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Efficacy of bendiocarb, chlorpyrifos, diazinon, ethoprop, and isofenphos was evaluated against last-instar larvae of European chafer, Rhizotrogus majalis (Razoumowsky), Japanese beetle,Popillia japonica Newman, and Oriental beetle, Anomala orientalis Waterhouse, by incorporating insecticides into soil at one-half New York State recommended rates in a laboratory bioassay. Mortality was assessed at 1, 2, 3, 4, and 5 wk. The experiment was repeated three times with white grubs collected at different times and from different locations in New York. White grub species differed significantly in their response to some of the insecticides; European chafer was generally least susceptible. Diazinon provided high mortality of Oriental beetle and European chafer grubs but very low mortality of Japanese beetles. Isofenphos provided generally low mortality of all three grub species, although the levels of mortality varied among species. Ethoprop provided uniform mortality of all three grub species. Results of these studies indicate the need to develop species-specific insecticide recommendations for the white grub complex.

Four species of entomogenous nematodes [Steinernema feltiae (Filipjev) [=Neoaplectana carpocapsae Weiserl (‘All’ strain), S. glaseri (Steiner), Heterorhabditis heliothidis (Khan, Brooks & Hirschmann), and Heterorhabditis sp. (‘Holland’ strain)] were compared with two insecticides (chlorpyrifos and isofenphos) for control of third- (last-) instar larval Japanese beetles (Popillia japonica Newman) and European chafers [Rhizotrogus majalis (Razoumowsky)] in potted Japanese yew (Taxus cuspidata Siebold & Zuccarini). Efficacy was evaluated 17-21 d after treatment. Heterorhabditis sp. (‘Holland’ strain) at 92 nematodes per cm2 of soil surface and H. heliothidis at 192 nematodes per cm2 provided >90% control of Japanese beetles compared with 71% for chlorpyrifos (9.0 kg [AI]/ha) and 84% for isofenphos (4.5 kg [AI]/ha). S. glaseri provided 84 and S. feltiae 29% control (both at 385 nematodes per cm2). Both nematodes and insecticides were less effective in controlling European chafer larvae. Control with nematodes ranged from 46 to 59% with S. glaseri, H. heliothidis, and Heterorhabditis sp. at 385 nematodes per cm2, whereas S. feltiae at 385 nematodes per cm2 did not significantly reduce larval survival compared with the untreated control. Chemical control of European chafer larvae resulted in reductions of 44 and 62% with isofenphos and chlorpyrifos, respectively.

In laboratory studies, infective juveniles of Steinernema feltiae Filipjev (=Neoaplectana carpocapsae Weiser) (All strain) and Heteorhabditis heliothidis (Khan, Brooks & Hirschmann) were tested for their ability to control third-instar European chafer (EC), Rhizotrogus majalis (Razoumowsky), in soil at rates from 19.4-310.0 nematodes per cm2 of soil surface. H. heliothidis provided better control of EC larvae than S. feltiae over the range of rates tested. After 25 d, treatment with H. heliothidis provided 94% control of larvae at the lowest rate tested (19.4 per cm2). In a field test in turf against a mixed population of Japanese beetle, Popillia japonica Newman, and EC larvae, H. heliothidis (310 per em2) provided >60% control (47 d after treatment), which was equivalent to the control achieved with the labeled rates of chlorpyrifos, trichlorfon, and isofenphos against this combination of white grubs.

Distribution of Japanese beetle, Popillia japonica Newman, grubs and dispersal of an entomopathogenic nematode, Heterorhabditis bacteriophora Poinar ‘Oswego’ strain (an isolate from New York state), were examined for 5 wk within soil-filled flats containing grass. Japanese beetle grubs uniformly dispersed to all sections of the flats not infested with H. bacteriophora ‘Oswego’ strain. In flats infested with H. bacteriophora ‘Oswego’ strain, however, greater proportions of Japanese beetle grubs were recovered in sections near the nematode release site or center sections of the flats. H. bacteriophora ‘Oswego’ strain dispersed to all sections of the flats but dispersed more rapidly within the flats infested with Japanese beetle grubs than in flats not infested with Japanese beetle grubs.

Japanese beetle, Popillia japonica Newman, European chafer, Rhizotrogus (Amphimallon) majalis (Razoumowsky), and oriental beetle, Anomala orientalis Waterhouse, were exposed to an ecdysone agonist, halofenozide, in the egg, 1st instar, and 3rd instar at 1.5, 3, 6, and 12 ppm, respectively, in soil. Species, stage, and physiological condition of larvae affected the response to halofenozide. Japanese beetle was the most sensitive, with maximal response of 1st instars at 3 ppm. First and 2nd instars were more susceptible than were 3rd instars. Sublethal exposure of 1st-instar European chafer and 3rd-instar oriental beetle resulted in dose-dependent accelerated development and successful molts. Field trials are needed in locations where there are mixed populations of scarabs to determine whether the species differences in susceptibility to halofenozide observed in this work will translate to increased relative importance of European chafer.

