Identifying critical research gaps that limit control options for invertebrate pests in Australian grain production systems

Ironically, pesticide applications in agriculture may result in the opposite of the intended reduction of the pest population. Following an initial treatment, the target population may resurge rapidly to greater than pre-treatment levels. In addition, populations of non-target species that were previously far below economic thresholds may increase greatly after applications and develop into pests of economic importance. Pesticide-induced outbreaks have been reported for very different groups of phytophagous arthropods and for several types of pesticides (Ripper 1956, Barbosa and Schultz 1987, Penman and Chapman 1988, Roush and Tabashnik 1990). This raises the question whether there are general principles underlying these outbreaks. One explanation for pesticide-induced outbreaks is that, for reasons rooted in their evolutionary past, phytophagous pest species are less susceptible to pesticides than their natural enemies. Hence, pesticide treatment will have a more drastic effect on natural enemies than on pests, resulting in outbreaks. However, this explanation ignores population dynamical effects on predator-prey balances. Furthermore, measurements of susceptibility to direct pesticide doses reveal that natural enemies are generally not more vulnerable to pesticides than their prey species (Hoy 1990) and may even show a trend towards lower predator susceptibility (Croft and Brown 1975). Thus, empirical support is lacking and (as we argue below) there is no good reason to expect that predatory arthropods would have been exposed to a narrower range of toxicants than their prey. A more sound explanation follows from consideration of the coupled population dynamics of predator and prey (May 1985, May and Dobson 1986). After pesticide application the densities of phytophagous arthropods are reduced. As soon as the harmful effects of the pesticide abate, conditions are favourable for herbivores: they suffer less predation and possibly experience reduced competition. Hence the numbers of pests and potential secondary pests will increase at a rate close to their maximum growth rate. Even if natural enemy densities are not directly affected, their densities will decrease after pesticide application since they are largely deprived of their main or only food source: phytophagous arthropods. Populations of predators can only increase after prey have attained sufficiently high densities. The increase in predator numbers therefore typically lags behind that of the pests. By the time the predators have returned to the pre-application densities, the pest populations have had the opportunity to increase unchecked for some time. The importance of food limitation to differential rates of recovery after pesticide application has been confirmed in a number of simulation studies (Tabashnik 1986 and 1990); even when the immediate mortality is similar for predator and prey, predator populations are more severely suppressed by pesticides than are pest populations (Waage et al. 1985). Pesticide induced outbreaks are often considered as transient events (Ripper 1956); after pesticide use is stopped, the ecosystem is expected to recover and predatorprey balances to restore. However, this need not be the case. Persistent outbreaks can result from the simultaneous existence of two stable states; one in which the predator controls the pest, and another in which the predator exists at very low levels, or is absent, and the pest is not controlled. After a small disturbance the system will return to its original state. For larger disturbances, however, the system may stabilize at either state, depending

Monitoring populations of pests and their natural enemies under different management situations and seasonal weather parameters provides extremely useful information for taking preventive measures against pest outbreaks. The abundance, spatial and temporal distributions of herbivorous insects and arthropod natural enemies on Alnus species were monitored at four sites in Kabale district, Uganda between June 1999 and August 2000. Chewing insects, dominated by Coleoptera (75%), constituted the majority of insect herbivores sampled. Dominant and potentially serious pests of Alnus included Apion globulipenne, an unidentified Chrysomelidae (Coleopt. 27), Phymateus viridipes, Coloborrtics corticina and a Cacopsylla species (Homoptera: Psyllidae). Spiders were the predominant natural enemies accounting for 64% of the total natural enemies encountered, followed by parasitic Hymenoptera (30%). There were marked spatial and temporal variations in arthropod abundance. Among sites, mean abundance of total insect herbivores and total natural enemies on A. acuminata over 15 months ranged from 3.8–8.5 and 3.3–4.7 individuals per 1-m branch length respectively. Over the same period, mean number of total insect herbivores and total natural enemies on A. nepalensis that was studied at only one site were 11.9 herbivores and 4.2 natural enemies per 1-m branch length. Populations of most insect orders increased in the wet season although the greatest herbivore abundance was evident in the dry season. Further studies are necessary on the impact and management strategies of the potentially important insect pests and natural enemies on Alnus.

