Grub Damage Research Articles

Phosphorus fertiliser is associated with reduced grass grub (Costelytra giveni) fitness in Epichloë endophyte-infected meadow fescue and perennial ryegrass.

Fertiliser applications are well-established tools in pasture-based agricultural landscapes. This study focuses on the impact of phosphorus (P) fertiliser on grass grub (Costelytra giveni), a major pasture pest. This research investigates the interplay between P, plant growth, and grass grub fitness in Epichloë endophyte-infected perennial ryegrass (Epichloë sp. LpTG-3 strain AR37) and meadow fescue infected with E. uncinata (strain MaxR; AR1017), alongside their endophyte-free counterparts. In a glasshouse trial, plants were grown in P-enriched soil with varying Olsen P levels (9, 18, 28 or 78 mg L-1), and grass grubs were introduced. Their survival and weight gain, and plant performance were measured. In a bioassay, grass grubs were placed in specimen vials with P-enriched soils (Olsen P levels 9, 18, 28 and 78 mg L-1) and provided with identical plant material to assess their diet consumption and weight gain. In the glasshouse trial, results highlighted a notable decrease in the survival of grass grub on plants infected with MaxR endophyte, but not with AR37, as well as increasing soil Olsen P levels in both plant species. While grass grub decreased plant performance at the low Olsen P level (9 mg L-1), this effect diminished with increasing P. Likewise, results from the bioassay showed a decrease in diet consumption with increasing soil Olsen P levels. In both trials increasing Olsen P levels correlated with diminished grass grub performance, revealing a nuanced relationship between soil fertility and pest dynamics. The study underscores the pivotal role of selected Epichloë endophyte-grass associations in mitigating grass grub damage across varying phosphorus levels. This study highlights the potential to integrate P applications for sustainable pest control against grass grub. Further field trials are required to validate these findings. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Enhancing Red Ginger Plant Growth through Eco-Friendly Pest Management: Synergistic Effects of Metarhizium anisopliae and Imidacloprid

This study explores the potential of a more environmentally friendly pest management approach for enhancing the vegetative growth of red ginger plants (Zingiber officinale Rosc.) by mitigating the damage caused by Lepidiota stigma (white grub) larvae. The study was conducted at the Experimental Garden of the Faculty of Agriculture, UPN “Veteran” Yogyakarta from April to August 2022, utilizing a factorial Completely Randomized Design. The application of the entomopathogenic fungus Metarhizium anisopliae at varying doses (0 g, 10 g, 20 g, and 30 g per 3 kg of planting media) and the systemic insecticide Imidacloprid (either absent or at a dose of 0.02 g per 3 kg of planting media) were the primary factors studied. Each treatment combination, executed on ten plants each infested with one larvae, was repeated thrice. The findings demonstrate that a combined application of M. anisopliae and Imidacloprid could significantly reduce the intensity of white grub damage to red ginger plants and improve their vegetative growth. Notably, a dose of M. anisopliae of 20 g per 3 kg of planting media maximized the plant height, leaf number, and tiller count. The findings highlight the potential of integrating biological and chemical controls for sustainable pest management and crop yield improvement, with broad implications for other similar agricultural contexts.

Evaluation of 12 Sweetpotato Clones in Coastal South Carolina for Yield and Insect Resistance Using Organic and Conventional Cultural Practices

