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Relationships among numbers of insects trapped by unbaited flight and probe traps, and grain trier and deep bin cup samples were studied in 1991 in three farm bins in North Central Oklahoma. Placement of flight traps at the eaves of bins resulted in higher insect catches than at other positions. In the grain mass, insects were more likely to be in the central core during the first weeks of storage. Insects favored the center of the grain mass, but no significant differences were found among temperatures and moisture contents at the different regions sampled. Increasing numbers of insects with depth and length of storage time combined with the capture pattern of grain insects by flight traps indicated that infestation occurred after grain binning. The most abundant species were Cryptolestes spp., Tribolium spp., Rhyzopertha dominica (F.), Ahasverus advena (Waltl) and Typhaea stercorea (L.). Action thresholds (the insect densities at which managers need to control insect populations) for the number of insects in weekly probe trap catches were 7.35 for R. dominica , 720.14 for Cryptolestes spp., and 101.34 for Tribolium spp. when compared with estimates from grain trier samples, and 8.04,749.03, and 68.14 insects per probe trap, respectively, when compared with estimates from cup samples.

We examined the effect of probe trap type and attractants on the capture of four insect species. Two commercially available pitfall probe traps were used. Treatments added to the traps consisted of a control, food bait, glycerol and either pheromone or pheromone-food bait combination if available. The insect species were Tribolium castaneum (Herbst), Sitophilus oryzae (L.), Rhyzopertha dominica (F.), and Cryptolestes ferrugineus (Stephens). There were significant differences in the numbers of insects collected by the two trap types. Also, the numbers of the different species captured were significantly different when compared across trap and treatment types. Species level analysis indicated that overall differences in numbers of the different species collected were largely the result of two species. A significant difference in capture resulting from any treatment occurred only for one of the four species. Different results might occur if feral insect populations were utilized or if trapping methods suitable for the warehouse environment were employed.

Reproductive phases, fecundity, and adult longevity of the squash bug, Anasa tristis (De Geer), were determined under laboratory conditions at a constant temperature of 26.7°C for five cucurbit hosts. Squash bugs on muskmelon, Cucumis melo L. ‘Hales Best #36’, had the longest premating phase. The preoviposition phase was shorter and the oviposition phase was longer on two cultivars of Cucurbita pepo L., yellow straightneck ‘Hyrific’ squash and ‘Jack O'Lantern’ pumpkin, than on watermelon, Citrullus lanatus (Thunberg) Matsumura and Nakai ‘Crimson Sweet’, and muskmelon. Females had the longest postoviposition phase on watermelon. The highest fecundity was observed on pumpkin seedlings. Host type did not affect egg mass size, egg hatch, percent hatch, or egg development. Higher percentages of egg masses were oviposited on the abaxial leaf surface than other plant locations on all hosts. Male squash bugs lived longer on pumpkin, squash, and watermelon than on muskmelon and cucumber, Cucumis sativus L. ‘Poinsett’, whereas females lived longer on pumpkin than on squash, muskmelon, and cucumber. Males lived longer than females on pumpkin and squash. The different host effects on reproduction, fecundity, and longevity indicate that host type is important when developing control strategies for the squash bug.

Variation in fecundity of apterous adults of three greenbug, Schizaphis graminum (Rondani), biotypes on seedlings of resistant and susceptible barley was studied in an environmental chamber programmed for 25:20°C and 16:8 (L:D) h. The objective of the test was to obtain baseline data on variability of biotypes B, C, and E on resistant and susceptible cultivars. Fecundity distributions for three biotypes (B, C, and E) on susceptible ‘Wintermalt’ were normal, but non-normality was evident for the three biotypes on resistant ‘Post’. For the non-normal distributions, significant skewness values were found in the direction of higher fecundity. Greenbug reproduction on some plants of ‘Post’ barley was greater than expected, but whether this was caused by variation in greenbug populations or variation in the host plants is unclear.

