School of Natural Resources & Extension
Non Technical Summary
Alaska is food insecure, due to the short growing season, limited selection of potential crops, lack of infrastructure, and remote location creating vulnerabilities in the food supply chain. Increasing in-state food production is one way to reduce food security. In Alaska, production of vegetables, bedding plants, and potatoes is growing. In many cases, insect pests of these crops limit production, or prevent the growing of certain crops altogether. Root maggots, thrips, aphids, and leafhoppers attack these crops in Alaska, but most insect pests in Alaska have not been thoroughly studied and their population fluctuations not well understood. Studies to reveal basic information like species presence, timing of emergence in spring, when eggs are laid, how many eggs, how long till the eggs hatch, etc. are lacking. Such information is needed to develop robust predictions of pest infestations and recommendations for pest management actions. This will enable growers to accurately time actions to prevent crop damage and lessen the need for remedial actions, such as insecticide applications.
Animal Health Component
Research Effort Categories
Goals / Objectives
To develop basic information regarding species composition, host-plant associations, life-history details, and phenology of common insect pests in Alaskan agriculture.To be able to predict timing of major developmental stages in most common species of root maggots from air and soil temperatures, and determine number of generations per year in agricultural regions of Alaska..Develop thrips population management recommendations in Alaskan protected environments based on knowledge of their biology.Determine life history attributes, such as overwintering sites and alternate hosts, for species of aphidsand leafhoppers found in protected environments and potato fields.Enable aphid population forecasts for potato producers.Transmit results of the preceeding objectives to the public through producers' meetings (e.g., Harvest Wrap-up in Delta Jct.), the Sustainable Agriculture Conference, extension Fact Sheets, and the Alaska extension website.
Root maggot identification and crop associations: Pupae will be collected in the fall from soil at infested sites in the interior and south-central Alaska. These pupae will be stored in vermiculite at 5 ºC for 12 weeks to terminate diapause. After chilling, pupae will be held at room temperatures until adults have emerged. Adult flies will be used for identification to associate species with region and crop.Root maggots will be raised on radishes or rutabagas in cages in the greenhouse to provide insects for temperature/developmental rates and diapause studies (Read 1965). Growth chambers capable of maintaining temperatures within a 0.5 ºC will be used to measure rates of development at a range of temperatures. Initial experimental temperatures will be 15, 20, 25 °C constant temperature, and two alternating temperature regimes on a 12:12 h thermoperiod of 5 and 20°C, and 5 and 25°C. Photoperiod will be maintained at 18:6 h for all temperature treatments to avoid diapause induction. Stages of development to be studied are post-diapause pupae to adult emergence, egg and larval stages. From this data linear degree-day or non-linear developmental unit, models will be developed (Fielding and Ruesink 1988, Fielding 2004, Dreves 2006, Fielding and DeFoliart 2010).Plots of vegetables favored by root maggots, turnips, broccoli, and onions, will be established at the AFES farm. Emergence cages (cages placed over the ground to capture emerging flies, Dreves 2006) will be used to determine timing of adult emergence. Soil temperatures will be monitored at depths of 5, 10, 15, and 20 cm to provide data for validation of degree-day models of fly emergence (post-diapause pupal development) and larval development. Air temperatures measured at the AFES farm will be used for validation of egg development. Other locations, particularly in the MatSu valley and Kenai Peninsula will be used to validate phenological models after protocols are tested in Fairbanks.These vegetable plots also will be used to evaluate control measures, such as field clean-up. Pulling plants after harvest and turning the soil may kill many larvae. Emergence cages placed in the field in the spring will quantify the efficacy of the previous year's control measures. Other control measures, such as barrier collars and diatomaceous earth may be tested as time permits.Information derived from these investigations will be transmitted to growers and extension personnel through grower workshops, fact sheets, and extension web site.Identification and quantification of thrips populations in commercial greenhouses, will take place during the main growing season for seedlings and bedding plants in Alaska, March through June, 2020 and 2021. At least 8 