Crop Protection 48 (2013) 57e62

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Crop Protection

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Transgenic Bt corn varietal resistance against the Mexican rice borer, loftini (Dyar) (: ) and implications to

Allan T. Showler a,*, Steven C. Cook b, Veronica Abrigo a a USDA-ARS IFNRRU, Kika de la Garza Subtropical Agricultural Research Center, 2413 East Highway 83, Bldg. 201, Weslaco, TX 78596, USA b USDA-ARS Honeybee Lab, Kika de la Garza Subtropical Agricultural Research Center, Weslaco, TX 78596, USA article info abstract

Article history: The Mexican rice borer, (Dyar), attacks crops including corn, Zea mays L., rice, Oryza sativa Received 19 November 2012 L., , Sorghum bicolor (L.) Moench, and sugarcane, spp. Strongly resistant varieties of Received in revised form any kind, native or otherwise, have not been identified. A field plot corn variety test using two transgenic 29 January 2013 Bt varieties, Pioneer 31G71, expressing the Cry1F insecticidal protein, and Golden Acres 28V81, Accepted 9 February 2013 expressing the Cry1A.105, Cry2Ab2, and Cry3Bb1 insecticidal proteins, and two non-Bt controls, Dekalb DKC 69-72 and BH Genetics 9050, all four commonly grown in the Lower Rio Grande Valley of , Keywords: showed that, although oviposition preference was not affected, 28V81 resisted larval stalk boring to the Bacillus thuringiensis Cultivar extent that Mexican rice borer injury was almost non-existent. Pioneer 31G71 was infested nearly as z Integrated pest management much as the controls, but larval development to adulthood was reduced by 70%. Rearing larvae on 5, Saccharum 50, 500, and 5000 mg of corn leaf tissue per ml of artificial diet showed that, while the three lowest Trap crop concentrations did not affect larval growth and development, the high concentration of 28V81 reduced Variety survivorship to the pupal stage, decreased weight of 4-wk-old larvae, and prolonged development to Zea mays pupation. Lower numbers of trap-captured adults at the edges of commercial Bt and non-Bt corn fields showed that populations were lower at the Bt cornfields, suggesting a lesser rate of adult production. Because corn is a preferred host plant over sugarcane, sorghum or rice, use of resistant transgenic Bt corn varieties will likely protect the crop from the substantial injury that can be caused by the pest. This study also suggests that Bt genes might result in similarly strong resistance when inserted in other vulnerable crops such as sugarcane. Published by Elsevier Ltd.

1. Introduction leaf tissue before boring into host plant stalks where the later instars tunnel vertically and horizontally (Van Zwaluwenberg, 1926; The invasive Mexican rice borer, Eoreuma loftini (Dyar) (Lepi- Legaspi et al., 1997), resulting in stunting, lodging, reduced juice doptera: Crambidae), originally from western Mexico (Van quality, and “dead hearts” (dead whorl center) (Legaspi et al., 1997). Zwaluwenberg, 1926; Johnson, 1984), is a stem boring pest which Larvae are exposed on the exterior of the sugarcane plant, and was first detected in the United States on sugarcane, Saccharum judging from the small diameter entry holes on corn, Zea mays L., for spp., of the Lower Rio Grande Valley, Texas, in the early 1980s only a day or two before boring into the host plant’s stalk, and the (Johnson, 1981; Johnson and Van Leerdam, 1981). Since then, the tunnels are packed with frass, protecting larvae from chemical and Mexican rice borer has become the dominant stem boring biological control tactics (Legaspi et al.,1997; Wilson et al., in press). pest of sugarcane (Youm et al., 1988; Legaspi et al., 1997), repre- Unlike sugarcane and sorghum, Sorghum bicolor (L.) Moench, which senting >95% of the total sugarcane stem borer population (Legaspi tend to resist lodging better than corn, infestations in susceptible et al., 1999). varieties of corn frequently result in stalk lodging, shattering, and Mexican rice borers mainly oviposit within folds of dry host plant collapse, each of which prevent the production of harvestable ears. leaves (Showler and Castro, 2010b), and early instars feed on green Larvae pupate within the stalks and adults emerge from corre- spondingly larger holes than the entry holes. In the Lower Rio Grande e e * Corresponding author. Tel.: þ1 830 792 0319; fax: þ1 830 792 0314. Valley, the life cycle requires 30 45 d, and there are 4 5 overlapping E-mail address: [email protected] (A.T. Showler). generations/yr (Legaspi et al., 1997; Showler and Reagan, 2012).