The yield and insect resistance of 12 sweetpotato (Ipomoea batatas) clones grown in two different production systems (organic black plastic mulch and conventional bare ground) were evaluated in 2016 and 2017 in coastal South Carolina. Significant differences in total storage root yield, marketable storage root yield, U.S. No. 1 storage root yield, and percent of U.S. No. 1 storage roots in all trials were found, except for percent of U.S. No. 1 storage roots in 2017 for the organic black plastic mulch trial. In the organic black plastic mulch trials, ‘Bonita’ and USDA-04-136 consistently produced high marketable yields, whereas ‘Ruddy’ and USDA-W388 consistently produced the lowest marketable yields. ‘Averre’, ‘Beauregard’, ‘Covington’, and USDA-09-130 exhibited variable performance, with marketable yields among the highest in a single year. For the conventional trials, USDA-04-136 consistently produced high marketable yields, whereas ‘Ruddy’ and USDA-W-388 consistently produced the lowest marketable yields. ‘Averre’, ‘Bonita’, ‘Covington’, and USDA-09-130 exhibited variable performance, with marketable yields among the highest in a single year. For the organic black plastic mulch, significant differences were detected in the percent of uninjured roots and percent white grub (primarily Plectris aliena) damage in 2016 and in wireworm (Elateridae)-cucumber beetle (Diabrotica)-flea beetle (Systena) severity index (WDS severity index) in 2016 and 2017. USDA-04-136 and USDA-W-388 consistently had the lowest WDS severity index, whereas ‘Covington’ consistently had the highest WDS severity index. For the conventional trials, significant differences were found among clones in both years for all insect rating variables, except for percent sweetpotato weevil (Cylas formicarius elegantulus) damage. ‘Ruddy’, USDA-04-136, and USDA-W-388 consistently yielded the highest percent of uninjured roots, whereas ‘Averre’, ‘Bonita’, SC-1149-19, and USDA-09-130 consistently had the lowest percent of uninjured roots. The research reported here for yield and insect resistance under conventional and organic production systems will be useful for producers in the selection of cultivars suitable for growth in South Carolina.

White Grub ‘Kurmula’ Holotrichia spp. an Agriculture Important Pest in India: A Review

White grubs are the distractive, public Importance and a genuine requirement to Kharif crops become under rainfed conditions. Both the grubs and grown-ups are polyphagous and univoltine. No single control measure is powerful for their administration consequently is the lone alternative for their compelling administration in the sloping zone. Therefore, the stock of the insects joins 24 species having a place with 13 genera under 5 subfamilies. White grubs are larvae of melolonthinae (Scarabaeidae : Coleoptera) but the term includes larvae of Rutelinae, Dynastinae, Cetoniinae and other families of Scarabaeidea superfamily. The use of the compound bug spray on the banks of the stream makes the water contamination the following towns and makes the odds of obstruction improvement in bother. White grub damage typically appears as stunted, wilted, discolored, or dead seedlings and/or as gaps in rows where plants fail to emerge. White grubs prune roots and can feed on the mesocotyl causing plant death.

Pot trial screening of chemical, biological and natural insecticides for the management of white grubs (Coleoptera: Scarabaeidae) during eucalypt and wattle establishment

In South African forest plantations, white grubs (Scarabaeidae larvae) can contribute to high transplant mortality following re-establishment. Currently registered insecticides are considered highly hazardous and their use is restricted by the Forest Stewardship Council (FSC). Therefore, there is an immediate need to find effective alternative products for the control of white grubs. To circumvent sporadic spatial variations associated with field trials, a pot trial bioassay method was developed to screen a broad range of alternative chemical, biological and natural products for the control of Schizonycha affinis on eucalypt (Eucalyptus grandis W.Hill) and black wattle (Acacia mearnsii De Wild.) seedlings. The first pot trial screened 14 insecticide options against two white grub instar stages. Treatments included two registered chemical insecticides (deltamethrin, imidacloprid), one alternative chemical insecticide (clothianidin), two natural insecticides (azadirachtin, diatomaceous earth), and four biological insecticides (two Beauveria spp., a Bacillus and a Trichoderma sp.). In addition, potassium silicate was tested in combination with natural and biological insecticides. The most promising insecticides were re-tested against a single larval stage. Results from both trials showed that treatment with imidacloprid tablets and liquid (registered products), clothianidin and B. brongniartii were significantly better than all other products in reducing the impact of white grub damage on E. grandis and A. mearnsii seedlings. The use of pot trials with planned inoculations of the viable target pest proved useful in the initial screening of control products. The information generated in this study will contribute to the development of an alternative FSC-compliant strategy for the control of white grubs in plantation forest regeneration.

