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Collections of lygus bugs, mainly Lygus hesperus Knight and L. elisus Van Duzee, were made at weekly intervals in the lower Yakima Valley and Columbia Basin in Washington from weed hosts and alfalfa. Early in the season the crucifers, hoary cress, Cardaria draba (L.) Desv., tumble mustard, Sisymbrium altissimum (L.), and flixweed, Descurainia sp., are the primary hosts. Pepperweed, Lepidium latifolium L., and Russian thistle, Salsola kali L., are common mid-season weed hosts. Lambsquarters, Chenopodium album L., kochia, Kochia scoparia (L.) Schrad., marsh-elder, Iva xanthifolia Nutt., pigweed, Amaranthus retroflexus L., and ragweed, Ambrosia artemisiifolia L., are major reproductive sites in late season and host the potential overwintering populations. When a disturbed site, e.g., ditch bank, roadside, or field edge, returns to some degree of ecological stability with a grass cover, the pioneer species of weeds frequented by the lygus bugs cannot compete with the natural grasses, and lygus populations are markedly reduced.

Predator traps constructed of several layers of corrugated fiberboard effectively substituted for natural overwintering sites for predators in pear orchards. Deraeocoris brevis (Uhler), Hemerobius ovalis Carpenter, and spiders were the major predators taken from the traps. The traps also offer an inexpensive means of collecting and storing overwintering predators.

Lygus bugs were swept from a variety of plant hosts in the Yakima Valley and Columbia Basin in Washington. Collected adults were identified to species, and nymphs were reared to adults for identification. Lygus elisus Van Duzee was the predominant species on weedy crucifers, chenopods, and composites. L. hesperus Knight populations predominated on volunteer alfalfa, the major weed legume. L. desertinus Knight occurred as a small proportion of the lygus bug population and generally in close association with L. elisus .

Populations of pear psylla, Psylla pyricola Foerster, in pear orchards receiving ca. 6 mm of volcanic ash from the eruption of Mt. St. Helens on 18 May 1980, continued to expand as in previous years. Orchards receiving 2.5 to 4.5 cm of ashfall generally had lower populations of pear psylla. Laboratory tests with whole ash and a fine fraction indicated that a 70 to 80% reduction of a generation of pear psylla exposed to the ash could be expected. Populations of winged predators were decimated, but Deraeocoris brevis (Uhler) populations revived due to oviposition in leaf tissue before the eruption.

Cover crops in pear orchards in the Yakima Valley in Washington harbored a large complex of general predators. The most common species were Nabis spp. and Coccinella transversoguttata richardsoni Brown. The major predators of the pear psylla, Psylla pyricola Foerster, Amthocoris spp. and Deraeocoris spp., were infrequent in cover crops. Plantings of small grains as cover crops were sporadically successful in retaining major pear psylla predators by supplying alternate prey, mainly the green bug, Schizaphis graminum (Rondani).

Dispersal of adult Psylla pyricola Foerster was heavy in the preoverwintering and over wintering generations. Adults departed and entered pear orchards in large numbers at heights up to 4 m, the maximum height studied. Populations up to 258,000/ha were detected in leaf duff during late fall, but few remained in the spring. Tillage of the leaf duff in late fall destroyed a disproportionate number of predators, with minimal impact on over wintering P. pyricola .

In Arizona, adult Anthonomus grandis Boheman from cultivated cotton emerged from buried and unburied bolls throughout the winter whenever the temperature exceeded the physiological threshold. Emergence was prevented by burying the bolls to a depth of 30 cm. A few weevils were found during the winter in desert trash adjacent to fields that had had large infestations the previous growing season. Most overwintering weevils in Arizona did not meet the criteria of full diapause associated with the southeastern boll weevil.

Anthonomus grandis thurbelriae Pierce, released from hibernation cells in bolls of wild cotton, Gossypium thurberi Todaro, in December and February survived until late June and July. Longevity of released weevils increased when moisture was made available. However, a large percentage of weevils remaining in hibernation cells were still alive when all released weevils had died. In laboratory tests, released weevils readily moved to moist niches.