0261-2194/$ e see front matter Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.cropro.2013.02.007 58 A.T. Showler et al. / Crop Protection 48 (2013) 57e62

By 1987, the Mexican rice borer’s range expanded from the Table 1 Lower Rio Grande Valley to encompass 40 counties in South Texas; Bt corn varieties and the pests against which they are registered. by 1989, the pest invaded rice producing areas of East Texas Variety Pests

(Browning et al., 1989), and by 2008 it was detected in western Common name Scientific name rice producing areas (Hummel et al., 2008, 2010). The ’ Pioneer 31G71 Black cutworm Agrotis ipsilon Hufnagel pest has been predicted to infest all of Louisiana s sugarcane and HX1 gene Corn earworma Heliothis zea (Boddie) rice growing areas by 2035 (Reay-Jones et al., 2008). Mexican rice European corn borer Ostrinia nubilalis Hübner borers, however, have recently been found to prefer corn over Fall armyworm Spodoptera frugiperda J.E. Smith sugarcane by as much as 8.2-fold (based on numbers of borer entry Lesser corn stalk borer Elasmopalpus lignosellus (Zeller) Southern corn stalk borer Diatraea crambidioides (Grote) holes on the stalks), and this suggests that Mexican rice borers Southwestern corn borer Diatraea grandiosella Dyar might have already spread into corn producing regions, and that Sugarcane borer Diatraea saccharalis (F.) hitherto noninfested areas of Texas, Louisiana, and possibly other Western bean cutworm Loxagrotis albicosta Smith states, might already be infested or at risk of infestation (Showler Golden Acres Corn earworm Heliothis zea (Boddie) et al., 2011). Similarly, in the Republic of , the eldana 28V81 Corn rootworm Diabrotica spp. VT3Pro gene European corn borer Ostrinia nubilalis Hübner borer, Eldana saccharina Walker, which also prefers corn over Fall armyworm Spodoptera frugiperda J.E. Smith sugarcane (Cochereau, 1982), was detected well outside sugarcane DKC 69-72 None growing regions (Assefa et al., 2008). Keeping et al. (2007) reported (non-Bt) that Bt corn did not deter eldana borer larvae from boring into BH Genetics None 9050 (non-Bt) stalks, but significantly fewer adults emerged than from non Bt a corn, making the Bt variety a “dead end” trap crop. “Suppression” only. The purpose of this study was to assess the resistance of vari- eties of Bt corn versus non-Bt corn varieties that are commonly 50 stalks were counted. On the same day, five randomly selected grown in the Lower Rio Grande Valley, Texas (where the Mexican stalks from each plot were cut at the base, stripped of leaves, di- rice borer is the predominant pest of sugarcane), but are not ameters 5 cm above the soil surface were recorded, as were necessarily isolines, with the aim of both protecting corn as well as numbers of internodes; Mexican rice borer entry holes, bored in- for identifying a possible source of resistance if applied to ternodes (determined by splitting the stalks to observe tunneling), sugarcane. and exit holes per stalk, and numbers of injured stalks. Treatment differences were detected using ANOVA with treatment and block 2. Materials and methods effects and a treatment block interaction in the model, and means were separated using Tukey’s HSD (Analytical Software, 1998). 2.1. Small plot field experiment Because normality and homogeneity of variance assumptions were not violated, data was not transformed in this experiment and in A 0.46-ha field at the USDA-ARS Kika de la Garza Subtropical the other experiments unless stated otherwise. Agricultural Research Center in Weslaco, Hidalgo County, Texas, was divided into eight blocks (replicates) with four plots in each 2.2. Excised dry leaf oviposition preference experiment block; each block was separated from the others by a 2-m bare buffer “alley”. Plots were 8 rows wide (8.5 m) and 15.25 m long Thirty dry leaves, each z20 cm long and from the lower third of (0.013 ha). Four treatments were randomly assigned to each plot a separate corn stalk, were excised from individual, randomly within each block and each block contained all four treatments. selected corn plants in each of the four field plot experiment Treatments were comprised of different corn varieties, each of treatments. Two leaves of each variety, each pre-inspected to which was commonly grown in the Lower Rio Grande Valley of ensure absence of eggs, were suspended in random order from the Texas where the Mexican rice borer is the key pest of sugarcane tops of 15.40 cm 40 cm 40 cm Plexiglass containers and five (Legaspi et al., 1997). Two of the varieties were Bt varieties and two newly-emerged adult male and five female Mexican rice borers were non-Bt varieties (controls). The Bt varieties were Pioneer were released into each container. After 7 d, the leaves were 31G71 with the HX1, Herculex 1 Insect Protection gene expressing removed from the containers and egg clusters and eggs were the Cry1F insecticidal protein (Pioneer Hi-Bred International, counted. Treatment differences for egg clusters and eggs were Johnston, IA) and Golden Acres 28V81 with the VT3Pro gene detected using one-way ANOVA (Analytical Software, 1998). expressing the Cry1A.105, Cry2Ab2, and Cry3Bb1 insecticidal pro- teins (Golden Acres, Waco, TX), and the controls were Dekalb DKC 69-72 (Monsanto, Chesterfield, MO) and BH Genetics 9050 (BH 2.3. Larval effects experiment Genetics, Ganado, TX). Although the Bt corn varieties are registered as being resistant to other pests of corn (Table 1), neither had been Five meridic foods, modified after Vanderzant (1974) were used assessed for efficacy against the Mexican rice borer. The seed was in laboratory bioassays. Each food consisted of a base diet having planted on 7 March 2011 z15 cm apart by a conventional me- added wither cellulose powder (control), or a mixture of cellulose chanical planter. Weeds were controlled by mechanical cultivation powder and lyophilized, powdered leaf material from each one of when the plants were still short, and removed manually when the the four corn varieties (treatment foods). The base diet was pre- corn plants were 60 cm tall. Conventional fertilizer and irrigation pared according to Martinez et al. (1988). One hundred ml of the practices were used. base diet was placed in a preheated (70 C) blender carafe and, for On 15 April and 18 July 2011, numbers of corn stalks were each of the treatment foods the powdered corn plant tissue was counted on two separate 3-m-long sections of row in each plot. On added to obtain 5, 50, 500, and 5000 mg per ml of base diet. Each 15 April, 50 consecutive corn stalks (beginning >5 stalks from the combination, and the control, was mixed at high speed for 1 min end of each row to avoid edge effects), were counted, and the first using a separate preheated carafe. Two ml of the final mixture of and fiftieth stalks were marked with plastic flagging. On 18 July, each food treatment was poured into each of 32 wells of 128-well when the crop was ready for harvest, numbers of total stalks and bioassay trays. The trays were covered with paper towels and non-yielding stalks (e.g., lodged, shattered, or collapsed) within the allowed to cool and harden for 24 h at room temperature. A.T. Showler et al. / Crop Protection 48 (2013) 57e62 59

