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We compared the effects of floral nectar from buckwheat, Fagopyrum esculentum Moench, and honeydew produced by the soybean aphid, Aphis glycines Matsumura (Homoptera: Aphididae), on longevity, nutrient levels, and egg loads of the parasitoid Diadegma insulare Cresson (Hymenoptera: Ichneumonidae). Diadegma insulare lived for 2 days in control treatments of water or clean soybean leaves, for 6-7 days with honeydew, and in excess of 2 weeks with buckwheat nectar. Potential reasons for the superiority of buckwheat nectar over soybean aphid honeydew for extending the longevity of parasitoids include: (i) parasitoids ingest more sugars from floral sources, (ii) oligosaccharides in honeydew have a lower nutritional value than nectar sugars, and (iii) honeydew has antagonistic compounds. Overall sugar levels were lower in honeydew- vs. nectar-fed female wasps, suggesting a lower feeding rate, but other explanations cannot be excluded. Diadegma insulare eclosed with high levels of lipids and glycogen, and low levels of gut and storage sugars. All carbohydrates increased over the life of both nectar- and honeydew-fed wasps, but remained low or decreased in starved wasps. Lipid levels declined over the lifespan of female wasps, but females fed floral nectar showed the slowest rate of lipid decline. Diet did not affect egg load, probably because the females were not given hosts in the experiment.

The effects of insecticides on the diamondback moth, Plutella xylostella (L)., and its parasitoid, Diadegma insulare (Cresson), were evaluated in the field. Insecticides applied for control of the diamondback moth caused variations in parasitism by D. insulare ranging from 20 to 84%. Permethrin applications were effective at controlling diamondback moth. Applications of spinosad also resulted in low diamondback moth populations; however, percent parasitism was higher than in untreated plots and over 4× higher than in plots treated with permethrin. Selective materials that conserve D. insulare populations and maintain diamondback moth populations below economic thresholds may reduce the frequency of application, thus prolonging the efficacy of these materials.

Three experimental plots were established and maintained during one year at two sites in the state of Queretaro, Mexico, in order to identify species of parasitoids attacking the diamondback moth (DBM) Plutella xylostella (L.) (Lepidoptera: Plutellidae), and to gather information concerning their relative importance and patterns of population fluctuation. At both sites, the plots were planted with broccoli, cabbage and cauliflower during three cropping seasons. Parasitoid species identified were: Diadegma insulare Cresson, Diadromus (= Thyraeella) collaris Gravenhorst (Hymenoptera: Ichneumonidae); Habrobracon sp. (Hymenoptera: Braconidae); Oomyzus (= Tetrastichus) sokolowoskii Kurdjumov (Hymenoptera: Eulophidae); and Spilochalcis (= Conura) sp. (Hymenoptera: Chalcididae). This last species is a hyperparasitoid of D. insulare. The most abundant and frequently occurring species was D. insulare, it occurred in both localities during all three cropping seasons. The highest levels of parasitism caused by D. insulare on DBM were registered in the spring-summer season of 1996 at `La Soledad' farm with averages of 42.7, 45.0 and 44.5% on cabbage, broccoli, and cauliflower, respectively. Because D. insulare was detected attacking the pest at very low population densities during the initial stages of the crop cycle, it is assumed that the parasitoid has a high searching capacity. Correlation (r) between DBM and D. insulare population numbers was positive and significant. The other species identified occurred sporadically and had little impact on pest populations. The identification of D. collaris represents the first record of this species in North America.

A flight tunnel bioassay was used to evaluate attraction responses of female Diadegma insulare (Cresson), a host-specific parasitoid of the diamondback moth, Plutella xylostella (L.), to collard plants (Brassica oleracea var. acephala L.) infested with host and nonhost caterpillars. Adult female wasps showed increased responses to odors of the plant-host complex after a brief contact experience with host-infested collard leaves. Such an increase shows evidence of associative learning in this parasitoid to the odor released from the larval-plant complex. The same experimental design was also used to determine responses of the parasitoid to plants infested with nonhost larvae-cabbage looper, Trichoplusia ni (Hübner), and imported cabbageworm, Pieris rapae (L.). The female wasps conditioned to the plants infested with host larvae also showed increased responses to plants infested with larvae of cabbage looper or imported cabbageworm. These results indicate that plants damaged by host and nonhost caterpillars may release general odors that are attractive to D. insulare. The general damage odors caused by host and nonhost larval feeding may enhance biological control of the diamondback moth. Host-search ability of the parasitoid increases after experiencing host damage. When host populations are low in fields, plant odors caused by generalist herbivore feeding may also attract D. insulare parasitoids to the vicinity, thereby improving encounter chances of the parasitoid encountering diamondback moth larvae.

Six field populations of the parasitoid Diadegma insulare (Cresson) were collected from Mexico and the United States and tested for their susceptibility to permethrin by using a glass-vial residue bioassay. Significant differences existed in susceptibility, with one population significantly more susceptible than the other five. Susceptibility of D. insulare increased when they were reared for several generations in the greenhouse in the absence of selection. D. insulare was less suceptible to permethrin than the adult stage of its host, Plutella xylostella (L.), from a laboratory colony, but more susceptible than those hosts collected from a commercial field. Our data suggest that a field population of D. insulare appeared to increase its tolerance to permethrin much more slowly than P. xylostella.