An opportunity was taken to study the nesting biology of Ancistrocerous wasps when they were found utilizing trap-nests which had been placed in the field for research primarily with Megachilidae. Most of the trap-nests were located in northern Wisconsin at the Ashland Branch Experiment Station or localities not more than 25 miles distant from the station. This report includes studies which were made during 1952, 1953 and 1954.

No adverse effects on eggs of the bollworm, Heliothis Zea (Boddie), resulted from exposures for 2, 4, 8, 16, and 24 hr to 35°C and 10, 20 and 40% RH, but some reduction in hatch occurred during the 2nd 4-hour exposure to 40° and 10% RH, and hatch of eggs exposed for the longer periods was low. Similar results were obtained with eggs of the tobacco budworm, H. virescens (F.), except that no hatch occurred during the 24-hour exposures at 35° and 10% RH and at 40°C, the 1st reduction in hatch occurred during the 3rd exposure period in 10% RH. Eggs of the beet armyworm, Spodoptera exigua (Hubner), failed to hatch after 1 exposure of 20 hours to 35° and 10% RH and 1 of 8 hours to 40°C and 10% RH; hatch was low in eggs exposed 8 hours or more to 40°C. Similar results were obtained with eggs of the cabbage looper, Trichoplusia ni (Hubner), but the eggs hatched somewhat better at the high temperatures and low humidities. Hatch of eggs of the saltmarsh caterpillar, Estigmene acrea (Drury), was severely reduced by exposures of 16 hours or more to 35° and 4 hours or more to 40°C. Hatch of eggs of the pink bollworm, Pectinophora gossypiella (Saunders), was severely reduced after 2 exposures of 16 hours or more to 35°C and 10 and 20% RH, after 4-hour exposures to 40°C and 10% RH, and by 1 or more exposures of 16 hours or more to 40°C.

Developmental periods of 5 strains of Anthonomus grandis Boheman from cultivated cotton ranged from 88 days at 15 to 17 days at 30; a temperature of 35 increased the period to 17.5 days. Developmental periods of I strain of thurberia weevils, A. grandis thurberiae Pierce, ranged from 72.5 days at 15°C to 17.5 days at 30; a temperature of 35°C extended the developmental period of the weevils to 18.5 days. Temperatures above an undetermined temperature between 30° and 35°C prolonged the developmental period of all strains. The deleterious effect of high temperatures partially explains the absence of boll weevil populations in Arizona in midsummer. Rearing at fluctuating temperatures did not increase the time required for development over that required at the constant temperatures if the heat input was similar and temperatures did not exceed 30°C.

Osmia atriventris Cr. and Megachile relativa Cr. are the most abundant bees accepting trap nests in the Black Sturgeon Lake area of Ontario. Hylaeus ellipticus (Kby.), H. verticalis verticalis (Cr.), Hoplitis albifrons albifrons (Kby.), and H. cylindrica (Cr.) are common while Hylaeus basalis (Sm.), Osmia proxima Cr., M. inermis Prov., and M. gemula Cr. are comparatively rare. All except Osmia atriventris are univoltine and overwinter as prepupae. O. atriventris is both univoltine and biennial. The major flight and nesting period for all bees is during July although M. relativa is active throughout August. Hylaeus spp. construct nests of silken membranous, secreted materials; Hoplitis spp. utilize macerated plant materials and pebbles to divide their nests; Osmia spp. partition their nests with macerated green plant material; and Megachile spp. line and plug their nests in typical leafcutter fashion. All bees provision their nests with pollen moistened with varying amounts of nectar. The sexes are probably almost equally divided in all species. Major parasites are Gasteruption assectator assectator (L.) for Hylaeus spp.; Chelynia subemarginata (Cr.) for Hoplitis spp.; Sapyga sp., for Osmia atriventris; and Coelioxys modesta Sm., and C. lucrosa for Megachile relativa. Melittobia chalybii Ashm. destroyed a few cells occasionally.

