Enhancement Of Natural Enemies Research Articles

Linking landscape structure, floral resource distribution, pollen use and movement distances of a generalist predator

Abstract Understanding the habitat use and movement patterns of natural enemies in agricultural landscapes is essential for enhancing biological pest control. Since many natural enemies rely on floral resources, the distribution of these resources in combination with movement behaviour likely influence biological control in field crops. Nevertheless, few studies have assessed natural enemy movement at the landscape scale. Here we estimated minimal movement distances of the green lacewing Chrysoperla carnea based on consumed pollen and the spatial distribution of the respective plant species in 24 agricultural landscapes (500 m radius). Lacewings were sampled using sticky traps in the centre of each landscape, and the consumed pollen were identified. The location of the most important pollen‐providing plants was mapped in each landscape. Distances to potential sources of pollen consumed by 346 lacewings were used to derive minimal movement distances. Lacewings consumed mostly pollen from insect‐pollinated plants that were present within 500 m from the sampling location. The distance to the nearest source of consumed pollen exceeded 200 m in 31% of lacewing individuals, demonstrating the relevance of the landscape scale to understand their population dynamics. Distances were shorter to insect‐pollinated than to wind‐pollinated plants, and shorter early than late in the season. Mean and median distances to pollen sources were negatively associated to flower availability and edge density in the landscape, but this was not the case for minimal distances. Synthesis and applications. Our findings suggest that the spatial distribution of flowering wild plants can inform movement patterns of lacewings and other flower‐visiting insects in agricultural landscapes. In addition, the location of floral resources in the landscape is important for its capacity to sustain natural enemies. Given the strong reliance of lacewings on pollen from nearby insect pollinated woody plants, the promotion of native shrubs and trees, such as Prunus, Salix and Castanea, should be prioritized for natural enemy enhancement in agricultural landscapes. Doing this in the form of hedgerows or agroforestry systems would lead to only minimal reduction in production areas and provide additional benefits such as biodiversity conservation.

Predacious Natural Enemies Associated With Suppression of Onion Thrips, Thrips tabaci (Thysanoptera: Thripidae), in Intercropped Onion-Barley Agroecosystems.

The effects of two possible factors, prevention of pest immigration and enhancement of natural enemies, in suppressing onion thrips, Thrips tabaci L., were estimated in a small-scale experimental system of spring-planted onions intercropped with barley. The population dynamics of the thrips and their potential predatory natural enemies were investigated in four treatments: control (bare ground), insect net barrier, and onion-barley intercropping with or without trimming. We found that intercropping significantly suppressed onion thrips. It is unlikely that this effect was due to the prevention of thrip immigration because they seemed to move over the camouflage and/or physical barriers of the barley and the net barrier surrounding the onions easily. Intercropping with barley significantly increased hoverfly (Syrphidae) larvae numbers on onion leaves, and that of some groups of ground-dwelling predators such as large carnivorous ground beetles (Carabidae), ants (Formicidae), and wolf spiders (Lycosidae). We conclude that the suppression of thrips in this system was associated with the enhancement of hoverfly larvae abundance, mainly Sphaerophoria macrogaster (Thomson) (Syrphidae: Diptera) because they were observed together with thrips on onions and have been reported to predate thrips as well as aphids. Some hoverfly larvae on barley might move to nearby onions to search for new food sources and attack thrips.

Different controlling methods of fall armyworm (Spodoptera frugiperda) in maize farms of small-scale producers in Cameroon

Fall armyworm (FAW) is a polyphagous and voracious pest, destroying maize plants in farms in Cameroon. An annual yield loss is estimated to range from15 to 78%, valued at US$ 2,481 to US$ 6,187 million. With most damage experienced in the mono-cropping system. Maize is the most widely grown cereal crop globally due to its several uses, namely human consumption, animal feed and biofuel. In Cameroon, maize is a staple food grown by small- scale producers in all ten regions. The control of FAW is unsuccessful with only the use of pesticide method, the application is knowledge-intensive, and misuse often leads to pesticide resistance, resurgence and increased production cost. The purpose of this review was to explore the different controlling methods adopted to suppress FAW from causing economic damage in maize farms of small-scale producers in Cameroon. Integrated pest management (IPM) approach was used to control FAW, including cultural control, chemical control, botanicals, push-pull farming system, biological control and indigenous knowledge. Results showed that push-pull farming system provides protection and improves maize nutrition, botanicals have similar efficacy like synthetic insecticide, and wood ash is a bio-pesticide. The combined application of pesticides and handpicking FAW was effective though feasible in small surface areas. Based on the general assessment, the push-pull farming system deserves to be promoted due to its numerous benefits: eco-friendly, enhancement of natural enemies, increased soil fertility and economic returns. Natural enemies and bio-pesticides application are essential to control FAW since farmers are resource-poor, causes no health problem and are environmentally friendly.

