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Aphid parasite larvae in early stages of development are frequently destroyed when insect predators feed on active aphid prey. Stary (1966) discussed insect predators that may feed on living aphids, and thus destroy parasite eggs or larvae. He noted, however, only one case of direct attack on an aphid mummy: that of chrysopid larvae on Aphis fabae Scopoli parasitized by the braconid Lysiphlebus fabarum (Marshall). No observations were reported of direct attacks on mummified aphids by coccinellids, syrphids, or other aphidophagous insects.

A basic parametric crop yield model (YIELD) that uses climatic and environmental data to calculate yield and associated parameters for grain corn (maize) was applied to a transect through the North American Great Plains. This paper continues our examination of the impact of probable climatic change scenarios on crop evapotranspiration and krigation requirements (Terjung et al., 1984). This study of grain corn yields showed highest yield for the first (or primary) harvest under full irrigation occurring under a sunny and cold scenario in Austin, TX, sunny and cool in Kansas City, KS, and sunny and warm in Bismarck, ND. Lowest irrigated yield was found with cloudy and hot and very dry climate change scenarios. Under rainfed-only conditions, minima were obtained under the sunny-hot and -warm scenarios and very dry conditions.

The model WATER provides feasible computational methods for the determination of temporal and spatial agricultural water consumption. A solution was sought through the creation of a crop‐specific, growth‐stage‐specific soil moisture model. This model, which has been programmed for digital simulation, is a compromise between area‐specific, data‐based regression models and expensive, complex energy‐mass exchange models. It is suitable for evaluating the impact of droughts and other climatic vagaries on crop water requirements. Input scenarios make possible the application of the model to regions where precise data are not available.

WATER, a parametric crop water use model, employs climatic data to calculate water consumption for a variety of crops, using a modification of the Penman equation which included specific crop and growth stage effects. The objective of this paper was to demonstrate the response of WATER, for a grain corn crop, to changes in a variety of important environmental and decision-making inputs: air temperature, solar radiation, relative humidity, irrigation frequency, and amount of irrigation water applied. Five temperature, five solar radiation, and six relative humidity regimes were examined for an entire growing season. Also, five different water application schemes and four irrigation frequencies were included in this experiment. Additionally, the effect of different soil types, wind regimes, and groundwater depths on crop water requirements were investigated. These analyses were performed using four annual climatic scenario combinations. Among the results, evapotranspiration (ET) increased on the average by about 2.5%/1øC increase in air temperature. One percent change in solar radiation resulted in a 1.5% change in ET, while a similar change in relative humidity caused a 0.4% response in ET. Contrasting soil types, in addition to affecting irrigation frequency, were capable of changing the responding ET by over 10%. 1539

A parametric crop water use and yield model was applied to a transect spanning the North American Great Plains to investigate the evapotranspiration demand on grain corn and the associated irrigation water applications needed for optimal crop production. The transect consisted of four sample stations, covering 25 degrees of latitude. 124 climate change scenarios for each of the transect stations, were created by systematically changing air temperature, precipitation, and incident solar radiation in terms of positive and negative departures from the normal, long-term record. This paper reports how grain corn evapotranspitation and irrigation water amounts would respond to climatic changes inherent in the scenarios if there were no changes in agricultural technology. Among the results, the seasonal response of evapotranspiration (ET) totals to air temperature perturbations was greatest in the higher latitudes and least in the lower latitudes. This impact of changing temperature was also greatest under sunny compared with cloudy conditions, and for fully irrigated in contrast to rainfed conditions. Changes in precipitation amounts caused greatest responses in rainfed fields under sunny conditions. The middle latitudes (e.g., Kansas City) were most sensitive. Perturbing solar radiation caused greatest evapotranspiration changes with irrigated conditions particularly in the middle latitudes. Percentage changes in solar radiation (or cloudiness) were of considerably greater importance than comparable precipitation changes. In the absence of temperature perturbations, the relative precipitation and solar radiation changes caused similar trends in amount of irrigation water applied. For temperature changes, the resultant irrigation watering responses were largely non-linear. A consecutive paper will report on the response of maize yield to the introduced climatic changes and associated irrigation schedules.

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