A survey of entomologists was conducted to estimate the value of present and potential losses from invertebrate pests for the six most important Australian grain crops: wheat, barley, oats, canola, lupins and grain sorghum. The survey provided data on the incidence and severity of 29 invertebrate pest groups across the six crops. These data were combined with crop production data to estimate the value of the losses in the northern, southern and western production regions of Australia. Aggregated across the six major Australian grain crops, the estimated present annual loss because of invertebrate pests totalled $359.8 million. The relative importance of invertebrate pests varied between regions. Nationally, the five most important invertebrate pests based on estimated present losses aggregated across the six crops were redlegged earth mite ($44.7 million), budworms ($36.3 million), blue oat mite ($35.5 million), lucerne flea ($28.4 million) and locusts ($28.4 million). Present cultural and pesticide controls of invertebrate pests effectively reduced losses, but pest management remained very dependent on pesticides. Nationally, pesticide treatment costs aggregated across all six crops totalled $159.1 million. Based on pesticide treatment costs, the three most costly invertebrate pests were various species of aphids ($28.0 million), redlegged earth mite ($20.5 million) and various species of budworms ($16.9 million). Results from this study will inform future investment decisions related to invertebrate pests.

Kairomones are chemical signals that mediate interspecific interactions beneficial to organisms that detect the cues. These attractants can be individual compounds or mixtures of herbivore-induced plant volatiles (HIPVs) or herbivore chemicals such as pheromones, i.e., chemicals mediating intraspecific communication between herbivores. Natural enemies eavesdrop on kairomones during their foraging behaviour, i.e., location of oviposition sites and feeding resources in nature. Kairomone mixtures are likely to elicit stronger olfactory responses in natural enemies than single kairomones. Kairomone-based lures are used to enhance biological control strategies via the attraction and retention of natural enemies to reduce insect pest populations and crop damage in an environmentally friendly way. In this review, we focus on ways to improve the efficiency of kairomone use in crop fields. First, we highlight kairomone sources in tri-trophic systems and discuss how these attractants are used by natural enemies searching for hosts or prey. Then we summarise examples of field application of kairomones (pheromones vs. HIPVs) in recruiting natural enemies. We highlight the need for future field studies to focus on the application of kairomone blends rather than single kairomones which currently dominate the literature on field attractants for natural enemies. We further discuss ways for improving kairomone use through attract and reward technique, olfactory associative learning, and optimisation of kairomone lure formulations. Finally, we discuss why the effectiveness of kairomone use for enhancing biological control strategies should move from demonstration of increase in the number of attracted natural enemies, to reducing pest populations and crop damage below economic threshold levels and increasing crop yield.

Many agricultural landscapes offer few resources for maintaining natural enemy populations and floral plantings have frequently been adopted to enhance biological pest control in crops. However, restored margins may harbour both pests and natural enemies. The aim was to compare the abundance of pests and natural enemies in three types of margins (unmanaged, sown herbaceous floral strips and shrubby hedgerows) as well as in adjacent melon fields. Besides, yield was compared among melon fields as way of testing the effect of the type of margin on biocontrol. The research was carried out during 2 years in twelve melon fields from four different locations in southern Spain. Arthropods were sampled periodically in margins and melon fields by visual inspections and Berlese extraction. Hedgerow and floral strips hosted higher numbers of both pests and predators than unmanaged margins. Besides, hedgerows had a similar or higher number of natural enemies than floral strips but lower number of pests. In just a few occasions, the type of margin had a significant effect on the abundance of pests and natural enemies in melon fields, but rarely there was consistency between the two growing seasons. No differences were found in yield. We hypothesised that the lack of association in the abundances of pests and natural enemies between margins and melon fields could be attributed to the overriding effects of the landscape and/or the internal population dynamics of arthropods in melon fields. Overall, shrubby hedgerows are more recommended than herbaceous floral strips.