Using a fine camelhair paintbrush, neonate Mexican rice borer per 3 m row on 14 April, by 18 July, only 58% and 58.5% of the stalks larvae were individually placed in the diet-filled wells. The wells were producing ears in 9050 and 69-72, respectively (F ¼ 11.94; were sealed with aerated bioassay tray covers, and the trays were df ¼ 7, 63; P < 0.0001), but in the 31G71 and 28V81 treatments kept in an incubator at 27 C, 75% RH, and on a 12:12 L:D photo- 87.7% and 99.1% of the stalks produced ears. Of the 50 consecutive cycle. Larvae were checked after 24 h to ascertain mortality from stalks counted in April, 50.8% and 40.4% failed to produce ears of handling. Neonates were allowed to feed on the diet for 2 wk, then corn in 9050 and 69-72, respectively, but 31G71 and 28V81 only the diet “plug” was gently removed from each well and examined lost production from 16.4% to 2.2% of the stalks, respectively for evidence of feeding (e.g., piles of debris on the surface, and (Table 2). Numbers of stalks that were producing ears in the 9050 tunneling into the diet). Numbers of surviving larvae were counted and 69-72 treatments were only 49.1% and 59.5%, respectively, of at the ends of wk 2, 3, and 4. Larvae were transferred by paintbrush the 50 original stalks (F ¼ 13.3; df ¼ 7, 63; P < 0.0001), but the from the diet to a scale for weighing at the end of the 4th wk, then numbers found in the 31G71 and 28V81 plots were 83.6% and they were placed on freshly prepared food in wells of clean bioassay 99.75% of the original number and a difference between the Bt trays, covered, and returned to the environmental chamber until varieties was not detected. larvae pupated. Numbers of pupae in each treatment were counted. At harvest, treatment differences between stalk diameters and There were seven replicates per treatment; each replicate was numbers of internodes per stalk were not detected (Table 3), but comprised of three larvae (each one in a separate container). the numbers of stalks with one or more Mexican rice borer- Because of mortality, there were five replications in the 5000 mg/ml injured internodes in 31G71 and 28V81 corn were 36% and 28V81 diet treatments at the ends of wks 3 and 4, and after pu- 97.3% less than in the controls (F ¼ 30.78; df ¼ 3, 31; P < 0.0001) pation. For larval weights and for determining time to pupation, (Table 3). Numbers of bored internodes per stalk were reduced by there were only enough larvae at the end of 4 wk for three repli- 99.1% in 28V81 corn but differences were not detected between cates in the high 28V81 concentration. Data across all treatments 31G71 and the controls (Table 3). Larval entry holes per stalk were and times was analyzed using ANOVA and means were separated 99% fewer on 28V81 than on the controls, but statistical differ- using Tukey’s HSD (Analytical Software, 1998). Percentages were ences between 31G71 and the other three varieties were not arcsine-square root-transformed before analysis. detected (Table 3). Exit holes, however, were reduced by z67.4% in 31G71, and no exit holes were found in 28V81 corn stalks 3. Results (Table 3).

