Studies were conducted across the southern United States to characterize the efficacy of multiple Bacillus thuringiensis (Bt) events in a field corn, Zea mays L., hybrid for control of common lepidopteran and coleopteran pests. Cry1F protein in event TC1507 and Cry1A.105 + Cry2Ab2 proteins in event MON 89034 were evaluated against pests infesting corn on above-ground plant tissue including foliage, stalks, and ears. Cry34Ab1/Cry35Ab1 proteins in event DAS-59122-7 and Cry3Bb1 in event MON 88017 were evaluated against the larvae of Mexican corn rootworm, Diabrotica virgifera zeae Krysan and Smith, which occur below-ground. Field corn hybrids containing Cry1F, Cry1A.105 + Cry2Ab2, Cry34Ab1/Cry35Ab1, and Cry3Bb1 insecticidal proteins (SmartStax) consistently demonstrated reductions in plant injury and/or reduced larval survivorship as compared with a non-Bt field corn hybrid. Efficacy provided by a field corn hybrid with multiple Bt proteins was statistically equal to or significantly better than corn hybrids containing a single event active against target pests. Single event field corn hybrids provided very high levels of control of southwestern corn borer, Diatraea grandiosella (Dyar), lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), and fall armyworm, Spodoptera frugiperda (J.E. Smith), and were not significantly different than field corn hybrids with multiple events. Significant increases in efficacy were observed for a field corn hybrid with multiple Bt events for sugarcane borer, Diatraea saccharalis (F.), beet armyworm, Spodoptera exigua (Hübner), corn earworm, Helicoverpa zea (Boddie), and Mexican corn rootworm. Utilization of field corn hybrids containing multiple Bt events provides a means for managing insect resistance to Bt proteins and reduces non-Bt corn refuge requirements.

The amount of Cry1Ac δ-endotoxin in transgenic Bacillus thuringiensis Berliner (Bt) or Bollgard cotton varies among commercial cultivars. These differences in expression have been correlated with survival levels in Lepidoptera, indicating that all Bollgard cultivars do not provide the same level of control. The objective of this study was to determine if differences in overall expression among commercial cultivars of Bollgard cotton were under simple genetic control. These findings could influence the way breeders select cultivars by evaluating for efficacy in insect control in addition to agronomic traits. Two sets of crosses were made in the greenhouse with cultivars that express the endotoxin at high and low levels. The parents and F 1 and F 2 generations were planted in the field. The amount of Cry1Ac was quantified using a commercial ELISA kit. Variances within the two F 2 breeding populations were highly significant because of genetic segregation for Cry1Ac expression. Using the modified Castle-Wright formula, the estimation of the number of contributing genes in both breeding populations was small. These data show that genetic background has a major effect on Cry1Ac expression. Because backcrossing is the primary method used by commercial cotton breeders, the selection and use of donor and/or recurrent parents that will result in a high level of Cry1Ac expression is crucial.

Studies were conducted across nine U.S. states, over 5 yr, to characterize the efficacy of transgenic corn (Zea mays L.) hybrids producing insecticidal proteins derived from Bacillus thuringiensis (Bt) for control of western corn rootworm, Diabrotica virgifera virgifera Le Conte. Hybrids tested had the same genetic background, contained one of two single events (DAS-59122-7 expressing Cry34Ab1/Cry35Ab1 or MON 88017 expressing Cry3Bb1) or a pyramid consisting of both rootworm-active events (SmartStax traits) and were compared with a non-Bt near isoline. Frequency analyses of root feeding data showed that hybrids containing both events sustained less root damage (0-3 node injury scale) than hybrids containing either event alone. The levels of root protection provided by MON 88017 and DAS-59122-7 were not different from each other. Efficacy was also evaluated based on consistency of protection, based on the proportion of plants with root ratings of either < or = 0.25 or < 1.00 on the node injury scale. The combination of two modes of action in SmartStax provided greater product consistency over a single mode of action at the 0.25 level and all hybrids producing Bt proteins provided equally high consistency at the 1.00 level. Overall these data show single and multiple mode of action hybrids provided high, consistent protection over the past 5 yr across the trial geography; however, pyramiding the rootworm Bt events provided greater and more consistent root protection. These findings also support that pyramided traits like SmartStax (Cry3Bb1 + Cry34Ab1/Cry35Ab1) remain a viable strategy for delaying resistance to either trait.