Squash bugs, Anasa tristis (De Geer), were intensively sampled in summer squash plots from three locations in Oklahoma in the spring and summer of 1987 and 1988. Data collected from whole-plant samples for adults, egg masses, and nymphs were fitted to the Poisson, negative binomial, and positive binomial frequency distributions, as well as Taylor’s power function and Iwao’s patchiness regression. None of the three theoretical distributions fit the squash bug populations on all sample occasions. Taylor’s power law provided a better fit to the count data than did Iwao’s patchiness regression. All life stages exhibited aggregated patterns of spatial dispersion; small nymphs exhibited the largest degree of aggregation, followed by large nymphs, adults, and egg masses. Sequential sampling plans for squash bugs were developed using estimated variance-mean relationships derived from Taylor’s power function. Because small nymphs were highly aggregated, greater numbers of plant samples were required to estimate population means of nymphs with specified levels of precision than were needed for adults or egg masses. Validation with Monte Carlo simulations indicated that these procedures may not always estimate mean population density at specified levels of precision.

Within-plant distribution of squash bug, Anasa tristis (De Geer), adults and egg masses on spring plantings of summer squash was determined by making whole-plant visual examinations. A significantly greater percentage of adults was found on the soil surface than on plants in early stages of crop phenology ( 90% of squash bug oviposition occurred on abaxial leaf surfaces. A significantly greater percentage (90%)of egg masses was deposited on leaves in the lower one-half of plants during vegetative plant growth. Average weighted mean egg mass location on plants was found to be highly correlated ( P < 0.01) with the number of leaves per plant. Results of this study suggest that sampling procedures should be developed separately for adults and egg masses. Monitoring for adults should include examination of both the plant and soil surface, whereas sampling for egg masses should concentrate primarily on the lower foliar canopy.

The effect of summer squash ( Cucurbita pepo L. cv. Hyrific) planting dates on the seasonal abundance of squash bug, Anasa tristis (De Geer), populations and fruit yields was investigated. Colonization by overwintered adult squash bugs was directly influenced by planting date. Significantly higher adult population densities developed on older, larger plants containing higher numbers of leaves than on younger plants with fewer leaves. As a result of adult preference for larger plants, egg mass and nymphal populations were significantly more abundant on early-planted squash. Mean numbers of squash bugs per leaf were correlated ( P < 0.05) with mean number of leaves per plant, suggesting that plant size may influence host plant selection. Regardless of planting date, squash bugs were most abundant on plants during flowering and fruit set. Manipulation of squash plantings may be a means of managing overwintered squash bug populations in spring crops to avoid yield losses.

Probing behaviors of first-instar squash bugs, Anasa tristis (De Geer), were electronically monitored and net weight gains of nymphs were determined on leaves of cucurbit hosts in the genera Cucurbita, Citrullus , and Cucumis . Force required to puncture cucurbit leaves was also examined. Squash bugs monitored for ≈8 h produced three waveforms (Wa, Wb, and We) on which comparisons could be made. We was the dominant waveform on all hosts. Histological examinations of squash bug salivary sheaths in leaf tissues taken during We revealed that the sheath tips were located in vascular bundles. Among hosts, differences were seen in mean probing duration per probe and in the waveform durations per probe for Wa and Wb. Net weight gains of squash bug nymphs were not different among hosts. Although leaf hardness was significantly different among hosts, it was not definitively determined to be a factor affecting squash bug feeding.

The occurrence of squash bug, Anasa tristis (DeGeer) on yellow summer squash grown under different cultural systems was studied in one experiment in 1987 and two experiments in 1988. The influence of row covers-black plastic and aluminized mulch-on the occurrence of squash bug was evaluated. Mulch production systems (black plastic or reflective) harbored more squash bugs than bare ground in 1987 studies. No differences in the density of squash bug were detected in plots with aluminum mulch (paper-backed) compared with either white plastic or aluminized black plastic. Early in both 1988 studies, significantly more squash bugs were observed in plots with aluminum mulch compared with those with black plastic. As plant development progressed, differences in squash bug numbers between the two mulch types decreased. However, squash grown in mulched plots, regardless of the type of mulch used, had consistently larger squash bug populations than those grown in bare ground. Row covers delayed squash bug colonization but when the covers were removed to allow plant pollination, squash bug colonized quickly. Mulch covers, regardless of type, provide a harborage for squash bug adults and nymphs. Greater numbers of squash bugs in mulched culture systems may result in increases in squash bug control costs, which could offset any production benefit gained by mulch systems.

