Doctor of Philosophy (PhD)



Document Type



Host plant preference and chemical ecology of the sugarcane beetle, Euetheola humilis were evaluated in greenhouse and laboratory studies. Sweet potato, Ipomoea batatas, was significantly preferred over all other plant species evaluated in a host plant preference test. Corn, Zea mays, and sugarcane, Saccharum spp., were the next most chosen plant species in the study. In olfactometer experiments, sugarcane beetles responded significantly more to beetle injured and mechanically injured roots vs. uninjured roots. Male and female beetles were also significantly more attracted to female conspecifics. Differences were not detected between sweet potato cultivars in olfactometer trials. Cultivar preference studies suggested that some cultivars may be more attractive than others. Susceptibility of sugarcane beetle and sweetpotato weevil, Cylas formicarius, to selected insecticides was evaluated in laboratory bioassays. Sugarcane beetles were significantly more susceptible to z-cypermethrin than to chlorpyrifos and bifenthrin. Sweetpotato weevils from two cohorts were most susceptible to methyl parathion and the cohorts were differentially susceptible to selected insecticides. Reduced susceptibility of a reference cohort of sweetpotato weevil was noted for all insecticides evaluated. A planting date study was conducted over two years in two locations in Louisiana. Damage from soil insects in sweet potato can be affected by many factors, such as insect abundance and life stage, and stage of the crop. A representative early, middle, and late planting date were used to assess soil insect abundance and damage throughout the sweet potato production season. Planting date affected damage from soil insects in sweet potato. Significantly more total insect damaged roots were sampled from late planting dates compared to early and middle planting dates. Cucumber beetle, Diabrotica spp., damage was greater in late planting dates, relative to early and middle planting dates. Late planting dates also had an increased probability of sugarcane beetle damage compared to early and middle planting dates. The majority of adult insects sampled were Diabrotica beetles and Diabrotica abundance was variable throughout the season and was positively correlated with percent larvae damaged roots at various seasonal intervals. Sweet potato soil insect abundance and damage was also investigated at various herbicide regimes in a two year study. Differences in soil insect damage or adult insect abundance were not detected between various herbicide regimes. U.S. No. 1 and 2 yield was significantly higher in herbicide treated plots vs. untreated control plots and weed densities were significantly reduced in some treated plots compared to untreated control plots. Sugarcane beetle studies have provided information on the biology, chemical ecology and possible management options for this insect in sweet potato. In addition, these studies have examined the importance of an integrated pest management system in sweet potato. Integrated pest management involves manipulating the crop as well as careful management of insect species.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Abner M. Hammond



Included in

Entomology Commons