Parasitism of Plutella xylostella (L.) third and fourth instars was evaluated in a cabbage field in Geneva, NY, in 1999. Over the entire season, average parasitism was 33.6% for third instars and 53.6% for fourth instars, and the main parasitoids were Diadegma insulare (Cresson) and Microplitis plutellae Muesbeck. In the early season, total parasitism was low, and mainly caused by D. insulare. However, later in the season, parasitism reached >80% for the fouth instars and 50% for the third instars. Our survey indicated that M. plutellae heavily parasitized P. xylostella, and provided higher parasitism rates than D. insulare in the late season. Comparison of these two species in laboratory bioassays indicated there were no significant differences in susceptibility to four insecticides commonly used in crucifer fields. For both parasitoids, an experience with P. xylostella on a damaged leaf increased their host-searching efficacy. Compared with M. plutellae, D. insulare was a better host-searcher both for the naive and the experienced adults. Although both parasitoids can cause high mortality rates of P. xylostella, D. insulare may be more suitable to be released in fields to enhance natural control against P. xylostella.

The effects of plant density of broccoli (Brassica oleracea L. var. italica) on the abundance of diamondback moth (DBM), Plutella xylostella (L.), and its parasitoid, Diadegma insulare (Cresson), were studied. There were no significant differences in the number of small DBM larvae (first and second instars) per plant across treatments (three different plant densities and three different spacings between plants) and sampling dates. The number of large larvae (third and fourth instars) and D. insulare pupae per plant were significantly influenced by plant density, sampling dates and the interaction of these two factors. However, the number of DBM pupae was not significantly different among treatments. Percentage parasitism of DBM larvae by D. insulare per plant did not vary significantly with either plant density or sampling date. Percentage parasitism of DBM larvae (field and laboratory-reared) per plant in the upper or lower one-third of the plant canopy was not significantly different among treatments an...

Studies were conducted to evaluate the toxicity of insecticides to adult Diadegma insulare (Cresson) and its host the diamondback moth, Plutella xylostella (L.). Leaf-dip and direct-dip bioassays for diamondback moth larvae and residual bioassays for adults of diamondback moth and D. insulare were used to assess mortalities. Larval mortalities at field rates were significantly higher with carbaryl, permethrin, spinosad, and tebufenozide when compared with Bacillus thuringiensis, or imidacloprid in the larval-dip bioassay 72 h after treatment. In the leaf-dip and residual bioassays, both permethrin and spinosad caused 100% mortalities to diamondback moth larvae and adults, respectively, 72 h after treatment. Of all the materials tested, only B. thuringiensis and tebufenozide were not toxic to D. insulare 24 h after treatment. Spinosad was not toxic to D. insulare 30 min after treatment. However, 100% mortality was observed 8 h after treatment.

Cocoons of Cotesia plutellae (Kurdjumov) were released for nine consecutive wk along the margins of two commercial cabbage (Brassica oleracea var. bravo L.) fields near Bunnell, Flagler Co., FL, in spring 1996. The larval parasitism of diamondback moth, Plutella xylostella (L.), by C. plutellae and by the native parasitoid Diadegma insulare (Cresson) was evaluated in release fields and in nearby cabbage fields using two methods-sentinel collard (Brassica oleracea var. acephala L.) or sentinel cabbage plants and non-sentinel plants. Total parasitism of diamondback moth larvae on sentinel plants in the release and adjacent fields was 35.7%. There were no significant differences in the level of parasitism by C. plutellae among sentinel plant locations within the release fields. In non-release fields, parasitoids spread as far as 1,500 m from the nearest release site during the release period, but parasitism of larvae on sentinel plants decreased as the distance from the release area increased. Parasitism of diamondback moth larvae by D. insulare was 8.3% in C. plutellae release and adjacent fields, but 14.6% in the nearby fields. Sampling of non-sentinel cabbage plants for diamondback moth larvae demonstrated a total of 37.4% larval parasitism by C. plutellae in the release and adjacent fields, similar to that recorded on sentinel plants. However, C. plutellae were detected only as far as 800 m from the release site on non-sentinel cabbage plants, and total parasitism in the dispersal fields also was very low. Diadegma insulare contributed only 1.1% parasitism of larvae sampled from non-sentinel plants in all cabbage fields. Cotesia plutellae was more effective than D. insulare in attacking diamondback moth larvae in this study where field populations of diamondback moth were low (

We studied the diurnal flight activity of Diadeg>ma insulare (Cresson) at the Collins Road Entomology Research Farm Michigan State University during the summers of 1992 and 1993. Foraging activity was measured using sticky traps placed within the broccoli canopy and by direct visual observation. Flight activity of D. insulare males was positively correlated with light intensity, whereas activity of females was positively correlated with light intensity, temperature, and wind speed. Relative humidity, percentage cloud cover, and time of day did not influence D. insulare catch. There was no significant difference between male and female catch. The patterns of males' and females' flight activity throughout the day were significantly different from a uniform distribution except on 14 and 22 August 1993 for males and 14 August for females. Activity generally began between 0800 and 1000 hours, peaked between 1100 to 1300 hours, and stopped by 2100 hours. There was no significant correlation between the numbers of males and females caught on the same trap, suggesting that an increase in numbers of females does not attract more males. Males were caught more frequently than females in September of both years, suggesting that males were more abundant or active at the end of the season. The total numbers caught (both sexes) at different times of the day in sticky traps were generally proportional to the numbers of parasitoid visually observed. The numbers of D. insulare caught were positively correlated with the numbers of diamondback moth larvae per plant. This information could be useful for developing a model that can predict the peak diurnal activity of D. insulare in the field which would help with decisions on whether pesticides should be sprayed.

