Host Plant Selection by Romalea Microptera (orthoptera: Romaleidae)

The eastern lubber grasshopper, Romalea microptera (Palisot de Beauvois) (Orthoptera: Romaleidae)[also known as R. guttata (Houttuyn)], is known to be polyphagous, but little else is known about its diet. Choice and no-choice tests were conducted to determine plant preference. In choice tests, 104 different plants were presented and relative preference was determined using ‘Romaine’ lettuce (Lactuca sativa L. var. longifolia; Asteraceae) as a standard. These included representative plants from several categories, including ornamental plants, weeds, shrubs, trees, vines, aquatic or semiaquatic plants, and vegetable crops. The grasshoppers did not display a statistically significant difference in selection, relative to ‘Romaine’ lettuce, for 20% of the plants evaluated; these should be considered very susceptible to injury because lettuce is a readily accepted plant. A few plants (3%) were more preferred than lettuce, and of course would also be at high risk for consumption. The majority of plants tested (77%) were significantly less preferred, but even some of these are at risk because, like other polyphagous insects, lubbers sometimes will feed on less acceptable plants when preferred plants are not available. A subset of these (n = 25) was also presented in no-choice tests, and the choice and no-choice responses compared. Plant preference in choice and no-choice tests was significantly correlated. A selection of ornamental plants (n = 10) that scored least-preferred in choice tests was assessed in no-choice ‘starvation’ tests, and 9 of the 10 proved to be quite resistant to grasshopper feeding. Several plants (n = 5) that produce foliage asynchronously were assessed in choice tests, with the grasshoppers preferring young foliage relative to old foliage. In field cage studies, the acceptability of plants significantly affected the efficacy of insecticide-containing baits, with significantly higher mortality found in cages containing non-preferred plants. Thus, host plant selection affects damage directly by regulating the amount of feeding, and indirectly by influencing acceptance of bait.