An evaluation of host-plant resistance to the wireworm-Diabrotica-Systena (WDS) complex of root-feeding insects in sweetpotatoes was performed on a total of 15 cultivars and advanced lines over the course of 4 years (2017-2020). It was found that sweetpotatoes varieties can differ significantly in amount of damage incurred. Several mechanisms of resistance were proposed and tested: periderm toughness, dry weight percentage, and volatile organic chemical defenses. No significant difference was found amongst the varieties tested concerning the physical properties. Chemical analysis was limited in scope but did show some differences between a susceptible variety when compared to a resistant variety in the volatile chemical composition of the foliage. Finally, a commercial kairomone lure with sticky card for Diabroticites was tested for efficacy when compared to sweep net sampling throughout the season. No correlation could be found amongst the methods in terms of number and species of insects caught by each.

Magistratūros studijų baigiamajame darbe pateikiama 2012 metais Aleksandro Stulginskio universiteto Agronomijos fakulteto Biologijos ir augalų biotechnologijos instituto Augalų apsaugos metodų laboratorijoje tirti veiksniai, kaip skirtingi spragšių (Elateridae) lervų kiekiai įtakoja žemės ūkio augalų vystymąsi. Darbo objektas - Agriotes sp., Selatosomus sp. ir Cidnopus sp. lervos. Darbo metodai: buvo vykdomi 3 bandymai norint išsiaiškinti spragšių lervų daromą žalą įvairiems žemės ūkio augalams. Pirmojo bandymo metu buvo stebima kaip Agriotes sp., Selatosomus sp. ir Cidnopus sp. skirtingi 2, 4 ir 6 lervų kiekiai įtakos kukurūzų, kviečių ir miežių vystymosi procesus. Antrojo bandymo metu buvo stebima kaip 3, 5 ir 7 Agriotes sp. lervos paveiks morkas, runkelius ir rapsus. Trečiojo bandymo metu stebėta kaip skirtingi 3, 5, ir 7 lervų kiekiai paveiks morkų, runkelių ir rapsų vystymąsi. Visuose bandymuose kontroliniame variante lervų naudota nebuvo. Eksperimentai buvo vykdomi trimis pakartojimais, pažeidimai augaluose stebėti 5 kartus, kas 5 dienas. Duomenys statistiškai įvertinti naudojant programą ANOVA iš paketo SELEKCIJA. Darbo rezultatai: 2012 m. Aleksandro Stulginskio universiteto Agronomijos fakulteto Augalų apsaugos laboratorijoje atlikus stebėjimus, kaip spragšių lervos įtakoja augalų vystymąsi gauti rezultatai parodė, kad didžiausias esminis kukurūzų pažeidimų skaičius lyginat su kontrolinių variantu buvo Selatosomus sp. 6 lervų variante. Pažeistų augalų buvo rasta... [toliau žr. visą tekstą] / Master's thesis submitted in 2012, Alexander Stulginskio University, Faculty of Agronomy in the laboratory to investigate factors such as different gaps (Elateridae) larvae affect the amounts of crop development. The object of the work - Agriotes sp. Selatosomus sp. and Cidnopus sp. larvae. Methods of the work - was carried out three tests for identifying gaps larval damage to various crops. The first test was observed as Agriotes sp. Selatosomus sp. and Cidnopus sp. Different 2, 4 and 6 of the larvae of the influence of corn, wheat and barley development processes. Second test was observed as 3, 5 and 7 Agriotes sp. larvae affect carrots, beet and oilseed rape. The third test was seen as different 3, 5, and 7 larvae affect the amounts of carrot, beet and oilseed rape development. All of the tests in the control larvae were used. Experiments were carried out in three replications, damage plants monitored 5 times every 5 days. Statistically evaluated using ANOVA program from the package SELEKCIJA. The results: 2012. Aleksandras Stulginskis University, Faculty of Agronomy Plant protection laboratory observations carried out as a gap in the larval development of the plant influences the results obtained showed that the highest corn substantial number of violations compared to the control variant was Selatosomus sp. 6 larvae version. Infected plants were found as much as 46 percent. Abundantly as much as 50 percent. damaged wheat was 6 Selatosomus sp. larvae version. Most barley... [to full text]

Root-feeding insects can have top-down influence on vegetative composition and ecosystem processes; however, they may respond to bottom-up factors such as soil resources, site productivity, and disturbance.  My research addressed the following questions: (1) Do disturbance (fire), vegetative composition, soil resources, and fine root standing mass influence the structure of root-feeding insect assemblages? (2) What types of roots do root-feeding insects eat, and do they forage selectively?  (3) Do root-feeding insects influence fine root productivity?  To address these questions, I studied root-feeding insect assemblages in longleaf pine wiregrass (Pinus palustris-Aristida stricta) ecosystems of southwestern Georgia, U.S.A.  On a random basis, study sites were burned at least every other year (B), or left unburned (UB) for about 9 years.  Fine root productivity and root-feeding insect abundances were sampled repeatedly across 54 random plots in UB and B sites.  In Chapter 2, I characterized spatial and temporal patterns of root-feeding insect abundance, understory plant composition, soil resource availability, and fine root standing mass within each plot.  Insect population densities were low overall, but abundance, patchiness, and diversity were greater in UB sites.  Abundance patterns were significantly related to vegetative composition.  In Chapter 3, I quantified the diet of root-feeding insects by measuring the natural abundance of carbon (C) and nitrogen (N) stable isotopes in insects and fine roots.  Using 13C abundance, I examined the contribution of warm season grass roots to insect diet, relative to the proportion of warm season grass roots within adjacent root standing crop samples; 15N abundance was used to detect omnivory.  Overall, insects appeared to be non-selective herbivores and omnivores that may alter foraging behavior to maintain a mixed diet (i.e. reducing or increasing warm season grass consumption when its abundance was high or low, respectively).  The extent of omnivory varied within and among taxa.  In Chapter 4, I estimated the top-down influence of root-feeding insects on fine root productivity by comparison of ingrowth cores with or without an insecticide treatment.  I detected a weak positive effect of herbivores on the productivity of non-grass fine roots (< 10% of fine root productivity). / Ph. D.

Separate field studies were started in fall 2005, which continued through fall 2007, to investigate the effect of different levels of European corn borer tunneling on yield in corn grown for grain and to predict spring infestation levels of early season soil insects, specifically white grubs (Coleoptera: Scarabaeidae) and wireworms (Coleoptera: Elateridae) in cornfields. In the first study, model variables included corn growth stage and larvae per plant. In both years of this study, larvae per plant had a significant effect on grain yield. Grain yield was reduced by 13.1 and 3.65% in plants infested with four larvae per plant in 2006 and 2007, respectively. For 2006, linear regression models provided average percent yield loss per larva per plant at 4.1, 6.8, and 1.8% during late vegetative (V12), early silking (R1), and blister (R2) growth stages, respectively. Economic injury levels (EILs) were calculated based on average percent yield reductions across each growth stage and year. In the second study, no significant differences were detected in both fall and spring between two sampling methods after correcting for differences in sampling volume. Strong correlations were observed between fall and spring grub densities in both years. In 2006, fields with grub densities above the spring nominal threshold had significantly greater stand and yield in the Poncho 1250 (1.25 mg clothianidin / kernel) treatment when compared to the Poncho 250 (0.25 mg clothianidin / kernel) and untreated plots. This information was used to develop fall EILs and economic thresholds for white grubs. / Master of Science in Life Sciences