We observed 5 nectar-collecting behaviors of Diadegma insulare (Cresson), a major parasitoid of diamondback moth, Plutella xylostella (L.). The most striking behavior of D. insulare was chewing at the base of Barbarea vulgaris R. Br. and Brassica napus L. flowers and creating holes that probably released the floral nectar. D. insulare visited more frequently and spent longer times on Rower species that supported longer life and high fecundity ( B. vulgaris, Brassica kaber (D.C.) Wheeler, B. napus and Daucus carota L.). Time spent per visit was positively correlated with the number of previous visits for B. vulgaris and B. kaber , flowers that support long life and high fecundity. Time spent per visit was negatively correlated with the number of previous visits for Berteroa incana L. (D.C.) and Erysimum cheiranthoides L. (flowers that cause shorter lives and low fecundity of D. insulare ). This suggests that D. insulare , after experience, was able to positively correlate nectar rewards with the Rower characters. Flower color did not affect parasitoid choice of flowers. D. insulare spent significantly longer time at the upper one-third of D. carota corolla and at the lower one-third of B. kaber and B. vulgaris corollas than oilier Rowers. Behavioral flexibility of D. insulare to flower characters and its nectar-collecting behaviors should be considered for increased impact of this parasitoid in diamondback moth management programs.

Examinations of cabbage plants in five fields near Bunnell, Flagler Co., FL, in spring 1995 showed that larvae of the diamondback moth, Plutella xylostella (L.), were more abundant on the field ends (perpendicular to cabbage rows) adjacent to weed-filled drainage ditches than the fields ends abutting wooded swamp areas. There were no significant differences in the numbers of diamondback moth larvae on cabbage plants on the ends next to other cabbage fields or at sites located within the interior of the fields. Cabbage heads rated for damage due to diamondback moth larvae at harvest showed a distributional pattern similar to that observed for diamondback moth larvae. Parasitism of diamondback moth larvae was not significantly different between field ends and interior fields. Cabbage damage ratings on field sides (parallel to cabbage rows) showed that no edge effect was detected on the sides abutting other cabbage fields, that edge effect only occurred on the first one or few rows on the sides adjacent to other cabbage fields but separated by irrigation ditches, and that edge effect occurred continuously and decreased from the first to the 12th row on sides adjacent to earlier planted cabbage or an open weed-filled ditch area. These results suggest that diamondback moth first invaded cabbage fields from outside areas, and that more diamondback moth spread to the interior of the fields from adjacent open, weed-filled ditches than from bordering wooded and bushy areas.

The tools of insect pest management include host plant resistance, biological control, and insecticides and how they are integrated will influence the durability of each. We created a detailed model of the population dynamics and population genetics of the diamondback moth, Plutella xylostella L., and its parasitoid, Diadegma insulare (Cresson), to study long-term pest management in broccoli Brassica oleracea L. Given this pest's history of evolving resistance to various toxins, we also evaluated the evolution of resistance to transgenic insecticidal Bt broccoli (expressing Cry1Ac) and two types of insecticides. Simulations demonstrated that parasitism provided the most reliable, long-term control of P. xylostella populations. Use of Bt broccoli with a 10% insecticide-free refuge did not reduce the long-term contribution of parasitism to pest control. Small refuges within Bt broccoli fields can delay evolution of resistance >30 generations if resistance alleles are rare in the pest population. However, the effectiveness of these refuges can be compromised by insecticide use. Rainfall mortality during the pest's egg and neonate stages significantly influences pest control but especially resistance management. Our model results support the idea that Bt crops and biological control can be integrated in integrated pest management and actually synergistically support each other. However, the planting and maintenance of toxin-free refuges are critical to this integration.

Background In nature, insects have evolved behavioural and physiological adaptations to cope with short term exposure to extreme temperatures. Extreme heat events may increase as a result of climate change; this in turn will affect insect population dynamics. We examined the effect of abrupt and ecologically relevant gradual exposure to high temperatures on the survival and hsp70 gene expression in diamondback moth (DBM) adults and the parasitoid Diadegma insulare , as well as in parasitized and non-parasitized DBM larvae. Principal Findings Tolerance to high temperatures in DBM adults was higher than in D . insulare adults. There was no difference in the survival of DBM adults between abrupt and ramped increases from 25 to 38°C; however, at 40°C survival was higher when the temperature increased gradually. In contrast, more D . insulare adults survived when the temperature was ramped rather than shifted abruptly to both 38 and 40°C. There was no heat stress effect of up to 40°C on the survival of either parasitized or non-parasitized DBM larvae. In adults of both species, more hsp70 expression was observed when temperatures increased abruptly to 38°C compared to ramping. In contrast, at 40°C significantly more expression was found in insects exposed to the ramping rather than the abrupt regime. Hsp70 expression level was in agreement with adult survival data and appears to be a good indicator of stress levels. In parasitized and non-parasitized larvae, hsp70 expression was significantly higher after abrupt shifts compared to ramping at both temperatures. Conclusions/Significance Hsp70 gene expression was responsive to extreme temperatures in both DBM and D . insulare , which may underlie the ability of these insects to survive in extreme temperatures. Survival and hsp70 expression upon abrupt changes are distinctly different from those after ramping indicating that experimental protocol must be considered before extrapolating laboratory results to natural field situations.

The interrelationship of Bacillus thuringiensis Berliner var. kurstaki to the diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), and its primary parasitoid, Diadegma insulare Cress. (Hymenoptera: Ichneumonidae), was investigated using laboratory colonies of the insects. The differential response of third-instar diamondback moth, parasitized and unparasitized, to B. thuringiensis (Bt), and the ability of D. insulare to oviposit in Bt-stressed hosts were determined. No significant difference (P > 0.05) was found between the mean mortality of parasitized and unparasitized larvae at each of three concentrations (154, 334, and 2,237 IU/ml) of Bt endotoxin. The three concentrations were equivalent to the LC30, LC50, and LC90 of Bt potency based on preliminary tests. Parallel line assay analysis, however, revealed that the linear dose-response regressions of parasitized and unparasitized larvae were highly significant (P = 0.0001). The LC50s of parasitized versus unparasitized larvae were 373 and 175 IU/ml Bt endotoxin, respectively, indicating that parasitized larvae were less susceptible to Bt. Female D. insulare oviposited in Bt-stressed hosts. The percentage of D. insulare females emerging from Bt-treated larvae (41.4%) was not significantly different from that of untreated larvae (32.0%).

