David B. Orr

Effect of Insecticides on Trichogramma exiguum (Trichogrammatidae: Hymenoptera) Preimaginal Development and Adult Survival

Abstract The effect of insecticides on Trichogramma exiguum Pinto & Platner emergence, adult survival, and fitness parameters was investigated. Insecticides tested were lambda cyhalothrin, cypermethrin, thiodicarb, profenophos, spinosad, methoxyfenozide, and tebufenozide. All insecticides, with the exception of methoxyfenozide and tebufenozide, adversely affected Trichogramma emergence from Helicoverpa zea (Boddie) host eggs when exposed at different preimaginal stages of development (larval, prepupal, or pupal). Regardless of the developmental stage treated, none of the insecticides tested had a significant effect on the sex ratio or frequency of brachyptery of emerged females. However, the mean life span of emerged T. exiguum females significantly varied among insecticide treatments, and was significantly affected by the developmental stage of parasitoid when treated. Based on LC50 values, spinosad and prophenofos were the most toxic compounds to female T. exiguum adults, followed by lambda cyhalothrin, cypermethrin, and thiodicarb. Insecticides field-weathered for four to 6 d on cotton leaves showed no activity against female T. exiguum adults.

Trichogramma Nontarget Impacts: A Method for Biological Control Risk Assessment

For much of its history, insect biological control has enjoyed a reputation as an environmentally safe and effective means of managing insect pests (DeBach 1974, Doutt 1972, Caltagirone 1981). However, over the past 15 years, questions have been raised regarding the potential impact of biological control on nontarget organisms (Howarth 1983, 1991; Simberloff 1992; Lockwood 1993a, b; Simberloff and Stiling 1996; Lockwood 1997). These concerns have prompted a much-needed discussion regarding the potential for nontarget effects and approaches for addressing this issue (Carruthers and Onsager 1993, Duan and Messing 1997, Van Driesche and Hoddle 1997, Frank 1998, Simberloff and Stiling 1998). Most of the discussion has focused on the risks posed by the importation and release of exotic natural enemies against exotic pests, i.e., classical biological control. Far less attention has been paid to the potential for nontarget effects from augmentative releases of natural enemies, even though this form of biological control may become more widespread in the future (Hoy et al. 1991, Moffat 1991, Parrella et al. 1992, Nordlund and Greenberg 1994, Nordlund et al. 1998).

Biological Control and Integrated Pest Management

The manipulation of beneficial organisms remains a very important tool in integrated pest management programs of insect pests worldwide. This chapter describes the approaches to using biological control and a historical perspective of each. Recent developments in genetics, systematics, population dynamics, pesticide chemistry, and public opinion have led to increased scrutiny and inclusion of beneficial insects into IPM programs. This chapter describes these developments and the variety of approaches that have been used to implement biological control as a useful tactic in IPM. It also describes how biological control interacts with other IPM tactics, and the potential for better integration into IPM programs.

Trichogramma releases in North Carolina cotton: why releases fail to suppress heliothine pests.

Abstract Field studies were conducted in 1996 and 1997 to determine the fate of naturally oviposited F3 heliothine eggs in cotton plots treated with augmentative releases of Trichogramma exiguum Pinto & Platner and nontreated plots. Four cohorts of newly oviposited eggs (<24 h old) were followed in 1996 and two cohorts in 1997. In 1996, mean ± SD percent parasitism, estimated by in-field studies following the fate of naturally oviposited eggs, ranged from 7 ± 7 to 61 ± 8% in T. exiguum release plots and 0 ± 0 to 35 ± 13% in control plots. The mean ± SD percent of eggs hatched in T. exiguum release plots ranged from 1 ± 2 to 11 ± 4% and 7 ± 4 to 28 ± 10% in control plots. In 1997, mean ± SD percent egg parasitism ranged from 27 ± 4 to 40 ± 3% in T. exiguum release plots and 15 ± 18 to 25 ± 8% in control plots. The mean ± SD percent of eggs hatched in T. exiguum release plots ranged from 7 ± 3 to 12 ± 2% and 18 ± 6 to 28 ± 8% in control plots. Despite increased parasitism and reduced egg hatch in T. exiguum release plots, overall, there was no significant difference in larval density (all instars combined) between T. exiguum release and control plots. Combined analysis of the heliothine larval populations and egg fate data revealed that the additional egg mortality produced by released T. exiguum was offset by lower larval mortality in release plots. Because of the occurrence of compensatory mortality, the egg stage of heliothines is not an appropriate target for biological control using Trichogramma wasp releases.

