White Grub Species Research Articles

Population dynamics of white grubs in the upland rice and maize environment of Northern Mindanao, Philippines

Soil sampling over a two-year period in Claveria, Northern Mindanao, Philippines, revealed the presence of five white grub species (Coleoptera: Scarabaeidae) in the deforested, infertile, and highly eroded grassland environment being converted to small farms. Population dynamics data point to Leucopholis irrorata (Chevrolat), Holotrichia mindanaoana Brenske, and H. flachi Brenske being biennial with Adoretus luridus Blanchard and Anomala humeralis Burmeister being annual species. The three biennial species are synchronized to even-numbered years. Small subpopulations of the biennial species show evidence of annual or allochronic cycles. L. irrorata has an annual cycle in other areas of the Philippines on sugarcane but takes two years to develop in Claveria probably due to infertile soils and a longer feeding period. Other subpopulations of young larvae and emerged adults occurring in the late rainy season were 'attempts' at multiple generations or delayed development, but were considered suicidal due to the impending dry season. Synchronization of life stages occurs with pupation and adult emergence with early rains. Habitat preferences of the five species were elucidated by topography, cultivation, and presence of trees. L. irrorata and H. mindanaoana adults were found in 30 flight trees. Most (81%) of the larval stages were found within the top 20 cm of soil but some dug to 70 cm depth. Peak third instar larval densities reached 25.5/m 2 for all five species combined, but due to the biennial cycles of the major species, white grubs present economic importance to upland rice and maize only in odd numbered years. Control efforts are most economically directed during even numbered years giving a two-year benefit in population reduction.

Host — parasite interaction between two species of white grubs infesting sugarcane and two species of entomopathogenic nematodes

Among the two entomopathogenic nematodes,Steinernema glaseri Steiner andHeterorhabdities indicus (Poinar, Karunakar, David) tested on different instars of white grubs,Holotrichia serrata f. andLeucopholis lepidophora Brum. In laboratory conditions, the later one took less time (3.80 days) to inflict mortality ofH. Serrata than fomer (4.37 days), while it showed a reverse trend inL. lepidophora. The mean time taken to cause host mortality of white grubs increased as the instar stages increased. Infective juveniles (KJs) of both the nematode species emerged earlier (12.08 days) from first instar grubs than in second and third instar grubs. IJs of H. indicus emerged for a prolonged period (24.22 days) thanS. glaseri (21.90 days) on different instars of white grubs. IJs of both the species emerged for significantly longer period (24.17 days) inL. lepidoptera than inH. serrata (21.95 days). The emergence of IJs of these nematodes was significantly more in third instar grubs (40.68 days) than in first and second instars (13.25 days).H. indicus multiplied higher in number per unit body weight of white grub (864.74 IJs) thanS. glaseri (262.07 IJs). The multiplication of these nematodes per unit body weight of white grubs was more in third instar compared to first and second instar grubs.

Synergism of imidacloprid and entomopathogenic nematodes against white grubs: the mechanism

AbstractEntomopathogenic nematodes and the chloronicotinyl insecticide, imidacloprid, interact synergistically on the mortality of third‐instar white grubs (Coleoptera: Scarabaeidae). The degree of interaction, however, varies with nematode species, being synergistic for Steinernema glaseri (Steiner) and Heterorhabditis bacteriophora Poinar, but only additive for Steinernema kushidai Mamiya. The mechanism of the interaction between imidacloprid and these three entomopathogenic nematodes was studied in the laboratory. In vials with soil and grass, mortality, speed of kill, and nematode establishment were negatively affected by imidacloprid with S. kushidai but positively affected with S. glaseri and H. bacteriophora. In all other experiments, imidacloprid had a similar effect for all three nematode species on various factors important for the successful nematode infection in white grubs. Nematode attraction to grubs was not affected by imidacloprid treatment of the grubs. Establishment of intra‐hemocoelically injected nematodes was always higher in imidacloprid‐treated grubs but the differences were small and in most cases not significant. The major factor responsible for synergistic interactions between imidacloprid and entomopathogenic nematodes appears to be the general disruption of normal nerve function due to imidacloprid resulting in drastically reduced activity of the grubs. This sluggishness facilitates host attachment of infective juvenile nematodes. Grooming and evasive behavior in response to nematode attack was also reduced in imidacloprid‐treated grubs. The degree to which different white grub species responded to entomopathogenic nematode attack varied considerably. Untreated Popillia japonica Newman (Coleoptera: Scarabaeidae) grubs were the most responsive to nematode attack among the species tested. Untreated Cyclocephala borealis Arrow (Coleoptera: Scarabaeidae) grubs showed a weaker grooming and no evasion response, and untreated C. hirta LeConte (Coleoptera: Scarabaeidae) grubs showed no significant response. Chewing/biting behavior was significantly increased in the presence of nematodes in untreated P. japonica and C. borealis but not in C. hirta and imidacloprid‐treated P. japonica and C. borealis. Our observations, however, did not provide an explanation for the lack of synergism between imidacloprid and S. kushidai.

