Lady Beetle Populations Research Articles

The role of exotic ladybeetles in the decline of native ladybeetle populations: evidence from long-term monitoring

Ladybeetles (Coleoptera: Coccinellidae) are ubiquitous predators which play an important role in suppressing pest insects. In North America, the coccinellid community is increasingly dominated by exotic species, and the abundance of some native species has declined dramatically since the 1980s. Several hypotheses have been proposed to describe the mechanism of invasion coupled with native species declines, e.g. vacant niche exploitation, intraguild predation, competitive exploitation and habitat compression. We analyze a 24-year dataset of coccinellid community structure in southwestern Michigan to elucidate the most likely mechanism(s) of native coccinellid decline and implications for their conservation. Correlation analyses indicated that impact of exotic species on native coccinellids varies with their degree of interaction. Although several native species were observed to be in numerical decline, only Adalia bipunctata and Coleomegilla maculata had declines that were statistically significant. The magnitude of decline in these two species varied with the degree of dietary overlap with invaders, thus their decline is most likely driven by competitive exploitation. Habitat use patterns by some native species (A. bipunctata and Coccinella trifasciata) changed during years when the exotic Harmonia axyridis reached high numbers, lending support to the habitat compression hypothesis, where native species survive in ancestral (i.e. natural or semi-natural) habitats when invaders dominate cultivated habitats. Coccinellid communities occurring in semi-natural forested habitats were unique in both composition and variability from those occurring in cultivated habitats. Such semi-natural habitats can act as refuges for native coccinellids and may play a role in maintaining the functional resilience of coccinellid communities.

Effects of three mealybug species on the development, survivorship and reproduction of the predatory lady beetle Cryptolaemus montrouzieri Mulsant

The lady beetle Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) is an important predator of mealybugs. The development, survivorship, longevity and reproduction of C. montrouzieri feeding on three different mealybug species [Dysmicoccus neobrevipes Beardsley, Ferrisia virgata Cockerell and Planococcus minor (Maskell)] were investigated in the laboratory at 26 ± 1°C, 75-–90% RH and 14:10 (L:D) h photoperiod. Results indicated that, when feeding on different mealybugs, no significant differences were observed between developmental periods and survivorship of C. montrouzieri (from egg to adult), but differences were recorded between the sex ratios, preovipositional periods, adult longevities and reproduction of the differently treated lady beetle populations. The highest sex ratio (0.56), the longest preovipositional period (6.6 days) and adult longevity (84.8 days for females and 93.9 days for males), and the maximum fecundity (659.0 eggs/female) of C. montrouzieri were recorded when feeding on F. virgata. Moreover, C. montrouzieri had a high net reproductive rate (313.66), intrinsic rate of increase (0.0816) and finite rate of increase (1.085) when feeding on F. virgata. Results indicated that the population growth of C. montrouzieri may increase faster when feeding on F. virgata than feeding on either of the other two mealybugs.

Effects of land use and insecticides on natural enemies of aphids in cotton: First evidence from smallholder agriculture in the North China Plain

Studies conducted in the USA and Europe have shown that diverse landscapes in general support greater natural enemy abundance. No quantitative evidence on the relationship between land use diversity and natural enemies has been reported from developing countries, where fields and farms are much smaller than in modernized agriculture in the west, and where insecticide use is often high and indiscriminate. This paper examines the effects of land use and farmers’ insecticide application on natural enemies of aphids in cotton production, based on a unique dataset that links household and cotton field surveys to a detailed assessment of land uses in the landscapes surrounding the cotton fields in the North China Plain (NCP), a major grain and cotton production region in China. Our results show that, in the NCP where farms are small and landscape is dominated by a few crops, Shannon or Simpson land use diversity index is not a good indicator for explaining the relationship between land use and densities of aphid natural enemies. Instead, the types and proportions of cropland habitat mattered. Landscapes with more maize and grassland have higher ladybeetle populations in cotton fields. Farmers’ pest management practices such as the amount and timing of insecticide use significantly affect ladybeetle densities. These results imply that there is a need to recognize the potential positive role of cropland use in pest management and call for more judicious insecticide use strategies by smallholder farmers in the North China Plain.

