[Show abstract][Hide abstract] ABSTRACT: Attempts to establish Cotesia flavipes Cameron (Hymenoptera: Braconidae) in Louisiana sugarcane fields to control the sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae) have been unsuccessful. Experiments were conducted to investigate the feasibility of using an alternative larval host and host plants to overcome barriers preventing establishment. In addition, we evaluated C. flavipes' ability to search for D. saccharalis in sugarcane without above-ground internodes. Diatraea evanescens Dyar (Lepidoptera: Crambidae) was investigated as an alternative host for C. flavipes. Cotesia flavipes was reared for five generations on D. evanescens without any indication of diminishing fitness as measured by days to parasite pupation and average cocoon mass weight. However, there was a significant reduction in percent parasitism, cocoon mass weight, and percent emergence when C. flavipes parasitized D. evanescens as compared with D. saccharalis, resulting in a 75% reduction in the gross reproductive rate (R0
). Greenhouse studies indicated little difference in parasitism of D. saccharalis on the weed hosts johnsongrass, Sorghum halepense (L.), and vaseygrass, Paspalum urvillei Steud. However, when planted as refuge plots, we found it difficult to establish infestations of D. saccharalis in either of these hosts, or in two energy sugarcanes. After 3 yr of infesting host plants and releasing parasitoids only one parasitized D. saccharalis larvae was recovered within the johnsongrass refuge. Diatraea evanescens readily established in vaseygrass; however, these larvae appear inaccessible to C. flavipes. In contrast, parasitism of D. saccharalis by C. flavipes infesting young sugarcane was 30%.
[Show abstract][Hide abstract] ABSTRACT: A 2-year field cage experiment was conducted in Beaumont, Texas to estimate parasitism of sugarcane borer, Diatraea saccharalis (F.), by Cotesia flavipes (Cameron) on rice. A lab experiment showed that the number of hosts parasitized per female per day reached a maximum (0.961) at 28°C. Parasitized larvae recovered from the field experiment produced an average of 27.9±19.1 (x¯±s.d.) parasitoids, with a 2.57:1 (female/male) sex ratio. A cohort-based age-structured model was developed to simulate the population dynamics and economic impact of sugarcane borer and C. flavipes in rice, as affected by overwintering larval density, timing and rate of parasitoid aerial release, and year-to-year climate (temperature and rainfall). The results suggest the cumulative seasonal damaging larval density (3rd or later instars) is negatively correlated with winter temperature, while maximum parasitoid density and maximum proportion parasitized are positively correlated with the cumulative seasonal damaging larval density. C. flavipes was most effective when released 40 or 50days after rice planting, with simulated yield loss reduced by up to 50.9% when the release rate was 10 females and 4 males m−2. The maximum simulated economic benefit ($59.48ha−1) is ca. 6.7% of that provided by insecticide-based control, which occurred when the release rate was 1 female and 0.4 males m−2. The inability of C. flavipes to provide economic control in temperate-subtropical areas is due to its high rearing cost, a low effective search rate, a low maximum number of hosts parasitized per female, and failure of the spring emerging parasitoids to find hosts.
Biological Control 02/2011; 56(2):159-169. DOI:10.1016/j.biocontrol.2010.10.005 · 1.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Sugarcane (Saccharum spp.) in Louisiana is colonized by two aphid species, the sugarcane aphid, Melanaphis sacchari (Zehntner), and the yellow sugarcane aphid, Sipha flava (Forbes) (Hemiptera: Aphididae). The main problem associated with M. sacchari is transmission of sugarcane yellow leaf virus, a casual agent of yellow leaf disease whose absence has been added to certification standards for micropropagated sugarcane in Louisiana. Greenhouse studies were conducted to categorize dominant commercial sugarcane cultivars for their ability to tolerate aphid injury and to express antixenotic or antibiotic effects on both aphid species. Antixenosis tests showed no preference among cultivars by either aphid species. Loss of chlorophyll content in tolerance tests also did not show differences among cultivars for both aphid species. However, antibiosis tests revealed that life history parameters such as the duration of the reproductive period and fecundity of both aphid species were negatively affected on 'HoCP 91-555' compared with 'L 97-128'. Estimation of demographic statistics indicated that both aphid species exhibited a significantly lower intrinsic rate of increase (1.8-2.8-fold) and longer doubling time (1.7-3.1-fold) on HoCP 91-555 relative to L 97-128. From these tests, cultivars in the current study can be ranked from most to the least susceptible as L 97-128 > 'LCP 85-384' > 'HoCP 96-540' > 'Ho 95-988' > HoCP 91-555 for M. sacchari and L 97-128 > LCP 85-384 > HoCP 91-555 for S. flava. Therefore, antibiosis is an important category of resistance in sugarcane to both aphid species, and HoCP 91-555 might provide useful germplasm for developing aphid resistant cultivars.
