Sorghum (Sorghum bicolor [L.] Moench) production in many areas of the world is reduced due to damage caused by sorghum midge (Stenodiplosis sorghicola). There are several methods of control to reduce losses due to sorghum midge, which include cultural practices, biological control, chemical control and resistant cultivars. The best long-term solution for sorghum midge control is the use of genetic resistance in cultivars and hybrids. Recently, sorghum midge resistant hybrids have been developed by several sorghum breeding programs, but there is limited information about agronomic performance relative to planting dates compared to susceptible standards. Thus, the objectives of this research project are: (1) to evaluate the value of sorghum midge resistant sorghum hybrids in the USA production system, (2) to confirm the presence of sorghum midge insect resistance in sorghum hybrids, and (3) to determine whether the resistance in eighteen sorghum hybrids is stable across two environments in Texas where sorghum midge is a damaging pest. Sorghum hybrids with different levels of resistance to sorghum midge were evaluated at College Station and Corpus Christi, Texas in 2003 and 2004, using two different planting dates and the presence or absence of an insecticide treatment. Agronomic data, sorghum midge incidence ratings and number of adult midges, were determined for all entries. All entries designated as resistant did have some resistance compared to susceptible checks. Across all hybrids, grain yield was higher in sorghum with normal planting dates compared to late planting. Under midge pressure resistant hybrids performed better than susceptible hybrids, but lacking midge pressure the susceptible hybrids were higher performing. The use of midge resistant hybrids in commercial production is only warranted when producers are reasonably sure that midge will be a problem. Otherwise, they should continue to plant early using traditional hybrids.

Two isoenzymes of malate dehydrogenase were isolated and partially purified from the midge larva Glyptotendipes barbipes. Differential centrifugation followed by cellulose acetate and polyacrylamide gel electrophoresis revealed one isoenzyme associated with the mitochondrial fraction and another form found only in the cytoplasm.

Abstract The effects of temperature on daily eclosion time and monthly eclosion days of the marine midge Pontomyia oceana were investigated. We changed temperature at different times on the eclosion day. The results show that P. oceana has started related metabolic processes at sunrise which lead to eclosion after sunset. Daily temperature cycles do not have concentrating effect on daily eclosion time. Two peaks of eclosion dates occurred from the same batch of fertilized eggs in the laboratory without cyclic environmental factors. High culturing temperature results in short interval (duration) between fertilization and eclosion, whereas more days are required at low temperature. The culturing temperature has a significant influence upon the numbers of P. oceana occurring in different eclosion peaks. High first/second peak ratio occurred at high temperatures whereas relatively more eclosed at the second peak at low temperature. The eclosion dates of offspring are not related to their parents with regard to the 2 peaks. There was an corresponding shift in eclosion days in eggs fertilized 2 days apart. It suggested that circasemilunar eclosion times were not caused by cues in the laboratory.

The mechanism of semilunar emergence rhythm of the marine midge, Pontomyia oceana, was investigated. We used night light (1 lux) to entrain the emergence of the midge. Night light of 4 nights or more can effectively synchronize the semilunar emergence. Moreover, the night light has to be given about 10 days after fertilization to be effective. A batch of fertilized eggs of the marine midge emerge in two semilunar cycles, a second round of night-light treatment is necessary to synchronize the second peak of emergence. We also investigate whether the semilunar rhythm is dependent on the daily rhythm of the midge. Using different day length, from 20 to 28 hours per day, with equal light and dark periods, we want to know if the midges are counting numbers of light-dark cycles, or are independent of light-dark cycles, in determining their semilunar emergence. The results were intermediate between the two hypotheses. We suggest that the midge was not affected by light-dark cycle for the first 14 days of their life, afterward they count 15 light-dark cycles before emergence. This also explains how the second emergence peak occurs about 45 days after fertilization.

[Abstract]: The development and commercial release of midge resistant grain sorghum hybrids in Australia has been one of the real success stories of the sorghum industry. Almost all the current commercial sorghum hybrids grown contain a significant baseline of midge resistance that has greatly reduced that pest status of this insect. However while breeding efforts have been successful, it seems only one mechanism of resistance remains present in commercial hybrids. This mechanism of resistance known as ‘ovipositional-antixenosis’ is polygenic in nature and has contributed to the gradual reduction in the genetic base of commercial sorghum hybrids, potentially limiting the advancement of other agronomic traits.In order to expand both the level of resistance and the genetic diversity within Australian commercial sorghum hybrids, research was undertaken to capture new sources of midge resistance. Initially the goal of this work was to isolate and characterise the most promising new antibiosis sources of midge resistance previously documented within international breeding lines. However as the work progressed the discovery of a previously undescribed tolerance source of midge resistance led to more detailed studies of midge larval biology within a narrow range of sorghum germplasm lines to better characterise the resistance mechanism.To complete this work a new water-injection technique was developed to allow more precise studies of midge larval biology where previous traditional screening methods were deemed inadequate. Using this method several antibiotic lines were shown to contain diverse modes of action, while the tolerance mechanism of resistance was confirmed and more accurately characterised. In all cases plant characters within the developing spikelet were associated with each resistance mechanism.Overall, one source of resistance, found in lines derived from the Indian land race line DJ6514, was identified as superior to the others tested. Germplasm derived from this source was found to confer inter-related antibiosis and tolerance mechanisms. Both mechanisms were indirectly shown to be caused by the unique antibiotic properties of the developing caryopsis. Larval mortality (antibiosis) increased in this line, in line with increased feeding against the developing caryopsis. A second tolerance mode of action was also linked to anti-feeding properties of the developing caryopsis. Larvae were recorded at higher than normal rates feeding away from the caryopsis resulting in the survival of both larvae and grain in a significant proportion of spikelets. This escape ‘tolerance’ mechanism of resistance was confirmed indirectly in several studies and could be artificially induced in other genotypes when larval feeding against the caryopsis was delayed. As such the resistance is better described as antixenosis to caryopsis feeding.When both resistance mechanisms are present, the resistance isolated from DJ6514 was found to cause a three to four fold increase in seed set in resistant lines. This source of resistance has been directly selected for incorporation into the Australian breeding program and has been shown to be inherited simply as a single gene that needs to be deployed on both sides of the breeding program to ensure stable expression. When breeding efforts are complete a new suite of highly resistant and genetically diverse midge resistant sorghum hybrids will emerge into the marketplace.