Refuge for native lady beetles (Coccinellidae) in perennial grassland habitats

The proportion of native individuals in North American lady bee- tle communities has declined precipitously over the past 30 years, particularly in annual cropping systems. At the same time, the number and abundance of exotic coccinellid species have been on the rise as beetles are introduced both inadvertently and intentionally for the purposes of biological control. 2. Perennial grasslands have been proposed as refuge habitats that promote native lady beetles, either by resisting the invasion of exotics or by providing a consistent source of shelter and resources. 3. Our objective is to compare the conservation value for native lady beetles of different perennial grassland habitats that vary in their degree of habitat modification and disturbance. 4. The abundance, species richness, and species composition of native and exotic lady beetles were compared across remnant native tallgrass prairies, native tallgrass prairies actively restored from cultivation and exotic tall fescue grasslands grown as forage crops. 5. Native species dominated the lady beetle community in all perennial grass- land habitats, with more than 95% of captured individuals being native in ori- gin. Exotic lady beetle species were equally rare across all habitat types. 6. The grassland habitat considered the most disturbed, agriculturally grown exotic tall fescue, had the highest abundance and species richness of native lady beetles and a unique composition of species as compared to prairie habitats. Lady beetle communities in remnant and restored tallgrass prairies were indistinguishable, indicating that prairie restoration successfully re-established coccinellid communities. 7. Promoting perennial grasslands, both natural and agricultural, within disturbed landscapes has the potential to enhance native lady beetle populations.

Influence of Garlic Intercropping or Active Emitted Volatiles in Releasers on Aphid and Related Beneficial in Wheat Fields in China

In order to develop biological control of aphids by a “push-pull” approach, intercropping using repellent emitting plants was developed in different crop and associated plant models. Garlic is one of the potential plant that could be inserted in crops to decrease the pest occurrence in neighboring crop plots. In this study, field works were conducted in wheat fields in Langfang Experimental Station, Hebei Province in China from October 2009 to July 2010 during wheat developmental season. The effect of wheat intercropping with garlic but also the volatiles emission on the incidence of the English grain aphid, Sitobion avenae Fabricius (Homoptera: Aphididae) was assessed. Natural beneficial occurrence and global yields in two winter wheat varieties that were susceptible or resistant to cereal aphid were also determined comparing to control plots without the use of garlic plant intercrop nor semiochemical releaser in the fields. S. avenae was found to be lower in garlic oil blend treatment (GOB), diallyl disulfide treatment (DD) and wheat-garlic intercropping treatment (WGI) when compared to the control plots for both two varieties (P<0.01). Both intercropping and application of volatile chemicals emitted by garlic could improve the population densities of natural enemies of cereal aphid, including ladybeetles and mummified aphids. Ladybeetle population density in WGI, GOB and mummified aphids densities in WGI, DD were significantly higher than those in control fields for both two varieties (P<0.05). There were significant interactions between cultivars and treatments to the population densities of S. avenae. The 1 000-grain weight and yield of wheat were also increased compared to the control. Due to their potential alternatives as a biological control agent against cereal aphid, garlic intercropping and related emitted volatiles are expected to contribute to the further improvement of integrated pest management systems and to potentially reduce the amount of traditional synthetic pesticides applied in wheat fields.

Inheritance of lambda-cyhalothrin resistance in the predator lady beetle Eriopis connexa (Germar) (Coleoptera: Coccinellidae)

Lambda-cyhalothrin is a pyrethroid insecticide widely used to control pests in various crop ecosystems, in which the lady beetle occurs naturally. Therefore, lady beetle populations are exposed to lambda-cyhalothrin sprays that may foster tolerance to this insecticide. This study was conducted to confirm the occurrence of resistance in the lady beetle Eriopis connexa (Germar) (Coleoptera: Coccinellidae) to lambda-cyhalothrin and to characterize the inheritance of resistance after eight progressive selection with insecticide dosages based on the LD50 determined for the F1 generation. Dose–mortality curves were determined for parental populations, F1 hybrids and backcross progenies. Parameters regarding the heritability of resistance to lambda-cyhalothrin in E. connexa allow estimating 10-fold increase in the initial LD50 after 54.5 generations of successive selections. The resistance of E. connexa to lambda-cyhalothrin was characterized as autosomally inherited and incompletely dominant, and influenced by a major gene with possible influence of secondary genes. Additionally, the resistance in E. connexa varies from functionally dominant to functionally recessive depending on the dose used. These findings indicate that insecticide resistance in E. connexa can be selected in the field as determined for field-collected individuals, and subsequently enhanced under laboratory conditions. Its characterization presented here is an important step toward linking biological and chemical control within pest management regarding the lady beetle and lambda-cyhalothrin targeting different pest groups.