Six squash cultivars, Cucurbita spp., were evaluated in the field during 1983 and 1984, and five cucurbit hosts were evaluated during 1985 for ovipositional preference by squash bugs, Anasa Tristis (De Geer). Yellow straightneck ‘Hyrific’ and crookneck squashes were found to be the most preferred in the squash study. In the cucurbit study, two cultivars of C. pepo L., yellow straightneck ‘Hyrific’ squash and ‘Jack o’ Lantern’ pumpkin, were most preferred. Relatively few egg masses were found on watermelon, Citrullus lanatus (Thunberg) Matsumura & Nakai ‘Crimson Sweet’; muskmelon, Cucumis mela L. ‘Hales Best #36’; and cucumber, Cucumis sativus L. ‘Poinsett.’ The abaxial leaf surfaces of all hosts in both studies were the favored ovipositional site of squash bugs. This phenomenon is important in developing squash bug sampling strategies and in insecticide applications.

The grain storage and marketing system in Oklahoma, consisting primarily of producers and local elevator operators, was characterized through surveys and on-site validation for utilization of integrated pest management (IPM) practices and insects present. Oklahoma grain producers and elevator operators used IPM practices such as sanitation, application of grain protectants, and aeration more frequently than previously reported in other states. Differences in management practices that occurred between the two segments of the storage system resulted primarily from differences in storage structures and in the time the grain is stored. Insect surveys revealed that commercial managers believed that granary weevil, Sitophilus granarius (L.), and lesser grain borer, Rhyzopertha dominica (F.), were the primary pests. Producers stated that weevils and Indianmeal moth, Plodia inrerpuncrella (Hubner), were the primary pests. Few producers said lesser grain borer was a serious pest. However, a few rice or granary weevils were found in samples taken from commercial or on-farm storage and the lesser grain borer, Cryprolesres spp., and Tribolium spp. were the primary pests found. Price discounts apparently were not sufficiently large to have an effect on the Oklahoma storage and marketing system. The stored-grain system appeared to minimize risk-dividing costs between producers and local elevator operators.

Hymenoptera that parasitize aphids are being widely employed as biological control agents for a variety of species including important cereal pests like the greenbug, Schizaphis graminum (Rondani), and the Russian wheat aphid, Diuraphis noxia (Mordvilko). Identification of these parasitoids using morphological markers is often difficult and requires a trained expert. This presents a serious obstacle to the successful selection, importation, rearing, mass release and tracking of these insects in biological control programs. The characterization of convenient biochemical markers for rapid identification of parasitoids is an important goal. This study was undertaken to determine if parasitoid epicuticular hydrocarbons might serve as useful markers to distinguish parasitoid species.

The efficacy of several insecticides was investigated in a test with small plots of watermelon grown on a clay laom soil at the Oklahoma Agricultural Experiment Station near Stillwater. Plots were established on 18 May by transplanting seedling plants into plastic mulch. Experimental plots were 30 ft long by 10 ft wide, arranged in a randomized complete block design and replicated 4 times. A single insecticide application was made on 11 Aug, using a CO2 powered backpack sprayer delivering 30 gal/acre at 50 psi through 3 TX-18 hollow-cone nozzles Efficacy of treatments was assessed by randomly selecting 4 areas (1 m2) in each plot and counting squash bug nymphs on all plant parts and the mulch surface within each sample quadrant. Counts were made on 12 Aug (1 DAT), 15 Aug (4 DAT), and 18 Aug (7 DAT). Data were subjected to ANOVA and DMRT.

Detailed investigation of the within-tree population system ofDendroctonus frontalisZimmermann has resulted in a large data base consisting of abundance estimates for various life stages. This data base was used to construct histograms for transformed estimates and several life stage indices. Histograms were also constructed for transformed values of adult residence time, brood development time, and several host-tree characteristics.

