William C. Nettles

In vitro culture of the egg parasitoid Telenomus heliothidis: the role of teratocytes and medium consumption in development

The solitary egg parasitoid Telenomus heliothidis Ashmead (Hymenoptera: Scelionidae) was reared from egg to adult in vitro. Both sexes of adults emerged, mated, and the females produced viable offspring in the natural host, Heliothis virescens F. (Lepidoptera: Noctuidae). While the rearing medium was important in rearing, wasp fitness was influenced by other factors. The presence of teratocytes influenced parasitoid survival and development. In addition, the quantity of medium ingested by larvae affected the survival, size, longevity, and fecundity of adults.

Response of parasitoidEucelatoria bryani to selected plant material in an olfactometer

The response of the parasitoidEucelatoria bryani Sabrosky to fresh plant material and several plant extracts was examined in an olfactometer. The plants tested can serve as a food source for hosts (Heliothis spp.) of the parasitoid. Females responded positively to 13 of the 19 fresh plant tissues tested, and all of the extracts tested. Males responded to only two of the fresh plant tissues and to none of the extracts. The significance of plant variety, morphology, and phenology on the host habitat-selection behavior of this parasitoid is discussed.

Synergistic Action of Potassium Chloride and Magnesium Sulfate on Parasitoid Wasp Oviposition

A dilute solution of potassium chloride and magnesium sulfate induces oviposition in artificial eggs by the egg parasitoids Trichogramma pretiosum and T. minutum. The ability to obtain large numbers of eggs through the use of this inexpensive solution is a major advance toward the development of diets and the large-scale production of Trichogramma spp. in vitro.

THREE METHODS FOR THE IN VITRO CULTURE OF TRICHOGRAMMA PRETIOSUM RILEY

Three methods, which are more efficient than previously reported techniques, are described for in vitro production of Trichogramma pretiosum Riley in numbers ranging from a few to thousands. Severa...

EFFECT OF CATIONS, ANIONS AND SALT CONCENTRATIONS ON OVIPOSITION BY TRICHOGRAMMA PRETIOSUM IN WAX EGGS

K+, Mg2+, Cl−, and SO42‐ were important components eliciting oviposition by Trichogramma pretiosum in aqueous solutions in wax eggs. Ca2+ inhibited oviposition in a KCl‐MgSO4 solution. The solutions most active in stimulating oviposition were 124.7–36.5 and 83.1–24.3 mM, respectively, of KCl‐MgSO4.

The partial purification of a Trichogramma pretiosum pupation factor from hemolymph of Manduca sexta

Abstract Factors responsible for pupation of Trichogramma pretiosum Riley reared in vitro were partially purified. The active material was extracted with 76% ethanol from Manduca sexta (L.) hemolymph. The water soluble active fraction was chromatographed first on a Sephadex G-10® column and then on a C 18 cartridge (reversed phase). After removing more than 99% of the original protein, 20% of the original pupation activity remained; this fraction, however, also contained about 20% of the original hemolymph carbohydrate. The pupation factor was further separated by DEAE-HPLC into two active carbohydrate containing fractions. HPLC of the active fraction from the C 18 cartridge on an amino column produced some separation of the original carbohydrate, but no pupation activity was found in single fractions after this separation. However, when certain fractions were re-combined, weak pupation activity was obtained. The results indicate that when T. pretiosum were fed nutritionally rich artificial diets, at least two and possibly several polar, low molecular weight chemicals in M. sexta hemolymph were also needed and were responsible for growth and development of the parasitoids to the pupal stage. This is the first report describing the partial purification of insect growth factors affecting the growth and development of parasitoids.

Effect of artificial diet media, glucose, protein hydrolyzates, and other factors on oviposition in wax eggs by Trichogramma pretiosum

Artificial diet media were clearly inferior to dilute KCl–MgSO4 solutions as ovipositional stimulants for Trichogramma pretiosum. Depending on their concentrations, glucose, protein hydrolyzates, and free amino acids either had no effect on or were inhibitors of oviposition when they were mixed with KCl–MgSO4 solutions. Oviposition into artificial eggs containing salt solutions formulated to correspond to the concentration of potassium, magnesium, and sodium in insect components revealed that the hemolymph mimic and the mimic of Sitotroga cerealella eggs were poor, and that the mimic of whole Heliothis spp. larvae, which was similar to the concentration of these cations in Heliothis virescens eggs, was the most active in eliciting oviposition.

Effect of ovipositional stimulants and diets on the growth and development of Trichogramma pretiosum in vitro

Ovipositional stimulants and diets were tested in vitro using several rearing methods to determine effects on the growth and development of Trichogramma pretiosum Riley. Highest yields of pupae were obtained when Manduca sexta (L.) hemolymph was added to a chicken egg yolk and milk diet. However, this hemolymph based diet (BD) produced low yields (6–7%) of adults. When a similar diet containing 20% M. sexta egg liquid (BDE) was used, the yields of adults increased 7–13 fold to as high as 75.9%. For T. pretiosum reared on the BDE diet in microtiter plates, the adult yields were 46.9 and 63.6%, respectively, when the ovipositional stimulants were either the KCl‐MgSO4 solution or the BDE diet. Thus, the harmful effects of the salt oviposition solution were significant but perhaps not so great as to prevent the use of this technique for in vitro mass production of T. pretiosum. Although the ovipositional salt solution reduced adult yields, the effect was much smaller than the nutritional or physiological effect of deleting M. sexta egg liquid from the diet.

Regulation of Helicoverpa zea larval behavior by the parasitoid Eucelatoria bryani

The parasitoid Eucelatoria bryani Sabrosky regulates the larval behavior of its host Helicoverpa zea (Boddie). Parasitized third, fourth and fifth instars burrow into the soil 0.7–3.4 days earlier than unparasitized larvae that normally enter the soil to pupate at the end of the fifth and final larval instar. Parasitized third instars molt once then burrow as fourth instars, one instar earlier than normal. When E. bryani pupariated on the soil surface in the field, none survived to the adult stage. However, E. bryani adults emerged from 49.2% of hosts that had burrowed into the soil. By accelerating the timing of H. zea burrowing behavior and causing host larvae to enter the soil before death, E. bryani ensures its pupariation in an environment with improved protection against natural enemies and lethal temperatures.

Contact stimulants fromHeliothis virescens that influence the behavior of females of the tachinid,Eucelatoria bryani.

Factors acting at contact or close range affected the behavior associated with host seeking of females, but not of males, of the tachinid,Eucelatoria bryani Sabrosky. Females were arrested by components of larvae ofHeliothis virescens (F.) and by a dichloromethane extract of okra leaves. A hexane extract ofH. virescens frass and a chloroform-methanol extract ofH. virescens larvae were both active. In addition to chemicals, shape and size were involved because females were arrested by small inert objects the size ofH. virescens larvae and frass.