BACKGROUNDBroad‐spectrum insecticides are extensively used to control pests and secure crop yields. However, insecticides may have unintended effects on natural enemies (e.g., predators and parasitoid wasps) and secondary pests. Cover crops can also be used as part of integrated pest management (IPM) programs to protect natural enemies and avoid secondary pest outbreaks. Yet, some pests can use cover crops as green bridges to colonize the crop. We explored the use of rye in commercial watermelon fields, with three intensity levels employed by growers: (i) no rye, (ii) 1:3 rye‐watermelon ratio and (iii) 1:1 rye‐watermelon ratio. Then, we tested the combined effects of insecticide programs (conventional vs. threshold‐based recommendations) and rye use (present vs. absent) at three research farms over 2 years.RESULTSIn both the on‐farm survey and research‐plot trial, rye weakly affected arthropods, with no impacts on cucumber beetles or natural enemies and marginally positive and negative effects on spider mites and melon aphids, respectively. In contrast, conventional insecticide programs in the research‐plot trial effectively controlled the main watermelon pest (striped cucumber beetle) but triggered 45.5 and 21.2% population increases in spider mite and melon aphid, respectively, while natural enemies decreased by 82.3% compared to threshold recommendations. Watermelon yield and quality were generally unaffected by treatments.CONCLUSIONWe show that insecticide practices are more relevant in shaping arthropod dynamics than cover crops in watermelon. Our study highlights the importance of IPM to protect natural enemies, prevent pest outbreaks, minimize costs on unnecessary insecticide applications and enhance sustainable agriculture. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Context The Australian dairy industry largely relies on grass-based pastures to feed cattle, yet these pastures also host dynamic invertebrate communities that can damage or benefit pasture productivity. While Australian dairy managers have traditionally focused on invertebrates that damage pastures (i.e. pests), invertebrates that provide valuable ecosystem services by acting as natural enemies to pests or delivering other beneficial functions (e.g. nutrient cycling) have received less attention. Aim Surveying the natural enemies and other beneficial invertebrate communities in pastures across seven Australian dairy regions and to explore how environmental and farm management factors impact these. Method Fifty seven pastures samples were collected during spring and autumn over two years. In doing so, we identified and counted 2 661 315 invertebrates or invertebrate colonies. Key results We found natural enemies and other beneficial invertebrate communities have a similar taxonomic composition across regions, with a small number of taxa dominating all regions, and rainfall the most consistent environmental driver in the abundance of these dominant taxa. Conclusions Farm management strategies to maintain or promote existing communities of beneficial taxa will likely be similar across regions. Associations between invertebrate communities suggest pest communities may indirectly impact the abundance and/or diversity of natural enemies and other beneficial invertebrates. Implications Although still an early step, our findings provide important baseline information that can be used to provide dairy managers with strategies to promote communities of beneficial invertebrates, and consequently maximise the benefits these invertebrates provide.

The effects of ploughing and previous crop on winter wheat pests and their natural enemies under an integrated farming system was investigated in an experimental area in Slovakia. The experiment consisted of 4 small plots (50 m2 each) to which both organic and inorganic fertilisers were applied. Moreover, there was one application of herbicide and a fungicide on each plot. The ploughing was either deep or shallow, and either silage‐maize or pea was used as a previous crop. The effects of the ploughing and previous crop was studied by means of multivariate redundancy analysis (RDA) and subsequent Monte‐Carlo permutation test. The results showed that there was a considerable temporal variation in the abundance of insect pests and their natural enemies. Of the two husbandry treatments, only ploughing caused significant difference in the composition and abundance of both pests and natural enemies. However, while most of the pests favoured deep ploughing, the majority of natural enemies occurred more abundantly on shallowly ploughed plots. The previous crop did not affect numbers of either pests or natural enemies. Two systems, integrated and organic, which have been surveyed previously, were mutually compared with respect to the abundance of insect pests. The organic farming system turned out to be more sustainable.