Infestations ofDendroctonus frontalis Zimm. are often observed to enlarge continuously by the colonization of new hosts in a pattern similar to a forest fire. This pattern of infestation growth presents unique problems in quantitatively estimating populations ofD. frontalis. Beetle populations on each infested tree in an infestation go through five processes: attack, oviposition, reemergence, survivorship, and emergence. These processes, which have been described mathematically in the literature, each take several days for completion. In order to follow the distribution and abundance ofD. frontalis throughout the course of development of a spot, we need a daily estimate of the number of beetles involved in each process on every tree. Since it is not practical to sample each tree daily, we developed a procedure whereby quantitative estimation procedures for within-tree populations were used in combination with the mathematical models for the life processes to produce a daily record of the number of adults successfully attacking trees, the number of eggs oviposited, the number of beetles reemerging, number of beetles surviving within the trees, and the number of beetles emerging. These daily estimates were then summarized for all trees in the spot for the duration of the infestation. The daily record of populations ofD. frontalis, used with information on infestation geometry, were suggested to be of value in describing and elucidating several important facets of population dynamics including dispersal patterns within infestations, between tree beetle loss (mortality), and time lags among the various population processes. The information reported can be used to develop simulation models of population dynamics or to validate existing models.

Development of the squash bug, Anasa tristis DeGeer, was observed at 12 constant temperatures between 20.0 and 40.0°C. Times required for development of all life stages at the different temperatures followed the classic “backwards-J” shape. A nonlinear biophysical model was fit to data representing each individual life stage as well as to several combinations of life stages. Generally a four-parameter model was selected with high-temperature inhibition of development. R 2 values for the individual models ranged from 0.901 to 0.994. The models indicate that the use of heat-unit accumulation techniques to predict development times is valid within the linear response range of A. tristis and may be used in the development of management strategies.

This laboratory study investigates the effects of constant temperature on reemergence of the southern pine beetle, Dendroctonus frontalis Zimmermann. Beetles reemerged at temperatures between 12.5 and 33.3°C, with the relationship of adult residence time and constant temperature forming a backwards “J”-shaped curve. Adult residence time was greatest at 12.5°C (46 days) and least at 27°C (12 days). The distributions of those times changed with temperature. At 12.5 and 15°C, the distributions were near uniform, but as temperature increased to 30°C, the distributions became peaked and skewed right. Above 30°C, the distributions became less peaked. About 90% of the beetles reemerged at temperatures between 12.5 and 30°C, whereas above 30°C the percentage dropped precipitously. Males reemerged 1 or 2 days before females at temperatures below 30°C, but the reverse condition was found at 30°C or above. A two-component model is used to predict reemergence as a function of temperature. The first component describes reemergence rates as a function of temperature. The second component distributes the reemerging population over physiological time. When combined, these components distribute reemergence over calendar lime, and are Suitable for incorporation into a larger population model of D. frontalis .

Changes in water quality along the Sone River, which is polluted by effluents from the Orient Paper Mills (OPM), Amlai, M.P., India were studied in the present work. The water samples from fifteen stations, covering a distance of about 216 km along the river course were subjected to hierarchical cluster analysis to determine similarity relations with respect to seven water quality parameters. Maximum pollution was observed up to 30 km downstream. Improvement in water quality was registered further downstream due to self-recovery and dilution. The greatest variability was observed between water samples taken at the OPM uptake site and at the effluent mixing point located 2 km downstream. Maximum similarity was found between stations located 2.0 and 2.1 km; 2.3 and 2.5 km; and 2.7 and 3.0 km downstream.

Sampling methodologies have been developed for various species of bark beetles including the mountain pine beetle (Carlson and Cole 1965), western pine beetle (Berryman et al. 1970, DeMars 1970), and the southern pine beetle (Coulson et al. 1975, Stephen and Taha 1976). Within-tree sampling involves removal of bark sections and utilization of dissection or radiography to obtain quantitative data for each life stage.

The occurrence of greenbug,Schizaphis graminum (Rondani), biotypes is a constant threat to the development and stability of pest-resistant cereal crop varieties. Of the five biotypes (A, B, C, D, E) reported, only biotype B can be differentiated in life from the others by the physical characteristics of color. The other biotypes are differentiated on the basis of their ability to kill certain hosts or to withstand selected insecticides. The purpose of this research was to differentiate biotypes of apterous viviparous female greenbugs by multivariate techniques.