The effects of wildflowers on the longevity and fecundity of Diadegma insulare (Cresson), one of the major parasitoids of diamond back moth, Plutella xylostella (L.), in North America, were studied in the field. Wildflowers provided nectar sources for D. insulare . Longevity and fecundity of the parasitoid female varied with wildflower species and the morphological characteristics of the flower. Several flowers. including Brassica kaber (D.C.) Wheeler, Barbarea vulgaris R. Br., and Daucus carota L., supplied nectar and resulted in D. insulare longevity and fecundity equal to when honey–water was supplied as food. Others, including Erysimum cheiranthoides L. and Thlaspi arvense L. , were not significantly better than no food at all. Chenopodium album L. and Sonchus arvensis L. did not provide available nectar, however, adult parasitoids fed on honeydew excreted by Aphis fabae (Scopli)feeding on the plants. Fecundity of D. insulare generally peaked 6–15 d after adult emergence. An increase in longevity and fecundity was correlated with flower corolla opening diameter. Shading also increased longevity and fecundity of D. insulare . The oviposition behavior within 1 min of exposure to diamond back moth larvae was highly correlated with longevity and fecundity of D. insulare , whichwe considered indices of food quality. Seasonal manipulation of the diversity and distribution of wildflowers in the cabbage field and adjacent habitats, as well as providing shade for D. insulare , could increase D. insulare effectiveness in management of diamondback moth.

Diadegma insulare (Cresson, 1865) (Figs 6 e and 6g) Angitia plutellae Viereck, 1912: 583; Campoplex hellulae Viereck, 1912: 622; Campoplex pygmaeus Viereck, 1925: 203; Limneria polynesialis Cameron, 1883: 191; Mesoleptus insularis Cresson, 1865: 15; Sagaritis congregator Walley, 1926: 225 Diagnosis. Characterized among Diadegma species by the area superomedia, apically narrowed and delimited (Fig. 6 e), and the tergites VI-VII of females not to slightly indented (Fig. 6 g). Description. Azidah et al. (2000). Host records. Plutella xylostella, P. operculella, P. omissa, P. a r m o r a c i a e (Lepidoptera: Plutellidae) and Hellula undalis (Lepidoptera: Pyralidae). Comments. The presence of D. insulare in Reunion is surprising. We expected to find instead D. semiclausum, which was introduced into Mauritius in 1991 from Taiwan (Dunhawoor & Abeeluck 1998). However, all the 12 examined specimens have an area superomedia distinctly narrowed posteriorly (for most of them the area is even distinctly apically closed). This character is the most reliable to differentiate D. insulare from its close relatives D. semiclausum and D. mollipla. Azidah et al. (2000) stated that D. semiclausum and D. insulare are very similar, both being also differentiated by the emargination of apical tergites in females (Figs 6 f���g). None of the females we examined bore a distinct indentation. Distribution records. Reunion (new record). North and Central America, Cuba, Jamaica, Colombia, Venezuela, Morocco, Israel, Tahiti, Hawaii, Society Islands. Material examined. 4 �� 333 St Paul / Tan Rouge, alt. 800m, VI. 2011, leg. Cirad; 1 �� 13 same locality, I. 2011, leg. Cirad; 13 St Pierre / Bassin Martin, alt. 290m, XII. 2010, leg. Cirad; 1 �� Le Tampon / Pont d���Yves, alt. 820m, III. 2003, leg. P. Rousse; 13 Le Tampon / Bras de Pontho, alt. 680m, IX. 1997, leg. Cirad., Published as part of Rousse, Pascal & Villemant, Claire, 2012, Ichneumons in Reunion Island: a catalogue of the local Ichneumonidae (Hymenoptera) species, including 15 new taxa and a key to species, pp. 1-57 in Zootaxa 3278 on page 12, DOI: 10.5281/zenodo.214150, {"references":["Cresson, E. T. (1865) On the Hymenoptera of Cuba. Proceedings of the Entomological Society of Philadelphia, 4, 1 - 200.","Viereck, H. L. (1912) Descriptions of five new genera and twenty six new species of Ichneumon-flies. Proceedings of the United States National Museum, 42, 139 - 153.","Viereck, H. L. (1925) A preliminary revision of the Campopleginae in the Canadian National Collection, Ottawa. Canadian Entomologist, 57, 176 - 181,198 - 204,223 - 228,296 - 303.","Cameron, P. (1883) Descriptions of new genera and species of Hymenoptera. Transactions of the Entomological Society of London, 1883, 187 - 197.","Walley, G. S. (1926) A new Sagaritis from western Canada (Hymen.). Canadian Entomologist, 58, 225.","Azidah, A. A., Fitton, M. G. & Quicke, D. L. J. (2000) Identification of the Diadegma species (Hymenoptera: Ichneumonidae, Campopleginae) attacking the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae). Bulletin of Entomological Research, 90 (5), 375 - 389.","Dunhawoor, C. & Abeeluck, D. (1998) Integrated control of Plutella xylostella (L.) (Lepidoptera: Yponomeutidae) in Mauritius. In N. S. Talekar (Ed), 2 nd Annual Meeting of Agricultural Scientist, 12 - 13 Aug. 1997, Reduit, Mauritius, 1998. Food and Agricultural Research Council, pp 181 - 187."]}