Using flower strips to promote green lacewings to control cabbage insect pests

Habitat management improves biological control by increasing the abundance and fitness of natural enemies through the provision of floral resources along field edges or between crops. Among the natural enemies reliant on flower resources, green lacewings often stand out due to their abundance, predation capacity and polyphagy. We evaluated the impact of tailored flower strips on the enhancement of natural enemies, especially green lacewings, in three organic cabbage (Brassica oleracea) farms in Southern Sweden. Insects were sampled from the flower strips, and cabbage pests and predators were visually recorded in the crop. In a laboratory assay, the pollen feeding preferences of Chrysoperla carnea (Stephens, 1836) were evaluated in a dual-choice test. The pollen consumed by the Chrysopidae was extracted from laboratory and field specimens, then quantified and identified. Flower strips were found to attract predators and parasitoids, whose abundance increased as flowers bloomed. Cabbage plants next to the flower strips showed lower pest infestation as compared to cabbage plant control, although no significant differences were observed in the number of predators. Chrysopidae used flower strips as feeding, reproduction and shelter sites and mainly consumed pollen from Phacelia tanacetifolia Benth. Under laboratory conditions, C. carnea showed a preference for P. tanacetifolia and Coriandrum sativum L. pollen over Borago officinalis L. and Fagopyrum esculentum Moench. We show that tailored flower strips could be an efficient tool for enhancing beneficial arthropods and should be considered in integrated pest management for cabbage crops.

Potato/Maize intercropping reduces infestation of potato tuber moth, Phthorimaea operculella (Zeller) by the enhancement of natural enemies

The potato tuber moth (PTM), Phthorimaea operculella (Zeller), is one of the most economically significant insect pests for potato in both field and storage worldwide. To evaluate the infestation, reduction of potato yield and the control efficacy for PTM, field tests were conducted in two seasons by intercropping of potato as the host plant with maize as a non-host plant of PTM. Three intercropping patterns were tested, which were 2 rows of potatoes with either 2, 3, or 4 rows of maize (abbreviated 2P:2M, 2P:3M, and 2P:4M), and the monocropped potato as the control, 2 rows of potatoes, without maize, (abbreviated 2P:0M). Results showed that the population and infestation of PTM in the 2P:3M intercropping pattern was significantly lower than those in 2P:2M, 2P:4M and the monocropping pattern of 2P:0M, due to the enhancement of natural enemies. Cumulative mines and tunneling in potato leaves in 2P:3M intercropping were significantly lower than those in 2P:2M and 2P:4M patterns. The population of parasitoids and the parasitism rate of PTM in intercropping pattern of 2P:3M were significantly higher than that in intercropping pattern of 2P:2M, 2P:4M and monocropping pattern of 2P:0M. We conclude that the potato intercropped with maize reduced the adult and larva populations, and reduced the damage from PTM by enhancing the number of parasitoids and the level of parasitism. The greatest population density of parasitoids and parasitism rate were in the intercropping pattern of 2 rows of potatoes with 3 rows of maize. These data indicate that the host/non-host intercropping patterns can be used as a biological control tactic against PTM by enhancing the density of natural enemies in the agro-ecosystems.