We have presented two transfer functions for allocating populations ofD. frontals adults in spots: a fixed probabilityTF and a time-temperature dependentTF. Both procedures produced essentially equivalent results when applied to actual population measurements taken from spots. The time-temperatureTF was more realistic than the constant probabilityTF, but introduced an added source of variation into the transfer. Temperature was demonstrated to have a significant effect on adult longevity. The time-temperature dependentTF provides a means of incorporating this important variable. TheF1 andF2 values obtained from this time-temperature dependentTF were also judged to be superior to the values obtained from the constant probabilityTF. Survival of reemerged and emerged beetles were shown to be cyclic and compensatory.

Morphometric variability in biotypes of the greenbug, Schizaphis graminum (Rondani), provided additional knowledge about differences among them. Twenty-four morphological structures of alate males of biotypes C and E, and alate viviparous females of biotypes B, C, and E were measured. Multivariate analysis of variance of the data indicated that morphometrically the biotypes and sexes form significantly different groups. Using discriminant analysis, all greenbugs were correctly classified into their appropriate groups. The coefficients of variation for different morphological structures were greater for biotype E, suggesting that this biotype is more variable than the other biotypes.

Capturing stored grain insects with drop traps in wheat was affected by insect species, grain temperature, and trapping duration. These results were obtained using four insect species (Tribolium castaneum (Herbst), Sitophilus oryzae (L.), Rhyzopertha dominica (F.), and Cryptolestes ferrugineus (Stephens), three grain temperatures (10.0, 21.1, and 32.2°C), and four trapping intervals (I, 2, 4, and 7 d). Higher grain temperatures resulted in significantly more insects trapped when all species were combined. This significance is largely due to the highly significant numbers of C. ferrugineus captured at high temperatures. The other species followed the same pattern. At each temperature, C. ferrugineus was caught in the greatest numbers and R. dominica in the least. S. oryzae and T. castaneum were captured in intermediate numbers. Across species, longer trapping durations resulted in significantly more insects being captured. Across durations, C. ferrugineus was caught the most, R. dominica the least, with the other two species intermediate. Within species, only C. ferrugineus . showed significant differences in the number trapped among the sampling periods. The trend, however, was consistent for all insect species. This study emphasizes the need to consider differences in insect species, grain temperatures, and trapping durations when drop traps are used to estimate insect abundance.

The population dynamics of the squash bug, Anasa tristis (DeGeer), and the seasonal development of the squash plant, Cucurmta pepo L. variety ‘Hyrific,’ were monitored during 1984 and 1985. Numbers of squash bugs increased dramatically throughout the season. Overwintered adults and subsequent oviposition occurred soon after plant emergence. The development of first-generation nymphs and adults slowly increased the total number of squash bugs in the field. The development of a second generation caused a pronounced increase in the total numbers present. The numbers of nymphs, adults, and eggs in the field increased at an exponential rate beginning about Julian date 192 (10 July). Late in the season the rate of oviposition decreased. Squash bugs complete two to three generations per year in Oklahoma. Our data suggest that early-season control of squash bugs is essential to prevent high densities of insects from occurring late in the year. Mean plant leaf area and the number of leaves followed a sigmoid-shaped growth curve, increasing slowly early in the season, becoming faster through midseason, and slowing again late in the season. The numbers of flower buds, flowers, and immature and mature fruit also followed a sigmoid-shaped growth curve throughout the season.

The reliability of life stage estimates derived from four limited data collection options for Dendroctonus frontalis Zimmermann was evaluated. The options included the following: (1) no data relative to host tree physical characteristics or beetle populations measured; (2) tree diameter at 2.0 m (D2M) measured; (3) D2M and height of infestation (IBH) measured; and (4) infested surface area measured. In general, the bias of estimates increased, and the variance decreased, as more information was provided for estimation. Interpolated values for all trees, using options 3 and 4, were biased from 8% for gallery to 98% for emerging beetles, and SD of the bias were 0.7 to 3 times the estimate. The accuracy and precision of estimates using tree physical characteristics decreased as the beetle’s life cycle progressed, due to an increase in variation associated with developmental mortality. The consequences of using limited data for predicting population trends were explored with model simulations. Values derived from the D2M × IBH procedure were compared with estimates calculated by a mathematical technique which uses quantitative sampling to produce unbiased estimates with defined precision and accuracy. Since the mathematical techniques provided estimates of D. frontalis with defined accuracy and precision, they served as a standard for comparison with the sampling procedures that used limited data collection. Tree mortality, using the reduced data option, was underestimated by ca. 40% relative to estimates based on single or miltiple-level sampling.