In the laboratory and in cages in the greenhouse, we evaluated the toxicity of two insecticides (lambda-cyhalothrin and spinosad) on the parasitoid, Diadegma insulare (Cresson), and the predator, Coleomegilla maculate (DeGeer), both natural enemies of the diamondback moth, Plutella xylostella (L.). Lambda-cyhalothrin was very toxic to both natural enemies. Spinosad was less toxic to C. maculata adults and larvae, and slightly toxic to D. insulare. Both natural enemies suppressed P. xylostella populations in cages with 80% spinosad-treated and 20% nontreated plants; such suppression was not seen when lambda-cyhalothrin was used. Using broccoli, Brassica oleracea L. variety italica, a common host for P. xylostella, we also studied direct and indirect effects of both natural enemies in the presence and absence of the two insecticides and to different P. xylostella genotypes: resistant to the insecticide, susceptible, or heterozygous. Neither natural enemy could distinguish host genotype if P. xylostella were feeding on nontreated plants. They could also not distinguish between larvae feeding on spinosad-treated plants and nontreated plants, but D. insulare could distinguish between larvae feeding on lambda-cyhalothrin treated and nontreated plants. Our studies suggest that lambda-cyhalothrin has direct toxicity to these two natural enemies, can affect their host foraging and acceptance of P. xylostella and consequently would not be compatible in conserving these natural enemies in a program for suppression of P. xylostella. In contrast, our studies suggest that treatment with spinosad has much less effect on these natural enemies and would allow them to help suppress populations of P. xylostella. These findings are discussed in relation to the evolution of insecticide resistance and suppression of the pest populations.

Insect-resistant Genetically Modified (IRGM) plants have become an important component of integrated pest management (IPM) programs worldwide. The currently available IRGM plants express insecticidal proteins from Bt (Bacillus thuringiensis), however additional insecticidal molecules are being investigated. In 2008, Bt crops were grown on 46 million ha, up from 42.1 million ha in 2007. However, the ecological safety of Bt crops continues to be debated. Much of the debate has focused on non-target organisms, especially predators and parasitoids that help control populations of pest insects in many crops. Thirteen years of commercial use of Bt plants in different parts of the world has documented their effectiveness in controlling target insects and delaying resistance development. The existing “high dose/refuge” insecticide resistance management (IRM) practices certainly contributed to delaying resistance development. However, natural enemies may have played an important role in diminishing the likelihood of resistance development, but this is an area that has not been explored to a great degree. Numerous individual case studies and recent meta-analysis studies of Bt plants and natural enemies indicate that the existing Bt plants have little or no adverse effects on predators, especially compared with conventional insecticides. However, negative effects were found on parasitoids in a few studies but such effects were most likely caused by poor prey/host quality. Using a unique system consisting of a strain of the insect pest, Plutella xylostella (herbivore), resistant to Cry1C that was allowed to feed on Cry1C broccoli plants and then become parasitized by Diadegma insulare, an important endoparasitoid of P. xylostella, our results indicated the parasitoid was exposed to toxic insecticidal protein residues while in the host but was not harmed by such exposure. Parallel studies conducted with several commonly used insecticides indicated they significantly reduced parasitism rates on strains of P. xylostella resistant to these insecticides. These results provide the first clear evidence of the lack of hazard to a parasitoid by Bt plants, compared to traditional insecticides, and help provide new insight on how to rigorously evaluate the ecological risks of Bt plants. Furthermore, these results also suggest that it is time to take a new look at the relationship be tween Bt plants and insect natural enemies. Bt plants can be a friend to natural enemies, rather than a foe. The potential role of natural enemies in regulating insect resistance development to Bt plants is discussed.

The effects of pesticides on the diamondback moth, Plutella xylostella (L.), and parasitism by Diadegma insulaTe (Cresson) was studied at the Michigan State University Entomology Research Farm during July and August 1990. The range of diamondback moth parasitism from three different locations in Michigan was 60.8–83.3%. Pesticides used were Bacillus thuringiensis var. Kurstaki (Berliner), thiodicarb, thiodicarb + B. thuringiensis , chlorpyrifos, permethrin, ICIA 0321 (pyrethroid), and esfenvalerate. Diamondback larval moth mortality was not Significantly different among the treated plots but was significantly higher than in untreated plots 3 d after spraying. The change in number of diamondback moth larvae (0 versus 3 d), and diamondback moth and D. insulare pupae (0 versus 6 d) was similar in all treatments. Parasitism by D. insulare in treated plots was not affected 6 d after spraying with any pesticide tested. Mean percentage parasitism by D. insulare in guard rows was also not different. However, the percentage parasitism in cages 3 d after treatment with permethrin, azinphosmethyl, or B. thuringiensis or untreated was 7.8, 13.3, 81.5, and 79.4%, respectively. Parasitism by D. insulare of the diamondback moth larvae seems to be influenced by the vegetation or refuge plants present outside the experimental plots. Diamondback moth parasitism by D. insulare may not be affected severely if pesticides are judiciously used.

Effects of pesticides on immature stages of Diadegma insulare (Cresson) and its host, the diamondback moth, Plutella xylostella (L.), were studied in the laboratory. Diamondback moth larvae parasitized by D. insulare were significantly less sensitive to ingested pesticides than were nonparasitized larvae 48 h after treatment. However, they were equally sensitive to pesticides through contact. Bacillus thuringiensis var. kurstaki (Berliner) and azinphosmethyl were significantly more toxic to parasitized larvae than permethrin, methomyl, and chlorothalonil if ingested. D. insulare adults emerging from pupae that formed from larvae surviving pesticide treatments tended to have more females than those in the control group. Except for B. thuringiensis and chlorothalonil treatments, percentage adults emerging from pesticide-treated pupae was significantly lower for D. insulare than for diamondback moth in either direct-dip or spraying bioassays. Lower pesticide sensitivity in immature stages of D. insulare may be important for effective integrated diamondback moth management.

