Postharvest Fumigation of Fresh Citrus with Cylinderized Phosphine to Control Bean Thrips (Thysanoptera: Thripidae)

Abstract

Bean thrips (BT), Caliothrips fasciatus (Pergande), is a pest of concern to certain countries that import fresh citrus fruit from California, USA. A series of laboratory-scale exploratory fumigations with phosphine at 4.9 ± 0.3 °C (mean ± 2 SD; x¯±2s) were conducted to evaluate the postharvest control of adult BT. Models of the duration–mortality response predicted ca. 99% mortality of BT populations when headspace concentrations of phosphine, [PH3], are maintained at levels ≥0.4 g m−3 (250 ppmv (µL L−1)) and ≤1.5 g m−3 (1000 ppmv (µL L−1)) for 12 h, with the duration representing the lower bound of the 95% confidence level (CL). Confirmatory fumigations, each lasting 12 h, were then conducted using BT-infested sweet oranges, Citrus sinensis (L.), at pulp temperature (T) ≤ 5 °C to corroborate the exploratory results. Three formulations of cylinderized phosphine were used: 1.6% phosphine by volume in nitrogen, VAPORPH3OS®, and ECOFUME®, all applied at two levels, ca. 1.5 g m−3 (1000 ppmv (µL L−1)), as well as 0.5 g m−3 (300 ppmv (µL L−1)). Collectively, across the formulations, an applied dose of ca. 1.5 g m−3 (1000 ppmv (µL L−1)) resulted in 0 survivors from 38,993 (probit 8.60, 95% CL; probit 9, 72% CL) treated BT, while an applied dose of 0.5 g m−3 (300 ppmv (µL L−1)) resulted in 0 survivors from 31,204 (probit 8.56, 95% CL; probit 9, 70% CL) treated BT. Results were discussed in the context of commercial and operational features of quarantine and pre-shipment (QPS) uses of phosphine to treat fresh fruit and, specifically, the control of BT in fresh citrus exported from California, USA, to Australia.

Ethyl formate dilution in carbon dioxide for fumigation control of the brown marmorated stink bug Halyomorpha halys, Stål (Hemiptera: Pentatomidae)

“…Insecticidal fumigants have different mechanisms and modes of action, which are known to influence the magnitude of z, a proxy for the relative importance of C versus t. 44,47 Efficacy data contributed by many investigators across a variety of targeted insect pests indicates that for methyl bromide z ≅ 1 (at least when t < 6 h), which is consistent with a first-order approximation of diffusion-limited reactivity likely including the alkylation of nitrogen-and sulfur-containing biomolecules. 46 For phosphine, z changes as a function of C. 47,48 Winks operationally defined the 'narcosis threshold' as the region where z ≅ 0, whereby increases or decreases in phosphine concentration did not change the duration required for the particular level of control (e.g. 99% mortality).…”

Egg Morphology and Chorionic Ultrastructure of Spotted Lanternfly, Lycorma delicatula (White) (Hemiptera: Fulgoridae)

“…With respect to the "non-reactive" fumigants, hydrogen cyanide poisons the mitochondrial electron transport chain within cells by binding to the a3 portion (complex IV) of cytochrome c oxidase, and several studies indicate phosphine also inhibits cytochrome c oxidase activity [23][24][25]. However, multiple pathways are involved with phosphine toxicity, as evidenced by the "narcosis threshold" in the seminal works of Winks and Waterford [26] and discussed as the "sweet spot" in works of Walse et al (2021) [27] and Lampiri et al (2021) [28]. Phosphine is registered in the U.S., in metal phosphide and cylinderized formulations, to treat many types of construction materials and wood products.…”

Effects of Temperature on the Developmental and Reproductive Biology of North American Bean Thrips, Caliothrips fasciatus (Pergande) (Thysanoptera: Thripidae: Panchaetothripinae)

“…2023). To mitigate quarantine issues, research on C. fasciatus has focused, in part, on the development of sampling, monitoring, and management programs in citrus [2,9,10] and fumigation strategies for harvested fruit [11,12].…”