Comparative Feeding and Development of Pseudoplusia includens (Lepidoptera: Noctuidae) on Kudzu and Soybean Foliage

Abstract Kudzu, Pueraria montana (Lour.) Merr. variety lobata (Willd.) Maesen & Almeida, a close relative of soybean, Glycine max (L.) Merr., is an adventive and widely distributed weed in the southeastern United States. Conventional wisdom says that native arthropods do not feed heavily on kudzu, but recent evidence has indicated this is not the case. To better understand the interaction of kudzu and native insects, the biology of the soybean looper, Pseudoplusia includens (Walker), was compared on kudzu and soybean. Insects fed on kudzu had higher mortality, longer development times with supernumerary molts, and lower pupal weights than those fed on soybean. Rearing for up to three generations on either plant host had an effect on length of development time but did not affect other measured parameters. Foliage consumption did not differ between treatments, and nutritional quality of soybean and kudzu did not differ. The instar at which insects were transferred from artificial diet to either kudzu or soybean significantly influenced development time, number of instars, foliage consumption, and pupal weights, with instar 4 being the optimum stage for transfer. In an oviposition test, females readily oviposited on kudzu in a no choice test, but when both kudzu and soybean were provided, more eggs were deposited on soybean than on kudzu. Our studies show that although kudzu is an acceptable host, soybean is a preferred and better quality host.

Trichogramma exiguum (Hymenoptera: Trichogrammatidae) Releases in North Carolina Cotton: Evaluation of Heliothine Pest Suppression

Abstract Field studies were conducted in 1996 and 1997 to reevaluate the use of augmentative releases of Trichogramma wasps for heliothine management in cotton. In 1996, nine releases of Trichogramma exiguum Pinto & Platner, spaced 3–4 d apart, were made into three 0.4-ha cotton plots. Six weekly releases were made in 1997, each containing two T. exiguum cohorts developmentally staggered by 45°C degree-days. Field release rates, estimated from laboratory and field quality control data, averaged 108,357 T. exiguum ♀♀ per hectare per cohort per release in 1996 and 193,366 ♀♀ per hectare per cohort per release in 1997. In 1996, mean ± SD adult emergence under laboratory conditions for released cohorts was 92 ± 7%; 62 ± 5% of emerged adults were females, 3 ± 2% of females displayed brachyptery (nonfunctional wings), mean female longevity under laboratory conditions was 15 ± 4 d, and mean ± SD field emergence was 97 ± 2%. Quality control measurements were similar in 1997. In 1996, mean ± SD percent parasitism of heliothine eggs in field plots on the sampled dates ranged from 67 ± 4 to 83 ± 5% in T. exiguum release plots and 25 ± 9 to 55 ± 8% in control plots. In 1997, parasitism levels ranged from 74 ± 4 to 89 ± 5% in T. exiguum release plots and 18 ± 18 to 69 ± 11% in control plots. Despite increased parasitism levels in T. exiguum release plots, there were no significant differences in density of fifth instars, boll damage, or yield between T. exiguum release and control plots. Therefore, it is concluded that Trichogramma augmentation is not an effective heliothine management tool in North Carolina cotton.

Overwintering Refuge Sites for Megacopta cribraria (Hemiptera: Plataspidae)