3.1. Small plot field experiment 3.2. Excised dry leaf oviposition preference experiment Forty one percent and 46% of the stalks in the susceptible 9050 and 69-72 varieties, respectively, were non-yielding because the Treatment differences were not detected for numbers of stalks were lodged, shattered, or collapsed, but only 12.7% and 0.9% Mexican rice borer egg clusters and for numbers of eggs. The pooled of the stalks failed to produce ears in the 31G71 and 28V81 plots, averages for number of egg clusters and number of eggs per leaf respectively (Table 2). Compared with the number of stalks counted was 0.87 0.17 and 4.9 0.9, respectively.

Table 2 Mean numbers of corn stalks/3 m row, and numbers of corn stalks that did not produce ears of corn because of lodging, shattering, and collapse, Hidalgo County, Texas, USA, 2011.

Varietya Bt versus No. stalks/3 m row No. non-yielding stalks/3 m row No. non-yielding stalks of 50 stalksc non-Bt 15 April 18 July Mean (SE) Mean (SE) Mean (SE) Mean (SE) 9050 Non-Bt 21.1 (0.4) 20.9 (0.4) 8.6 (2.0) ab 25.4 (5.0) a 69-72 Non-Bt 22.5 (0.7) 21.5 (1.2) 9.9 (2.4) a 20.2 (5.1) ab 31G71 Bt 21.9 (0.2) 21.6 (0.2) 2.7 (1.3) bc 8.2 (3.9) bc 28V81 Bt 21.6 (0.3) 21.4 (0.2) 0.2 (0.1) c 1.1 (0.5) c Fb 1.59 0.51 9.58 8.09 P 0.2226 0.6943 0.0003 0.0009

Means within the same column followed by different letter are significantly different (P < 0.05), Tukey’s HSD. a BH Genetics 9050, DKC 69-72, Pioneer 31G71, Golden Acres 28V81. b df ¼ 3, 31, n ¼ 8 replicates. c The 50 stalks were consecutive, counted on 14 April, the data shown was collected 18 July.

Table 3 Mean stalk diameters and numbers of internodes and Mexican rice borer damage per corn stalk, n ¼ 5 stalks/plot, Hidalgo County, Texas, USA, 18 July 2011.

