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The article presents a research study, which examines if tarnished plant bug (TPB) control complaints are due to its resistance to acephate. Furthermore, it evaluates the acephate use rates for farm performance. It relates that TPB is a key pest of cotton production in Louisiana with a reported significant tolerance to acephate. On the other hand, the study reveals that 80% control was observed in the field efficacy tests but only 50% mortality was observed at the highest dosage of acephate. The dose glass vial bioassays shows that about 96% of the plant bug population could be resistant to acephate.

A laboratory bioassay was developed for testing tarnished plant bug populations for resistance development to the neonicotinoid insecticides imidacloprid and thiamethoxam. The bioassay allows for the determination of LC50 values by feeding known doses of the insecticides to adult tarnished plant bugs in a honey-water solution. Field populations of plant bugs from several locations in the mid-South were tested with the oral bioassay for resistance to imidacloprid in 2005 and 2006. Resistance to imidacloprid increased 2.46-fold on average in 2006 as compared to 2005. Thiamethoxam was first used in the oral bioassay to test field populations of plant bugs in 2006. The data collected in both years with both insecticides will provide a basis for comparison to determine changes in resistance in future resistance monitoring studies. [ABSTRACT FROM AUTHOR]

A survey was conducted in August and September 2006 in which tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois), were collected from wild hosts near cotton and tested for resistance to acephate with a glass-vial bioassay. Plant bug populations from twenty locations in the Mississippi River Delta and ten locations in the "hills" of Mississippi were tested. Eighteen populations from the Delta and five from the hills were found to have elevated resistance to acephate as indicated by three-fold or higher resistance as compared to a susceptible population. This was a large increase in the number of locations with elevated resistance in the Delta as compared to 2005. At the same locations in 2005, only six of the populations had elevated resistance to acephate. The average LC50 value for acephate for the 20 Delta locations went from 6.8 μg/vial in 2005 to 16.1 μg/vial in 2006 which was a 2.4-fold increase in one year. Adults from a population found in cotton near Vance, MS that had 7.1-fold resistance to acephate were tested by caging them on cotton treated with commercial insecticides. Mortalities in treatments with acephate at 0.5 and 1.0 lbs AI/acre at 48 h after treatment were 33 and 23%, respectively. Mortalites in treatments with dicrotophos (0.5 lbs AI/acre), and thiamethoxam (2 oz/acre) were 88 and 95%, respectively. These results showed that the plant bug population from Vance could not be controlled with acephate. Plant bug populations from all thirty sample locations will be tested in 2007 to again determine their insecticide resistance. [ABSTRACT FROM AUTHOR]

Multiple experiments were conducted on cotton in Mississippi to investigate control of insecticide resistant tarnished plant bugs. Experiments that controlled native vegetation during the early spring with a single herbicide application reduced tarnished plant bug numbers in cotton and increased economic returns for growers in the herbicide treated areas. Another experiment demonstrated the benefits of planting an early season cotton variety (Deltapine 444 BR) versus a later season cotton variety (Deltapine 555 BR). Deltapine 444 BR reached cutout approximately one week earlier than Deltapine 555 BR and required two fewer foliar applications with insecticides for tarnished plant bugs. Several insecticide screening studies showed that foliar control with currently registered insecticides ranged from 17 to 71 percent control and control with experimental insecticides ranged from 34 to 57 percent control. In an experiment investigating application intervals, plant bug control approached 100 percent when two applications were made four or five days apart while 70 and 20 percent control was seen when the applications were made six and seven days apart, respectively. Rotation with alternative chemistries was shown to improve control of tarnished plant bugs compared to multiple applications with organophosphates. Plots treated with two applications of Orthene (0.5 lb ai/A) five days apart reached threshold before plots treated with Orthene (0.5 lb ai/A) followed by Centric (2 oz./A). Spray coverage was shown to significantly influence plant bug control. Tarnished plant bug control was higher on okra-leaf cotton than on normal leaf cotton and with hollow cone nozzles than with air induction nozzles. Temik, applied as a side dress at first flower, reduced plant bug numbers for up to 20 days. Based on these experiments, no one method will provide adequate control of resistant tarnished plant bugs in flowering cotton including foliar insecticides. Therefore, growers and consultants will need to consider alternative strategies integrated with foliar applications to prevent economic losses from tarnished plant bugs. [ABSTRACT FROM AUTHOR]

The tarnished plant bug, Lygus lineolaris, has become a serious pest because of the widespread adoption of Bt cotton and resistance development to synthetic insecticides. Previous reports indicated that the tarnished plant bug developed a metabolic resistance to permethrin and malathion through increased gene expression of a cytochrome P450 and an esterase. Glutathione S-transferase (GST) is another important metabolic enzyme for detoxification and resistance development to malathion. To understand resistance mechanisms and to develop resistance management strategies, we compared GST enzyme activity between susceptible and resistant strains, and examined if the GST inhibitors synergized malathion toxicity through suppression of the GST activity. Results showed that the resistant strain had significantly higher GST enzyme activity than a susceptible strain. GST inhibitors significantly suppressed GST activity and substantially increase susceptibility to malathion in the resistant bugs. [ABSTRACT FROM AUTHOR]