Laboratory and field dispersal studies indicated that one Arizona strain of Trichogramma minutum Riley would he a poor inundative control agent for lepidopter ous pests of cotton because it was short-lived, had low fecundity, and dispersed poorly. The searching adults and the wasps emerging from parasitized host eggs on soil surfaces were vulnerable to high temperatures. In ideal laboratory conditions the wasps searched rapidly and ovi posited freely. but when the complexity of the searching area was increased or the temperature was raised, their efficiency declined markedly. The wasps searched upper portions of artificial plants where host eggs would usually be concentrated on field plants. Patterns of emergence that would be suitable for effective release could be developed by placing parasitized host eggs of the proper age in centralized release stations. The wasps showed no preference when eggs of the bollworm, Heliothis zea (Boddie); tobacco budworm, H. virescens (F.); and cabbage looper, Trichoplusia ni (Hubner); were proffered at the same time. Oviposition in eggs of salt-marsh caterpillar, Estigmene acrea (Drury) and pink bollworm, pectinophora gossypiella (Saunders) occurred only under forced conditions.

Mortality in populations of immature boll weevils, Anthonomus grandis Boheman, in fallen cotton squares on the soil surface commenced when the summation of the index of time (1-hour period) × temperature >38°C reached 60. All the weevils died when the summation reached 550. Soil surface in Arizona cotton fields attains a mean temperature of 38°C when the mean air temperatures are 30°C. Soil surface temperatures of 38°C are com mon when air temperatures are lower than 30°C and may reach 60°C when air temperatures are at maximums. Frequent and prolonged periods with temperatures >38°C impose a strong bioclimatic control on the boll weevils until late season, when shading by maturing cotton plants enables the survival of the immature weevils in the squares on the soil surface.

Input of bioclimatological factors (cumulative number of degree-days above 55°F, mean and minimum relative humidities, cumulative number of rainy days, and cumulative rainfall) in 1 acre of cotton at florence from 1957 to 1959, were linear in time during the 3 years. The deviations from the linear inputs provide an interpretive backgound for analyzing major changes in populations of Anthonomus grandis Boheman. Varying numbers of overwintering weevils in the climatic regimes of the 3 years resulted in population increases dependent upon the climatic inputs. Damage was poorly correlated with the number of adult weevils. Late-season migration was triggered by lack of oviposition sites in cotton squares.

Enumeration samples of various insects associated with cotton were collected over a 3-year period in commercial cotton fields to evaluate their statistical properties. Samples from relatively low-density populations agreed with Poisson expectations while samples indicating relatively dense insect populations agreed with expectations of the negative binomial distribution. The number of plants per sample unit influenced the statistical distribution of the samples, Cotton-insect populations tend to be clustered, but the clustering is detected only under very intensive sampling or when population density is high. Several biological models can lead to the same statistical properties of the sampling distributions.

Regeneration plots were established near Laniel, P.Q., and in the Black Sturgeon and Cedar Lake areas of northwestern Ontario in 1950 to study the origin and development of regeneration in stands devastated by the spruce budworm. Results of tallies in 1950 and 1955 have been published, and this paper presents subsequent changes up to 1962. New balsam fir and spruce seedlings continue to become established on favourable seed beds in stands where seed trees survived the budworm outbreak. Some advanced growth, developing on the plots since the overstory was removed, began producing seed in 1962, although roadside trees of similar age and size were producing seed earlier. Balsam fir and spruce seedlings released by the budworm outbreak have grown rapidly, and are now retarding the height growth of some of the reproduction. The ratios of balsam fir to spruce reproduction calculated in 1950, 1955, and 1961 show considerable fluctuation within the same plots. Nevertheless, the general trend, toward a higher proportion of balsam fir in the reproduction than in the original stand of trees, which was established before the spruce budworm outbreak, has remained virtually unaltered.