Varietya Stalk diam (cm)b No. internodes No. bored internodes No. entry holes No. exit holes

Mean (SE) Mean (SE) Mean (SE) Mean (SE) Mean (SE) 9050 2.7 (0.1) 13.0 (0.1) 2.28 (0.25) a 5.12 (0.34) a 1.40 (0.21) a 69-72 2.7 (0.1) 13.0 (0.1) 2.15 (0.21) a 4.82 (0.78) a 1.38 (0.17) a 31G71 2.7 (0.1) 13.1 (0.1) 1.30 (0.44) a 2.52 (0.89) ab 0.45 (0.20) b 28V81 2.7 (0.1) 13.0 (0.1) 0.02 (0.02) b 0.05 (0.05) b 0 (0) b Fc 0.41 0.47 12.61 11.96 14.41 P 0.7538 0.7094 0.0001 0.0001 <0.0001

Means within each column followed by different letters are significant (P < 0.05), Tukey’s HSD. a BH Genetic 9050 (non-Bt), DKC 69-72 (non-Bt), Pioneer 31G71 (Bt), Golden Acres 28V81 (Bt). b 5 cm above soil surface. c df ¼ 3, 31. 60 A.T. Showler et al. / Crop Protection 48 (2013) 57e62

3.3. Larval effects experiment 10 Control a At the high rate (5000 mg corn leaf tissue per ml artificial diet) of 9050 ¼ DKC6972 28V81 there were 68.6% fewer pupae than in the control (F 4.22; 8 31G71 df ¼ 19, 133; P < 0.0001). The three low rates of corn tissue did not 28V81 b affect larval weights after 4 wk, but the high rate of 31G71 was bc bc associated with 47.4% lower weight than the control, and larval 6 weight on 28V81 was 87.2% less than on 31G71 (F ¼ 12.92; df ¼ 4, c 30; P < 0.0001) (Fig. 1). Similarly, the numbers of weeks until pu- pation were not influenced by the three lowest rates, but at the high 4 rate, 31G71 was associated with a 37.5% longer development time

