Trichogrammatid Species Research Articles

Functional and Numerical Responses of Trichogramma euproctidis (Hymenoptera: Trichogrammatidae) to Helicoverpa armigera (Lepidoptera: Noctuidae) Under Laboratory Conditions.

The tomato fruitworm Helicoverpa armigera (Hübner) is regarded as a serious pest that affects a great number of field crops globally. One of the environmentally safe alternatives to the utilization of insecticides is controlling H. armigera via the release of biological control agents by employing parasitoids, e.g., trichogrammatid species. One of the desired parasitoids indigenous to southwestern Iran is Trichogramma euproctidis (Girault). To anticipate the outcomes of augmentative releases of T. euproctidis in the field, the numerical and functional responses of female T. euproctidis that parasitizes the eggs of H. armigera were determined in the laboratory. The densities of host eggs per glass tube arena (length: 10cm, diameter: 1cm) were 2, 4, 8, 16, 32, 64, or 128 individuals. The functional response to the eggs of H. armigera indicated Holling's type II response. The estimated handling time and attack rate from the random parasitoid equation were 0.6898h and 0.00823h, respectively. This indicates that, at the maximum level, each T. euproctidis was capable of parasitizing 34.79 eggs a day. At the 128 host egg density, the number of eggs laid, that is, the numerical response, ascended as the density of host eggs increased up to a maximum of 89.90 eggs per female. According to the obtained results of the present investigation, T. euproctidis can serve as an appropriate candidate for augmentative biological control of H. armigera. Nevertheless, it is necessary to conduct complementary experiments in greenhouses and open fields.

Performance of two dominant trichogrammatid species of fall armyworm from China and Africa under contrasted temperature and humidity regimes

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), has become an international pest with its ability to spread rapidly. The FAW has successfully invaded Africa, Asia, and Australia, and recently China. It has become a serious threat to food security as a major pest of cereals and other crops. Trichogrammatid parasitoids are the dominant biological control agents that have been applied to control lepidopteran pests of crops, vegetables and forests worldwide. The aim of this study was to evaluate parasitism, development, and emergence of two trichogrammatid species, Trichogramma dendrolimi and Trichogrammatoidea lutea, from China and Africa on FAW at four temperatures (21, 25, 29, 33 °C) and three relative humidity (RH) (30, 60, 90 %) conditions. The temperature and humidity significantly affected the performance of the two trichogrammatid species on their host, including parasitic ability and development. The parasitism of T. dendrolimi was significantly higher than that of T. lutea (except for the treatment of 33 °C × RH 60 %) under various temperature and humidity conditions, however, T. lutea could not parasitize host eggs at 33 °C × RH 90 %. The higher parasitism was observed at 25 °C and 29 °C, while the lower at 21 °C and 33 °C for both two trichogrammatid species. The developmental time of T. dendrolimi and T. lutea significantly decreased with the increase of temperature under all three humidity treatments. The developmental time of T. dendrolimi under different temperature and humidity conditions (except for the treatment of 33 °C × RH 30 %), was significantly shorter than that of T. lutea. Temperature and humidity significantly influenced the sexual ratio of T. dendrolimi, the highest female ratio (94.6 %) was recorded at 33 °C × RH 60 %, while the lowest (79.5 %) was recorded at 25 °C × RH 60 %, but had no effect on T. lutea. The emergence rate of T. dendrolimi and T. lutea under different temperature and humidity conditions was only significantly different at 25 °C. Generally, T. dendrolimi had a better temperature and humidity adaptation than that of T. lutea, thus, T. dendrolimi appears to be a potential candidate for the control FAW under varying environmental conditions.

Performance of Two Trichogrammatid Species from Zambia on Fall Armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae).