When conditions are ideal, the thurberia weevil, Anthonomus grandis thurberiae Pierce, may be moved in thurberia bolls in flood drainage water from the mountainous areas where thurberia grows into the valleys where cotton is cultivated. However, the necessary conditions seldom occur. Tests in the laboratory indicated that vertical air velocities of 2.5–5.5 meters per second are necessary to suspend passive boll weevils, A. grandis Boheman, and that velocites in excess of 31.3 meters per second may be needed to free a weevil from its foothold on cotton leaves. In the late summer in Arizona and northern Sonora, Mexico, the necessary air turbulences (thermal convection and dust devils) are present to elevate boll weevils into the upper wind currents. Then these upper wind currents and their associated turbulences could move the weevils in the direction of the airflow.

Individuals in the overwintering populations of Heliothis Zea (Buddie) and H. virescens (F.) apparently had varying intensities of diapause; fewer H. virescens than H. zea entered diapause in Arizona. No beet armyworms, Spodoptera exigua (Hubner), were found in diapause. The multivariate triggers of diapause in the fall and of emergence in the spring seriously complicated the prediction of the date of emergence.

Uni- and bi-voltine strains of the eumenine wasps, Rygchium leucomelas (Sauss.), Ancistrocerus catskill albophaleratus (Sauss.), A. c. catskill (Sauss.), and A. tigris tigris (Sauss.) occur in the Black Sturgeon Lake region of Ontario. Another eumenine, Symmorphus cristatus cristatus (Sauss.), is univoltine. All the eumenids plug and divide their nests with partitions of clay. Generally, females emerge from cells larger than those of males. A double partition with an intervening space between cells is introduced occasionally in summer-generation nests and frequently in overwintering-generation nests. Generally, individuals of the bivoltine summer generations were predominantly female but overwintering generations were predominantly male.All eumenine wasps, except S. c. cristatus, provision their nests with lepidopterous larvae. A broad spectrum of prey was utilized but at any given time the female wasp shows considerable fidelity in searching for prey on a given host plant.Limited parasitism of the eumenids by the genus Chrysis and the ichneumonid genus Ephialtes was observed. The dipteran Amobia distorta Allen was found in nests of A. c. catskill and R. leucomelas.A single species of pompilid, Dipogon sayi sayi Banks, occupied the trap nests in small numbers. The prey of this wasp consists mainly of spiders in the genus Xysticus.The sphecids include Passaloecus ithacae Krombein, which was common, an unidentified Pemphredon sp., and Passaloecus mandibularis (Cr.). P. ithacae provisioned mainly with aphids of the genus Cinara; Pemphredon sp. utilized C. abieticola; and P. mandibularis preyed upon a wide range of species including several aphids from deciduous trees.Partitions in Passaloecus nests were primarily resin but female P. ithacae often incorporated chips of pith. Cell sizes were frequently out of proportion to the volume of prey and the size of the wasp larvae. Limited parasitism by the chrysidid genus Omalus and the ichneumonid genus Poemenia was noted.

Adult boll weevils, Anthonomus grandis Boheman, collected from cultivated cotton in Arizona lived an average of 6 months in the laboratory, and a few lived as long as 11 months; in the field this longevity was abbreviated. Thurberia weevils, A. grandis thurberiae Pierce, were lived than weevils from cultivated cotton, and overwintering thurberia weevils lived longer than the 1st square-reared generation. The fecundity of Arizona boll weevils was highly variable, and the potential was drastically reduced in the field. The ovipositional pattern of weevils from cultivated cotton was relatively consist-tent and apparently was closely associated with longevity.

Surveys of boll weevils, Anthonomus grandis Boheman, in selected cottonfields in Arizona in 1965 and 1966 indicated infestations of the boll weevil were widespread. Populations were greater in 1965 than in 1966, and larger populations occurred in stub cotton than in planted cotton. The boll weevil complex in cultivated cotton in Arizona attacks bolls throughout the season. Large populations of potential overwintering weevils in bolls were destroyed with stalk shredders and clean plowing.