An innovation systems approach to understanding the impacts of grass grub damage in irrigated Canterbury dairy pastures

An innovation systems approach involving agribusiness representatives, researchers and farmers identified that damage caused by grass grub (Costelytra giveni) was a key factor contributing to areas of reduced yield within high-producing pastures. Using a recognised yield mapping technique, areas of ‘Low’ and ‘High’ pasture height were identified in different paddocks over 3 years; ‘Low’ areas had significantly higher numbers of grass grub larvae than ‘High’ areas. Pasture production was measured for the ‘Low’ and ‘High’ pasture height areas, and the difference was calculated to be 6800 kg DM/ha for 2018/19. This difference persisted after grass grub larvae were no longer active. Farm systems modelling analysis estimated this ‘yield gap’ led to a $650/ha/year difference in profit. A survey of farmer perceptions of grass grub damage on 23 central Canterbury dairy farms estimated 19% of pastures were affected by grass grub, with 11% of the area in those paddocks being damaged. Econometric modelling showed differences in farmer perceptions of grass grub damage. Data from the survey and the pasture measurements were combined with the farm systems modelling results to estimate a $1,870,000/year regional-scale impact of the ‘yield gap’. An integrated pest management approach is suggested to control grass grub damage.

Warming increased feeding of a root-chewing insect at the soil surface and enhanced its damage on a grass

Air and soil warming influences both plants and root herbivorous insects, but how warming alters their interactions is largely unknown. Because both the intensity of herbivory and plant susceptibility to the herbivory depend on temperature, it is difficult to predict the effects of insect herbivory on plant growth under warming. To analyse changes in belowground plant-insect interaction due to warming, we conducted a pot experiment using one grass species, Lolium perrene, and one beetle grub Anomala cuprea. Temperature (17 °C or 20.3 °C), presence or absence of a grub, and presence or absence of organic matter (OM) on the surface of the potted soil were manipulated. OM at the soil surface is an important resource for grubs, and contains neutral lipid fatty acids (NLFA) that can serve as a bacterial marker. NLFAs can be used as a tracer to determine whether grubs had fed upon OM, so we evaluated the consumption and vertical movement of a grub in response to warming. In the absence of grubs, plant biomass increased with warming, but was not affected by the OM treatment. In the presence of grubs, plant biomass was significantly decreased. Moreover, the interaction term between the temperature and grub treatments was significant, demonstrating that grub damage was more severe under warmer conditions. Grub mortality was not affected by any treatment. The bacterial NLFAs in a grub were significantly more detectable when OM was added relative to those without OM, and the amount increased with warming treatments. This suggests that the grub fed near the soil surface under both temperature conditions, but increased consumption rates under the warmer condition. The mean relative soil moisture content in the warmer conditions was significantly lower than that in the control conditions. OM additionally increased soil moisture, but it had no effect on herbivory damage, suggesting that plant susceptibility to herbivory was not attributable to soil moisture. These results show the importance of biological-context dependency of warming on a plant. Temperature changes will alter the root-herbivore interactions not by changing the plant susceptibility to herbivory but by increasing the consumption of the grub.

Exploring Efficacious Microbial Bio-agents and Insecticides Against White Grubs in Sugarcane in Indo-Gangetic Plains

White grubs are polyphagous subterranean insect pests which have recently emerged as a major threat to sugarcane cultivation. For effective management of these pests in sugarcane, studies were undertaken to evaluate various locally isolated as well as commercially available microbial biocontrol agents, entomopathogenic nematodes and novel chemical pesticides against white grubs. Attempts were made to isolate effective bio-agents associated with white grubs in indo-gangetic plains of India. Altogether, nine local bacterial isolates associated with infected white grubs were isolated and tested for their bio-efficacy under laboratory condition. However, none of the isolates were found effective against the predominant species, Holotrichia consanguinea. Hence, attempt was made to assess the field efficacy of already available five microbial bio-agents, viz., Metarhizium anisopliae, Beauveria bassiana, Bacillus cereus strain WGPSB-2, Heterorhabditis indica, Steinernema carpocapsae and three insecticides, viz., Chlorantraniliprole 0.4 G, Fipronil + Imidacloprid 80 G and Chlorpyriphos 10 G at their recommended doses. Results of the experiments conducted for 2 years under randomized block design revealed that treatment of Bacillus cereus strain WGPSB-2 @10 kg/ha (1 × 1013 cfu/ha) could reduce the white grub damage to the extent of 59.8%, while other bio-agents could reduce the damage in the range of 24.3–39.5% over untreated control. All the insecticides were found effective in reducing white grub damage, and in most of the observations, difference in reduction in the white grub damage was statistically non-significant. However, Chlorantraniliprole 0.4 G @ 20 kg/ha was most effective, which could reduce the grub damage to the extent of 89.10% over untreated control.

