017). Pseudophilothrips ichini was approved by the US Department of Agriculture, Animal and Plant Health Inspection Service, Riverdale, Maryland, USA, for field release in Florida in May 2019 (Wheeler et al. 2022). Brazilian peppertree is a woody shrub to small, multi-stemmed tree that is highly invasive in Florida in both urban and natural landscapes (McJunkin 1977; Loope & Dunevitz 1981; Cunningham 1991; Schmalzer 1995; Schmitz et al. 1997; Rodgers et al. 2014). Pseudophilothrips ichini has 2 larval instars and they feed in groups along with adults on tender flushing leaves and stems. First instars are yellow to pale orange, second instars are bright orange, and adults are black, averaging 0.7 mm, 1.0 mm, and 2.5 mm in length, respectively (Wheeler et al. 2016b). As part of our surveys for P. ichini establishment and spread at release sites, as well as in mass rearing operations, we have noted novel interactions between P. ichini and naturalized arthropods. This is the first formal report documenting predation of P. ichini in a field setting by an oligophagous thrips predator, specifically one that is a biological control agent for the Cuban laurel thrips, Gynaikothrips ficorum (Marchal) (Thysanoptera: Phlaeothripidae), on cultivated Ficus spp. (Moraceae).

El pimentero brasileño, Schinus terebinthifolia Raddi (Anacardiaceae), es una maleza invasora de áreas naturales y agrícolas de California, Florida, Hawái y Texas, EE. UU. Un trips, Pseudophilothrips ichini (Hood) (Thysanoptera: Phlaeothripidae), fue autorizado y liberado en el 2019 como el primer agente de control biológico para esta maleza invasora en Florida, EE. UU. Los trips se alimentan de las hojas enrojecidas que se producen durante la temporada vegetativa del hospedero. Juntos, el USDA-ARS, la Universidad de Florida y el Departamento de Alimentos y Servicios al Consumidor de Florida combinaron esfuerzos para producir en masa y liberar P. ichini en toda la zona de distribución invadida por pimenteros brasileños en Florida. Entre mayo del 2019 y diciembre del 2021, se liberaron más de 2 millones de P. ichini en 567 sitios de Florida. Durante este período, P. ichini persistió en el 60% de los sitios de estudio durante al menos 1 generación, como lo indica la recuperación de adultos de trips al menos 60 días después de la liberación. Estos resultados indican que este trips, un agente de control biológico clásico, ha persistido en el área de distribución invadida por el pimentero brasileño en Florida con poblaciones evidentes en muchos de los sitios de liberación. Este agente de control biológico proporcionará a los administradores de tierras un medio seguro y rentable para controlar el pimentero brasileño.

Pseudophilothrips ichini is a recently approved biological control agent for the highly invasive Brazilian peppertree in Florida, USA. Prior to approval for field release in 2019, thrips colonies used for host specificity testing were produced and maintained in small cylinders to fit in restricted quarantine spaces. This next segment in the classical biological control pipeline is mass production and distribution of P. ichini. To accomplish this, we developed novel techniques to expand from small colony maintenance to large-scale production. We first quantified the productivity of the small cylinders, each containing a 3.8 L potted plant and producing an average of 368 thrips per generation. Given the amount of maintenance the cylinders required, we investigated larger cages to see if greater numbers of thrips could be produced with less effort. Acrylic boxes (81.5 × 39.5 × 39.5 cm) each contained two 3.8 L plants and produced an average of 679 thrips per generation. The final advancement was large, thrips-proof Lumite^® screen cages (1.8 × 1.8 × 1.8 m) that each held six plants in 11.4 L pots and produced 13,864 thrips in as little as 5 wk. Screen cages and cylinders had the greatest thrips fold production, but screen cages required ten times less labor per thrips compared to either cylinders or boxes. The efficiency of these large screen cages ensured sustained mass production and field release capacity in Schinus-infested landscapes. The screen cage method is adapted and used by collaborators, and this will expand the literature on beneficial thrips mass rearing methods.

Dioscorea bulbifera has invaded, smothered, and disrupted ecological functions of native plant communities in Florida. Vines senesce in late fall, then overwinter as tubers and aerial bulbils which sprout in spring and repeat the growth cycle. A foliage-feeding beetle Lilioceris cheni, introduced from Asia as a biocontrol agent has established throughout D. bulbifera's range in Florida. Synchronies among the growth phenology of the weed, life stages of biocontrol agents and weather conditions, are considered essential for the successful suppression of an introduced weed. We conducted a common garden study that encompassed pre-biocontrol release attributes of D. bulbifera followed by a 5-yr post-L. cheni release impacts study on its natural infestations in four sites. We gathered monthly data on D. bulbifera and L. cheni and assessed possible synchronies between their life stages and with local weather variables. Air and soil temperatures and total rainfall showed positive correlation with timing of D. bulbifera vine emergence/senescence, vine coverage, adult beetle emergence from diapause, and their life stages (egg clutches, larvae, and adults). Vine sprouting and beetle emergence in two southern sites began in February and April, and in the remaining two northern sites in March and May, respectively. Vine sprouting and beetle emergence was initiated at 15 and 20°C, respectively. All sites achieved maximum vine coverage in July. Bulbil development, oviposition by overwintering adults, and vine damage by adult and larval feeding began in June. These sequences of events indicated phenological synchrony of the beetle and air potato life stages in Florida.

Understanding the effects of hurricanes and other large storms on ecological communities and the post-event recovery in these communities can guide management and ecosystem restoration. This is particularly important for communities impacted by invasive species, as the hurricane may affect control efforts. Here we consider the effect of a hurricane on tree communities in southern Florida that has been invaded by Melaleuca quinquevervia (melaleuca), an invasive Australian tree. Biological control agents were introduced starting in the 1990s and are reducing melaleuca in habitats where they are established. We used size-structured matrix modeling as a tool to project the continued possible additional effects of a hurricane on a pure stand of melaleuca that already had some level of biological control. The model results indicate that biological control could suppress or eliminate melaleuca within decades. A hurricane that does severe damage to the stand may accelerate the trend toward elimination of melaleuca with both strong and moderate biological control. However, if the biological control is weak, the stand is resilient to all but extremely severe hurricane damage. Although only a pure melaleuca stand was simulated in this study, other plants, such as natives, are likely to accelerate the decline of melaleuca due to competition. Our model provides a new tool to simulate post-hurricanes effect on invasive species and highlights the essential role that biological control has played on invasive species management.