Most populations of fruiting forms and cotton insects found in the upper two or three 6-inch increments of cotton plants are correlated with populations in the remainder of the plants. However, the correlations are not of sufficient magnitude to allow estimates for the lower portions to be derived from counts made in the upper two or three 6-inch increments. From 70 to 100% of the insects observed were in the upper 2 feet of the plants.

Simple linear regression models of the temperatures of dry bolls, soil surface, cotton stalk trash, trash-soil interface, and growing tips from cotton stubs on air temperature gave good estimates of temperatures and heat flux in the places that insects over winter. Multiple linear regression models that included other variables such as moisture, trash depth, or boll diameters, usually improved the estimates.

Populations of wasps and bees are larger and more diverse in areas of recently disturbed boreal forest than in non-disturbed areas. Population differences are correlated directly with light penetration which also results in a larger array of pioneer ground cover. The ground cover provides abundant floral forage for the bees and adequate lepidopterous prey for the wasps. The regeneration of the forest results in a decline in the quantity and diversity of the ground cover and the attending aculeate populations. Results from timed census studies, glass-pane barrier traps, and trap nests reflected similar relative attractiveness of the study sites to wasps and bees.

Control of the late-season reproductive generation and of diapausing Anthonomus grandis Boheman by aerial application of ultra-low-volume spray beginning in early September reduced overwintering populations to a very low level. The 8 applications of malathion in 1965 and 1966 and the 8 applications of azinphosmethyl in 1967 protected the top crop. The program did not achieve eradication, probably because of the difficulty of thorough treatment of small farms and the high reproductive potential of the surviving weevils. The level of suppression achieved indicates that the method could be used to reduce populations low enough to permit delivery of a high ratio of sterile to surviving native weevils the following season.

In small-plot experiments at Florence, S. C., against the boll weevil ( Anthonomus grandis Boh.), Guthion-DDT, Thiodan, methyl parathion-DDT, EPN-DDT, and endrin dusts gave comparable control and yields. Sprays and dusts of Guthion and endrin and a spray of Dipterex were equally effective. Guthion- DDT spray gave significantly better control and yield than toxaphene and heptachlor-DDT sprays. Sprays of Guthion-DDT, Dipterex-DDT, methyl parathion-DDT, EPN-DDT, and endrin gave comparable control and yields. Dusts of Sevin, malathion, Guthion-DDT, and endrin gave comparable control. Sprays and dusts of Guthion, malathion, and endrin were equally effective. In a spray malathion was more effective at 2 pounds per acre than at 1 pound. Malathion plus endrin was more effective than endrin alone. Sprays of Sevin, Thiodan, endrin, toxaphene with and without methyl parathion, and methyl parathion gave comparable control. Against the bollworm (Heliothis zea (Boddie)) malathion dusts were ineffective. Against the cotton leafworm (Alabama argillacea (Hbn.)) methyl parathion, malathion, and Guthion were more effective than BHC, endrin, and toxaphene. In field-cage experiments against the boll weevil, malathion and methyl parathion gave consistently high 24-hour mortalities. Combinations of malathion with endrin or toxaphene were usually more effective than endrin or toxaphene alone. Guthion was more effective than toxaphene and BHC. Thiodan was less effective than endrin. Sevin at 2 pounds per acre gave high 48 hour kills. Monsanto CP-7769 and Chipman R-6199 were comparatively ineffective. Malathion was residually more effective than endrin, methyl parathion, or Thiodan.

Linear regression analyses of the temperatures and heat flux in pyramidal, Lumite®, small wooden-frame screen cages, and buried cage bases indicated that crude estimates can be obtained by using easily obtained temperature parameters. However, if a high degree of precision is required, direct measurements are mandatory.

