Evaluation of potential trap plant species for the wheat bug Nysius huttoni (Hemiptera: Lygaeidae) in forage brassicas

1. The wheat bug Nysius huttoni is a major pest of brassica seedlings. Management of this insect currently relies on seed treatment with neonicotinoids and spraying with chlorpyrifos and pyrethroid insecticides. These practices can generate severe external costs, including human health, the environment and biodiversity. Trap cropping is one alternative option to protect brassica seedlings from N. huttoni.
2. Trap crop species evaluated in field cage experiments were: alyssum (Lobularia maritima L. Desvauxcv. Benthamii White), wheat (Triticum aestivum L. cv. Morph), coriander (Coriandrum sativum L. cv. Santo) and clover (Trifolium repens L. cv. Nomad). These were compared with kale (Brassica oleracea L. cv. Kestrel). In open‐field experiments, alyssum (L maritima), wheat (T. aestivum) and a mixture of alyssum (L. maritima) and wheat (T. aestivum) were used. All of these were compared to kale (B. oleracea).
3. Alyssum and wheat were the most favoured potential trap plants for N. huttoni. Results indicated that two treatments: alyssum (used as a single trap crop) or ‘alyssum plus wheat’ (a multiple trap crop), may be useful in brassica fields to protect the seedlings from N. huttoni damage.
4. Such a trap cropping protocol potentially reduces pesticide use in forage brassicas and can also deliver multiple ecosystem services such as biological control of insect pests.

     

The effect of allatectomy and photoperiod on the supercooling point in Pyrrhocoris apterus adults

Abstract Adults of Pyrrhocoris apterus (L.) (Heteroptera: Pyrrhocoridae) reared at 26°C had a considerably lower supercooling point (SCP) in diapause-inducing (LD 12:12 h) than in diapause-inhibiting (LD 18:6 h) photoperiodic regimes. Exposure of the insects to diapause-inducing acclimation conditions (LD 8:16 h and a temperature of 20°C during photophase and 5°C during scotophase) for 2–3 weeks had very little effect on the SCP, irrespective of the rearing photoperiod. Allatectomized adults kept continuously at LD 18:6 h and 26°C had high SCP similar to intact or sham-operated insects. In contrast to non-allatectomized insects, the SCP of allatectomized insects decreased after an exposure of from 2 to 3 weeks to diapause-inducing acclimation conditions (see above) almost to the level found in the intact diapausing insects. The relationship between the decrease of SCP and ‘diapause syndrome’ (de Wilde, 1970) is discussed.     

The influence of feeding on predatory tactics in a water bug

Abstract. The tropical belostomatid Diplonychus indicus Venk. & Rao (Heter-optera: Belostomatidae) forages both actively and from ambush, changing frequently from one predatory mode to the other. Analyses presented here of the influence of feeding and of developmental stage on several locomotory and predatory parameters show that the fact that a bug was eating did not prevent it from reacting to and from seizing prey items, but it did influence the mode of predatory attempts. Feeding bugs were less active and they foraged actively less frequently, but feeding did not affect the frequency of predatory attempts from ambush. No important variations during development were found and first stadium larvae behaved similarly to adults. Capture success rates were higher at all developmental stages during a meal than when a bug was not eating and rejection rates were lower during a meal. These results suggest that, when eating, Diplonychus indicus bugs aim more successfully at prey items they are more likely to capture and to eat.     

Local and landscape scale drivers of Euschistus servus and Lygus lineolaris in North Carolina small grain agroecosystems

1. Crop production sequences influence arthropod populations in temporally unstable row crop systems. Winter wheat (Triticum aestivum L.) represents one of the earliest abundant crops in south-eastern United States. This study aims to understand primary source habitats driving brown stink bug, Euschistus servus (Say), and tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), population abundance in wheat.
2. To better understand these relationships, adult and nymphal densities were in wheat fields weekly from flowering through harvest in 2019 and 2020. Geospatial data were used to measure landscape composition surrounding sampled fields. We investigated the influence of landscape predictors on E. servus and L. lineolaris abundance using generalized linear mixed modelling.
3. Field size, proportion of agriculture, proportion of wheat area, and proportion of soybean Glycine max L.) area from the previous year in the surrounding landscape were associated with E. servus abundance in wheat. Similarly, L. lineolaris abundance was associated with proportion of wheat area and soybean area from the previous year.
4. These results reveal the influence of soybean area planted the previous year on insect pest densities the following spring in wheat. Further, results suggest agricultural landscapes dominated by wheat are associated with decreased pest abundance across the sampled region.