Habitat Management for Pest Management: Limitations and Prospects

AbstractHabitat management is an important strategy for pest control in integrated pest management (IPM). Various categories of habitat management such as trap cropping, intercropping, natural enemy refuges such as ‘beetle banks’, and floral resources for parasitoids and predators, have been used in applied insect ecology for many years. In a broader sense, two mechanisms, the ‘enemies hypothesis’ and the ‘resource concentration hypothesis’ have been identified as acting independently or combined in pest population dynamics. The ‘enemies hypothesis’ directly supports the conservation and enhancement of natural enemies, floral resources such as shelter, nectar, alternative food sources, and pollen (SNAP) to improve conservation biological control. The ‘resource concentration hypothesis’ emphasizes how the host selection behavior of herbivores in a diverse habitat can reduce pest colonization in crops. This review emphasizes the potential of these approaches, as well as possible dis-services, and includes limitations and considerations needed to boost the efficacy of these strategies worldwide.

Habitat Management: A Key Option to Enhance Natural Enemies of Crop Pest

Enhancement of natural enemies through habitat management developed sustainable pest management systems. Landscape composition; especially complex and permanent habitat mainly woody vegetation increased the abundance of natural enemies of crop pest. Alternatively, temporary vegetation like horticultural systems decreased the abundance of natural enemies as for monocropping. The rate of parasitism is higher in diverse ecosystems than in non-diverse ecosystems due to the availability of food source, provision of nectar and sugar, as well as alternative hosts. The intensification of agricultural practices disturbed the diversity of ecosystem and ultimately reduced the abundance of natural enemies and consequently diminished the efficacy of biological control of pests in a particular ecosystem. Moreover, plant characteristics especially in long blooming period, larger floral area, maximum flower height, narrow and deepest corolla and higher number of open flower increase the accessibility of nectar or pollen for natural enemies. As a result, the fecundity and longevity of predator and parasitoid are increased. Manipulation of food sources for natural enemies especially honey dew and artificial food spray like sucrose with the supplement of protein helps to enhance the activities of natural enemies, predators and parasitoids. For example, the widely applicable shelter habitats such as beetle banks are suitable over wintering sites for predatory beetles especially for Carabidae, Staphylinidae and spiders. Increase of non-crop habitats for instance, field margins, fallow land, hedgerows etc. might improve the shelters for natural enemies. Apart from the plants in that habitat under attack from herbivore, they make responses towards natural enemies by producing Herbivore Induced Plant Volatiles (HIPVs) known as indirect plant defense. The habitat with abundant natural enemies makes such continuous support for plant by means of plant indirect defense. In a nutshell, habitat management not only conserves biological control but also provides other indirect services like increasing biodiversity, photosynthesis, the activity of soil biota, and reduced soil erosion. Besides, it can also ultimately maximize the yield and profitability of crops for the farmers and stabilize the sustainable pest management system.

The effect of resident vegetation cover on abundance and diversity of green lacewings (Neuroptera: Chrysopidae) on olive trees

Understorey habitats are optimal ecological structures for natural enemy enhancement in fruit orchards. A large-scale experiment was carried out to establish the effect of resident vegetation cover (VC) on green lacewings as compared to bare soil, the dominant soil management strategy used in Spanish olive orchards. Lacewings were sampled using baited McPhail traps for adults, and suction was used to collect adults and larvae from olive canopies. Additionally, we monitored the presence of the lacewing’s main target pest, olive moth eggs, as well as VC composition and density. McPhail trapping showed higher Chrysopidae abundances in VC plots during two consecutive years even though flowering plants represented 29.7 % of the total. Multivariate analysis identified Chrysoperla carnea s.l. and Pseudomallada prasinus as contributing to differences in abundance. VC slightly increased capture diversity; however, no specific link between any Chrysopidae species and VC was detected. No differences were observed in individuals collected through suction in 2009, which could be attributed to low sampling efficiency. In 2010, when sampling was increased considerably, higher adult and larval abundances were recorded in VC only with respect to C. carnea s.l. A delay was detected between McPhail captures and suction collection peaks. The fact that VC promoted higher abundance detected earlier through trapping, and later on olive canopies through suction, coinciding with P. oleae presence, suggests that resident VC may contribute to a build-up of green lacewing populations moving onto the crop at the time of the pest attack.