Crude extracts of five plant species which in previous experiments significantly limited corn wireworm, Melanotus communis Gyllenhal, feeding damage were tested for deterrence of the southern corn rootworm, Diabrotica undecimpunctata howardi Barber. When offered extract-treated and untreated corn seeds, rootworms damaged significantly fewer treated seeds than untreated seeds with four of the extracts. In a “no-choice” test design, with the three most effective extracts, there was a significantly lower frequency of damage to treated baits compared to control baits.

Mortality of last-instar Japanese beetles, Popillia japonica Newman, was highest when exposed to isazophos, bendiocarb, and chlorpyrifos in 30-ml arenas containing California soils in laboratory assays. Carbaryl and two nematodes, Heterorhabditis bacteriophora Poinar and Steinernema glaseri (Steiner), were less effective treatments in these arenas. Soil × treatment (insecticides and nematodes) interactions were highly significant, often changing larvicide rank order of efficacy within soils. Soil characteristics identified by regression analysis as affecting insecticidal activity were organic matter (chlorpyrifos, bendiocarb, and S. glaseri) and pH (carbaryl and isazophos). In arenas (7.6-cm diameter by 15 cm) simulating turf conditions, S. glaseri was the most effective treatment, followed by chlorpyrifos, then bendiocarb. The influence of irrigation on improving insecticide efficacy increased with higher soil organic matter. Because no treatment was completely effective against larvae, eradication of Japanese beetles cannot depend entirely on control tactics directed against the immature stages.

A control decision rule for European chafer, Rhizotrogus (Amphimallon) majalis (Razoumowsky), larvae infesting turfgrass was developed using data from 317 residential sites. Larvae were often abundant enough to cause damage to turf in portions (patches) of properties when average density over an entire site was much less than a damage threshold of 5–10 grubs per 950 cm2. To account for this, an empirical relationship between the size of the largest patch of European chafer larvae at a site and site-wide density was used in the development of the decision rule. Properties with a patch of grubs in excess of ˜30 m2 were deemed to require insecticide treatment. Site characteristics (lawn age, shade, and percentage of Kentucky bluegrass) were related to site-wide density and this relationship was used to formulate a risk assessment system. This system is used to determine whether a site should be sampled or not. Properties that are not sampled are not to be treated. Other treatment decisions are based on the outcome of sampling. The relationship between site-wide density and patch size did not allow clear identification of a density that could be used as a threshold in a sampling program. Therefore, several sampling plans were constructed that classified density according to different threshold values. Operating characteristic functions were used in combination with the aforementioned relationship between density and patch size to calculate two types of errors for each sampling plan: the probability of not treating when treatment was necessary and the probability of treating when treatment was not required. Based on these error functions, a threshold of 0.25 grubs per ll-cm diameter turf plug was advocated. Use of the proposed control decision rule should result in few treatment errors but could lead to considerable reductions in pesticide use.

A laboratory technique is described in which “soft” radiographs are used to study wireworm, Melanotus communis Gyllenhal, movement patterns within a soil matrix. Advantages of this technique as compared with destructive sampling are discussed and examples of several possible applications are given.

Movement patterns of japanese beetle, Popillia japonica Newman, and European chafer, Rhizotrogus (Amphimallon) majalis (Razoumowsky), grubs as influenced by gravity, host plant position, and external disturbances were studied in laboratory soil–turfgrass microcosms. Second through third instars just before pupation were monitored using radiographic techniques. Neonates were monitored using destructive sampling. Results demonstrate significantly different movement patterns between species and among age groups. The development stage of the grub had a large effect on Japanese beetle grub behavior and a measurable, but lesser effect, on European chafers. All larval stages of European chafers and all larval stages of Japanese beetle, except neonates and postoverwintering third instars, displayed a downward movement in response to disturbance. Neonate Japanese beetles showed little movement while postoverwintering. Japanese beetles moved upward when disturbed. European chafer grubs of all age classes displayed random vertical movement with some arrestment in or near sod. Preoverwintering and postoverwintering third-instar chafers showed less dramatic arrestment behavior than other instars tested. Second-instar Japanese beetles behaved similarly to European chafers; however, third instars behaved very differently. All third instars except those tested in late winter and early spring showed some innate downward movement in the soil microcosms. Japanese beetles tested in late winter displayed random movement with some arrestment in sod, whereas those tested in early spring exhibited upward movement and arrestment in sod.