Simple SummaryTwo egg parasitoid species (Trichogramma mwanzai and Trichogrammatoidea lutea) from parasitized eggs of fall armyworm (FAW) Spodoptera frugiperda in Zambia were identified by using a combination of both molecular and morphological characters. We compared the parasitism capabilities of the two species with three native Chinese trichogrammatid species (T. ostriniae, T. leucaniae and T. japonicum) using 0- to 2-day-old FAW eggs. Both parasitoid species accepted eggs of all ages tested and completed their development successfully. Trichogrammatoidea lutea females showed the highest parasitism rate of host eggs among the five tested species. T. mwanzai had the shortest developmental time on all test age eggs. Of the five parasitoid species reared on FAW eggs, T. lutea performed the best overall, while T. japonicum was the worst performing of the parasitoids.The fall armyworm, Spodoptera frugiperda (J.E. Smith), is a noctuid moth native to the tropical and subtropical Americas that has successfully invaded Africa and Asia, where it is has become a serious threat to food security as a pest of cereals and other crops. Biological control is an environmentally friendly means of combating the pest and contributes to an integrated pest management approach. In our study, two egg parasitoid species (Trichogramma mwanzai and Trichogrammatoidea lutea) found in parasitized fall armyworm eggs in Zambia were identified by using a combination of both molecular and morphological characteristics. To evaluate their potential and efficiency on 0- to 2-day-old fall armyworm eggs, we compared their parasitism capabilities with three Trichogramma species native to China (T. ostriniae, T. leucaniae and T. japonicum) under laboratory conditions. The results showed that both parasitoid species would accept 0-, 1- and 2-day-old fall armyworm eggs, and complete their development successfully. Trichogramma mwanzai and T. lutea preferred parasitizing 0- and 1-day-old eggs over 2-day-old eggs. Trichogrammatoidea lutea females supplied with fall armyworm eggs produced the highest parasitism rate of host eggs among the five tested species, while T. mwanzai had the shortest developmental time on all test age eggs. In general, T. lutea was the best performing of the five species when reared on fall armyworm eggs, while T. japonicum was the worst. There were no significant differences, however, in percent emergence in the five test species when reared on fall armyworm eggs.

Predilection for host egg and host plant by Trichogrammatid species collected from different Crops

The host egg preference studies revealed that Trichogramma chilonis, which was collected from 8 crops, preferred the eggs of Corcyra cephalonica most (84.8% parasitism), followed by Chilo partellus (55.1%) and Helicoverpa armigera (47.9% parasitism) and Samia ricini eggs were least preferred, T. achaeae was recorded from eggs collected from 3 crops only. The parasitoids obtained from rice, sugarcane, cabbage and dolichos were more robust rather than other 4 crops. The parasitoids collected from sugarcane showed strong recognition to the crop when released back on sugarcane, while parasitoids from other crops did not show any pattern of host-plant recognition. Sugarcane appeared to be the most preferred crop for T. chilonis releases with parasitism of 30.5%, followed by paddy (18.9%), cotton (18.3%) and tomato was the least preferred host plant.

Nicosulfuron Plus Atrazine Herbicides and Trichogrammatidae (Hymenoptera) in No-Choice Test: Selectivity and Hormesis.

The aim of this study was to evaluate the effect of the herbicide mixture nicosulfuron + atrazine on 10 trichogrammatid species. A female of each trichogrammatid was placed in a test tube (no-choice) with a card with 45 Anagasta kuehniella eggs. Parasitism was allowed over a 48h period, then the cards were sprayed with a solution containing nicosulfuron (30gha-1) + atrazine (1500gha-1), besides the control (distilled water). The nicosulfuron + atrazine mixture increased the Trichogramma atopovirilia and T. pretiosum female emergence. The percentage of T. acacioi, T. atopovilia and T. pretiosum male parasitoids emerged was higher in the control, and for T. demoraesi and Trichogrammatoidea annulata with nicosulfuron + atrazine. Sex ratio of the trichogrammatids was similar with nicosulfuron + atrazine.

Evaluation of persistence and relative toxicity of some pest control products to adults of two native trichogrammatid species in Kenya