IntroductionSoil-transmitted helminth (STH) infections are predominately controlled by providing children with preventive chemotherapy with either albendazole or mebendazole. However, neither has a high efficacy against Trichuris trichiura. This low efficacy limits the overall effectiveness of the current STH control programmes against T. trichiura. It has been demonstrated that co-administering ivermectin with albendazole or mebendazole significantly increases the efficacy of current treatments, which may increase the overall effectiveness of control programmes. MethodsUsing a STH transmission mathematical model, we evaluated the potential impact of co-administering ivermectin with albendazole or mebendazole to treat T. trichiura within a preventive chemotherapy programme targeting children (2–15year olds). We evaluated the impact in terms of reduction in prevalent infections, mean worm burden, and prevalence of heavy infections. ResultsAlthough the current treatment strategy reduced T. trichiura worm burden and prevalence of heavy infections, due to their poor efficacy the long term impact of preventive chemotherapy for children was smaller compared to the other STH. Co-administering ivermectin increased the projected impact of the preventive chemotherapy programme in terms of all three of the explored metrics, practically in high transmission settings. Furthermore, ivermectin co-administration greatly increased the feasibility of and timeframe for breaking transmission. ConclusionsCo-administering ivermectin notably increased the projected impact of preventive chemotherapy in high transmission settings and increased the feasibility for breaking transmission. This has important implications for control programmes, some of which may be shifting focus from morbidity control to interruption of transmission, and some of which may be logistically unable to provide preventive chemotherapy twice a year as recommended. However, the benefit of co-administering ivermectin is limited by the fact that 2–5year olds are often ineligible to receive treatment.

Soil nutrients can influence the population dynamics of arthropod pests and their natural enemies. Previous research has revealed that overfertilization increases the likelihood of pest outbreak in a subsequent soybean [Glycine max (L.) Merr.] crop following winter wheat (Triticum aestivum L.). Improving biological control from natural enemies is an important aspect of integrated pest management. Our objectives in this field study were to (i) determine the effect of soil nutrition on population densities of the predators Geocoris spp. (bigeyed bugs), Nabis and Hoplistoscelis spp. (damsel bugs), and spiders (Araneae) in a soybean canopy and (ii) relate densities of each predator to pest densities and determine if previously reported effects of overfertilization on pest densities were the indirect result of influences of soil nutrients on predator populations. Soil nutrient levels were four levels of P and three levels of K and Mg. The study was conducted in 1986 and 1987. High P favored population density of damsel bug nymphs in 1986 only, but populations were not significantly affected by K or Mg. High P significantly affected population densities of bigeyed bug nymphs each year. Density estimates of spiders were significantly increased by P only in 1986. Densities of spiders were not affected by K and Mg either year. Increased pest outbreaks from overfertilization of soybean were not the result of fertility effects on population densities of these major predators.

Effects of agroforestry on pest, disease and weed control: A meta-analysis

Experiment was conducted during winter season to study the diversity and equitability of insect pest species and natural enemies in insecticide treated brinjal fields. Highest number of insect pests were recorded in` Tracer 45 SC, Bactoil (Bt), Nimbicidene 0.03 EC and lowest was in Necstar-50 EC and Proclaim-5 SG treated plots. The highest total abundance of insect pest was recorded in the plots treated with Bactoil and Tracer-45 SC and lowest total abundance was in Helicide (HNPV), Proclaim-5 SG and Booster-10 EC treated plots. The diversity index and equitability of insect pest species were highest in the plots treated with Nimbicidene 0.03 EC and Bactoil in visual search and sweep net methods while Bactoil and Booster 10 EC in pitfall trap method. However, lowest diversity index and equitability were obtained from the plots treated with Booster 10 EC, Proclaim-5 SG, Necstar-50 EC, Tracer-45 SC in visual search and sweep net methods but also in plots treated with Nimbicidene 0.03 EC in pitfall trap method. In case of natural enemies, the highest number of families were recorded in Tracer-45 SC, Nimbicidine 0.03 EC and Bactoil treated plots while lowest was in Helicide, Booster 10 EC, Proclaim-5 SG and Necstar-50 EC treated plots. The highest total abundance of natural enemy was recorded in the plot treated with Bactoil and Tracer-45 SC while lowest abundance was in the plot treated with Necstar-50 EC and Boster-10 EC. The diversity index and equitability of natural enemies were the highest in the plots treated with Proclaim-5 SG, Bactoil, Helicide and Necstar-50 EC in visual search, sweep net method and pitfall trap method while lowest was in Booster 10 EC, Tracer-45 SC treated plots in visual search method, Booster 10 EC and Nimbicidene 0.03 EC treated plots in sweep net method, Necstar-50 EC and Nimbicidene 0.03 EC treated plots in pitfall trap method. Bactoil and Tracer-45 SC were relatively safe for natural enemies and therefore would be fit well into integrated pest management (IPM) against BSFB of brinjal crop.Jahangirnagar University J. Biol. Sci. 4(1): 71-80, 2015 (June)