Thesis (Ph.D.) - University of Queensland, 2004. / Includes bibliographical references.

Jamaican farmers are experiencing constraints to hot pepper (Capsicum chinense) export production due to a quarantine pest -- the gall midge (Contarinia lycopersici; Prodiplosis longifila). There is a threat of gall midge introduction into the United States, where the insect pest is not known to occur. This research tests the significance of a range of variables to gall midge incidence. The purpose was to explain the spatial patterns that result from the relationships between gall midge incidence in hot pepper production and production methods and/or environmental conditions. There were three components to the sample of 47 farm visits: the interview, the hot pepper sampling, and the measurements of physical and locational attributes. Producers responded to questions about production methods, marketing, and quarantine issues. The percent of infested fruits per plot was calculated. GPS was used to record farm location. Using ArcView, environmental and climatic datasets were overlaid with farm locations and their attributes. Multiple regression was used to measure significance of variables to gall midge incidence. Cluster analyses were used to demonstrate the spatial patterns of the variability of gall midge incidence and its associated variables. There was significant effect on incidence by farm elevation, observance of pesticide-use recommendations, producer awareness of pre-clearance fumigation, and the use of intercropping in hot pepper production. / Master of Science

No description available.

This thesis is an investigation of several aspects of diapause in the swede midge, Contarinia nasturtii (Kieffer). After developing methodology for induction and quantification of diapause entry in the laboratory, heritability of diapause entry was assessed for sibling larvae reared under diapause-inducing conditions. The diapause-quantification technique was efficient, but diapause frequencies were highly variable across studies employing similar diapause-inducing conditions. The diapause entry trait may be weakly heritable. A field study was conducted on diapause entry and emergence patterns. Diapause frequency was inversely correlated with photoperiod and absolute maximum air temperature. Photoperiod did not influence emergence timing. Two emergence phenotypes were observed before mid-July and a third minor emergence phenotype may exist in mid-to-late August. Approximately one third of emergence in the field was attributed to larvae in diapause for two or more years. Avenues of future research on diapause regulation in both the laboratory and field are discussed. / Natural Science and Engineering Research Council (CGS-M), Ontario Ministry of Agriculture, Food, and Rural Affairs (University of Guelph Sustainable Production Program)

Bacillus-derived larvicides, which selectively target mosquito (Diptera: Nematocera: Culicidae) populations to reduce nuisance and health risks, were applied in the South March Highlands Conservation Forest near residential neighbourhoods in Ottawa, Ontario. The objective was to assess effects of application on the nontarget mosquito relative, Chironomidae (Diptera: Nematocera: Chironomidae), and other nontarget aquatic taxa captured using emergence traps. A secondary objective was to assess physicochemical variables that influence Chironomidae emergence. Study ponds received an application of Bacillus thuringiensis var. israeliensis, a subset also received an application of Bacillus sphaericus, and a group of control ponds were left untreated over 3 years (2016-2018). Weekly sampling included trap collections and measurements of water temperature, pH, water depth, conductivity, dissolved oxygen, ammonia, nitrate, and sulphate. Drought in 2016, high precipitation throughout 2017, and seasonal precipitation in 2018 influenced variable physicochemical conditions. Principal component analyses identified differences between sampling groups and between years. Redundancy analyses correlated insect emergence with pond pH, average water depth and water temperature and indicated a strong relationship between Chironomidae emergence and average water depth. Although significantly less Chironomidae annual emergence was observed at treated sites in 2017 and 2018, zero-inflated negative binomial generalized linear mixed modelling failed to detect a significant Bti treatment effect when controlling for within group variation. Rather, variations in pH, mean water depth and water temperature were identified as drivers of Chironomidae emergence. Culicidae emergence was reduced to zero briefly following treatment in 2017 and 2018. The model detected a marginal negative treatment effect on Culicidae in 2017 only, and a positive treatment effect in 2018 at the onset of a secondary hydroperiod, in the absence of treatment. Variations in pH and water temperature were also identified to be drivers of Culicidae emergence. Modelling failed to detect treatment effects on any of the nontarget taxa abundance, including Diptera, Lepidoptera, Ephemeroptera, Odonata, Coleoptera, Hymenoptera, and Arachnida. An inverse relationship between insectivore and prey taxa abundance was observed. In 2018, taxa richness increased between years and trended higher at treated sites and a positive relationship between insectivore and prey taxa richness was observed. In 2017, Shannon-Weiner index and Simpson’s index of diversity were higher at untreated sites, and in 2018 diversity indices were higher at treated sites, with taxa richness increasing between years and higher evenness trending at treated sites. Our data suggest that treatment effects were potentially shrouded by natural variability of physicochemical variables, especially due to the varying hydroperiod observed over the three years of sampling. Additional work is needed to capture average conditions and separate confounding variables from treatment effects. This study provides an inventory of the current wetland insect community in the South March Highlands Conservation Forest landscape that offers a reference for ongoing mosquito management.