The utilization of native trichogrammatids for biocontrol of Helicoverpa armigera (Hbn.) and their potential integration with pesticide use are currently receiving attention. In this study the interaction of adults of Trichogramma sp. nr. mwanzai and Trichogrammatoidea sp. nr. lutea with commonly used pesticide products was investigated. The toxicity of eight pest control products commonly used in vegetable crops in Kenya, were evaluated by exposing the adults of the two species to detached potted tomato leaves at different intervals after spraying. Two biologically derived products, Achook® (neem-based) and Dipel® (Bt ssp. kurstaki)—were found to be harmless and had no persistent toxicity on both the trichogrammatid species. Two organophosphate products tested, dimethoate (Rogor®) and malathion (Malathion®) were found to be ‘slightly harmful’ and ‘moderately persistent’ respectively. Three other synthetic insecticides, lambdacyhalothrin (Karate®), bifenthrin (Brigade®) and alpha-cypermentrin (Fastac®) were found to be ‘moderately harmful’ and ‘persistent’ respectively. Polytrin® (mixture of cypermethrin and profenofos) was also found to be persistent but only ‘slightly harmful’. On the basis of five concentrations tested (0.032, 0.016, 0.008, 0.004 and 0.002 of the recommended field rates) the LC50 values for adult T. sp. nr. mwanzai were estimated as 285, 411, 435 and 1,916 (μg active ingredient (a.i) ml−1) for dimethoate; malathion; lambdacyhalothrin as well as cypermethrin + profenofos respectively. The corresponding values for T. sp. nr. lutea were 247, 251, 278 and 697 respectively. Further, Karate® appeared to be the least toxic among the four products, across all the respective concentrations. The study was an attempt to adopt the methodologies of the IOBC (International Organization for Biological Control) on non-target risk assessment for pest control products to cater for the local needs of integrating the use of the trichogrammatids along with other pest control products.

Egg laying and development of Neotropical trichogrammatid species in artificial eggs

AbstractThe goal of this work was to assess the suitability of two artificial diets for egg laying and development of Trichogramma atopovirilia Oatman & Platner, Trichogrammatoidea annulata De Santis, and Trichogramma bruni Nagaraja (all Hymenoptera: Trichogrammatidae). Additionally, the quality of wasps reared in vitro was compared with those reared in vivo. The ‘standard’ diet consisted of Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae) pupal holotissues (65%), chicken egg yolk (18%), fetal bovine serum (8.5%), lactalbumin hydrolysate (8.5%), and anticontaminants (0.3%). The ‘modified’ diet differed from the standard one only in the D. saccharalis pupal holotissues, that were replaced with Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae) ones. Females of the three trichogrammatid species laid eggs in artificial eggs containing any artificial medium, but the modified one received more eggs. Although the standard diet was accepted for oviposition by the three wasp species, no development occurred. On the modified diet, only T. atopovirilia was able to develop to adult emergence. Adult F1 were of a quality that was similar to insects reared in vivo.

Scope for genetic enhancement of the parasitisation potential of four native strains of Trichogrammatoidea sp. nr. lutea Girault (Hymenoptera: Trichogrammatidae) in Kenya

In response to emerging interest in commercial mass production of Trichogramma for Helicoverpa armigera biocontrol in eastern Africa, laboratory experiments were undertaken to assess the scope for genetic enhancement of the parasitisation potential of native strains of the local common trichogrammatid species, Trichogrammatoidea sp. nr. lutea. Four promising strains (ex-Kilifi – Kilifi District, ex-Kwa Chai – Kibwezi District, ex-Rarieda – Bondo District and ex-Ebuhayi, Kakamega District) were tested for cross-mating in reciprocal combinations with focus on fecundity and progeny female ratio. While all the crosses resulted in F1 progeny of both sexes, significant differences were observed between homogamic and reciprocal heterogamic crosses in fecundity, progeny production, proportion of female progeny and adult longevity. Among all the crosses, the cross between ex-Rarieda strain females and ex-Kilifi strain males resulted in progeny that was significantly superior in fecundity and progeny female ratio. Conversely, Kilifi strain females crossed to males from ex-Rarieda strain gave rise to progeny with relatively low fecundity and female ratio. There were significant differences between homogamic crosses and most reciprocal heterogamic crosses in the major biological attributes. Genotypic and phenotypic variance-covariance matrices generated for six life-history traits showed high positive correlations for most traits in both inbred (P<0.05) and reciprocal heterogamic crosses (P<0.05 and P<0.001). Fecundity and number of female offspring were the most important factors in the heterogamic crosses. The results confirmed the scope for genetic enhancement through inter-strain crossing for improving the field impact potential of T. sp. nr. lutea being targeted for commercial mass production.