A survey was conducted in August and September 2005 to measure tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois), and resistance to acephate with a glass-vial bioassay. Plant bug populations collected from wild hosts near cotton fields from twenty locations in the Delta region of Mississippi and ten locations in the hills region of Mississippi were tested. A population near Crossett, AR was used as a standard susceptible population to which collected populations were compared for relative resistance. Six populations from the Delta and four from the hills were found to have elevated resistance to acephate as indicated by three-fold or higher resistance ratios as compared to a susceptible population. Adults from a population found near Rolling Fork, MS that had 3.6-fold resistance to acephate were tested by caging them on cotton treated with commercial insecticides at labeled rates. Mortalities in treatments with acephate at 0.5 and 1.0 lbs AI/acre at 48 h after treatment were 39 and 48%, respectively. Mortalities in treatments with dicrotophos (0.5 lbs AI/acre), cyfluthrin (0.033 lbs AI/acre) and oxamyl (0.33 lbs AI/acre) were 44, 25, and 20%, respectively. These results showed that the plant bug population from Rolling Fork had resistance to three different classes of insecticides high enough to cause control failures in the field. Plant bug populations from all thirty sample locations will be tested in May and August-September of 2006 to again determine their insecticide resistance. [ABSTRACT FROM AUTHOR]

Overwintering tarnished plant bug adults, Lygus lineolaris (Palisot de Beauvois), were collected near Stoneville, MS, from henbit, Lamium amplexicaule L., or plant debris during December 2003 and January 2004 and dissected to determine their reproductive status. Diapause in adults collected from henbit was broken during December, and most males and females were reproductive by the end of December. Adults collected from plant debris were in a more intense diapause which was broken during January, and most adults were reproductive by the end of January. Previous research showed that in winters when henbit bloomed in December through March new generation adults were produced on henbit by mid-March. In the current study, a cold period from mid-January through mid-February stunted henbit and new generation adults were not produced on henbit until April. This new generation produced in April resulted from adults that overwintered in plant debris along with any surviving adults that overwintered on henbit. These adults utilized henbit that began to regrow and bloom in late-February along with other hosts that bloomed in March and April. Our results again showed that the tarnished plant bug has an overwintering population with two intensities of diapause. This enabled the tarnished plant bug to produce new generation adults in March and April in warm winters in the mid-South. In winters with cold periods that kill or stunt winter hosts, the part of the population that breaks diapause in January is better able to survive and produce new generation adults in April. The tarnished plant bug is well adapted to its winter habitat in the mid-South. [ABSTRACT FROM AUTHOR]

Reproductive diapause in the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), was studied by dissection of field collected adults or adults reared from field collected nymphs in 1999-2001 near Stoneville in Washington County, MS. The critical photoperiod for diapause induction was about 12.5:11.5 (L:D) h, or 12 September. Overwintering adults collected from winter host plants in December 1999 and 2001 began breaking diapause in the second and third weeks of December at a day length near 10:14( L:D) h. Most of the overwintering females collected on winter host plants had mature eggs by the end of December in both winters. In the winters of 1998-1999 and 1999-2000, tarnished plant bug nymphs were found in January and produced an early new generation of adults by the second or third weeks of March. In these mild winters, host plants were not killed or stunted by cold weather. In the cold winter of 2000-2001, nymphs were not found until March with new generation adults produced in April. The effects of diapause on control of tarnished plant bugs by non-insecticidal methods which could be developed are discussed. [ABSTRACT FROM AUTHOR]

Broadleaf weeds found in marginal areas by fields, roads, and ditches were controlled with the herbicides Trimec® or Strike 3™ in nine-square-mile areas of the Mississippi Delta in March or April of 1999, 2000, and 2001. These weeds serve as early season food and reproductive hosts for tarnished plant bugs and population buildups occur on these weeds prior to movement of plant bugs into cotton. Cotton fields in the treated areas and in untreated nine-square-mile areas were sampled for tarnished plant bugs weekly during June and July of all three years. Overall mean numbers of tarnished plant bug adults and nymphs were significantly lower in cotton in the treated areas. The average reduction in overall mean numbers of plant bugs was 45.5 and 47% for adults and nymphs, respectively, for the three-year period. Grower costs for insecticides used to control plant bugs were lower in cotton in the treated test sites in all three years. Elimination of broadleaf weeds was found to be an effective method for reducing numbers of plant bugs in cotton. However, it did not reduce numbers of tarnished plant bugs in any year to a level in cotton where additional control with insecticides was not needed. [ABSTRACT FROM AUTHOR]