Novel bacterial seed treatment protects wheat seedlings from insect damage

Insecticidal seed treatments are used commonly worldwide to protect seedlings against root feeding insects. Organophosphate insecticides that have been used for seed treatments are being phased out and replaced with neonicotinoid insecticides. Concerns about the environmental impact of neonicotinoids have prompted a search for alternatives. Microbial insecticides are a biological alternative for seed treatments to target root feeding insects. Six field trials with organophosphate granules (diazinon, chlorpyrifos), neonicotinoid seed treatment (clothianidin) and microbial (Serratia entomophila) seed treatment targeting grass grub, a New Zealand scarab pest, were conducted in wheat crops at several sites over 4 years (2012–2015). Sites were selected each year that had potentially damaging populations of grass grub present during the trials. Untreated seeds led to significant losses of plants and wheat yield due to lower seedling establishment and ongoing plant losses from grass grub damage. Insecticide and microbial treatments increased plant survival in all trials compared with untreated seeds. Better plant survival was associated with higher yields from the insecticide treatments in four out of six trials. Neonicotinoid seed treatment alone gave similar yield increases to combined neonicotinoid seed treatment and organophosphate granules. Microbial seed treatment with S. entomophila gave similar yield increases to insecticide treatments in two out of six trials. Seed treatment with S. entomophila is an alternative for grass grub control; however, development of a commercial product requires effective scale-up of production, further research to improve efficacy, and viability of the live bacteria needs to be maintained on coated seed.

Field Evaluation of Entomopathogenic Fungi against White Grub, <I>Holotrichia consanguinea</I> Blanch in Sugarcane

Field experiments were conducted on sugarcane for white grub management using two entomopathogenic fungi i.e., Beauveria bassiana and Metarhizium anisopliae in Andhra Pradesh during 2013-14. Among the treatments imposed at the time of planting, M. anisopliae @ 5×10 13 spores ha -1 mixed with farm yard manure (FYM) was found effective followed by B. bassiana @ 5×10 13 spores ha -1 applied in FYM enriched field and registered 93.6 % and 88.09 % decrease in white grub damage and 77.22 % and 74.08 % decrease in white grub population. The highest cane yield was recorded when M. anisopliae @ 5x1013 spores ha -1 (81.44 t ha -1 ) applied with FYM followed by B. bassiana @ 5×10 13 spores ha -1 (76.6 t ha -1 ) with FYM . Similar trend was observed by imposing treatments at one month after planting i.e., after the onset of monsoon in the month of july. M. anisopliae @ 5×10 13 spores ha -1 (79.73 t ha -1 ) recorded highest cane yield followed by B. bassiana @ 5×10 13 spores ha -1 (76.45 t ha -1 ) when applied with FYM at one month after planting. However, highest percent yield increase was recorded in M. anisopliae @ 5x10 13 spores ha -1 (71.56 %) applied with FYM at the time of planting.