Over the past 200 years agriculture has expanded throughout Australia. The culmination of clearing and cultivating land at the farm scale has resulted in highly modified landscapes and a perceived loss of ecosystem services from pest control and pollination. We examine the literature: (i) to identify the appropriate spatial scale for managing pests, natural enemies and pollinators; and (ii) for evidence that farm-scale changes (due to agricultural intensification) across a landscape have resulted in a tipping point favouring pests and hindering pollinators. Although there is limited information to draw firm conclusions, the evidence suggests that actions undertaken on individual farms have an impact both on their neighbours and regionally, and that the culmination of these actions can lead to changes in population dynamics of pests, natural enemies and pollinators. For major pest species, there is reasonable evidence that grain growers may benefit from improved management and higher yields by implementing area-wide pest management strategies on a landscape scale in collaboration with growers of other crops that also share these pests. As yet, for natural enemies and pollinators there is little direct evidence that similar area-wide initiatives will have a greater effect than management strategies aimed at the field and farm level. Managing pests, natural enemies and pollinators beyond the scale of the field or farm is technically and socially challenging and will required a well defined research agenda, as well as compromise, balance and trading among stakeholders. We highlight critical knowledge gaps and suggest approaches for designing and managing landscapes for ecosystem services.

Landscape composition and its related functional agrobiodiversity (FAB) was severely simplified during the last decades. As landscape composition is expected to influence the interrelated microclimate and arthropod community at different scales, this simplification might have led to a decline in multiple agro‐ecosystem services, with potential impacts for the growth of crops with different demands from the environment. To study landscape‐scale effects on multicrop yield and herbivory in combination with its potential drivers, including functional arthropod community and microclimate, we used standardised 1 m2 mini‐gardens planted with ten different vegetable crops as phytometers. The gardens were installed at locations varying in surrounding landscape composition and the vegetables were selected to have contrasting requirements in terms of growing conditions, pollination services and susceptibility to pests. Monitoring of the mini‐gardens was performed in 2018 and 2019 in Flanders (Belgium). We found no relationship between landscape composition in a 500 m radius and crop yield. Considering possible mechanisms, we found that an increasing share of woody vegetation (>3 m high) in the surrounding landscape is important to buffer the temperature and soil moisture variation in the mini‐gardens. The share of agricultural land use and urban green (<3 m high) is, respectively, positively and negatively related with the activity‐density of natural enemies and pollinators. The growth of different crops responded differently to higher temperature ranges and we found no relation between natural enemies and herbivory. In conclusion, these abiotic and biotic pathways did not cause an overall relationship between landscape composition and yield. Synthesis and applications. These outcomes indicate that woody vegetation in the rural landscape buffers soil moisture and temperature variation, which will become even more important due to climate change. Furthermore, pollinators and natural enemies were most active in rural environments and less active in areas with residential green and built‐up surfaces. Local, flower rich habitat, such as road sides, can further support natural enemies and buffer soil moisture variation. Yet, high arthropod activity is no assurance for arthropod mediated ecosystem service delivery nor is microclimate buffering an assurance for higher crop yields.

