H. L. Hackerott

Bio: H. L. Hackerott is an academic researcher from Kansas State University. The author has contributed to research in topics: Aphid & Sorghum. The author has an hindex of 6, co-authored 9 publications receiving 141 citations.

Recognition of a Greenbug Biotype Injurious to Sorghum

Abstract: A collection of greenbugs, Schizaphis graminum (Ron-dani) (C-biotype), from a population causing extensive damage to sorghum, differed from green bugs (B-biotype) originating on wheat. ‘Piper’ Sudan grass, Sorghum Sudanese (Piper) Staff., in the seedling stage was highly resistant to the B-biotype and susceptible to the C-biotype. Differences in green bug reaction or plant injury caused by the 2 biotypes were recorded also for wheat, Triticum aestivum L.; rye, Secale cereale L.; oats, Avena sativa L.; barley, Hordeum vulgare L.; and sorghum Sorghum bicolor (L) Moench . With few exceptions, survival rates of nymphs of the 2 biotypes were similar on 30 species of Gramineae.

Chemical control of a greenbug on sorghum and infestation effects on yields.

Abstract: All recommended insecticides (disulfoton, parathion, demeton, malathion, and diazinon) provided satisfactory initial control but little or no residual control of C-biotype Schizaphis graminum (Rondani) on sorghum, Sorghum bicolor (L.) Moench. Losses in grain production in untreated compared with treated plots varied from 2% (1.4 bu/acre) to 45% (27.0 bu/acre) depending on time and intensity of greenbug infestations.

Pea Aphid Injury to Resistant and Susceptible Alfalfa In the Field

Abstract: Alfalfas resistant and susceptible to Acyrthosiphon pisum (Harris), were compared under both natural and artificial infestations in the field. Plants with little injury were identified and paired with adjacent, severely damaged plants in a heavily infested ‘Cody’ alfalfa field in which most top growth had been killed. Plants selected for lack of injury showed resistance in laboratory tests. Increases in forage yields for resistant over susceptible plants on successive cuttings in 1968 and 1969 were 211, 188, 107, 114, and 78%. Increased yield apparently was due to resistance, because in absence of pea aphids, clonal propagules of susceptible plants yielded more than did resistant plants. When infested with aphids in field cages, a resistant strain ‘KS 6’ produced 72% more forage than did susceptible Cody. For KS 6, both numbers and weights of pea aphids were depressed. Resistant ‘Kanza’ and susceptible Cody were compared in varietal-yield trials at different locations and in years with various intensities of pea aphid infestations. At a location in 1968, when the infestation was severe, Kanza forage yields were 167% of Cody, compared with 99 to 125% in previous and subsequent years when pea aphids were not of economic importance. In 1968, at 2 locations where aphid populations were low, Kanza yields were 103 and 109% of Cody, compared with 155 and 188% at heavily infested locations, Kanza also out yielded Cody in protein and carotene after heavy infestations in 1968. Our results indicated that pea aphids cause losses in forage quality as well as in quantity and that losses are reduced by resistant cultivars.

Plant Resistance to a Greenbug Biotype Injurious to Sorghum

Abstract: Seedlings of barley ( Hordeum vulgare L.), rye ( Secal cereal L...), wheat ( Triticum aestivum L..), and sudangrass ( Sorghum sudanense (Piper) Stapf.) with resistance to Schizaphis graminum (Rondani) (B-biotype, originally (collected on wheat) were tested for resistance to a greenbug (C-biotype, originally collected on sorghum) that extensively damaged sorghums in 1968. ‘Piper’ sudangrass. ‘Caribou Selection’ rye and ‘CI 9058/7 *Bison’ wheat were resistant to the B-but susceptible to the C-biotype. ‘Dicktoo’ barley and ‘Insave F.A.’ rye were the only cultivars resistant to both biotypes.

Pea Aphid-Resistant Alfalfa Selected in the Field

Abstract: Selecting uninjured ‘Cody’ alfalfa plants in the field following a heavy infestation of Acyrthosiphon pisum (Harris) expediently obtained resistant plants. Resistance appeared comparable to that obtained by selection in the greenhouse. Progeny testing facilitated selection of highly resistant plants.