Characterization of midgut proteinase activities of white grubs: Lepidiota noxia, Lepidiota negatoria, and Antitrogus consanguineus (scarabaeidae, melolonthini)

AbstractThe proteinases in the midguts of three scarab white grub species, Lepidiota noxia, L. negatoria, and Antitrogus consanguineus, were investigated to classify the proteinases present and to determine the most effective proteinase inhibitor for potential use as an insect control agent. pH activity profiles indicated the presence of serine proteinases and the absence of cysteine proteinases. This was confirmed by the lack of inhibition by specific cysteine proteinase inhibitors. Trypsin, chymotrypsin, elastase, and leucine aminopeptidase activities were detected by using specific synthetic substrates. A screen of 32 proteinase inhibitors produced 9 inhibitors of trypsin, chymotrypsin, and elastase which reduced proteolytic activity by greater than 75%. © 1995 Wiley‐Liss, Inc.

Evaluation of a Preplant Method for Detecting Damage to Germinating Corn Seeds by Multiple Species of Insects

Field studies were conducted in Virginia cornfields from 1989 to 1991 to evaluate a preplant method for detecting damage to germinating corn seeds by multiple species of insect pests, including seedcorn maggots, Delia platura (Meigen); several species of wireworms in the genera Melanotus, Conoderus , and Aeolus ; and several species of white grubs in the genera Popillia, Cyclocephala, Cotinis , and Maladera . The method used consisted of evaluating feeding damage to com seeds in wire-mesh traps (i.e., baited wire traps) that were buried in cornfields for ≍2 wk before planting. In the 1989 study conducted in a cornfield with a large infestation of wireworms, a significantly greater proportion of com seeds exhibited feeding damage in the baited wire traps (38.3%) compared with corn seeds planted by hand at conventional plant spacings (i.e., simulated commercial plantings) (31.5%). Further evaluation in 47 cornfields in 1990 and 1991 revealed no significant difference between the proportion of damaged corn seeds in the baited wire traps (2.7%) and simulated commercial plantings (2.0%). A Significantly greater proportion of com seeds exhibited feeding damage in the commercial plantings (5.4%) compared with the baited wire traps; however, mean stand loss associated with insect feeding in the commercial plantings was only 0.4%, which was substantially less than the proportion of damaged com seeds in the haited wire traps. Significant linear regressions were obtained between the proportion of damaged seeds in the baited wire traps and the proportion of damaged seeds in the simulated commercial plantings, commercial plantings, and proportion of stand loss in the commercial plantings. However, the lack of economic stand loss in the commercial plantings and low regression coefficient of determination precluded the development of a baited wire trap damage threshold to predict stand loss in fields subsequently planted with corn.