     

Responses of insect herbivores to sharing a host plant with a hemiparasite: impacts on preference and performance differ with feeding guild

1. Root hemiparasites are common components of many ecosystems and can affect both the biomass and the nutritional quality of the plants they infect. The consequences of these modifications for the preference and performance of three herbivore feeding guilds sharing a host with the hemi‐parasite were examined. 2. It was predicted that as the hemiparasite increased in biomass its impact on the host would increase, as would the indirect impacts on the herbivores. It was also predicted that herbivores from different feeding guilds would respond differently to the presence of the hemiparasite, reflecting the extent to which they utilise resources disrupted by the parasite and hence are in competition with it. 3. The preference and performance of phloem‐feeding aphids, xylem‐feeding spittle bugs, and leaf‐feeding grasshoppers were measured on the host grass species, Holcus lanatus L. (Poaceae), with and without attachment from the hemi‐parasite, Rhinanthus minor L. (Orobanchaceae). 4. The effects of R. minor on the host were dependent on the hemiparasite's stage of growth, being most pronounced when it was at peak biomass. At this stage it caused a significant reduction in the biomass, water content, and total nitrogen content of the host plants. 5. Overall, herbivores benefited from, or preferred, shared host plants more than uninfected plants. The aphid benefited from sharing a host with R. minor, showing increased population growth on, and preference for, parasitised plants. The spittle bug also showed a preference for parasitised plants. The grasshopper, Chorthippus brunneus Thunberg (Orthoptera: Acrididae), did not show a preference for, or a performance response to, parasitised hosts, but it consumed significantly more plant material when caged on parasitised plants. 6. These data support the prediction that invertebrate herbivores responded to changes in host plant traits driven by the hemiparasite, and strongly suggest that these indirect interactions could impact on population and community processes within natural communities.     

Soldier bug predation on swallowtail caterpillars (Lepidoptera: Papilionidae): Circumvention of defensive chemistry

All larvae in the family Papilionidae possess osmeteria, eversible glands that release defensive chemicals upon disturbance. These chemicals have been shown to be repellent to ants, mantids, and other predaceous arthropods with chewing mouthparts. In this study, we demonstrate that the pentatomid Podisus maculiventris,an important predator of the black swallowtail Papilio polyxenes,is capable of piercing the body wall of the caterpillar and consuming body fluids without eliciting osmeterial eversion. Tenebrio molitorlarvae coated with osmeterial secretions of Papilio polyxeneswere universally rejected by Podisus maculiventris,suggesting that the predator is in fact repelled by the swallowtail defensive chemistry. By circumventing the defensive behavior of the caterpillar, the pentatomid is able to utilize an otherwise chemically unsuitable prey species.     

A non-invasive technique to bleed incubating birds without trapping: a blood-sucking bug in a hollow egg

We describe a non-invasive technique to obtain blood samples from incubating birds without trapping and handling. A larval instar of the blood-sucking bug Dipetalogaster maximus (Heteroptera) was put in a hollowed artificial egg which was placed in a common tern (Sterna hirundo) nest. A gauze-covered hole in the egg allowed the bug to draw blood from the brood patch of breeding adults. We successfully collected 68 blood samples of sufficient amount (median=187 μl). The daily success rate was highest during the early breeding season and averaged 34% for all trials. We could not detect any visible response by the incubating bird to the sting of the bug. This technique allows for non-invasive blood collection from bird species of various sizes without disturbance.     

Do Egg Carrying and Protracted Copulation Affect Mobility in the Golden Egg Bug?

Golden egg bug Phyllomorpha laciniata (Heteroptera, Coreidae) females oviposit on male and female conspecifics that carry ova until they hatch. Embryos benefit from being carried because of diminished risks of predation. Female carriers are never the parents of carried eggs, and males are only rarely the fathers of any carried eggs. Eggs develop and hatch without being carried in the laboratory. Egg carriers may be viewed as victims, exploited by females that encumber them with eggs. The intensity of selection favouring resistance to egg carrying should be proportional to the costs of this behaviour. One possible cost could be a reduction in mobility caused by carried eggs. We compare movement rates among encumbered and unencumbered golden egg bugs of both sexes. Protracted copulations (often exceeding 20 h) typical of this species and mating may also cause reduction in bugs mobility. Therefore, we also evaluate rates of movement of coupled pairs of bugs. Our results indicate that egg loads do not affect the mobility and speed of either males or females. However, copulating pairs are significantly slowed as compared to single bugs. Thus protracted copulations have a clear cost in rates of movement and possibly risks of predation, but there are no apparent mobility costs for egg carrying.