Concern over pesticide pollution of the atmosphere and increased resistance of numerous species of insects to insecticides has caused entomologists to seek alternate means of control of pest insect populations. Recently the term “pest management” has been coined for the Integration of the various available control measures for pest populations into Systems that minimize the use of insecticides. New emphasis has been placed on the potential utilization of biological control agents for the control of pest populations. Basically, the following presentation will consider ecosystem analysis of the use of parasites and predators both in attempts to establish the agents as permanent, recurring controls and in inundative release attempts to replace insecticides on a short-term basis. The examples cited pertain mainly to two cotton pests, the pink bollworm, Pectinophora gossypiella (Saunders), and the bollworm, Heliothis zea (Boddie). The bollworm is a horticultural pest attacking corn, tomatoes, beans and a host of other crops; the pink bollworm is restricted to cotton. However, the concepts and the approach to the introduction of integrated control is similar, regardless of the crop under consideration. An analytical approach will be employed. However, a paralleling use of the data for the development of models for insect population dynamics is possible (20).

Feeding damage by Lygus hesperus Knight to seedlings of onions, radishes, turnips, rape, clovers, alfalfa, lentils, peas, beans, dill, and carrots ranged from slight with full recovery to relatively heavy damage and mortality of young seedlings. Crucifer, forage, and umbellifer seedlings were the most heavily damaged, whereas damage to bean, pea and lentil seedlings was light or quickly outgrown.

Bollwonns, Heliothis zea (Boddie), and tobacco budwonns, H. virescens (F.), pupated in and emerged successfully from soils that ranged from sifted to cloddy and from dry to wet. Beet armyworms, Spodoptera exigua (Hubner), preferred cloddy soils for pupation and avoided sifted and very wet soils. Prepupae of the 3 species avoided pupation sites where temperatures were in excess of 38°C. Emergence declined as the pupae were buried in successive 2.5-cm increments from 2.5–15 cm of soil. Emergence of Heliothis moths improved if the buried pupae were in cells. Pressure from cultivation will result in high mortality of the 3 specices.

In studies conducted in eastern Washington, seven species of weeds provided the food source of pre-overwintering lygus bugs, Lygus spp. The two major weed species were volunteer alfalfa, Medicago sativa , and lambsquarters, Chenopodium spp. Winter survival of lygus bugs feeding on several species of weeds in the fall did not differ significantly. Winter survival of lygus bugs was low when the material in which the lygus bugs were overwintering was maintained under 10% of dry weight. Deciduous orchard duff was found to be the major overwintering site of adult lygus bugs, but considerable numbers overwintered in large mullein, Verbascum thapsis L., plants.

Feeding damage by Lygus elisus Van Duzee to seedlings of onions, radishes, turnips, rape, clovers, alfalfa, lentils, peas, beans, dill, and carrots ranged from slight damage with full recovery to relatively heavy damage and seedling mortality. Crucifer and umbellifer seedlings were damaged heavily, whereas damage to legume seedlings was light or quickly outgrown.

Surveys in August-October 1968 in areas in Presidio, Texas, and Ojinaga, Chihuahua, Mexico, that were treated in 1965-1967 in a reproductive-diapause control program against Anthonomus grandis Boheman indicated that the populations were increasing in several fields. The locations of these fields in the Rio Grande and Rio Conchos valleys is such that the weevils may soon repopulate the entire sprayed area if conditions are favorable.

Field experiments at Florence, S. C. (1956-1959) strongly indicated the value of an insecticidal control program that started just prior to the formation of the first squares on the cotton plant and was directed primarily at the over wintered boll weevil ( Anthonomus grandis Boh.). Early insecticide application programs conducted prior to July 1 were nearly as effective as the same programs with additional later sprays when the infestation reached 10%. In 1958 the 10% level was not reached for 5 and in 1959 for 4 weeks after the early program was discontinued. There was some tendency for bollworm buildups when the early program was practiced.