than the control, and 28V81 was associated with a 32.6% longer Weeks to pupation development time than in the 31G71 high rate treatment 2 (F ¼ 20.29; df ¼ 4, 27; P < 0.0001) (Fig. 2). 0 4. Discussion Fig. 2. Mean (SE) numbers of week until pupation by larval Mexican rice borers Our field experiment demonstrated that Mexican rice borers reared on artificial diet incorporated with 5000 mg of corn leaf tissue per ml diet, one- ’ e can cause substantial damage to susceptible varieties of corn. In way ANOVA, Tukey s HSD (5 7 replicates, 3 larvae per replicate). regions that have large populations of Mexican rice borers, such as the Lower Rio Grande Valley, the insect’seconomicimpactagainst et al., 1994) and US$10e20 million annually throughout the re- locally grown corn varieties should be assessed. Varieties of Bt gion (Legaspi et al., 1997, 1999). Larval tunneling also provides corn grown in 2009 accounted for 63% of the United States’ portals for red rot, Colletotrichum falcatum Went, infection, which 22 million ha of corn (Hutchinson et al., 2010); our results suggest results in the breakdown of sugar (Van Zwaluwenberg, 1926; that, where the Mexican rice borer is present, Bt varieties will Osborn and Phillips, 1946). Both the Mexican rice borer and the likely constitute the first and greatest defense. The extent of eldana borer cause more damage to sugarcane that is drought tunneling injury to the susceptible corn varieties used in our study stressed or provided with excessive nitrogen fertilizer, indicating precludes growing them for economic profit unless the crop is their orientation toward host plant nutritional quality, particularly adequately protected by one or more cultural, chemical, and in terms of nitrogenous and carbohydrate biochemicals (Showler biological tactics. and Reagan, 2012). In many parts of Africa, the eldana borer is a severe pest of Our study demonstrated that the expression of resistance by sugarcane (Girling, 1972; Atkinson and Carnegie, 1989; Keeping and transgenic Bt corn against the Mexican rice borer closely resembled Meyer, 2002), and although there are a number of differences be- that found against the eldana borer in corn producing Bt Cry1Ab tween the eldana borer and the Mexican rice borer, other aspects toxin (Keeping et al., 2007). That variety did not affect oviposition are similar (Showler and Reagan, 2012). Unlike the sugarcane borer, preference and was as infested with eldana borers as the non-Bt Diatraea saccharalis (F.), which was displaced in the Lower Rio control (Keeping et al., 2007). Similarly, our study showed that, Grande Valley by the arrival of the Mexican rice borer (Van Leerdam statistically, 31G71 was not different from the controls either, but et al., 1984; Legaspi et al., 1997), the eldana and Mexican rice borers the mean numbers of bored internodes and total numbers of larval are cryptic, inserting their eggs in tight folds and curls of leaf tissue entry holes were substantially lower (by z40% and z48%, (Showler and Castro, 2010b), and blocking larval tunnels with frass, respectively) than on the controls; levels of injury were highly posing challenges to chemical and biological control (Legaspi et al., variable between the 31G71 plots. Because of the observed vari- 1997; Showler and Reagan, 2012). The insect’s prevalence and the ability and lower numbers of larval entry holes, and because 31G71 extent of its injury make it the key sugarcane pest of South Texas curtailed 70% of adult emergence, 31G71 is not as effective for (Legaspi et al., 1997). The pest damages z20% of the sugarcane trapping Mexican rice borers as the South African variety was for internodes in that region, causing losses of US$575/ha (Meagher eldana borers (Showler and Reagan, 2012). Ideal dead end trap cultivars would be as attractive, or more so, compared with sus- ceptible varieties, and stalks would be tolerant to shattering, lod- ging, and stalk rot diseases to extend the effectiveness of each plant 60 a Control (Showler and Reagan, 2012) while reducing adult emergence as 9050 DKC6972 much as 28V81. Because a Bt Cry1Ab variety reduced the survival of 50 ab ab 31G71 the sugarcane borer to nearly zero, it was suggested as a trap crop 28V81 for that pest (McAllister et al., 2004). 