To conserve and utilize natural enemies for comprehensive control of insect pests in peach orchards,the seasonal and annual variations of population quantities of the five kinds of insect pests with their natural enemies were systematical investigated in the Yuhualu juicy peach orchard.The findings of a paired t-testing demonstrated that the t values of five kinds of main pest numbers,i.e.Empoasca flavescens,Myzus persicae,Tetranychus viennensis,Cleoporus variabilis and Stephanitis nashi,indicating that no significant differences existed in the numbers of five kinds of insect pests in Yuhualu juicy peach orchard between the two spring-summer seasons of 2010 and 2011.Whilst the t values of the seven kinds of natural enemy numbers,i.e.Erigonidium graminicola,Misumenops tricuspidatus,Theridion octomaculatum,Clubiona japonicola,Propylaea japonica,Chrysopa sinica and Epistrophe balteata,all were significantly lower than 2.16(t0.05 value),revealing that there were also no significant differences in the numbers of the seven kinds of natural enemies between the two spring-summer seasons of 2010 and 2011.Surprisingly,the t value of Harmonia axyridis was 2.39 2.16(t0.05 value),showing that the difference in numbers was significant between the two spring-summer seasons of 2010 and 2011.The further analysis indicated that the t values of Empoasca flavescens,Stephanitis nashi,Misumenops tricuspidatus,Harmonia axyridis,were,respectively,5.63,76.38,3.28 and 4.82 3.01(t0.01),indicating that there were significant differences in their numbers in Yuhualu juicy peach orchard between the spring-summer season and the autumn season of 2010,whereas no significant differences existed in the others.Moreover,the quantity,time and space framework of Myzus persicae,Empoasca flavescens,Tetranychus viennens,Cleoporus variabilis,Stephanitis nash and their predatory natural enemies in 2010 spring-summer season and autumn season,as well as 2011 spring-summer season were systematically studied using grey system analysis,ecological niche analysis and aggregated-intensity index analysis of spatial patterns.The synthetic ranking results indicated that,in 2010 spring-summer season,the orders of main natural enemies of Empoasca flavescens were Misumenops tricuspidatus,Chrysopa Sinica and Theridion octomaculatum,whereas the ranks of main natural enemies of Tetranychus viennensis were Clubiona japonicola,Theridion octomaculatum and Erigonidium graminicola.In 2011 spring-summer season,the orders of main natural enemies of Myzus persicae,Empoasca flavescens,Cleoporus variabilis,Stephanitis nashi and Tetranychus viennensis,were,respectively,Epistrophe balteata,Harmonia axyridis and Misumenops tricuspidatus;Erigonidium graminicola,Propylaea japonica and Misumenops tricuspidatus;Erigonidium graminicola,Misumenops tricuspidatus and Theridion octomaculatum;Misumenops tricuspidatus,Propylaea japonica and Erigonidium graminicola;Clubiona japonicola,Theridion octomaculatum and Erigonidium graminicola.In 2010 autumn-winter season,the ranks of main natural enemies of the Empoasca flavescens and Stephanitis nashi,were,respectively,Chrysopa Sinica,Erigonidium graminicola and Misumenops tricuspidatus;Theridion octomaculatum,Erigonidium graminicola and Misumenops tricuspidatus.The further analyses showed that the average λ values of Empoasca flavescens,Stephanitis nashi and Tetranychus viennensis in 2010,and Myzus persicae,Cleoporus variabilis,Stephanitis nashi and Tetranychus viennensis in the spring-summer season of 2011 all are more than 2,and in the four different directions of peach tree crown,the λ value of Tetranychus viennensis in the 2010 spring-summer season,and Empoasca flavescens in the 2010 autumn-winter season,as well as Cleoporus variabilis in the 2011 spring-summer season all are also more than 2,suggesting that the gathering cause of the insect pests resulted from themselves.However,the λ values of the other insect pests and natural enemies all were less than 2,indicating that their gathering was caused by certain environment factors.