Polistes exclamans arizonensis Snelling was successfully overwintered in a cage provided with stacks of cardboard interspersed with spacers. When the wasps emerged in the spring they readily nested in a 1.2×1.8×1.2-m shelter with screen on 3 sides. The wasps were fed 4th- to 6th-stage larvae of the tobacco budworm, Heliothis virescens (F.), and provided with kraft paper torn into small bits for nesting material. A mean of 5.3 budworm larvae was rcquired for nutrition of each wasp.

The heterogeneity of populations of the bollworm, Heliothis zea (Boddie), was investigated during 1967 in 4 irrigated cotton fields. Grid stratification slightly improved relative efficiency of population level estimates over simple random sampling, and stratum variability was significant for only 22 of the 124 samples. The heterogeneity was greater for samples of bollworm-damagef fruiting forms than for larval samples.

Experiments were conducted to determine the effectiveness of seed treatments of Thimet and Bayer 19639, in-furrow applications of granulated Thimet made at time of planting, and side dressing applications of granulated Thimet for the control of cotton insects and the effect on the cotton plant itself. The treatments tested afforded virtually no control of the boll weevil but gave good to excellent aphid control throughout the complete growing period of the plant. There was no evidence that Thimet was taken up or translocated more readily in soils with a lower level of phosphorus. Seed treatments of Thimet and Bayer 19639 adversely affected stands. In-furrow treatments of Thimet did not affect stands. None of the treatments affected plant height. Only one treatment, the Thimet 2-pound in-furrow treatment, adversely affected fruiting. The treatments tested had no adverse effect on grade and staple or on the germination of seed produced with these treatments. Likewise, such properties as fiber strength, maturity, fineness, boll size, seed index, lint index, and per cent of lint were not affected by any of the treatments.

Study of the time a cotton square remains on a plant after it has been punctured by a boll weevil (Anthonomus grandis Boh.) showed that there was no difference in this respect between Empire WR, Dixie King, and Coker 100 W varieties. The number of punctures and the type of puncture, whether feeding or oviposition, had little or no effect. Squares were retained an average of 11 to 13 days. Twenty per cent of the squares remained on the plant and produced usable lint. Plants treated with gibberellic acid retained more punctured squares than untreated plants.

Both the bollworm, Heliothis zea (Boddie), and the tobacco budworm, H. virescens (F.), are very important pests of cotton in the Presidio, Tex., area. Infestation levels often require an extensive insecticidal spray program over most of the cotton produced in the area.

Studies made with temperature-control cabinets set for the average day and night soil temperatures at Stanfield, Arizona, and with several levels of moisture showed that winter survival of the boll weevil, Anthonomus grandis Boheman, complex was affected by moisture. Longevity after emergence increased when the levels of moisture in the bolls and in the simulated trash in which the weevils were hibernating were above 0.5 and 0.044 g of water/g of boll and trash, respectively. Some weevils freed from the bolls early in the winter survived long enough to oviposit in the 1st squares produced by cotton plants in the subsequent season and could serve as precursors for later damaging generations.

Publisher Summary This chapter discusses some crop simulation models in agronomic systems. Many crop models or parts of crop models have been built to help the researcher and students understand the operation of some part of an agronomic cropping system, for example, soil water flow, stomata1 control, or fertilizer nutrient movement. In addition to understanding various parts of agronomic systems, the modelers want to see what can be expected to happen if some change is made in that system. Field tests are very expensive, especially as the numbers of variables and/or treatments increase, and years of results are needed. A proven model of the system helps to evaluate these treatments and indicates which ones could be expected to give the desired results. The cotton model, GOSSYM, has been widely validated. GOSSYM has been used in a user-friendly form on a PC microcomputer as a tool for on-farm management decisions pertaining to nitrogen fertilizer applications, irrigation scheduling, and timing of harvest-aid chemicals. By combining GOSSYM with an expert system program, COMAX, the on-farm management decisions have been run in several combinations to give the user an optimal plan for fertilizer and irrigation scheduling.