Lessons from lady beetles: accuracy of monitoring data from US and UK citizen‐science programs

Citizen scientists have the potential to play a crucial role in the study of rapidly changing lady beetle (Coccinellidae) populations. We used data derived from three coccinellid‐focused citizen‐science programs to examine the costs and benefits of data collection from direct citizen‐science (data used without verification) and verified citizen‐science (observations verified by trained experts) programs. Data collated through direct citizen science overestimated species richness and diversity values in comparison to verified data, thereby influencing interpretation. The use of citizen scientists to collect data also influenced research costs; our analysis shows that verified citizen science was more cost effective than traditional science (in terms of data gathered per dollar). The ability to collect a greater number of samples through direct citizen science may compensate for reduced accuracy, depending on the type of data collected and the type(s) and extent of errors committed by volunteers.

Within‐field distribution of Aphis gossypii and aphidophagous lady beetles in chili, Capsicum annuum

AbstractUnderstanding the spatial distribution of insect pests and their natural enemies can be very important for a successful integrated pest management approach. In Malaysia, Aphis gossypii Glover (Hemiptera: Aphididae) is the only aphid species colonizing and responsible for significant crop losses in chili, Capsicum annuum L. (Solanaceae). Several species of aphidophagous lady beetles (Coleoptera: Coccinellidae) occur naturally, of which three species [Menochilus sexmaculatus (Fabricius), Coelophora inaequalis (Fabricius), and Coccinella transversalis (Fabricius)] predominate in chili ecosystems. In this study, we investigated the spatial distribution of A. gossypii and associated lady beetle predators during two growing seasons of C. annuum, using Spatial Analysis by Distance Indices (SADIE). Both aphid and lady beetle populations were spatially aggregated, the strength of aggregation being strongest mid‐way through the cropping cycle. We concluded that the aggregated distribution of adult lady beetles is driven by the spatial distribution of A. gossypii.

Susceptibility of lady beetles (Coleoptera: Coccinellidae) to entomopathogenic nematodes

We investigated differential susceptibility of lady beetles to entomopathogenic nematodes, for two reasons: (1) to estimate potential nontarget effects on natural lady beetle populations, (2) to compare the susceptibility of exotic versus native lady beetle species. We hypothesize that successful establishment of some exotically introduced arthropods may be due, in part, to a lower susceptibility relative to competing native species. In laboratory studies, we compared the pathogenicity, virulence, and reproductive capacity of Heterorhabditis bacteriophora and Steinernema carpocapsae among two native ( Coleomegilla maculata and Olla v-nigrum) and two successfully established exotic ( Harmonia axyridis and Coccinella septempunctata) lady beetles, and a known susceptible lepidopteran host, Agrotis ipsilon. After 1 and 2 days of exposure to either nematode species, mortality of A. ipsilon was higher than in all lady beetles. Thus, we predict that nematode field applications would have significantly less impact on lady beetle populations than on a susceptible target pest. Additionally, the impact of soil-applied nematodes may be lower on lady beetles than on soil-dwelling hosts because the former spends relatively less time on the soil. Exotic lady beetles were less susceptible to nematode infection than native species. Reproductive capacity data also indicated lower host suitability in H. axyridis, but not in C. septempunctata. Overall, the hypothesis that low susceptibility to pathogens in certain exotic lady beetles may have contributed to competitive establishment was supported (especially for H. axyridis). Additional studies incorporating different hosts and pathogens from various geographic locations will be required to further address the hypothesis.

Generation cycles in Indonesian lady beetle populations may occur as a result of cannibalism

Generation cycles, population cycles with a period of approximately one generation, have been observed in a variety of field and laboratory studies. Such dynamics are predicted to arise through the effects of resource competition and cannibalism or involve consumer-natural enemy interactions. We first show, using a new highly simplified model, that generation cycles are a very common outcome of strongly age-structured intraspecific interactions involving cannibalism. We then analyse a series of unique long-term time-series of ladybeetle (Coccinellidae) abundances from tropical Indonesia. Some of the time-series display clear generation cycles, and we argue that there is strong evidence that these are caused by intraspecific cannibalism.

