Paul A. Weston

Relative prawn production and benthic macroinvertebrate densities in unfed, organically fertilized, and fed pond systems

Abstract Relative prawn production rates in unfed, organically fertilized, and fed pond systems were evaluated. Populations of benthic macroinvertebrates that potentially serve as forage organisms in these systems were also evaluated and compared with ponds without prawns to evaluate forage preferences. Juvenile prawns (x = 0.36 ± 0.02 g) were stocked into nine 0.04 ha ponds at a density of 39 520 ha −1 . Prawns in three ponds were not fed, prawns in three ponds were fed a complete diet, and three ponds received organic fertilization. Three additional ponds (0.02 ha) served as controls (not stocked with prawns and received no nutrient input). Survival averaged 86%, overall, and was not significantly different among treatments. Average weights of prawns fed complete feed or raised in fertilized ponds (36 and 33 g, respectively) were not significantly different ( P > 0.05). Prawns in unfed ponds were significantly ( P ≤ 0.05) smaller (13 g). Average prawn yields in fed, fertilized, and unfed ponds (1261, 1056, 426 kg ha −1 , respectively) were all significantly different ( P ≤ 0.05). In ponds receiving no nutrient input, macroinvertebrate densities were significantly higher ( P ≤ 0.05) in ponds without shrimp (controls) than in those stocked with shrimp. In ponds stocked with shrimp, macroinvertebrate densities in fed and fertilized treatments were significantly greater ( P ≤ 0.05) than in the unfed treatment, but not significantly different ( P > 0.05) from each other. Insect taxa showed a greater negative response to prawn predation than non-insects. Non-insect taxa demonstrated a more positive response to fertilizer and feed than insects. Although prawn production in organically fertilized ponds was surprisingly high (>1000 kg ha −1 ), economic analysis demonstrated higher net returns when prawns were fed a prepared diet, principally due to the production of greater numbers of large, high value prawns.

Effects of complete and supplemental diets and organic pond fertilization on production of Macrobrachium rosenbergii and associated benthic macroinvertebrate populations

Growth and population characteristics of freshwater prawns, Macrobrachium rosenbergii, fed either a complete diet, a supplemental diet (with fish meal replaced and vitamin and mineral supplements deleted), or the supplemental diet with an adjunct organic pond fertilization regime were examined. Effects of these treatments on potential forage organisms (benthic macroinvertebrates) were also evaluated. Juvenile prawns averaging 0.46 ± 0.49 g were stocked into nine 0.02 ha earthen ponds at 39 520 ha−1. Treatments were evaluated in triplicate ponds. There were significant differences (P 0.05) between regression lines for prawns fed the complete diet and those fed the supplemental diet with an organic pond fertilization regime. At harvest, yield, survival, individual weight, and feed conversion averaged 943 kg ha−1, 76%, 31 g, and 3.9, respectively over the three treatments. Deletion of vitamin and mineral supplements and replacement of fish meal in prawn diets was associated with a significant reduction (P < 0.05) in total benthic macroinvertebrate populations, possibly due to increased predatory pressure by prawns. In ponds in which prawns were fed the supplemental diet, organic fertilization resulted in a significant increase (P < 0.05) in total benthic macroinvertebrates and a 15% increase in average prawn weight at harvest. Results indicate that prawns may increase predation when essential nutrients are deleted from prepared diets and that the supply of potential forage organisms may be increased by organic fertilization.

Progeny production by Tribolium castaneum (Coleoptera: Tenebrionidae) and Oryzaephilus surinamensis (Coleoptera: Silvanidae) on maize previously infested by Sitotroga cerealella (Lepidoptera: Gelechiidae).

Abstract A laboratory experiment was conducted to quantify the effects of infestation of maize by Sitotroga cerealella (Olivier) on progeny production by two common secondary colonizers of grain, Tribolium castaneum (Herbst) and Oryzaephilus surinamensis (L.). Adults of both secondary pest species were allowed to oviposit for 3 wk on intact kernels of ‘DeKalb 689’, mechanically split kernels, kernels that had been infested for 3 mo by S. cerealella, and kernels that had been infested for 6 mo. Progeny of both species reached highest numbers on 6-mo infested maize. Prior infestation for 6 mo by S. cerealella makes maize a more suitable medium for reproduction by T. castaneum and O. surinamensis, much more than can be accounted for by mere disruption of kernel integrity resulting from larval feeding. The results highlight the importance of limiting establishment by S. cerealella on maize in storage.

Ovipositional Stimuli of Angoumois Grain Moth (Lepidoptera: Gelechiidae), a Primary Pest of Stored Grains

Ovipositional preferences of Sitotroga cerealella (Olivier) were measured in the laboratory to characterize the stimuli eliciting oviposition in this widespread pest of stored grains. Substrates us...

Survey of insect pests in shelled corn stored on-farm in Kentucky.

Shelled corn stored in metal bins was sampled for insects on farms in the three westernmost crop reporting districts of Kentucky during 1989 and 1990 to identify pest insects present, determine the relative abundance of insect pests, and determine their geographic distributions. Thirty-six species or species groups were found in this survey. The most abundant insects were maize weevil, Sitophilus zeamais Motschulsky; Angoumois grain moth, Sitotroga cerealella (Olivier); flat grain, rusty grain, and flour mill beetles, Cryptolestes spp.; sawtoothed grain beetle, Oryzaephilus surinamensis (L.); foreign grain beetle, Ahasverus advena (Waltl); red and confused flour beetles, Tribolium spp.; and hairy fungus beetle, Typhaea stercorea (L.). Greater densities and numbers of species were caught later during the storage season and greater numbers were captured from the center versus edges of bins. The unexpectedly high abundance and widespread distribution of maize weevil and Angoumois grain moth suggests that gre...

Efficacy of Malathion Against Coleopteran Populations in Newly-Harvested Versus Year-Old Stored Corn

The impact of malathion treatment and duration of storage prior to treatment on species composition and relative abundance of beetle pests was investigated in shelled corn in newly-constructed galv...