Indigenous generalist predators and plant residues: conservation biological control of pests in an organically managed cabbage field

Plant residues are viewed as an important source for organic matter in farmlands. We studied if wheat straw and weed residues applied to an organically managed cabbage field by favoring alternative prey may improve the suppression of lepidopteran pests by indigenous generalist predators. The trophic characteristics of predators were determined by a stable isotope approach (δ13C and δ15N). The relative contribution of alternative prey in predators species' (i.e. wolf spiders) diet was estimated using a mixed model based on their stable isotope signatures. As expected, densities of alternative prey became significantly higher in the plots with added plant residues. Consequently, population densities of predators (wolf spiders, predacious carabids and Japanese tree frogs) also became relatively higher and pest densities lower in these plots. We also note that, besides lepidopteran pests, alternative prey accounted for approximately 80% of predator diets. This finding suggests that they may play an important role in population persistence of generalist predators. The application of organic matter to the field for the enhancement of natural enemies’ impacts through increased alternative preys, which might be useful to manage lepidopteran pests in organic cultivation of cabbage.

Bee Preference for Native versus Exotic Plants in Restored Agricultural Hedgerows

Habitat restoration to promote wild pollinator populations is becoming increasingly common in agricultural lands. Yet, little is known about how wild bees, globally the most important wild pollinators, use resources in restored habitats. We compared bee use of native and exotic plants in two types of restored native plant hedgerows: mature hedgerows (>10 years from establishment) designed for natural enemy enhancement and new hedgerows (≤2 years from establishment) designed to enhance bee populations. Bees were collected from flowers using timed aerial netting and flowering plant cover was estimated by species using cover classes. At mature hedgerow sites, wild bee abundance, richness, and diversity were greater on native plants than exotic plants. At new sites, where native plants were small and had limited floral display, abundance of bees was greater on native plants than exotic plants; but, controlling for floral cover, there was no difference in bee diversity and richness between the two plant types. At both mature and new hedgerows, wild bees preferred to forage from native plants than exotic plants. Honey bees, which were from managed colonies, also preferred native plants at mature hedgerow sites but exhibited no preference at new sites. Our study shows that wild bees, and managed bees in some cases, prefer to forage on native plants in hedgerows over co‐occurring weedy, exotic plants. Semi‐quantitative ranking identified which native plants were most preferred. Hedgerow restoration with native plants may help enhance wild bee abundance and diversity, and maintain honey bee health, in agricultural areas.

An introduction device for the aphidophagous hoverfly Episyrphus balteatus (De Geer) (Diptera: Syrphidae)

Augmentative biocontrol constitutes a safe option to reduce pest populations through the enhancement of natural enemies’ activity. In this context, the aphidophagous syrphid Episyrphus baltetaus (De Geer) (Diptera: Syrphidae) is a promising candidate for aphid biological control: larvae of this syrphid attack and consume a wide range of aphid species and are found on many vegetable crops. Because natural populations of beneficial insects are not always sufficient to regulate the pest infestations, this work has focused on the conception of a biological control device containing syrphid eggs which ones can easily be introduced in fields or greenhouses. Using semiochemicals [E-(β)-farnesene, R-(+)-limonene and (Z)-3-hexenol], honeydews and “artificial honeydews” (10% or 30% aqueous solutions of sucrose, fructose and glucose), the syrphid oviposition was artificially induced on an inert surface. Specifically, E-(β)-farnesene and concentrated mono-sugars (30%) were identified as the most efficient ovipositional stimulants. To test and validate the biological control device described above, laboratory and field experiments were performed: a plastic lamella covered with syrphid eggs was suspended on aphid infested plants in order to measure the efficiency of the device. The results obtained were promising since populations of 500 aphids were eliminated in 10 days when 15 syrphid eggs were introduced. The use of such a biological control device could certainly contribute to the biological control to reduce the aphid infestations.