Phyllopertha horticola (Coleoptera: Scarabaeidae) larvae in eastern Austrian mountainous grasslands and the associated damage risk related to soil, topography and management

The soil-dwelling larvae of several Scarabaeidae species (white grubs), like the cockchafer (Melolontha melolontha) and the garden chafer (Phyllopertha horticola), are serious pests in European cultivated grassland, reducing grass yield and destroying the turf by root-feeding. Nevertheless, the factors responsible for the development of large grub populations and the associated damage risk are poorly understood. The objectives of the study were to survey grub densities in grassland sites with different damage histories and find correlations with environmental and management variables. Data on grub densities were collected at 10 farms in the eastern Austrian Alps in September and October 2011. At each farm, one recently damaged site (high risk) and one site at which grub damage had never been observed by the farmers (undamaged site = low risk; each site: 500 m2) were sampled. All sites were dominated by P. horticola (99% of 1,422 collected individuals; maximum density 303 grubs/m2), which indicates that grub damage there is mainly caused by that species. Recently damaged sites tended to higher grub densities than undamaged sites. However, 3 out of 10 undamaged sites harbored high grub populations as well. Humus content together with the depth of the A-horizon significantly explained 38% of P. horticola grub density variance, with highest densities in deeper humus-rich soils. The risk of grub damage was positively connected to the humus content and negatively related to the cutting frequency. For the investigated mountainous grassland sites, these results suggest an important role of humus for the development of high grub densities and an effect of management intensity on grub damage.

<I>Plectris aliena</I> (Coleoptera: Scarabaeidae): A New Invasive Soil Pest in North Carolina Agro-Ecosystems

Plectris aliena Chapin (Coleoptera: Scarabaeidae) emerged as a new invasive soil pest in North Carolina in 2006, and it has caused significant economic loss in sweetpotato every year since that time. The insect is known to also occur in the southeastern United States in Alabama, Florida, Georgia, and South Carolina where it has been reported in turf and as an occasional pest of sweetpotato. Though P. aliena only recently became an economic problem in North Carolina, its presence in the southern United States and the recent upward trend in sweetpotato acreage make the insect a potential threat in most sweetpotato producing states. White grub feeding creates surface lesions on sweetpotato storage roots, rendering them unmarketable. P. aliena has a univoltine life cycle, with adult emergence occurring from mid-May to mid-June. Larvae have three instars and overwinter in the third instar. P. aliena is able to survive and complete development on several commonly-grown crop plant species other than sweetpotato including: soybean, corn, peanut, tobacco, and pasture grasses. To date, no control measures have consistently reduced P. aliena grub damage to subeconomic levels in sweetpotato. Initial research studies aim to develop management strategies for P. aliena as part of an integrated pest management program for sweetpotato growers.

Review of current knowledge on the population dynamics of Dermolepida albohirtum (Waterhouse) (Coleoptera: Scarabaeidae)

The greyback canegrub, Dermolepida albohirtum, is a major sugarcane pest that occurs between Mossman to Sarina in Queensland, Australia. Over a period of more than 100 years, BSES Limited has conducted extensive field and laboratory studies on this pest species and information is available in several reports, articles and scientific papers. This document summarises much of the published work on D. albohirtum as well as anecdotal observations on its biology, ecology and management. D. albohirtum has an annual life cycle, and adult beetles usually lay eggs in cane crops around December–January, by which time the crop has become well advanced making pesticide application difficult. Hence, fields that require chemical treatment need to be carefully selected prior to beetle flights and egg laying. To assist in field selection, a prediction system is currently being developed to ensure that chemicals are strategically applied in areas likely to receive grub damage. Knowledge of the life cycle and population dynamics of this pest is essential in developing robust forecast systems. This document is designed to serve as a comprehensive reference for both researchers and cane growers seeking detailed information on the biology, ecology and management of this pest species.

Pre-visible Detection of Grub Feeding in Turfgrass using Remote Sensing

Japanese beetle grubs (Popillia japonica Newman) are rootfeeding pests of turfgrass in the Midwest and eastern United States causing millions of dollars of damage annually. To reduce unnecessary pesticide output by applying only where needed, turfgrass managers need a practical, noninvasive method to locate patchy infestations before unsightly damage has occurred. Spectrometer data and multispectral aerial imagery were evaluated for detecting pre-visible symptoms of grub damage in turfgrass, to facilitate sitespecific grub management. Using spectrometer reflectance data, first derivatives of reflectance, narrow-band vegetation indices, and linear combinations of multiple bands/indices, infested turfgrass plots were distinguished from un-infested plots 10 to16 days before visual differences appeared in the year when visual ratings were conducted. Pre-visible symptoms of grub feeding were not detected using the position of the red edge or edge of the red edge. Results using multispectral imagery were mixed, with early symptoms detected in only one of two years.