greenhouses in the state will be visited in Alaska during the growing season to collect thrips. Both immature and adult populations will be sampled by tapping into white pans. The terminal growth of plants will be held above a white pan (about 10x 20 cm) and tapped vigorously for 10 sec. Thrips falling into the pan will be transferred to vials of 100% alcohol and stored in a freezer. Specimens will be sent to experts for identification and possible DNA analysis. A database will be developed to record and analyze information gathered, including species of thrips, host plant collected from, location, and date. Specimens will be deposited in the entomology collection of the University of Alaska Fairbanks Museum. Based on the mean and variance of these preliminary counts, sampling protocols will be developed to enable population estimates with known confidence limits. After the most common species of thrips are determined, their life histories and control tactics will be investigated. Colonies of thrips will be established and maintained to provide insects for laboratory studies (Murai and Loomans 2003). Life history parameters to be investigated will include incidence and timing of diapause, characterization of overwintering sites, the relationship of thrips to nearby weeds as alternate hosts and refugia, and the relationship of different host plants to thrips population growth rates. These life-history studies will suggest control tactics to be investigated, such as weed barriers, efficacy of beneficial insect predators, methods of augmenting naturally occurring insect predators, or enhancing host plant resistance through exposure to UV-B light or other methods.Results of these studies will be transmitted to growers and extension personnel through fact sheets, grower workshops, IPM scout trainings, and the extension web site.Aphid Life History : In northern regions on every continent, the green peach aphid (Myzus persicae ) overwinters as eggs on its primary host, species of Prunus (Blackman, 1974). Similarly, the primary host of Rhopalosiphum padi is Prunus padi. In the fall, males are produced, sexual reproduction and oviposition occurs. Egg production by Myzus persicae and R. padi, during the fall will be monitored each year in the Fairbanks area. Twigs of chokecherry Prunus virginiana and Bird cherry, Prunus padus of local trees will be inspected weekly to determine timing of the fall oviposition. Thirty twigs from each of five trees in the area will be collected at the end of the season (sample size may change based on mean and variance of the samples). These will be dissected and eggs counted. Alternatively, twigs will be stored at 4°C for six months to break diapause. The twigs with eggs will then be transferred to 24°C environment and number of aphids hatching will be enumerated and species identified. In the spring, the same sampling will be conducted, and number and species of aphids hatching will be determined. This will give an estimate of overwintering population size, over-wintering mortality, the size of the founding generations which will enable predictions of the severity of aphid infestations, particularly in potato crops, during the growing season.Leafhoppers and aphids in potato: Tile traps will be used to monitor and collect aphids in potato fields. Tile traps consist of a 10 x 10 cm yellow-green tiles immersed in soapy water in a shallow plastic tray. Ten to 20 traps will be placed around the perimeter of each of at least 3 potato fields in the interior of Alaska. Aphids collected in this manner will be curated and sent to experts for identification. Yellow sticky traps, 15 x 25 cm, to capture leafhoppers will also be deployed around the perimeter of potato fields in same time and place as the tile traps described above. From the trap collections the species of aphids and leafhoppers, as well as the phenology of their colonization of potato crops, will be determined from this data. After the major species of leafhoppers have been identified, studies will be conducted to determine aspects of their life history, such as overwintering sites and alternate hosts.Collaboration with plant pathologists will be developed and tests of presence or absence of pathogens will be conducted. Information derived from these studies will be relayed to IPM pest scouts through training workshops.Outreach Activities. Results from the preceeding studies will be disseminated to Extension pest scouts, producers, and the general public through training sessions with pest scouts and other extension personnel; producer meetings; fact sheets and other extension publications; and the Alaska Extension website. Interactions with the scientific community will involve presentations at scientific societies, such as the Alaska Entomological Society and the Entomological Society of America, and through peer-reviewed publications in scientific journals.