Laboratory studies were done to evaluate differential toxicity of pesticides to adult Diadegma insulare (Cresson) and its host, the diamondback moth, Plutella xylostella (L.). Leaf-dip and direct-dip bioassays (diamondback moth larvae) and residual (adult diamondback moth and D. insulare ) bioassays were used. None of the pesticides caused 100% mortality to diamondback moth larvae or adults at 1.0 mg (AI)/ml concentrations (except Bacillus thuringiensis var. kurstaki and esfenvalerate on larvae and adults, respectively). However, at 1.0 mg (AI)/ml, all insecticides except B. thuringiensis kurstaki were extremely toxic to D. insulare within 30 min after treatment. Chlorothalonil was not toxic to diamondback moth larvae or adults or to D. insulare at concentrations tested. Methomyl was the least toxic insecticide to diamondback moth larvae and adults, but caused 100% mortality of D. insulare 24 h after the insects were exposed (1.0mg [AII/ml). An integrated approach for control of diamondback moth with B. thuringiensis and D. insulare might permit control of diamondback moth without directly affecting D. insulare . The use of chlorothalonil for controlling crop diseases is compatible with management of diamondback moth because this fungicide does not affect D. insulare . However, it may affect entomopathogenic fungi that attack diamondback moth larvae or adults in the field.

The ecological implications on biological control of insecticidal transgenic plants, which produce crystal (Cry) proteins from the soil bacterium Bacillus thuringiensis (Bt), remain a contentious issue and affect risk assessment decisions. In this study, we used a unique system of resistant insects, Bt plants and a parasitoid to critically evaluate this issue. The effects of broccoli type (normal or expressing Cry1Ac protein) and insect genotype (susceptible or Cry1Ac-resistant) of Plutella xylostella L. (Lepidoptera: Plutellidae) were examined for their effects on the development and host foraging behavior of the parasitoid, Diadegma insulare (Cresson) (Hymenoptera: Ichneumonidae) over two generations. Parasitism rate and development of D. insulare were not significantly different when different genotypes (Bt-resistant or susceptible) of insect host larvae fed on non-Bt broccoli plants. D. insulare could not discriminate between resistant and susceptible genotypes of P. xylostella, nor between Bt and normal broccoli plants with different genotypes of P. xylostella feeding on them. No D. insulare could emerge from Bt broccoli-fed susceptible and heterozygous P. xylostella larvae because these larvae were unable to survive on Bt broccoli. The parasitism rate, developmental period, pupal and adult weights of D. insulare that had developed on Bt broccoli-fed Cry1Ac-resistant P. xylostella larvae were not significantly different from those that developed on non-Bt broccoli-fed larvae. Female D. insulare emerged from Cry1Ac-resistant P. xylostella that fed on Bt plants could successfully parasitize P. xylostella larvae. The life parameters of the subsequent generation of D. insulare from P. xylostella reared on Bt broccoli were not significantly different from those from non-Bt broccoli. The Cry1Ac protein was detected in P. xylostella and in D. insulare when hosts fed on Bt broccoli. These results are the first to indicate that Cry1Ac did not harm the development or host acceptance of an important endoparasitoid after two generations of exposure. We suggest that using other Bt crops and resistant insect species would likely lead to similar conclusions about the safety of the presently used Bt proteins on parasitoids.

Three primary parasitoids in three genera were reared fromPlutella xylostella (L.) larvae and pupae collected in various crucifer producing regions of Honduras. The ichneumonidDiadegma insulare (Cresson) was by far the most abundant species. TwoSpilochalcis species, facultative hyperparasitoids attackingP. xylostella andD. insulare, were encountered as well as eleven species in nine genera of obligate hyperparasitoids attackingD. insulare. Three vespid predators are noted as predating on larvae.

La palomilla dorso de diamante (PDD) Plutella xylostella L. (Lepidoptera: Plutellidae) es la plaga más importantes de las crucíferas. Reduce severamente el rendimiento y la calidad de la cosecha, y tiene la característica de desarrollar fácilmente poblaciones resistentes a insecticidas sintéticos y biológicos que se usan para su combate. Este estudio se realizó en el Campo Experimental Valle del Fuerte del INIFAP, en Juan José Ríos, Sinaloa, en un cultivo de canola Brassica napus L. var. napus (Brassicaceae) sin aplicación de insecticidas. Se obtuvieron larvas y pupas de la PDD y sus parasitoides en hojas recolectadas durante la etapa de formación y llenado de vaina. Los parasitoides fueron identificados por taxónomos especialistas. Se determinó el parasitismo natural, el porcentaje de mortalidad de la PDD por causas desconocidas, así como la relación densodependiente hospederoparasitoide. Los parasitoides obtenidos fueron: Diadegma insulare (Cresson) (Hymenoptera: Ichneumonidae), Cotesia sp. (Hymenoptera: Braconidae) y Conura sp. (Hymenoptera: Chalcididae). D. insulare presentó un parasitismo de 25.0 a 80% (promedio 49.5%); Cotesia sp. entre 0.0 y 75.0% (promedio 23.1%); y Conura sp., entre 0.0 y 20% (promedio 3.2%). D. insulare tuvo una estrecha relación densodependiente con el hospedero (R2=0.85).

Diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae) is a serious pest of crucifer vegetables (Brassica sp.) worldwide because of a lack of effective natural enemies in certain regions and because of insecticide resistance. In 2003, laboratory and field studies were initiated in Virginia to better understand P. xylostella, its primary natural enemies, and their susceptibilities to insecticides in order to develop an economically and environmentally sound integrated pest management program for collards in the state. Ecological life table studies of P. xylostella immature stages on collards located on the Eastern Shore and on Kentland Farm, near Blacksburg at the New River Valley, VA revealed that most (98 to 99%) of P. xylostella died from natural causes. Mortality factors varied between the two regions. Neonates, small larvae, and large larvae disappearing were major mortality factors. Rainfall, predation, and dispersal probably contributed the most to this mortality. Egg mortality played a bigger role at the New River Valley compared with the Eastern Shore. Three parasitoid species were found that contributed to the mortality of P. xylostella: Diadegma insulare (Cresson) (Hymenoptera: Ichneumonidae); Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae); and Microplitis plutellae (Muesebeck) (Hymenoptera: Braconidae). Additional studies conducted in the laboratory using leaf-dip bioassays revealed that P. xylostella collected from the Eastern Shore of Virginia, showed significant tolerance levels to esfenvalerate, acetamiprid, methomyl, methoxyfenozide, indoxacarb, and acephate compared with a susceptible strain of P. xylostella. The highest tolerance ratio (1,876 fold) was to esfenvalerate, a commonly-used pyrethroid. All of the insecticides tested in this study were quite toxic to the adult stage of the parasitoids, D. insulare and O. sokolowskii. The insect growth regulator, methoxyfenozide was considerably less toxic than other insecticides such as esfenvalerate, methomyl, acephate, spinosad, indoxacarb, and emamectin benzoate at field-rate and 1% of field-rate concentrations. The aforementioned insecticides as well as some other insecticides were evaluated several times in the field for efficacy against P. xylostella as well as other pests of collards. The most efficacious insecticides over five field experiments included acephate, emamectin benzoate, esfenvalerate, methomyl, methoxyfenozide, novaluron, indoxacarb, and spinosad. These insecticides were followed in relative efficacy by Bt kurstaki, acetamiprid, and azadirachtin, which provided relatively inconsistent control of lepidopteran larvae over the experiments. Effective insecticide options in collards that are less toxic to natural enemies and that can fit well into integrated pest management programs include indoxacarb, spinosad, novaluron, emamectin benzoate, methoxyfenozide, and Bacillus thuringiensis subsp. kurstaki. Ph. D.

There were no differences in mortality, plant preference, or plant damage when diamondback moth (DBM) (Plutella xylostella L.) larvae were tested in no-choice and free-choice tests using leaf disks of resistant (`Green Glaze') or susceptible (`Vates', standard commercial cultivar) collards (Brassica oleracea Acephala group). No residuals of the pyrethrin insecticide Asana-XL (esfenvalerate) were detected 6 days after its application when DBM larvae were exposed to excised foliage for 72 hours. In a field test, more imported cabbage worm (ICW) (Pieris rapae L.) eggs were found on `Vates' treated with the insecticide than on nontreated Vates' or nontreated or treated `Green Glaze'. The fewest ICW, cabbage looper (CL) (Trichoplusia ni Hubner), and DBM larvae were found on the insecticide-treated cultivars. Fewer caterpillars were found on `Green Glaze' than Yates'. An additive effect of plant resistance and insecticide application lowered counts of DBM, ICW, and CL larvae. Percent parasitism of DBM by Diadegma insulare Cresson (Hymenoptera: Ichneumonidae) was lower on cultivars treated with the insecticide. Field plant damage ratings were higher for nontreated `Vates' and lowest for treated cultivars, but nontreated `Green Glaze' had a significantly lower feeding damage rating than nontreated `Vates'. Chemical name used: (S)-cyano (3-phenoxy phenyl) methyl-(S)-4 chloro-alpha (1-methylethyl) benzeneacetate [esfenvalerate (Asana-XL)].

The susceptibility of a population of diamondback moth, Plutella xvlostella L (Lepidoptera: Plutellidae), collected from Montgomery County, Virginia, and its ability to develop resistance to Bacillus thuringiensis was evaluated. The field population of diamondback moths was found to be susceptible to B. thuringiensis. Selection pressure at 153 I.U. of B. thuringiensis endotoxin per ml for nine generations did not cause any significant difference in mean mortality of third instar diamondback moths although there was a trend towards lower mortality, there was significant negative linear correlation between generation and mean mortality of diamondback moth larvae (P = 0.003, r²= 0.73). LC₅₀ increased from 264 I.U. of B. thuringiensis endotoxin per ml in generation I to 514 LU/ml in generation IX. The interrelationship of B. thuringiensis to diamondback moth and its primary parasitoid, Diadegma insulare Cress (Hymenoptera. Ichneumonidae), was studied by determining: the differential response of third instar diamondback moth, parasitized and unparasitized, to B. thuringiensis, and the ability of D. insulare to discriminate between B. thuringiensis-treated and untreated hosts. There was no significant difference (P > 0.05) between mean mortality of parasitized and unparasitized larvae at each of the three concentrations consisting of 154, 334, and 2237 I.U. of B. thuringiensis endotoxin per ml. The regressions of the response of parasitized and unparasitized larvae, however, were highly significant (P = 0.0001). The LC₅₀s of parasitized versus unparasitized larvae were 373 and 176 I.U./ml B. thuringiensis endotoxin, respectively. Female D. insulare did not discriminate between B. thuringiensis-treated and untreated hosts. The percentage of D. insulare females emerging from B. thuringiensis-treated larvae (41.4%) was not significantly different from that of untreated larvae (32.0 %). Mean mortality of third instar diamondback moth subjected to B. thuringiensis endotoxin at 153, 334, and 2237 I.U./ml were not significantly different at temperatures of 15 and 20 °C, but were significantly lower than that at 30 °C. The effects of B. thuringiensis endotoxin residues on leaves under room conditions [27 ± 1 °C, RH 27 ± 72%, and 8:16 (L:D)] were not significantly different at 2 and 192 hours after treatment. Master of Science

The pressure to escape natural enemies may shape how herbivorous insects use their plant resources. On wild crucifers, ovipositional preferences of the diamondback moth (Plutella xylostella; DBM) were similar to searching preferences of its main parasitoid, an ichneumonid wasp (Diadegma insulare). But on cultivated crucifers, these species had opposite preferences. In addition, DBM ovipositional preferences did not correlate with growth or reproduction on several foodplants. We interpret these patterns as evidence of evolution for use of enemy-free space in agricultural systems.