[Show abstract][Hide abstract] ABSTRACT: Extensive ecological studies have been conducted on insects inhabiting native stands of smooth cordgrass, Spartina alterniflora Loisel; however, this is not the case for insects found in smooth cordgrass in a nursery habitat. We investigated species composition and larval disposition among stemborers (Lepidoptera: Coleophoridae and Crambidae) infesting stems of smooth cordgrass in nursery plots. One thousand and forty stems of smooth cordgrass were randomly selected in 2003 and examined for presence of stemborer larvae. Height of larvae on or within stem, height of stem from ground level to top-visible dewlap, and condition of the leaf-whorl were documented. Stemborers representing six species of Lepidoptera were recovered. These species were Blastobasis graminea Adamski (Lepidoptera: Coleophoridae); a four-species complex comprised of Diatraea saccharalis (F.), Chilo demotellus Walker, Chilo plejadellus Zincken, and Thaumatopsis probably actuella Barnes & McDunnough (Lepidoptera: Crambidae); and Donacaula probably unipunctella Robinson (Lepidoptera: Crambidae). Larvae were generally on different parts of the stem and, with the possible exception of larvae of the four-species complex, seemed unlikely to contact one another. Blastobasis graminea was the most abundant species collected ( n = 128; 52%) and was located at the base of the stem (eq x eqx- = 6.7 ± 5.4 cm). The four-species complex was the next most abundant (n= 85; 35%) and was always found within the stalk about mid-way up the stem (eqx= 16.7± 8.6 cm). Donacaula sp. was the least abundant species (n= 32; 13%) and was always found in the tight leaf-whorl just above the stem meristem (eq x = 23.6 ± 15.4 cm). A total of 544 (52%) of the stems sampled had a dead leaf-whorl, but only 140 (26%) were infested. Stemborer species did not significantly affect the number of plants with and without deadhearts.
[Show abstract][Hide abstract] ABSTRACT: The leafminer, Elachista saccharella (Busck) (Lepidoptera: Elachistidae) was found in Louisiana on 12 Jul 2006 and documented as a new distribution record for Louisiana. The leafminer was found in 17 of 20 sugarcane producing parishes surveyed. Although distributed generally throughout the sugarcane growing region, only 11% of the stalks sampled (n = 1600) were infested and 69% of the samples collected were parasitized. The lesions made by the leafminer constituted only 3% of the total leaf area, and were usually detected on older leaves deep within the canopy. For these reasons, it does not appear that E. saccharella will be an economic threat to sugarcane in Louisiana.
[Show abstract][Hide abstract] ABSTRACT: This research assesses the potential for using different economic injury thresholds in management of a key insect pest on susceptible and resistant commercially produced cultivars of sugarcane (Saccharum spp. hybrids). In a 2-yr sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae), study involving four commercially produced sugarcane cultivars and four insecticide treatment thresholds, 'LCP 85-384' and 'HoCP 91-555' were the most susceptible based on percentage of bored internodes compared with the more resistant 'HoCP 85-845' and 'CP 70-321'. In 2001, the 10% infested stalks threshold was not as effective as the 5% early season-10% late season and 5% full season for HoCP 91-555. Based on D. saccharalis injury under natural infestation conditions, susceptible cultivars seem to require a lower infestation threshold than the more resistant cultivars to achieve adequate injury reduction. Among yield components, only the theoretical recoverable sugar per stalk was significantly increased by applying insecticides. With the resistant HoCP 85-845, differences were not detected for percentage of bored internodes among treated versus untreated management regimes. The resistant HoCP 85-845 had higher levels of fiber in our study; however, no clear pattern on resistance mechanisms was established, because the resistant cultivar CP 70-321 had comparatively low levels of fiber. The development of cultivar-specific thresholds is expected to lower the amount of insecticide used for D. saccharalis management in the sugarcane industry, reduce selection pressure, and delay the development of insecticide resistance.