Spatio-temporal distribution of corn leaf Aphids (Homoptera: Aphididae) and lady beetles (Coleoptera: Coccinellidae) in Iowa cornfields

Abstract Prey–predator interactions are spatially and temporally dynamic and influenced by environmental factors. Field studies were conducted to investigate the dynamics of spatio-temporal interactions among corn leaf aphids, lady beetles, and environmental factors in cornfields by mapping and comparing their distributions. Lady beetle species in this study included Harmonia axyridis Pallas, Coleomegilla maculata (DeGeer), and Coccinella septempunctata L. A global positioning system, geostatistics, and a geographic information system (GIS) were used to locate sample points, characterize distribution patterns, and map the distributions of corn leaf aphids, lady beetles, and environmental factors. Geostatistical analysis showed that both corn leaf aphid and lady beetle populations were aggregated during the peak population period and randomly distributed early and late in the season. Map-correlation analysis, however, showed that the distribution of lady beetles did not always coincide with that of corn leaf aphids. The results also showed that none of the environmental factors we sampled were significantly correlated with corn leaf aphid and lady beetle distributions. This study documents the dynamic relationships in time and space between lady beetles and corn leaf aphids.

Estimating susceptibility of biological control agents to pesticides: influence of life history strategies and population structure

Abstract In this study we examined the influences that differing life history strategies and population structures at the time of pesticide exposure have on population susceptibility to pesticides. We used life table data and a matrix projection model to incorporate combinations of mortality (lethal effect) and reductions in fecundity (sublethal effect) into estimates of intrinsic population growth rates ( r ) for a predator, the seven-spot lady beetle, Coccinella septempunctata L., and its prey, the pea aphid, Acyrthosiphon pisum Harris, and an aphid parasitoid, Diaeretiella rapae (M’Intosh). All three species exhibited differences in key life history variables. The aphid had the highest r and shortest generation time, the ladybeetle had the lowest r and longest generation, while the parasitoid exhibited intermediate life history characteristics. When the model was run with populations started as neonates (aphids) or eggs (lady beetle, parasitoid) for each species, ladybeetle populations were much more susceptible than either aphid or parasitoid populations 30 days after simulated exposure to a pesticide. For example, 50% mortality and a 50% reduction in fecundity resulted in a population headed toward extinction (negative r ) for the ladybeetle while the parasitoid population grew exponentially (positive r ) even after sustaining 70% mortality and a 70% reduction in fecundity. The aphid species maintained exponential growth after sustaining 80% mortality and an 80% reduction in fecundity. Thus, differences in life history variables accounted for the greater susceptibility of the ladybeetle to a pesticide than its aphid prey or the parasitoid over a set time interval. These differences in susceptibility were greatly reduced when the model was run starting with a mixed age/stage population (the stable age distribution) for each species indicating that population structure at the time of pesticide exposure plays a critical role in population susceptibility. These results suggest that life history attributes as well as population structure at the time of pesticide exposure both play a major role in population susceptibility to pesticides, highlighting the need to explicitly consider differences in life history variables among species when calculating compatibility of pesticides and biological control agents as well as the population structure of beneficial species at the time of pesticide application.

Long-term Dynamics of Phytophagous Lady Beetle Populations under Different Climate Conditions in Sumatra and Java, Indonesia.

Since 1990 we have studied population dynamics of the phytophagous lady beetles, Epilachna vigintioctopunctata, E. enneasticta and Epilachna sp. 3 (aff. emarginata), (Coleoptera: Epilachninae) in Padang, Sukarami (West Sumatra), Bogor (West Java) and Purwodadi (East Java), Indonesia. These sites have distinctly different climate conditions, e.g. Padang has a typical tropical rainforest climate without a clear alternation of wet and dry seasons, while Purwodadi has a strong dry season of 6-7 months. We have conducted censuses at 3-7 day intervals, including mark-recapture of beetles and construction of life tables for up to 9 consecutive years in order to clarify the seasonal change in abundance and mortality of the populations. In most populations the adult number changed greatly with the formation of high peaks from time to time at intervals of 6-12 months. Their increase or decrease was gradual, progressing over 3-5 months. Even under conditions with sufficient amount of rainfall in Padang, Sukarami and Bogor, oviposition intensity, number of the following immature stages and, as a result, adult emergence frequently showed discrete peaks at a fixed interval. These “generation cycles” were especially clear during the phase of population increase. There was no simple relationship between the seasonal change in rainfall and that of the beetle populations. We also discussed the impacts of the strong droughts in 1994 and 1997-1998 caused by El Nino, and the degree of synchronization in the trends of the populations among the adjacent study sites.

Population Dynamics: New Approaches and Synthesis.