Impact of gamma radiation on the developmental characteristics of the gypsy moth, Lymantria dispar (Lepidoptera: Lymantriidae) preparatory to their use as supplemental hosts/prey for natural enemy enhancement

The developmental characteristics of irradiated and non-irradiated gypsy moth, Lymantria dispar L. eggs and larvae were compared. Gypsy moth eggs were irradiated a few days before hatching at 10, 20, 30, 40, 50, 60, 80, or 110 Gray (Gy) and first instar larvae at 50, 80, or 110 Gy of gamma radiation and tested for differences in their development by comparison with non-irradiated controls. Untreated larvae developed to the adult stage more rapidly than irradiated larvae treated either as eggs or as larvae and this was dose-dependent. Larval mortality and pupal developmental anomalies were dose-dependent. Pupal morphological abnormalities occurred in only 1.6% of controls, but in the 110 Gy group, they occurred in 93.2 and 95.1% of individuals treated as eggs or larvae, respectively. The tests showed that 50 Gy was optimal for irradiating gypsy moth eggs and larvae to achieve F1 sterility and extend larval development without excessive mortality. This may facilitate use of these sterile larvae as supplemental hosts in augmentative biological control programmes.

Filth fly parasitoids on dairy farms in Ontario and Quebec, Canada

AbstractHymenopterous parasitoids of filth flies (Diptera: Muscidae) were surveyed during 2 years on dairy farms in Ontario and Quebec near Ottawa, Ontario, using freeze-killed sentinel house fly (Musca domestica L.) pupae and naturally occurring fly pupae collected on site. Musca domestica and Stomoxys calcitrans (L.) (stable fly) represented 98.3% of the natural fly hosts from which parasitoids emerged. Muscidifurax raptor Girault et Saunders, Nasonia vitripennis Walker, Pachycrepoideus vindemiae (Rondani), Spalangia cameroni Perkins, S. nigra Latreille, Trichomalopsis viridescens (Walsh), and Urolepis rufipes (Ashmead) (Pteromalidae) were recovered from both sentinel and natural fly pupae. Another eight species, S. drosophilae Ashmead, S. endius Walker, S. haematobiae Ashmead, S. nigroaenea Curtis, S. subpunctata Förster, Trichomalopsis dubia (Ashmead) (Pteromalidae), Aphaereta pallipes (Say) (Braconidae), and Phygadeuon ?fumator Gravenhörst (Ichneumonidae), were recovered only from natural pupae. Over the 2 years, M. raptor comprised 90.7% of emerged parasitoids from sentinel pupae but only 17.0% of emerged parasitoids from natural pupae. From natural pupae, S. cameroni, S. nigra, and S. nigroaenea collectively comprised 60.3% of emerged parasitoids; P. ?fumator comprised 13.5% and the remaining nine species 9.2%. The recoveries of S. endius and S. nigroaenea represent new distribution records for Canada, and several new host records are identified based on structure of the host fly puparium. The parasitoid fauna is compared with that known for western Canada, and recommendations are made for both regions concerning potential natural enemy enhancement for filth fly control.

The population consequences of natural enemy enhancement, and implications for conservation biological control

AbstractWe explore models for the management of invertebrate pests by enhancing the efficacy or local abundance of existing natural enemies. Different aspects of natural enemy biology had different effects on prey density. Enhancement of enemy search rate or prey conversion efficiency showed the greatest potential for reducing prey density, while maximum consumption rate by predators, and parasitoid fecundity, had less effect. The effect on prey density of increased natural enemy longevity depended on its interaction with other parameters. The degree of manipulation needed to achieve a given reduction in prey populations was largely determined by the enemy's potential reproductive rate. Spatial ‘‘attraction’’ of enemies to a target site had an almost linear effect on local prey density. We conclude that successful conservation biological control benefits from a directed approach, targeting the most important aspects of natural enemy ecology, and that there is considerable potential for further research in this area.

Trap cropping effect on oviposition behaviour of the leek moth Acrolepiopsis assectella and the diamondback moth Plutella xylostella

AbstractThe potential of trap cropping as a pest control strategy was explored for two specialist moth species, where oviposition behaviour determines larval distribution. Oviposition behaviour was studied at three different scales: Individual plants in the laboratory, small scale field experiments with and without cages, and medium scale field trials. The study insects were the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), a specialist on Brassica species and the leek moth, Acrolepiopsis assectella (Z.) (Lepidoptera: Acrolepiidae), a specialist on Allium species. The diamondback moth preferred Indian mustard, Brassica juncea (L.) over white cabbage, B. oleracea var alba (L.). The leek moth did not show preference when offered leek, Allium porrum (L.) and chives, A. schoenoprasum (L.). However, the leek moth did prefer to oviposit on plants of a larger biomass over smaller plants. In both the small scale and the medium scale field studies the trap crops reduced the number of eggs laid on the primary crop. The total number of eggs laid in the monoculture and the trap crop treatments were the same in the small scale field cage study, but the females distributed their eggs differently. More eggs were laid on trap crops compared with primary crops and this pattern was also validated in the medium scale field trials. In this study only the direct effects of trap cropping were considered. Indirect effects of vegetation diversity such as enhancement of natural enemies could potentially increase the efficacy of trap cropping.