The Effectiveness of Trichogramma chilonis, Trichogramma pretiosum and Trichogramma brasiliense (Hymenoptera: Trichogrammatidae) as Parasitoids of Helicoverpa armigera (Lepidoptera: Noctuidae) on Sunflower (Helianthus annuus) and Redgram (Cajanus cajan)

The performance of three species of trichogrammatids on the pest, Helicoverpa armigera was evaluated in the laboratory and screenhouse conditions in Karnataka, India during 1996-97. Laboratory studies indicated that Trichogramma chilonis and Trichogramma pretiosum were more effective parasitoids of H. armigera than Trichogramma brasiliense. In screenhouse conditions, T. chilonis was the most effective parasitoid of H. armigera eggs on sunflower plants in comparison to the other two trichogrammatid species. When releasing 50 000 per ha on sunflower and redgram, T. chilonis parasitised 50.1 and 11.4% H. armigera eggs, respectively. The position of H. armigera eggs on different plant parts of sunflower had no effect on parasitism by T. chilonis. However, parasitism by the same trichogrammatid among different plant parts of redgram varied significantly. It parasitized 43.4 and 18.7% H. armigera eggs on leaves and flowers, respectively, and significantly fewer, 3.9%, on pods (P<0.05). The growth stage of redgram plants also had an effect on parasitism by T. chilonis, parasitism being extremely low on plants with pods.

Effects of host age on parasitism and progeny allocation in Trichogrammatidae

AbstractThe impact of host age on the number of hosts killed, survival of progeny, progeny allocation, and sex allocation was examined for several Trichogrammatidae (Hymenoptera) species in laboratory choice tests. Individual female parasitoids were provided with young, medium‐aged and old eggs of one of three lepidopterous host species: Trichoplusia ni (Hübner) (Noctuidae), Pieris rapae (L.) (Pieridae), or Plutella xylostella (L.) (Plutellidae). Trichogrammatid species behaved as gregarious parasitoids with the first two host species, and as solitary parasitoids with eggs of the smaller latter one. They mostly preferred young eggs of T. ni, but did not discriminate among P. rapae eggs of different ages, and often preferred young or medium‐aged P. xylostella eggs over old eggs. Survival of progeny did not vary constantly with host age, although it was often very low in P. rapae eggs of any age. Clutch size frequently decreased with host age in both T. ni and P. rapae. Offspring sex ratio did not change with age of T. ni and P. rapae eggs, and rarely did so in P. xylostella eggs. In regard to host age, the results with T. ni are the ones which are the most in agreement with optimal foraging theoretical predictions, as clutch size was the highest in preferred younger eggs.

Studies on three species of Trichogramma. I. Foraging behaviour for food or hosts

The foraging strategies for both food or hosts of three trichogrammatid species: Trichogramma evanescens, Trichogramma cacoecia and Trichogramma dendrolimi were compared using artificial patches of Sitotroga cerealella eggs. In all experiments, inexperienced and newly emerged wasps of &lt; 1 h old were singly tested. When the females were allowed to land upon the hosts, the decision‐making process for initial acceptance or rejection was species‐dependent. The initial search in T. evanescens was for food, whereas T. dendrolimi or T. cacoeciae start to oviposit immediately after their emergence. When honey‐deprived or undeprived females were each exposed to single patches for 20 or 60 min, variations in mean number of probing females ‘drilling and ovipositing’ were also species‐dependent. Acceptance of host eggs by honey‐deprived females and subsequent egg deposition were higher in both T. cacoeciae and T. dendrolimi than in T. evanescens. For all species, the probing of honey‐undeprived females was higher than that of deprived ones. When the exposure period was prolonged to 24 or 48 h and the number of patches per female increased to three, most of the honey‐deprived or undeprived T. evanescens females attacked one patch, and only a few of them attacked two patches. Foraging activity of honey‐deprived females of T. cacoeciae was restricted to single patches, whereas most undeprived ones attacked more than one patch. In contrast, honey‐deprived or undeprived T. dendrolimi females attacked more than one patch. The experiments showed that T. dendrolimi females have more powerful ovipositing urges than looking for food and that the opposite was the case for T. evanescens, with T. cacoeciae being intermediate.