Introduction. N. Cappuccino, Novel Approaches to the Study of Population Dynamics. Observation and Comparative Approaches: P. Turchin, Population Regulation: Old Arguments and a New Synthesis. A.F. Hunter, Ecology, Life History and Phylogeny of Outbreak and Nonoutbreak Species. N. Cappuccino, H. Damman, and J.-F. Dubuc, Spatial Behavior and Temporal Dynamics of Outbreak and Nonoutbreak Species. M.J. Auerbach, E.F. Connor, and S. Mopper, Minor Miners and Major Miners: Population Dynamics of Leaf-Mining Insects. Mechanisms and Processes of Population Dynamics: R.F. Denno and M.A. Peterson, Density-Dependent Dispersal and its Consequences for Population Dynamics. S. Harrison and N. Cappuccino, Using Density-Manipulation Experiments to Study Population Regulation. I. Hanski and M. Kuussaari, Butterfly Metapopulation Dynamics. S.J. Walde, Internal Dynamics and Metapopulations: Experimental Tests with Predator-Prey Systems. J. Roland and P.D. Taylor, Herbivore-Natural Enemy Interactions in Fragmented and Continuous Forests. G. Dwyer, Simple Models and Complex Interactions. J.H. Myers and L. Rothman, Field Experiments to Study Regulation of Fluctuating Populations. M.C. Rossiter, Impact of Life History Evolution on Population Dynamics: Predicting the Presence of Maternal Effects. Case Studies: C. Solbreck, Long-Term Population Dynamics of a Seed-Feeding Insect in a Landscape Perspective. T. Ohgushi, Adaptive Behavior Produces Stability in Herbivorous Lady Beetle Populations. P.W. Price, T.P. Craig, and H. Roininen, Working Toward Theory on Galling Sawfly Population Dynamics. J.D. Reeve, M.P. Ayres, and P.L. Lorio, Host Suitability, Predation, and Bark Beetle Population Dynamics. G.E. Belovsky and A. Joern, The Dominance of Different Regulating Factors for Rangeland Grasshoppers. Conclusion: P.W. Price and M.D. Hunter, Novelty and Synthesis in the Development of Population Dynamics. Subject Index.

Population dynamics of a phytophagous lady‐beetle, Epilachna vigintioctopunctata (Fabricius), living in spatio‐temporally heterogeneous habitats. III. Effects of habitat structure on population dynamics

Temporal changes in the population size of a phytophagous lady-beetle were analyzed to identify mechanisms affecting lady-beetle population dynamics at different spatial scales. The study area (15 ha) included 18 habitat patches. The major host plants were potato for first generation larvae and eggplant for second generation larvae. The habitat patches were classified into three groups according to the major host plants in each patch: P-E patches (both host plants available), P patches (potato only), and E patches (eggplant only). The winter disappearance of adults in the whole study area, and larval mortality in E patches were apparently the most important factors disturbing the overall population density. Density-dependent movement of females appeared to have the greatest stabilizing effect on the yearly fluctuation of population density. Rate of increase of female adults from the first to the second generation, R, was generally higher on eggplants in E patches than in P-E patches because the adult density of the first generation was much higher in P-E patches. The yearly fluctuation of adult density in each generation tended to be less in patches with all habitat components necessary for the full life cycle (P-E patches). However, such patches were not favorable for first generation females, as indicated by the lower rate of increase from the first to the second generation. The density and stability of lady-beetle populations is discussed in relation to habitat structure.

PERENNIAL LEGUME GROUND COVERS INCREASE BENEFICIAL ARTHROPODS AND SUPPLY NITROGEN IN PECAN ORCHARDS

Perennial legumes ground covers were evaluated in pecan (Carya illinoinensis) orchards to supply nitrogen and increase beneficial arthropods. Ground covers were `Kenland' red clover (Trifolium pratense), `Louisiana S-1' white clover (Trifolium repens), a mixture of these two legumes, or bermuda grass (Cynodon dactylon), each in 5 ha plots. Nitrogen was applied at 0-200 kg·ha-1 N in 50 kg intervals to bermuda grass plots, and was omitted on the legumes. Aphids feeding on the legumes attracted lady beetles; however, lady beetle populations in the tree canopies were not affected by ground cover treatment. The most abundant lady beetle species in legumes were Coleomegilla maculata lengi (77%) and Coccinella septempunctata (13%); whereas, dominant species in tree canopies were Coleomegilla maculata lengi (33%). Olla v-nigrum (20%). Cycloneda munda (18%) and Coccinella septempunctata (15%). Several other beneficial arthropods were sampled in legumes and tree canopies. Aphid populations feeding on pecans were low (peak population ≈ 2 aphids/leaf), and not affected by ground cover treatment. Legumes supplied the equivalent of applying 68-156 kg·ha-1 N.

