Asian citrus psyllid, Diaphorina citri, transmits Candidatus Liberibacter asiaticus (CLas), the putative causal agent of Huanglongbing disease. Although they primarily feed on the phloem of Citrus and related plants, when grove or host conditions are unfavorable, D. citri may be able to use weed species as alternate food sources for survival. To explore this possibility, electrical penetration graph (EPG) recordings (18 h) were performed to investigate the feeding behavior of psyllid adults and nymphs on three common south Florida weeds (Bidens alba, Eupatorium capillifolium, and Ludwigia octovalvis). EPG recordings revealed that the proportion of time spent by D. citri feeding on xylem was similar on all tested weed species (19%–22%) and on the positive control (20%), the preferred host, Citrus macrophylla. Very little to no phloem feeding was observed on weed species by either nymphs or adults. Histological studies using epifluorescence microscopy showed that salivary sheaths were branched and extended into xylem of weed species, whereas they ended in phloem on citrus plants. No choice behavioral assays showed that adults can obtain some nutrition by feeding on weed species (xylem feeding) and they may be able to survive on them for short intervals, when host conditions are unfavorable.

Herbicide resistance has been studied extensively in agronomic crops across North America but is rarely examined in vegetables. It is widely assumed that the limited number of registered herbicides combined with the adoption of diverse weed management strategies in most vegetable crops effectively inhibits the development of resistance. It is difficult to determine if resistance is truly less common in vegetable crops or if the lack of reported cases is due to the lack of resources focused on detection. This review highlights incidences of resistance that are thought to have arisen within vegetable crops. It also includes situations where herbicide-resistant weeds were likely selected for within agronomic crops but became a problem when vegetables were grown in sequence or in adjacent fields. Occurrence of herbicide resistance can have severe consequences for vegetable growers, and resistance management plans should be adopted to limit selection pressure. This review also highlights resistance management techniques that should slow the development and spread of herbicide resistance in vegetable crops.

Weeds are managed in Florida strawberry production systems with plastic mulches, fumigants, and herbicides. There are limited post-transplant options to control weeds that emerge in the planting holes on the plastic-covered beds, but flumioxazin at 107 g ai ha-1 can be applied pre-transplant under the plastic mulch to control broadleaf and grass weeds. Three research trials were conducted in Balm and Dover, Florida, in 2017 and 2018 to evaluate tolerance of the strawberry cultivar ‘Radiance’ to flumioxazin rates ranging from 54 to 6854 g ha-1 and to estimate herbicide persistence under the plastic mulch. Shoot damage was observed at 428-857 g ha-1, which is 4X and 8X the label rate, respectively, but a significant increase in the number of dead plants was not observed until 857 g ha-1 at one site and 3427 g ha-1 at a second site (8 and 32X the label rate respectively). Berry yields were unaffected by rates lower than 857 g ha-1. Flumioxazin persisted throughout the growing season (~ 150 days) with no reduction in soil concentration. We conclude that label rate flumioxazin application is a safe pre-transplant weed management option for season-long weed control in strawberry with no yield reduction at rates below 8X the label rate. Caution is recommended for growers that plant a second crop on the same bed.