Scarabeid larvae control in sugarcane using Metarhizium anisopliae

Sugarcane white grubs (Coleoptera: Scarabeidae) account for 75% of all insect pest losses to sugarcane in Australia. They damage roots causing lodging, reduced plant growth, and death of the cane plant. From the 10-12 major economic white grub species in Queensland, Antitrogus par&us is important in the Bundaberg-Isis districts. Both Mocap and SuSCon, the two insecticides used generally for white grub control, are less effective against A. parvulus than against other species, mainly because of the high (53-74%) clay content of the soil. Damage by A. parvulus occurs mostly in the second (final) year of the life cycle, with major impact from the third instar between September and February. Wild-type isolates of the fungus Metarhizium anisopliae were found to be highly pathogenic in the laboratory toward A. parvulus and other white grub species (K. D. Z. Samuels, D. E. Pinnock, N. E. Featherstone, and R. M. Bull, unpublished). A field trial was established to monitor the effect of field conditions on M. anisopliae spore applications and to assess crop protection potential. We report here significant field control of A. parvulus following M. anisopliae spore applications. Spores of M. anisopliue strain WF2X isolated from Lepidiota negatoria (Scarabaeidae: Melolonthinae) from Bundaberg, Australia, were mass produced on wheat, rice, or maize. Two-kilogram batches of sterile grain in autoclavable bags were each inoculated with 0.5 liter of a 5-day-old liquid culture of WF2X, and through which sterile air was passed for up to 1 month until heavily sporulated. The resultant culture on grain was applied to lOOto 125-mm-deep furrows along each side of the row of 6month-old first ratoon sugarcane var. CP44-101, then the soil was replaced. Doses of the unprocessed culture on grain were applied on 4 March 1986 at 1 x 10” spores/ha to 15-m-long plots of three cane rows each, set out in two 45-m columns (three treatments per column) separated by a three-row untreated control. Four replicates constituted culture on rice (A-D) with one each on wheat (E) and maize (F). Differences between means were tested by Student’s t test while goodness of tit was tested by x2 analysis, as indicated in the tables. Immediately prior to treatment, a series of 10 cane stools (45 x 45 x 30 cm deep) were dug by spade at random across the trial area and a population of 20 (2 10) larvae found beneath each. All three instars were found in approximately equal numbers. Soil samples were collected on eight occasions to October 1988 to monitor spore survival, while A. parvulus populations were periodically assessed from live 300mm cubes of soil dug from each plot (Table 1). No visible effect on crop vigor was detected in the first or second ratoon, despite A. parvulus larvae being present, with yields for both years of 90 tonnes cane/ha. The young third ratoon exhibited strong growth responses in the treated plots, while the untreated had retarded growth and yellow foliage (Table 2). Population assessment confirmed all treated plots (except C) had lower numbers of A. parvulus larvae by December 1987, with a number of infected cadavers being recorded prior to this during 1987 (Table 1). Treatment C inoculum was contaminated by a Penicillium sp. at application, which may have initially affected infectivity of the M. anisopliae spores. However, by March 1988, 3.88 x lo5 M. anisopliae spores/g soil were recorded in this plot. Two infected cadavers were found in

Differential Susceptibility of Japanese Beetle, Oriental Beetle, and European Chafer (Coleoptera: Scarabaeidae) Larvae to Five Soil Insecticides

Efficacy of bendiocarb, chlorpyrifos, diazinon, ethoprop, and isoJenphos was evaluated against last-instar larvae of European chafer, Rhizotrogus majalis (Razoumowsky), Japanese beetle, Popillia japonica Newman, and Oriental beetle, AnOmala orientalis Water­ house, 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 mor­ tality 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.

Seasonal Phenology of White Grubs (Coleoptera: Scarabaeidae) in Florida Sugarcane Fields

The seasonal phenology of two white grub species found in Florida sugarcane was determined under field conditions. Both Cyclocephala parallela Casey and Ligyrus subtropicus Blatchley had 1-year life cycles, and third-instar larvae were the longest enduring and the overwintering stage of both species. Developmental stages of C. parallela preceded corresponding stages of L. subtropicus by 2 to 6 weeks in sugarcane fields. Morphometric data for the two species are also given. The relationship of these preceding data to grub damage in Florida sugarcane fields is discussed.

Spatial Distribution of White Grubs (Coleoptera: Scarabaeidae) in Florida Sugarcane

The spatial distribution of two white grub species was measured in 40 Florida sugarcane fields. The highest density of third-instar grubs of both Cyclocephala parallela Casey and Ligyrus subtropicus Blatchley was found from 0 to 15 cm directly under sugarcane stools. Both species were aggregated among sugarcane stools in > 90% of the fields sampled. However, C. parallela was more evenly spread throughout fields than L. subtropicus, which infested field edges most heavily.