Interactions between specialist and generalist natural enemies: parasitoids, predators, and pea aphid biocontrol

Abstract: Most biological control systems involve a diverse community of natural enemies. We investigated how specialist and generalist natural enemies differ as biological control agents of pea aphids (Acyrthosiphon pisum), and how interactions among natural enemies affect successful control. In alfalfa, pea aphids are attacked by a specialist parasitoid wasp, Aphidius ervi, and a guild of generalist predators primarily made up of Nabis and Orius bugs, coccinellid and carabid beetles, and web-building spiders. In three field experiments, we manipulated the parasitoid, then the generalist predator guild, and finally both classes of natural enemy, and recorded resulting impacts on pea aphid population control. The parasitoid caused little immediate reduction in aphid population growth but caused a large decline after a delay corresponding to the generation time of the parasitoid. In contrast, the generalist guild caused an immediate decline in the aphid population growth rate. However, the generalists did not exert density-dependent control, so aphid densities continued to increase throughout the experiment. The third field experiment in which we simultaneously manipulated parasitoids and predators investigated the possibility of “nonadditive effects” on aphid control. Densities of parasitoid pupae were 50% lower in the presence of generalist predators, indicating intraguild predation. Nonetheless, the ratio of parasitoids to aphids was not changed, and the impact of the two types of natural enemies was additive. We constructed a stage-structured model of aphid, parasitoid, and predator dynamics and fit the model to data from our field experiments. The model supports the additivity of parasitoid and predator effects on aphid suppression but suggests that longer-term experiments (32 d rather than 20 d) would likely reveal nonadditive effects as predation removes parasitoids whose response to aphid densities occurs with a delay. The model allowed us to explore additional factors that could influence the additivity of parasitoid and predator effects. Aphid density-dependent population growth and predator immigration in response to aphid density would likely have little influence on the additivity between parasitism and predation. However, if a parasitoid were to show a strong Type II functional response, in contrast to A. ervi whose functional response is nearly Type I, interactions with predators would likely be synergistic. These analyses reveal factors that should be investigated in other systems to address whether parasitism and predation act additively on host densities. Corresponding Editor: E. Evans.

Resistance of plants to insects.

Abstract: Publisher Summary This chapter discusses the resistance of plants to insects. Resistance is the ability of a certain variety to produce a larger yield of good quality than other varieties at the same initial level of infestation and under similar environmental conditions. Three basic components or mechanisms are involved in plant resistance. First, plants may be nonpreferred for oviposition, shelter, or food, primarily, because of the lack of or presence of chemical or physical factors. Second, resistant plants may affect the biology of the insect adversely that is called antibiosis. Third, resistant plants may be tolerant, surviving under levels of infestation that would kill or severely injure susceptible plants. Several problems may occur at various stages in the development of any host plant resistance program. Some of these problems include: proper finance, entomological problems, and problems in technique development. Resistance is most often found in off types or exotic wild species, and considerable crossing and selection is required to move the resistant genes into a desirable agronomic background. The greatest use of resistant varieties would undoubtedly be as one component part of pest management system.

Generalist predators disrupt biological control by a specialist parasitoid

Abstract: Two broad classes of arthropod natural enemies attack insect herbivores: specialists and generalists. The tight dynamical linkage of specialist natural enemies and their prey may make the specialists able to respond numerically to, and perhaps suppress, herbivore outbreaks. Because generalist predators may attack not only herbivores, but also the herbivores' specialist natural enemies, generalist predators may disrupt control of herbivore populations rather than contribute to it. We examined interactions between pea aphids (Acyrthosiphon pisum), a specialist parasitoid wasp (Aphidius ervi) that attacks the aphids, and a common generalist predator, carabid beetles (primarily Pterostichus melanarius). In two field experiments in alfalfa, we manipulated carabid densities to measure their direct (through predation) and indirect (through intraguild predation on A. ervi) impact on aphid population dynamics. The first experiment was initiated when plants were short (following cutting), and carabid predation of a...

Plant penetration by feeding aphids (Hemiptera, Aphidoidea): a review

Abstract: The factors responsible for determining the host-plants and feeding sites of aphids, and the various probing activities (the role of the labium, stylet insertion, surface saliva deposition, the behaviour of the aphid, virus transmission) are examined. There is a brief review of stylet structure and movement and the possible sensory nature of these organs, followed by a detailed review of the characteristics of aphid stylet paths in plant tissues. The penetration of epidermis and vascular tissues is treated separately while that within the intermediate tissues is covered in relation to leaves and stems, roots, trees, galls and excised tissue as well as in separate sections on Aphis fabaeScopoli and Myzus persicae (Sulzer). Stylet destinations and behaviour in the sieve tubes are discussed together with general features such as rate and depth of penetration, guidance to the feeding site, effects of tissue hardness and stylet withdrawal. The ingestion rate of plant sap is reviewed and its constitution and importance examined together with the significance of artificial diets. The salivary secretions including sheaths and tracks, their functions and their role in the transference of material between aphid and host are dealt with. The nature of the physical and internal damage resulting from aphid feeding is briefly covered, and also some plant-insect interrelations. The aphid species whose stylets have been examined in plant tissue are listed.