Abstract. The objective of this study was to estimate the economic impact of the sugarcane aphid (SCA) outbreak in the Rio Grande Valley (RGV), Texas. Local producers were surveyed to gather detailed information about crop production and pest control practices. Collected data were used to estimate the reduction in profit associated with the SCA infestation, as well as the monetary value of the prevented loss attributed to control efforts. Sorghum industry losses were then used to assess the overall economic impact of the SCA outbreak in the RGV economy.

Plant species in the family Solanaceae are the usual hosts of potato psyllid, Bactericera cockerelli (Šulc) (Hemiptera: Psylloidea: Triozidae). However, the psyllid has also been shown to develop on some species of Convolvulaceae (bindweeds and morning glories). Developmental success on Convolvulaceae is surprising given the rarity of psyllid species worldwide associated with this plant family. We assayed 14 species of Convolvulaceae across four genera (Convolvulus, Calystegia, Ipomoea, Turbina) to identify species that allow development of potato psyllid. Two populations of psyllids were assayed (Texas, Washington). The Texas population overlaps extensively with native Convolvulaceae, whereas Washington State is noticeably lacking in Convolvulaceae. Results of assays were overlain on a phylogenetic analysis of plant species to examine whether Convolvulaceae distantly related to the typical host (potato) were less likely to allow development than species of Convolvulaceae more closely related. Survival was independent of psyllid population and location of the plant species on our phylogenetic tree. We then examined whether presence of a fungal symbiont of Convolvulaceae (Periglandula spp.) affected psyllid survival. These fungi associate with Convolvulaceae and produce a class of mycotoxins (ergot alkaloids) that may confer protection against plant-feeding arthropods. Periglandula was found in 11 of our 14 species, including in two genera (Convolvulus, Calystegia) not previously known to host the symbiont. Of these 11 species, leaf tissues from five contained large quantities of two classes of ergot alkaloids (clavines, amides of lysergic acid) when evaluated by LC-MS/MS. All five species also harbored Periglandula. No ergot alkaloids were detected in species free of the fungal symbiont. Potato psyllid rapidly died on the five species that harbored Periglandula and contained ergot alkaloids, but survived to adulthood on seven of the nine species in which ergot alkaloids were not detected. These results support the hypothesis that a plant-fungus symbiotic relationship affects the suitability of certain Convolvulaceae to potato psyllid.

Abstract Our previous study provided correlative evidence that morning glory species harboring endophytic fungi (Periglandula) are resistant to potato psyllid [Bactericera cockerelli (Šulc)], whereas species free of fungi often allowed psyllid development. In this study, we manipulated levels of ergot alkaloids in host tissues by inoculating clippings from potato plants with extracts from morning glories that harbor Periglandula [Ipomoea leptophylla Torrey, Ipomoea imperati (Vahl) Grisebach, Ipomoea tricolor Cavanilles, Ipomoea pandurata (L.) G. F. Meyer, and Turbina corymbosa (L.)] and one species (Ipomoea alba L.) that does not harbor the endophyte. Ergot alkaloids (clavines, lysergic acid amides, and ergopeptines) were detected in potato clippings, thus confirming that leaves had taken up compounds from solutions of crude extracts. Psyllid mortality rates on inoculated clippings ranged between 53 and 93% in treatments producing biochemically detectable levels of alkaloids, when compared with 15% mortality in water controls or the alkaloid-free I. alba. We then tested synthetic analogs from each of the three alkaloid classes that had been detected in the crude extracts. Each compound was assayed by inoculating clippings of two host species (potato and tomato) at increasing concentrations (0, 1, 10, and 100 µg/ml in solution). Psyllids exhibited a large and significant increase in mortality rate beginning at the lowest two concentrations, indicating that even very small quantities of these chemicals led to mortality. Feeding by nymphs on artificial diets containing synthetic compounds resulted in 100% mortality within 48 h, irrespective of compound. Further testing of ergot alkaloids to characterize the mode of action that leads to psyllid mortality is warranted.

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The Rio Grande Valley is one of the most productive agricultural areas in the U.S and is located in the southernmost part of Texas. In October 2013, we detected an exotic plant bug, Nesidiocoris tenuis Reuter (Hemiptera: Miridae: Bryocorinae) occurring in the region. Nesidiocoris tenuis has zoophytophagous habits; however, in the absence of insect prey, it feeds on its plant hosts. After its morphological and genetic identification, this study monitored the population of N. tenuis in its introduction phase in commercial fields and corroborated its establishment in research fields for three years. Populations of N. tenuis were high during the fall and low during winter. This study found that N. tenuis populations were higher in tomato fields as compared to adjacent pepper, okra, and squash fields, indicating its host preferences during the introduction phase. Recurrent population growth patterns suggest that N. tenuis was established in Rio Grande Valley with permanent populations in tomato fields. In addition, N. tenuis populations were affected by tomato cultivar selection and by plastic mulch color. The presence of N. tenuis could establish a new trophic insect relationship for vegetable production. However, it is unknown if the presence of N. tenuis may help to control pests of economic importance, such as whiteflies in cotton, or become a pest on sesame, an emerging crop.