White Grub Control on a Home Lawn in Doylestown, Pa, 1982

Abstract Thirteen insecticide treatments were applied Aug 16 to a home lawn infested with white grubs. The predominant white grub species present was Japanese beetle (70%) with the remaining species present in equal numbers (Coborealis, 15%; Phyllophaga spp, 15%). The lawn consisted of Kentucky bluegrass (25%), fescue (25%), and a wide array of weeds (50%). Treatment plots were 10 × 10 ft, arranged in a randomized complete block design and replicated 4 times. Liquid formulations were applied in 3 gal water with a hand-held sprinkling can. Granular formulations were applied with a hand-held shaker, followed by watering in with 3 gal water. At treatment time, the following environmental conditions existed: air temperature, 85°F; soil temperature, 76°F; soil type, silt-loam; soil pH, 5.0; percent organic matter, 2.9; soil condition, moist; amount of thatch, 0.06 in; and skies were clear and sunny. Post treatment counts were made 43 days later (Sep 29). Four ft2 sod samples were randomly taken from each replicate, and the total number of living white grubs was recorded for each ft2 sample.

White Grub Control on a Home Lawn in Bucks County, Pa, 1982

Abstract Seven insecticide treatments were applied Aug 20 to a home lawn infested with white grubs. The predominant white grub species present was Japanese beetle (70%), with the remaining species present in equal numbers (C. borealis, 15%; Phyllophaga spp, 15%). The lawn consisted of Kentucky bluegrass (25%), fescue (25%), and a wide diversity of weeds T50%). Treatment plots were 10 × 10 ft, arranged in a randomized complete block design and replicated 4 times. Liquid formulations were applied in 3 gal water with a hand-held sprinkling can. Granular formulations were applied with a hand held shaker, followed by watering in with 3 gal water. At treatment time, the following environmental conditions existed: air temperature, 83°F; soil temperature, 76°F; soil type, silt-loam; soil condition, moist; soil pH, 5.4; percent organic matter, 2>.5; amount of thatch, 0.06 in; and skies were partly cloudy. Post-treatment counts were made 41 days later (Sep 30). Four ft2 sod samples were randomly taken from each replicate, and the total number of living white grubs was recorded for each ft2 sample. An average of 17 white grubs per ft2 was recorded Aug 20 prior to treatment.

The Search for Parasites of White Grubs (Melolonthids) in Zanzibar, Algeria, Morocco and France

(1) An extensive survey covering a period of 18 months was carried out in Zanzibar, Algeria, Morocco and some parts of France with a view to obtaining parasites of white grubs for furthering the control of Phytalus smithi, Arrow, in Mauritius.(2) In Zanzibar the results of the survey showed that white grubs are of no great economic importance in clove plantations in this Island. Larvae of several species of white grubs were obtained, viz.: Entyposis impressa, Kolbe, Schizonycha spp., Anomala delagoa, Pèr., etc. ; these larvae are parasitised by the Dexiid fly, Microphthalma disjunctum, Wied. The percentage of parasitism at the time of the survey was from 0·10 to 0·53 per cent. Scoliids were not in great number ; the parasitism amounted to 0·6 per cent. Parasites of adult beetles were obtained on the following insects: Entyposis impressa, Kolbe, Schizonycha spp. and Anomala plebejus, Ol., the parasites being Pexopsis pyrrhaspis, Villen., and an Adapsilia, not yet determined. The parasitism on the above mentioned beetles varied from 1 to 9·7 per cent.

The Fauna of injurious Soil Insects of Arable Land

Clean summer fallow is often recommended for reducing wireworm and white-grub infestations, but our investigations on this subject, conducted during the years 1933–35 at the Ukrainian Rubber Plants Experimental Station (near Kremenchug) showed that in arable fertile “ chernozem ” soil there is no significant decrease in the number of these pests after a clean summer fallow. These divergent results led us to suppose that the reaction of various species of wireworms and white-grubs to soil cultivation and fallow may be different.

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