40 In the excised dry leaf experiment, we observed no oviposition preference between the varieties, but 28V81 was almost b 30 completely resistant to larval boring. Larval entry holes in the other three varieties were found almost exclusively on the six lowermost internodes, but on 28V81 what appeared to be whitish larval 20 feeding “tracks,” 1 cm in length each, scarred the outermost tissue Larval weight (mg) without penetrating the stalk. Because adult Mexican rice borers 10 c deposited eggs on 28V81, the basis of resistance appears to be antibiotic rather than antixenotic. Hence, 28V81 is also a suitable 0 trap plant for Mexican rice borer eggs with negligible risk to the stalk. Our observation that only artificial diet incorporated with the Fig. 1. Mean (SE) weights of 4-wk-old Mexican rice borer larvae reared on artificial diet incorporated with 5000 mg of corn leaf tissue per ml diet, one-way ANOVA, highest concentration of Bt-corn tissue interfered with larval Tukey’s HSD (5e7 replicates, 3 larvae per replicate). development and survival indicates that the Bt toxin must be A.T. Showler et al. / Crop Protection 48 (2013) 57e62 61 available in relatively substantial concentrations to be effective. Acknowledgments Because the Bt-corn plants in the field were not diluted by artificial diet, effects against Mexican rice borer larvae were apparent. The We thank Carlos Gracia, Jaime O. Cavazos, Eloy Rodriguez, Elias larval diet assay also demonstrated that percentage larval survival P. Showler, Andy Cruz, Jaime Luna, Martín Galvan, Tony Bautista, to pupation is reduced by Bt-corn tissue to a greater extent in and John Adamczyk. 28V81 than in 31G71. The greater reduction in 4-wk-old larval weight by 28V81 than by 31G71, and the low survivorship and References longer time needed for pupation on the 28V81 diet show that the Bt toxin in 28V81 was more deleterious to larval development. This Analytical Software, 1998. Statistix for Windows. Analytical Software, Tallahassee, FL. helps to explain the strong reduction in adult emergence holes in Assefa, Y., Conlong, D.E., Van den Berg, J., Le Rü, B.P., 2008. The wider distribution of our field-grown 28V81 corn, decimating the next generation of Eldana saccharina (Lepidoptera: ) in South Africa and its potential risk e Mexican rice borer at the larval stage before the crop is injured. to production. Proc. S. Afr. Sugar Technol. Assoc. 81, 290 297. Atkinson, P.R., Carnegie, A.J.M., 1989. Population dynamics of the sugarcane Adoption of corn that is as resistant to Mexican rice borers as 28V81 borer, Eldana saccharina Walker, in Natal, South Africa. Bull. Entomol. Res. on an area-wide basis might have area-wide implications in terms 79, 61e80. of reducing overall populations of the pest. Browning, H.W., Way, M.O., Drees, B.M., 1989. Managing the Mexican rice borer in Texas. Tex. Agric. Ext. Serv. Bull. B-1620 All four varieties used in our study could each serve as trap crops Carnegie, A.J.M., 1981. Combating Eldana saccharina Walker, a progress report. Proc. to divert Mexican rice borers away from sugarcane, but 31G71 and S. Afr. Sugarcane Technol. Assoc. 48, 107e110. the controls would likely need to be destroyed before they Cochereau, P., 1982. Observations on the borer Eldana saccharina Walker (Lep., Pyralidae) in maize and sugarcane in Ivory Coast. Proc. S. Afr. Sugarcane contributed toward the production of adults developing within the Technol. Assoc. 49, 82e84. stalks. Growing 28V81, and varieties with similarly high levels of Girling, D.J., 1972. Eldana saccharina Wlk. (Lepidoptera: Pyralidae), a pest of sug- resistance to Mexican rice borers, commercially within the regional arcane in East Africa. Proc. Int. Soc. Sugarcane Technol. 14, 429e434. fi Huang,F.,Parker,R.,Leonard,R.,Yong,Y.,Liu,J.,2009.Frequencyofresistance agricultural landscape, intermingled with sugarcane elds might be alleles to Bacillus thuringiensis-corn in Texas populations of the sugarcane the best way of “deploying” corn as a dead end trap crop to protect borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae). Crop Prot. 28, the sugarcane. Perhaps the most obvious possibility to emerge from 174e180. our results, however, is development of sugarcane varieties with Bt Hummel, N.A., Reagan, T.E., Pollet, D., Akbar, W., Beuzelin, J.M., Carlton, C., Saichuk, J., Hardy, T., Way, M.O., 2008. Mexican Rice Borer, Eoreuma loftini resistance to the Mexican rice borer similar to that of 28V81 corn. (Dyar). Louisiana State University AgCenter Pub. 3098, Baton Rouge, LA. Insertion of a Bt gene, for example, that is as protective of sugarcane Hummel, N.A., Hardy, T., Reagan, T.E., Pollet, D., Carlton, C., Stout, M.J., Beuzelin, J.M., fi against the Mexican rice borer as the VT3Pro gene found to be in Akbar, W., White, W.H., 2010. Monitoring and rst discovery of the Mexican rice borer, Eoreuma loftini (Lepidoptera: Crambidae) in Louisiana. Fla. Entomol. 