[Show abstract][Hide abstract] ABSTRACT: Recent discoveries of Blastobasis graminea Adamski (Lepidoptera: Coleophoridae) in Mexico have prompted interests that this insect pest, originally discovered in South America, may be moving northward. A survey in Texas and Louisiana was conducted in 2002 to determine if B. graminea has extended its range into the U.S. Surveys included five nights of blacklight trapping in Texas and three nights of blacklight trapping plus diurnal surveys of 23 fields in Louisiana. Field surveys in Louisiana included examination not only of sugarcane (interspecific hybrids of Saccharum spp.) but also of maize, Zea mays L., and sorghum, Sorghum bicolor (L.) Moench, as well as non-cultivated gramineous species. We did not collect B. graminea during blacklight trappings nor did we detect it in association with cultivated host species (i.e., sugarcane, maize, and sorghum). We did, however, discover B. graminea in smooth cordgrass, Spartina alterniflora Loisel., in Louisiana in a non-agricultural environment. Finding B. graminea only in cordgrass suggests the possibility that rather than expanding its geographic range, B. graminea may be a widespread tropical species that is expanding its host range from native grasses to sugarcane. Finding B. graminea in Louisiana represents a new U.S. record for the species. Also, from this survey, new U.S. hosts records for Pyroderces badia (Hodges) (Lepidoptera: Cosmopterigidae) and Dicymolomia julianalis (Walker) (Lepidoptera: Crambidae), moths reared from grain sorghum seedheads, are documented.
[Show abstract][Hide abstract] ABSTRACT: After 15 failures to establish Cotesia flavipes (Cameron) as a parasitoid of the sugarcane borer, Diatraea saccharalis (F.), in Louisiana sugarcane fields (Saccharum spp.), four release refuges were established as sites for an intensive study of the crop, host, and parasitoid interaction for a full crop cycle. These refuges were maintained with minimal disturbance from June 2001 to June 2002 to encourage the establishment of C. flavipes. Refuges were managed in a manner such that (1) sugarcane borer larvae were abundant, (2) predation of parasitoids by the red imported fire ant, Solenopsis invicta (Buren), was minimized, (3) host and parasitoid were not exposed to insecticide applications used to control economically damaging sugarcane borer infestations, (4) presence of parasitoids was insured through repeated releases during the growing season, and (5) the sugarcane was not harvested to enhance overwintering opportunities for C. flavipes. C. flavipes was successfully recovered in all established refuges and overwintered in three of the four refuges. However, parasitoids were not collected during May of the following spring. The inability of the parasitoid to use first-generation sugarcane borer larvae seems to be a major limiting factor preventing establishment of C. flavipes in Louisiana sugarcane. In May, the sugarcane stalks have not formed internodes, which may preclude important host finding and host acceptance cues such as frass and silk in the tunnel entrance. Although efforts were made to suppress the red imported fire ant at the study sites, ant predation on C. flavipes was also a major factor limiting establishment.
[Show abstract][Hide abstract] ABSTRACT: The sugarcane aphid, Melanaphis sacchari (Zehntner) was found in Louisiana on 9 September 1999 and documented as a new record and potential pest for the state. The aphid was found in 8 of 21 sugarcane growing Parishes that were surveyed in Louisiana, indicating the pest is already widely distributed across Louisiana. The coccinellid Diomus terminatus Say was identified as one several biological control organisms attacking the aphid in Louisiana.