The Influence of Exotic Lady Beetle (Coleoptera: Coccinellidae) Establishment on the Species Composition of the Native Lady Beetle Community in Missouri.

The diversity and abundance of native lady beetles (Coccinellidae) in North America has declined in recent decades. This decline is often correlated with the introduction and establishment of exotic lady beetle species, including Coccinella septempunctata L. and Harmonia axyridis Pallas, suggesting that exotic species precipitated the decline of native lady beetles. We examined species records of native coccinellids in Missouri over 118 yr and asked whether the species composition of the community experienced a shift following the establishment of the exotic species. We found that the contemporary native coccinellid community is different from the community that was present nearly a century ago. However, there was no evidence for a recent abrupt shift in composition triggered by the establishment of exotic species. Instead, our data suggest that the native lady beetle community has been undergoing consistent and gradual change over time, with some species decreasing in abundance and others increasing. While not excluding exotic species as a factor contributing to the decline of native lady beetle species, our findings suggest that other continuous factors, like land use change, may have played a more influential role in determining the composition of the native coccinellid communities within our region.

Effect of depth of flooding on the rice water weevil, Lissorhoptrus oryzophilus, and yield of rice.

The rice water weevil, Lissorhoptrus oryzophilus (Kuschel) (Coleoptera: Curculionidae), is a semi-aquatic pest of rice and is the most destructive insect pest of rice in the United States. Adults oviposit after floods are established, and greenhouse studies have shown that plants exposed to deep floods have more eggs oviposited in leaf sheaths than plants exposed to a shallow flood. Experiments were conducted in three mid-southern states in the USA to determine if the depth of flooding would impact numbers of L. oryzophilus on rice plants under field conditions. Rice was flooded at depths of approximately 5 or 10 cm in Arkansas in 2007 and 2008 and Louisiana in 2008, and at depths between 0-20 cm in Missouri in 2008. Plants were sampled three and four weeks after floods were established in all locations, and also two weeks after flood in Missouri. On all sampling dates in four experiments over two years and at three field sites, fewer L. oryzophilus larvae were collected from rice in shallow-flooded plots than from deep-flooded plots. The number of L. oryzophilus was reduced by as much as 27% in shallow-flooded plots. However, the reduction in insect numbers did not translate to a significant increase in rice yield. We discuss how shallow floods could be used as a component of an integrated pest management program for L. oryzophilus.

Distribution of the long-horned beetle, Dectes texanus, in soybeans of Missouri, Western Tennessee, Mississippi, and Arkansas.

The long-horned beetle, Dectes texanus LeConte (Coleoptera: Cerambycidae), is a stem-boring pest of soybeans, Glycine max (L.) Merrill (Fabales: Fabaceae). Soybean stems and stubble were collected from 131 counties in Arkansas, Mississippi, Missouri, and Tennessee and dissected to determine D. texanus infestation rates. All states sampled had D. texanus present in soybeans. Data from Tennessee and Arkansas showed sample infestations of D. texanus averaging nearly 40%. Samples from Missouri revealed higher infestation in the twelve southeastern counties compared to the rest of the state. Data from Mississippi suggested that D. texanus is not as problematic there as in Arkansas, Missouri, and Tennessee. Infestation rates from individual fields varied greatly (0-100%) within states. In Tennessee, second crop soybeans (i.e. soybeans planted following winter wheat) had lower infestations than full season soybeans. A map of pest distribution is presented that documents the extent of the problem, provides a baseline from which changes can be measured, contributes data for emergency registration of pesticides for specific geographic regions, and provides useful information for extension personnel, crop scouts, and growers.

Tarnished plant bug (Hemiptera: Miridae) thresholds and sampling comparisons for flowering cotton in the midsouthern United States.

The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), has become the primary target of foliar insecticides in cotton, Gossypium hirsutum L., throughout the Midsouth over the past several years. This prompted a reevaluation of existing action thresholds for flowering cotton under current production practices and economics. A trial was conducted at 19 locations throughout the Midsouth during 2006 and 2007. Threshold treatments ranged from a weekly automatic insecticide application to a very high threshold of 10 tarnished plant bugs per 1.5 row-m on a black drop cloth. Individually, all locations reached the lowest threshold, and eight locations had a significant yield loss from tarnished plant bugs. Across all locations, lint yield decreased 0.85 to 1.72% for each threshold increase of one tarnished plant bug per 1.5 row-m. Yield loss was most closely correlated to pest density during the latter half of the flowering period. The relationship between plant bug density or damage and yield was similar for drop cloth, sweep net, and dirty square sampling methods, but the correlations among these sampling methods were not high. Incorporating actual insecticide application data from the trial and average production and economic factors for Midsouth cotton, the economic threshold, if monitoring once per week, should be between 1.6 and 2.6 tarnished plant bugs per 1.5 row-m during the flowering period. More frequent monitoring or situations where insecticide applications are more efficacious may alter this threshold.

Tarnished plant bug (Hemiptera: Miridae) thresholds for cotton before bloom in the Midsouth of the United States.

Insecticide applications to control tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), during cotton, Gossypium hirsutum L., bud formation are common throughout the Midsouth of the United States. Cultivation practices and the pest complex have changed since action thresholds were established for this pest. A trial was conducted at 33 locations over 3 yr throughout the Midsouth to evaluate tarnished plant bug damage to cotton during the prebloom period. There was no consistent yield response to action thresholds, but average tarnished plant bug density and average square loss were both significant factors impacting lint yield. Based on the yield responses and application frequency of the various action thresholds, the best economic scenario occurred when tarnished plant bug density during the prebloom period averaged eight per 100 sweeps and square retention averaged 90%. The action thresholds required to achieve these averages are expected to be higher than these levels because pest pressure is not normally constant during the prebloom period. When insecticides are required, an application interval shorter than one week may be needed to obtain satisfactory control.

Allele frequency of resistance to Bacillus thuringiensis Cry1ab corn in Louisiana populations of sugarcane borer (Lepidoptera: Crambidae).

Transgenic Bacillus thuringiensis (Bt) corn, Zea mays L., has been widely used to manage a corn borer complex in the mid-southern region of the United States. The sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae), has become a dominant cornstalk boring species in some areas of this region, especially in Louisiana. Therefore, management of sugarcane borer resistance to Bt corn is critical to ensure the long-term sustainability of Bt corn for the region. This study screened 280 two-parent family-lines of sugarcane borer from four geographical populations in Louisiana during 2005 to determine whether Bt resistance allele frequency in sugarcane borer is sufficiently low to meet the rare resistance assumption of the current "high dose/refuge" resistance management strategy for Bt corn. These sugarcane borer family-lines were examined for Bt resistance by using novel F2 screening procedures. No major Bt resistance alleles were detected in these four populations. The estimated frequency of major Bt resistance alleles was < 0.0027, with a 95% probability and a detection power of 94%. The estimated minor resistance allele frequency was 0.0063, with a 95% CI of 0.0025-0.0117. During a previous study, a major Bt resistance allele was detected in one individual from 213 family-lines of another Louisiana population of sugarcane borer. Combining these data with the current screen, the frequency of major Bt resistance alleles across the five populations was 0.001, with a 95% credibility interval of 0.0001-0.0028 and a detection power of 95%. Major Bt resistance allele frequencies in Louisiana sugarcane borer populations seem to be low, and they should support the rare resistance allele requirement of the high dose/refuge strategy.