93, 28V81 corn might provide a cornerstone tactic for sugarcane in- 123e124. tegrated pest management in areas where the Mexican rice borer is Hutchinson, W.D., Burkness, E.C., Mitchell, P.D., Moon, R.D., Leslie, T.W., problematic. Fleischer, S.J., Abrahamson, M., 2010. Areawide suppression of European corn borer with Bt maize reaps savings to non-Bt growers. Science 330, Currently there is no integrated strategy in place for Mexican 222e225. rice borers in corn, but integrative tactics are being developed for Johnson, K.J.R., 1981. Acigona loftini (Lepidoptera: Pyralidae) in the Lower Rio protecting sugarcane, some of which are already being used for Grande Valley of Texas, 1980e1981. In: Proc. 2nd Inter-American Sugar Cane Seminar (Insect and Rodent Pests), Miami, FL, pp. 166e171. eldana borer control in parts of Africa (Showler and Reagan, 2012). Johnson, K.J.R., Van Leerdam, M.B., 1981. Range extension of Acigona loftini into the Because both species are more attracted to drought stressed than to lower Rio Grande Valley of Texas. Sugar Azucar 76, 119. well-watered sugarcane, irrigation sufficient to avoid water deficit- Johnson, K.J.R., 1984. Identification of Eoreuma loftini (Dyar) (Lepidoptera: Pyr- alidae) in Texas, 1980: forerunner for other sugarcane boring pest immigrants associated nutritional increases, and heightened infestations of the from Mexico? Bull. Entomol. Soc. Am. 30, 47e52. two pests, has been recommended (Carnegie, 1981; Keeping and Keeping, M.G., Meyer, J.H., 2002. Calcium silicate enhances resistance of sugarcane Meyer, 2002; Reay-Jones et al., 2005; Showler and Castro, 2010a). to the African stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae). e In the Republic of South Africa, reduction of nitrogen fertilizer to Agric. For. Entomol. 4, 265 274. Keeping, M.G., Rutherford, R.S., Conlong, D.E., 2007. Bt-maize as a potential trap 30 kg/ha is recommended to minimize eldana borer problems in crop for management of Eldana saccharina Walker (Lep., Pyralidae) in sugar- sugarcane (Carnegie, 1981), especially during periods of water cane. J. Appl. Entomol. 131, 241e250. deficit stress (Keeping and Meyer, 2002). Relatively high concen- Legaspi, J.C., Legaspi Jr., B.C., Irvine, J.E., Saldana, R.R., 1997. Mexican rice borer, Eoreuma loftini (Lepidoptera: Pyralidae) in the Lower Rio Grande Valley of trations of organic matter amended to soil in the Lower Rio Grande Texas: its history and control. Subtrop. Plant Sci. 49, 53e64. Valley (and fertilized with nitrogen as per convention) resulted in Legaspi, J.C., Legaspi Jr., B.C., Irvine, J.E., Meagher Jr., R.L., Rozeff, N., 1999. Stalkborer 18% more stalk production per sugarcane stool, but this effect was damage on yield and quality of sugarcane in the Lower Rio Grande Valley of Texas. J. Econ. Entomol. 92, 228e234. offset by substantially increased Mexican rice borer infestation, Martinez, A.J., Baird, J., Holler, T., 1988. Mass Rearing Sugarcane Borer and Mexican causing reductions in stalk weight, length, and percentage brix Rice Borer for Production of Parasites Allorhoga pyrophagus and Rhaconotus relative to sugarcane with conventional nitrogen fertilizer or roslinensis. USDA-ARS-PPQ, APHIS 83-1. McAllister, C.D., Bischoff, D.P., Gravois, K.A., Schexnayder, H.P., Reagan, T.E., 2004. chicken litter (ATS, unpublished data). Although sugarcane vari- Transgenic Bt-corn affects sugarcane borer in Louisiana. Southwest. Entomol. eties that are partially resistant to Mexican rice borers were better 29, 263e269. protected than susceptible varieties under drought conditions, Meagher Jr., R.L., Smith Jr., J.W., Johnson, K.J.R., 1994. Insecticidal management of fi z Eoreuma loftini (Lepidoptera: Pyralidae) on Texas sugarcane: a critical review. water de cit nevertheless increased injury by 2.5-fold to sus- J. Econ. Entomol. 87, 1332e1344. ceptible and resistant cultivars (Reay-Jones et al., 2005); hence, the Osborn, H.T., Phillips, G.R., 1946. Chilo loftini in California, , and Mexico. in fluence of water deficit stress, and excessive nitrogen, on the J. Econ. Entomol. 39, 755e759. efficacy of resistant Bt corn varieties (e.g., 28V81) should be Reay-Jones, F.P.F., Showler, A.T., Reagan, T.E., Legendre, B.L., Way, M.O., Moser, E.B., 2005. Integrated tactics for managing the Mexican rice borer (Lepidoptera: assessed. Crambidae) in sugarcane. Environ. Entomol. 34, 1558e1565. Although some stalkborers might become resistant to Bt corn Reay-Jones, F.P.F., Wilson, L.T., Reagan, T.E., Legendre, B.L., Way, M.O., 2008. Pre- varieties (Huang et al., 2009), the level of resistance we dicting economic losses from the continued spread of the Mexican rice borer (Lepidoptera: Crambidae). J. Econ. Entomol. 101, 237e250. observed in 28V81 against the Mexican rice borer offers a Showler, A.T., Castro, B.A., 2010a. Influence of drought stress on Mexican rice borer valuable tool for integrated pest management. 28V81 minimized (Lepidoptera: Crambidae) oviposition preference and development to adult- loss of stalks and accompanying ears, making it a strong tactic hood in sugarcane. Crop Prot. 29, 722e727. Showler, A.T., Castro, B.A., 2010b. Mexican rice borer (Lepidoptera: Crambidae) capable of providing nearly complete protection against the oviposition site selection stimuli on sugarcane, and potential field applications. Mexican rice borer. J. Econ. 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