Role of Climatic Factors on Damage Incidence by <I>Dermolepida albohirtum</I> (Coleoptera: Scarabaeidae), in Burdekin Sugarcane Fields, Australia

Inconsistent control of Dermolepida albohirtum (Waterhouse) (Coleoptera: Scarabaeidae) in the period after the removal of organochlorines allowed us to study the impact of climatic variables and insecticide application on subsequent damage in sugarcane (Saccharum spp.). D. albohirtum damage records from the Invicta and Inkerman mill areas of the Burdekin district of North Queensland were compared with climatic averages during spring from 1989 to 2003. D. albohirtum damage demonstrated autocorrelation, indicating that the area of damage will increase from one year to the next if the grub is not effectively controlled. Insecticide use did not significantly impact on the area of damage between 1989 and 2003. Of the climatic variables evaluated, only pan evaporation was significant, and it was inversely related to the subsequent area of grub damage. Therefore, we suggest that weather conditions in spring impact on beetle emergence, feeding, and oviposition. Hot and dry spring weather may reduce beetle activity and ultimately the severity of crop damage, whereas wet and mild spring weather may favor beetle activity and an increase in the area of potential crop damage.

Bean seedling damage by root-feeding grubs ( Schizonycha spp.) in Kenya as influenced by planting time, variety, and crop residue management

Use of legume cover crops to improve soil productivity has had unexpected effects on cropping system components in a maize ( Zea mays L.) and bean ( Phaseolus vulgaris L.) cropping system in Trans Nzoia district, Kenya. Smallholder farmers who recently adopted relay cropping of lablab ( Lablab purpureus L.) observed a decline in bean yields where lablab residues had been incorporated prior to maize and bean planting. We investigated chafer grub ( Schizonycha spp.) damage to beans and studied the impact of lablab and maize stover residue management strategy, planting time, and bean cultivar selection on seedling damage. Seedling assays (germination to flower initiation), involving four different bean varieties (GLP2, KK15, KK22, and KTL3), were carried out in three consecutive planting periods. The assays were superimposed on a long-term, factorial experiment where soils had been subjected to differential lablab and maize stover residue management strategies for 7 years. Factors were (1) lablab residues removed (L0) or retained (L1); (2) maize stover removed (S0) or retained (S1) and (3) residues left on the soil surface (I0) or incorporated (I1). Planting time significantly affected the degree of chafer grub damage, with later planted beans sustaining substantially more damage. Of the four bean varieties, KK15 and GLP2 were more grub tolerant than KK22 and KTL3. Grub damage was most severe in plots where lablab residues had been retained and maize stovers had been removed (L1S0). This factor combination had the highest seedling mortality, the poorest stand establishment, and the largest proportion of plants with severed roots systems. The results of this study show that the current farmer practice (lablab residue retention and maize stover removal) is conducive to increased grub-induced bean seedling damage and suggest that early planting, retention of maize stover, and selection of grub-tolerant varieties are important management strategies to reduce damage and subsequent productivity decline.

Carrot seed coating with bacteria for seedling protection from grass grub damage

Carrot seedlings are susceptible to damage from grass grub larvae The biological control bacterium Serratia entomophila was applied to the surface of carrot seeds via pelleting or as a biopolymer seed coating and the activity against grass grubs determined in pot trials Seedling mortality caused by grass grub larvae was significantly reduced (Plt;005) in two trials from 88 and 64 in untreated pots to 26 and 13 in pots containing pelleted seed and 7 and 16 in pots containing biopolymercoated seed Shelf life studies showed formulations were stable at 4C for at least eight weeks and for two weeks at 20C after which cell viability decreased over time Bioassay results showed little difference between the two treatments despite a higher concentration of bacteria on the biopolymercoated than the pelleted seeds The potential of seed coating as a delivery mechanism for biocontrol agents has been demonstrated and future possibilities are discussed