Studies were conducted to determine nature and amount of morphometric variability within the greenbug, Schizaphis graminum (Rondani), in an effort to further understand biotypes of this species. Data on morphometrics of the four morphs (males, apterous/viviparous, apterous/oviparous, and alate/viviparous females) were pooled for three biotypes (B, C, and E) and various multivariate statistical analyses were performed. The data suggested that the three biotypes formed significantly different groups. The four morphs were also significantly different from each other. When morphs and biotypes were considered simultaneously, the canonical discriminant analysis grouped greenbugs of different morphs into four different, well-isolated clusters. Within each cluster, individuals of each biotype were further grouped into small subclusters. The Mahalanobis distance analysis suggested that biotype E is closely related to biotype C. The distance analysis also indicated that biotype C is closely related to biotype B. Similar Mahalanobis distance analysis also suggested a close association between apterous females and alate females, as stated in the literature.

An equation was developed which may be used to estimate the area of all sizes of developing squash (Cucurbita pepo L.) leaves. The equation uses two leaf measurements (midrib length (ML) and the distance between tertiary lobes (TD)) which may be taken quickly in the laboratory or field without disturbing the host plant. The equation is:[Formula: see text]The equation is applicable in monitoring individual leaf expansion as well as total plant leaf area increase and in examining the dynamics of the plant under various environmental conditions.Key words: Cucurbita pepo L., leaf area, growth, development, leaf expansion

The influence of five cucurbit hosts on survival, developmental time, and adult weight of the squash bug, Anasa tristis (De Geer), was determined. Percentage survival from egg to adult was significantly affected by host. Survival to the adult stage on the five hosts was highest on pumpkin, Cucurbita pepo L. var. pepo (70.0%), followed by squash, Cucurbita pepo L. var. melopepo (49.0%); watermelon, Citrullus lanatus (Thunb.) Matsum. & Nakai (14.4%); cucumber, Cucumis sativus L. (0.3%); and muskmelon, Cucumis melo L. (0%). Host type had a significant effect on developmental time to third and fifth instar and to adult, with a longer developmental time on watermelon. The adult sex ratio was 1:1. Adult females were significantly heavier than males. Greater adult weights for both males and females resulted when insects developed on squash. However, the effect of host on adult weight was significant only for males.

The test was conducted at the Oklahoma Agricultural Experiment Station, Stillwater. ‘Hyrific’ summer squash was direct seeded on 20 Aug into single-row beds (48-inch centers) on a clay loam soil. The experiment was arranged in a double latin square design (5 by 5) and overlaid on plots consisting of a single-row of 5 plants seeded at 3-ft intervals. Granular formulations of the systemic insecticides were applied in a 6-inch band over the row at planting. The granules were lightly raked into the soil and the rows were irrigated using a surface trickle irrigation system. The treatments were evaluated by counting the dead SB (nymphs and adults pooled) and SCB on or directly beneath each plant at 1, 4, 7, 14, and 21 d after the squash plants emerged from the soil.

Straight-neck ‘Hyrific’ summer squash was direct seeded 6 Aug at the Oklahoma Agricultural Experiment Station, Perkins. Plots consisted of a single row of 5 plants seeded at 3-ft intervals. Rows were separated by 5-ft alleys. The experiment was arranged in a randomized complete block design with 10 replicates. Foliar sprays were applied on 24 Aug with a CO2-powered backpack sprayer mounted with 3 TX-18 nozzles/row, calibrated to deliver 78 gal/acre at 50 psi. Efficacy was evaluated at 1, 4, and 7 DAT by counting SB nymphs on 3 randomly selected plants/plot. Data were subjected to ANOVA.