Cotton, Cossypium hirsutum L, plants expressing Cry1Ac and Cry1F (Phytogen 440W) insecticidal crystal proteins of Bacillus thuringiensis (Bt) Berliner, were evaluated against natural populations of tobacco budworm, Heliothis virescens (F.), and bollworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), across 13 southern U.S. locations that sustained low, moderate, and high infestations. The intrinsic activity of Phytogen 440W was compared with nontreated non-Bt cotton (PSC355) and with management strategies in which supplemental insecticides targeting heliothines were applied to Phytogen 440W and to PSC355 cotton. Infestations were composed primarily of bollworm, which is the least sensitive of the heliothine complex to Cry toxins. Therefore, damage recorded in these studies was primarily due to bollworm. Greater than 75% of all test sites sustained heliothine infestations categorized as moderate to high (10.6-64.0% peak damaged bolls in nontreated PSC355). Phytogen 440W, alone or managed with supplemental insecticide applications, reduced heliothine-damaged plant terminals, squares (flower buds), flowers, and bolls equal to or better (1.0-79.0-fold) than managing a non-Bt cotton variety with foliar insecticides across all infestation environments. Rarely (frequency of < or = 11% averaged across structures), sprayed Phytogen 440W reduced damaged structures compared with nontreated Phytogen 440W. Protection against heliothine-induced plant damage was similar across the three levels of infestation for each viable management strategy, with exception to damaged squares for nontreated Phytogen 440W. In situations of moderate to high heliothine infestations, cotton plants expressing Cry1Ac and Cry1F may sustain higher levels of damage compared with that same variety in low infestations. No significant difference in yield was observed among heliothine management strategies within each infestation level, indicating cotton plants may compensate for those levels of plant damage. These findings indicate Phytogen 440W containing Cry1Ac and Cry1F provided consistent control of heliothines across a range of environments and infestation levels.

Commercial field corn (Zea mays L.) hybrids transformed to express some or all of the lepidopteran insect-resistant traits present in SmartStax corn hybrids were evaluated for insecticidal efficacy against a wide range oflepidopteran corn pests common to the northern United States, during 2008 to 2011 at locations in 15 states. SmartStax hybrids contain a pyramid of two Bacillus thuringiensis (Bt) derived events for lepidopteran control: event TC1507 expressing Cry1F protein and MON 89034 expressing CrylA.105 + Cry2Ab2. These studies focused on characterization of the relative efficacy of each event when expressed alone or in combination, and compared with non-Bt hybrid. Corn hybrids containing pyramided insecticidal proteins Cry1F + Cry1A.105 + Cry2Ab2 (SmartStax) consistently showed reduced plant feeding damage by a wide range of lepidopteran larvae compared with single event and non-Bt hybrids. Corn hybrids expressing TC1507 or MON 89034 as single or pyramided events were consistently efficacious against Ostrinia nubilalis (Hübner). SmartStax hybrids had less injury from Agrotis ipsilon (Hufnagel) and Striacosta albicosta (Smith) than corn hybrids containing only event MON 89034 but were not more efficacious than single event TC1507 hybrids. Corn hybrids with event MON 89034 provided better control of Helicoverpa zea (Boddie), than event TC1507 alone. Spodoptera frugiperda (J.E. Smith) efficacy was higher for hybrids with pyramid events and single events compared with the non-Bt hybrids. The spectra of activity of events TC1507 and MON 89034 differed. The combination of TC1507 + MON 89034 provided redundant control of some pests where the spectra overlapped and thereby are expected to confer a resistance management benefit.

The petri dish method is an attractive alternative to the water bath method. Set-up is less complex, quicker, multiple jars of bed bugs can be fed at the same time, petri dishes of blood are disposable for easy clean-up and the potential of fatality due to flooding with blood or water is reduced.

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A complex of thrips species infests seedling stage cotton, Gossypium hirsutum (L.), in the southern United States. Preventive control tactics are recommended to manage early season infestations, but foliar insecticides may be necessary to prevent injury for the duration of seedling development. The objective of this work was to compare efficacy of spinetoram to that of spinosad and current standard products, and to define the minimum effective spinetoram rate for satisfactory control of thrips. Foliar applied insecticides were applied with and without a surfactant against varying thrips infestation levels in field plots. Results demonstrated that infestations comprised primarily of tobacco thrip, Frankliniella fusca (Hinds), were more sensitive to spinetoram than spinosad at equivalent rates of active ingredient. Spinetoram applied at 13.0 to 26.0 g a.i./ha provided control comparable to commercial standards under moderate infestation levels. Consistency and numerical increases in efficacy were observed when applying spinetoram (13.0 g a.i./ha) with a surfactant. Efficacy of spinetoram at 13.0 g a.i./ha in combination with a surfactant was confirmed against onion thrips, Thrips tabaci (Lindeman), and in commercial scale plots. Spinetoram alone was not adequate for managing extremely high (>269 fold greater than a threshold of one thrip per plant) populations of tobacco thrips. These experiments demonstrate that spinetoram, applied at 13.0 to 26.0 g a.i./ha, has utility in the management of thrips infesting cotton seedlings.