Management of Whitefringed Beetle (Coleoptera: Curculionidae) Grub Damage to Sweet Potato with Adulticide Treatments

Field experiments in sweet potato, Impomoea batatas (L.) Lamarck, were done to evaluate the impact of insecticides applied to foliage on whitefringed beetle ( Naupactus spp,) adult and larval populations and on larval feeding damage to sweet potato roots. Analysis of transformed data combined over all sample dates in 1994 indicated that adult means in both the weekly and biweekly spray treatments were significantly lower than in the nontreated control plots, and nonparametric analysis indicated that adult means were significantly lower in the weekly insecticide treatment. Counts of adults combined over all 1996 sample dates were significantly lower in all adulticide treatments compared with the non treated control. In 1994, numbers of whitefringed beetle grubs in soil core samples were significantly lower in the adulticide treatments compared with the non treated plots, indicating that adulticides had an indirect negative effect on the offspring larval population, The mean percentages of sweet potato roots damaged by larval feeding were lower in the weekly or biweekly adulticide treatments (carbaryl plus methyl parathion) than in the nontreated control in 1994 (differences not significant) and in 1995 (differences were significant). In 1996, root damage was significantly lower in plots sprayed weekly with phosmet or carbaryl than in nontreated plots, In 1997, root damage in nontreated plots averaged >2.5-fold greater than in the insecticide treated plots, but differences among treatments were not significant. Collectively, these results indicate that application of adulticides may be an effective alternative to soil insecticides for management of whitefringed beetle in sweet potato.

The effect of root damage caused by simulated white grub attack on the growth, yield and water-use of groundnut plants

White grubs (larval scarabaeids) are now recognized as being important pests of groundnut (peanut) in many parts of the world because of their ability to damage roots. A method of simulating white grub damage to groundnut plants was developed to obtain an indication of how the feeding activity of these insects influences plant growth. The effect of root cutting and drought stress on water uptake and biomass production was evaluated, with roots being cut at three depths in the late vegetative and early podfilling stages. As groundnut plants are often grown under conditions of drought stress, the effects of which would be accentuated by root damage, this factor was introduced into the experiment. Plant water-use measurements indicated that the root systems of plants cut 30 days after emergence (DAE) and watered twice a week became fully functional again after 40 days. Pod and total biomass production were however significantly less than those of the uncut control plants, with drought stress reducing yields below the well-watered controls, particularly when cut at 10 cm below the soil surface. The root systems of plants cut 51 DAE did not regrow to any appreciable extent, and rates of plant water-use remained less than half of the uncut control plants. Over all treatments, there was a strong positive correlation between total (and pod) biomass and plant water-use. It was concluded that the phenological stage of the plant at which root damage occurred had a profound influence on the subsequent recovery in root growth and function, and ultimately on pod yield.

Tenlined June Beetle Control, 1993

Abstract The experiment was performed in two commercial orchards. Trees in Orchard #1 were in the second leaf, while those in Orchard #2 varied between second and fourth leaf. Both orchards were planted on sandy soil. Trees used in the experiment showed visible signs of stress (abnormally small leaves, reduced terminal growth, water stress) associated with grub damage to the root sytem. Each treatment was replicated ten times, with a replicate consisting of a single tree. All treatments were applied 10-11 Jun. A second application to the Diazinon plot was made 25 Jun. A strip of sheet metal ca. 15 cm wide was formed into a circle 39 cm in diameter and centered around the trunk of the tree. The bottom edge was worked into the soil to form a seal such that the drench solution could not escape. Two gallons of test insecticide mixtures were poured around the base of test tree, and allowed to soak into the soil before the metal strip was removed. Trees and the surrounding soil (39 cm diameter × 46 cm deep) were excavated 22-30 Jul about six weeks after the first application date. Live and dead grubs were recorded.