Conservation and enhancement of natural enemies in biological control

Conservation and enhancement of natural enemies in biological control

Influences of trees on abundance of natural enemies of insect pests: a review

In this article we review the use of natural enemies in crop pest management and describe research needed to better meet information needs for practical applications. Endemic natural enemies (predators and parasites) offer a potential but understudied approach to controlling insect pests in agricultural systems. With the current high interest in environmental stewardship, such an approach has special appeal as a method to reduce the need for pesticides while maintaining agricultural profitability. Habitat for sustaining populations of natural enemies occurs primarily at field edges where crops and edge vegetation meet. Conservation and enhancement of natural enemies might include manipulation of plant species and plant arrangement, particularly at these edges; and consideration of optimum field sizes, number of edges, and management practices in and near edges. Blending the benefits of agricultural and forestry (windbreak) systems is one promising approach to field edge management that has additional benefits of wind protection and conservation of desirable wildlife species.

Field margins: can they enhance natural enemy population densities and general arthropod diversity on farmland?

The interactions of predatory arthropods between natural habitats and arable land were explored. Three questions were asked: (1) Does habitat quality in field margins determine the density of natural enemies overwintering in field margins? (2) Are good sites for natural enemies also habitats which support greater general arthropod diversity? (3) Does the density of predators overwintering in field margins determine their distribution and abundance in adjacent cereal fields in spring? The value of field margins to agriculture was assessed as the density of arthropods overwintering in these habitats. The arthropod groups used for the assessment were known aphid predators which moved out into cereal crops in the spring. This assessment was compared with general arthropod diversity at each site to test whether field margins supporting high densities of predators were also of value to nature conservation in supporting greater arthropod biodiversity. In spring, the spatial dynamics of predatory arthropod species were investigated in cereal crops adjacent to field-margin overwintering sites. The influence of field-margin habitats on natural enemy populations within adjacent crops was evaluated. The enhancement of natural enemies and general arthropod conservation are discussed as components of overall biological diversity at the farm scale.

Low‐Input/Sustainable Agricultural Research and Education—Challenges to the Agricultural Economics Profession

Over the past decade, a number of different terms have been used to describe agricultural technologies that seek to substitute management and scientific knowledge for synthetic chemical pesticides and fertilizers-terms such as organic, regenerative, alternative, sustainable, and reduced-input have become widely used in various contexts (Wagstaff; Lowrance, Hendrix, and Odum). The term is used in California and other states to describe their new research and education programs. The term low-input has become the latest entry in the vocabulary of agricultural technology because this term is used in the FY 1988 federal appropriations legislation. Low-input/sustainable agriculture encompasses a wide array of approaches to farming that reduce the farmer's dependence on certain kinds of purchased inputs in ways that increase profits, reduce environmental hazards, and ensure a more sustainable agriculture for generations to come. Low-input farming methods range from release of exotic natural enemies to rather commonplace methods such as controlling weeds by mechanical cultivation and crop rotations. Also included in this category are various integrated pest management strategies such as biological control of pests through enhancement of natural enemies, use of legume crops in place of some purchased fertilizers, and application of livestock manures and compost. A low-input/sustainable farming system is a combination and sequence of low-input farming methods or technologies integrated into a whole-farm managerial plan. While many of the concepts underlying low-input farming methods have been known for decades or even centuries, the essence of this approach is not a reversion to the technologies of previous decades or centuries but a combination of the best of modern agricultural science and technology with the practical experience of farmers who are profitably substituting management for most or all of their purchased inputs of synthetic chemical pesticides and fertiliz-