The effects of sweet alyssum (Lobularia maritima) (Brassicaceae) flowers on the longevity of two augmentatively-released parasitoids, Cotesia marginiventris (Cresson) (Hymenoptera: Braconidae) and Diadegma insulare (Cresson) (Hymenoptera: Ichneumonidae), were studied in a greenhouse experiment. C. marginiventris and D. insulare survived approximately 4.8 and 12.7 times longer, respectively, when provisioned with honey or with sweet alyssum than with water alone. Sweet alyssum planted in northern Florida cabbage fields may be one way to improve biological control by augmentatively-released natural enemies of lepidopteran pests by increasing adult parasitoid longevity during times when few wild plants are in bloom.

Two species of parasitoids, Cotesia plutellae (Hymenoptera: Braconidae) and Diadegma insulare (Hymenoptera: Ichneumonidae), of diamondback moth, Plutella xylostella, (Lepidoptera: Plutellidae), were colonized in cages in cabbage fields west of Bunnell, Florida, from November 1996 to February 1997. Two kinds of cages were used: large-screened cages and screened laundry hampers. Both parasitoids attacked their host during the winter, completed development within the host, and increased in numbers within field cages. Parasitism of diamondback moth larvae by C. plutellae was 36-42% in laundry hampers, and 35-65% in large screened cages. The sex ratio of emerging C. plutellae was 1:1-1.2 ( f : m ) in laundry hampers and 1:0.8-1.3 in large screened cages. Parasitism of diamondback moth larvae by D. insulare was 55-90%, parasitoid adults emerged from 89% of the cocoons, and the sex ratio was 1:1.4-2.1 ( f : m ) in large screened cages. The results showed that it is possible to rear these parasitoids in field nursery cages to provide parasitoid sources for release to control diamondback moth in cabbage in Florida.

Cotesia plutellae Kurdjumov was evaluated as a potential biological control agent for diamondback moth, Plutella xylostella (Linnaeus), in cabbage in spring 1993 and 1994. The parasitoids were reared in a commercial insectary in Texas, delivered overnight via air express, and released 24-48 h after receipt in cabbage fields in Northeast Florida. In 1993, only adult parasitoids were released, but adults and cocoons were released in 1994. The numbers of C. plutellae released ranged from 456 per ha per wk in 1993 to 1,334 per ha per wk in 1994. Four consecutive releases were made each year beginning in early February. Parasitism of diamondback moth larvae by C. plutellae ranged from 3.6 to 10.9%, and the level of parasitism was related to the total numbers of parasitoids released. C. plutellae parasitoids were complimentary to the naturally occurring parasitoid Diadegma insulare (Cresson), and the combined mean seasonal parasitism of diamondback moth exceeded 34% in some fields. There was no evidence that C. plutellae became established in the general area although > 124,000 parasitoids were released over the 2-year test period.

Laboratory tests with Diadegma insulare (Cresson), a parasitoid of the diamondback moth (Plutella xylostella (L.)), were conducted to evaluate the viability of cocoons stored at 4°C for varying lengths of time and also the effects of parasitism by D. insulare on the feeding rate of diamondback moth larvae. The percentage of adults emerging from cocoons declined steadily with time spent in storage at 4°C and was predictable (r2=0.9603; Y=98.3-2.06X; P

In the laboratory, second- and third-instar Plutella maculipennis (Curtis) larvae were about equally susceptible to parasitism by Diadegma insularis (Cresson) or by Microplitis plutellae Muesebeck. The fourth and last instar was less susceptible than the second and third. Larvae of the first instar, although usually within the tissues of the food plant, could be parasitized. Maximum progeny obtained from female parasites during a lifetime, with regularly renewed supplies of hosts, averaged 516 in D. insularis, and 232 in M. plutellae. Effectiveness of D. insularis among a given number of host larvae improved slightly, reaching 85/100 as cage size increased from 50 to 200 sq. in., and declined somewhat, from 124/200 to 94/200, when cage size was further increased from 200 to 1500 sq. in. In field cages of 1, 2, and 4 sq. yd, with 200 host larvae, single female D. insularis parasitized about 35, 20, and 7% of hosts respectively. With 50, 100, 200, and 400 host larvae in 200-sq.-in. cages, and one female per unit, average progeny of D. insularis were respectively 39, 70, 113, and 150; of M. plutellae, approximately the same. In competition, two females, one of each species, operating among the same lot of larval hosts, produced more total progeny than two of the same species. Increasing constant temperatures from 20° to 30° favoured D. insularis slightly, but viability and effectiveness of M. plutellae at 30° was reduced.

De septiembre a diciembre de 2000 se compararon dos sistemas de manejo de Plutella xylostella, el manejo convencional calendarizado que hacen los productores de repollo y un sistema de Manejo Integrado de Plagas (MIP). La cantidad de larvas de plutella en el repollo manejado bajo el sistema MIP fue menor que en el manejado convencionalmente. Diadegma insulare parasitó a P. xylostella 30% en el sistema MIP y 7% en el sistema convencional (P = 0.001). Los costos diferenciales y totales fueron mayores en el sistema MIP, así como los ingresos bruto y neto (P = 0.04). El costo total aumentó 10% y el ingreso neto 201%, al cambiar del sistema tradicional al MIP. Palabras clave: Costo diferencial, MIP, parasitoide, plutella. DOI: http://dx.doi.org/10.5377/ceiba.v48i1-2.438 Ceiba, 2007. Volumen 48(1-2): 83-87

This document is EENY-124 one of a series of Featured Creatures from the Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Published: March 2000. https://edis.ifas.ufl.edu/in281