Effect of Transplantation Date on the Seasonal Abundance of the Green Peach Aphid (Homoptera: Aphididae) and Two Aphid Predators on Flue-Cured Tobacco

The effects of flue-cured tobacco transplantation date on the seasonal abundance of the green peach aphid, Myzus persicae (Sulzer), a stilt bug, Jalysus wickhami Van Duzee, and the convergent lady beetle, Hippodamia conoergens Guerin-Memeville, were investigated in south-central Virginia during 1979–1981. Tobacco was transplated ca. 10 days apart on three dates from 10 to 29 May 1979 and on five dates from 28 April to 9 June 1980 and 1981. Aphid populations were highest on the first two transplantings (10 and 20 May) in 1979, the first three (29 April, 9 and 19 May) in 1980, and the third and fourth (18 and 28 May) in 1981. Populations were lowest on late-transplanted tobacco. In 1981, tobacco transplanted on the first two dates matured 14 to 29 days earlier and, thereafter, had lower aphid populations than comparable treatments in 1979 and 1980. Populations usually declined on tobacco after topping (removal of terminal floral branch) was initiated. Lady beetle populations were closely related to aphid abundance in 1980, but the relationship was less distinct in 1981. Stilt bug populations peaked in all trans plantings during the first half of August, and they were significantly more abundant in the last two transplantings than the first three during the last half of August and early September. In 1980 and 1981 yields, returns (dollars per hectare), and values (dollars per kilogram) were similar for the first three trans plantings, but all were significantly reduced in the fourth and fifth transplantings during at least 1 year.

Soybean Cultural Practices: Effects on Populations of Geocorids, Nabids, and Other Soybean Arthropods

Arthropods were monitored in soybean, Glycine max L. Merrill, of early-, medium-, and late-maturity groups planted from April through July in several row spacings at four locations in Mississippi for 1 to 3 years. There were four major predator groups at each location: geocorids [mostly Geocoris punctipes (Say)], nabids ( Nabis spp.), lady beetles (Coccinellidae), and spiders. Geocorid, nabid, and spider populations gradually increased during the summer, but lady beetle populations peaked in midseason. Predator populations were not strongly affected by the three cultural practices: Geocorid, nabid, and spider populations (but not lady beetles) were higher in late-planted than in early-planted soybean; nabid populations (but not geocorids, lady beetles, and spiders) were higher in late-maturing than in early-maturing cultivars; and geocorid and spider populations (but not nabids and lady beetles) were higher in narrow- than in wide-row soybean. Predator population responses to cultural practices were generally similar to responses observed among the defoliating caterpillars. The effects of soybean cultural practices on phytophagous beetles and stink bugs are also discussed.

Insect management in deciduous orchard ecosystems: Habitat manipulation

Current literature pertaining to habitat manipulation of deciduous fruit and nut orchards for pest control is reviewed. The hypothesis of pesticide-induced pest problems in deciduous orchards as well as the changing pest population dynamics of deciduous orchards is discussed An experimental habitat manipulation program for pecans, utilizing vetch cover crops to enhance lady beetle populations for pecan aphid control is presented

Linear and Directional Effects in Predator Populations, Insect Damage, and Yield, Associated with Cotton Interplanted with Corn and Sorghum1

Predatory arthropods were collected from cotton interplanted with corn and sorghum. Collections were made on rows 1, 5, 9, 13, 17, and 21, as one moved away, both north and south, from the grain crops. Predators collected in the greatest numbers were lady beetles, lacewings, nabids, and hooded beetles, Notoxus monodon (F.). No linear or directional effects could be determined in conjunction with the total predator population. On Aug. 23 the lady beetle and lacewing populations exhibited a linear decrease as one moved away from the grain crops. The predator population and percent Heliothis damaged squares was greatest on the 1st row north of the grain crops. There was a significant difference in yield among the rows (5% level). The yield decreased as one moved away from the grain crops and 78% of this decrease could be attributed to linear effects. The drop in yield amounted to 2.27 lb of stripper cotton per sampling unit or 57.04 1b per acre.