Megacopta cribraria F. (Hemiptera: Plataspidae) was first reported in the United States near Atlanta, Georgia, in fall 2009 (Suiter et al. 2010, J. Integr. Pest Manag. 1: 1–4) and has since spread throughout the southeastern United States (http:// www.kudzubug.org/distribution_map.cfm). In Asia and the United States, it is commonly associated with its preferred host plant, kudzu, Pueraria montana Lour (Merr.) var. lobata (Willd.) (Fabales: Fabaceae) (Medal et al. 2013, Fla. Entomol. 96: 631–633). Nonetheless, M. cribraria has emerged as a significant pest of soybean, Glycine max (L.) Merrill and may damage a few other legumes in the United States (Eger et al. 2010, Insecta Mundi 0121: 1–11; Hu and Carroll 2012, htpp://agfax.com/2012/05/18/Alabama-soybean-kudzubugs-making-their-move/). In Georgia and South Carolina, yield losses in untreated soybean fields averaged 18% and ranged up to 59.6% (Greene et al. 2012, United Soybean Board, Chesterfield, MO; Seiter et al. 2012, J. Econ. Entomol. 106: 1676–1683). Apart from being odoriferous, crushed nymphs have reportedly caused skin rashes, thereby raising health concerns for workers in soybean fields (Ruberson et al. 2013, Appl Entomol Zool. 48: 3–13). Megacopta cribraria is also viewed as a nuisance pest in fall through spring when adults aggregate on or around homes to overwinter, apparently close to kudzu patches (Eger et al. 2010, Insecta Mundi 0121: 1–11; Ruberson et al. 2013). Little is known about the biology and ecology of M. cribraria in North America. Prominently, we do not understand their behavior and population dynamics when host plants are not available, as in the winter. Knowledge of the overwintering behavior and biology of this species could inform surveillance and management. This study was undertaken to identify overwintering refuge areas preferred by M.

Evaluation of a Commercially Available Beneficial Insect Habitat for Management of Lepidoptera Pests

A field study was conducted in 2003 and 2004 at the Center for Environmental Farming Systems in Goldsboro, NC, to evaluate the effectiveness of a commercially available beneficial insect habitat in decreasing pest caterpillar populations in organically managed tomato, Lycopersicon esculentum Mill., plots. Six pairs of tomato plots were established and a commercial beneficial insect habitat seed mix (Peaceful Valleys Good Bug Blend) transplanted around the perimeter of treatment plots, whereas a brown-top millet, Brachiaria ramose (L.) Stapf., border was planted around control plots. Egg predation, egg parasitism by trichogrammatid wasps, and larval parasitism by braconid wasps was monitored throughout the growing season to determine whether habitat increased their activity. In both years of this study, the density of Helicoverpa zea (Boddie) and Manduca spp. eggs was not significantly different between treatment and control plots. Although parasitism was the most important component of egg mortality (19-49%), parasitism was not significantly different between habitat types. Identifiable predation was a minor component (3-9%) of egg fate; it is possible that unidentified predation may be part of the approximately 35-52% of eggs that met unknown fates. Larval parasitism levels ranged from approximately 10 to 90% but was not significantly influenced by the presence of beneficial insect habitat in either year of the study. These results demonstrate that natural enemy activity in organic tomatoes was not amplified, and pest populations were not reduced by the presence of a commercially available beneficial insect habitat.

Insect Communities Associated with Beneficial Insect Habitat Plants in North Carolina

Abstract This study recorded the arthropod communities present in three commercially available beneficial insect habitat seed mixes (Peaceful Valley’s Good Bug Blend, Clyde Robin’s Border Patrol, and Heirloom Seed’s Beneficial Insect Mix) and three commonly grown cut flower/herb plantings (Zinnia, Celosia, and fennel). Communities were sampled three ways: (1) foliar and floral collections were made using a D-Vac and aerial nets, and insects were identified to family and assigned to feeding groups; (2) pitfall traps were used to collect ground beetle and ground-dwelling spider populations; and (3) evening observations recorded visits by noctuid (Lepidoptera: Noctuidae) and hawk moths (Lepidoptera: Sphingidae) to flowers. Overall, Good Bug Blend had the highest abundance and diversity of beneficial parasitoids, predators, and ground beetles. However, along with Border Patrol, it also harbored the highest diversity and abundance of crop-feeding herbivores. The Border Patrol plantings had the highest diversity and abundance of insect herbivore crop pests and the highest number of feeding visits by pest moth species during evening observations. The moth visits were most likely caused by the presence of evening primrose in this mix that blooms at dusk when moths are most active. Celosia harbored the greatest diversity and abundance of predators and parasitoids in the cut flower/herb plots. Fennel had the lowest overall abundance and diversity of all the plantings, but this may have been caused by late summer flowering.

Attraction of insect natural enemies to habitat plantings in north carolina

Two studies were conducted to evaluate the relative attractiveness of floral habitats that may provide nectar and pollen food resources to natural enemies of agricultural insect pests in North Caro...