Exploiting physical defence traits for crop protection: leaf trichomes of Rubus idaeus have deterrent effects on spider mites but not aphids

Plants possess anti‐herbivore defences that could be exploited for crop protection. The potential for deploying physical defence traits for more sustainable pest management (i.e. reduced pesticide application) has not been fully realised. Using a perennial crop (red raspberry, Rubus idaeus), we take the novel approach of quantifying within‐ and between‐genotype variation in a resistance trait, leaf trichome density, to determine precisely the effect of trichomes on host plant preference and suitability for two shoot‐feeding arthropods, the European large raspberry aphid (Amphorophora idaei) and two‐spotted spider mite (Tetranychus urticae). Additionally, we tested whether this trait influenced searching behaviour of a generalist herbivore predator (lacewing larvae, Chrysoperla carnea). Although there was no consistent genotypic variation in R. idaeus suitability for T. urticae, our hypothesis that T. urticae would avoid high leaf trichome density was supported on certain genotypes. The deterrent effect was mainly on egg deposition rather than leaf selection by adults, with up to sixfold differences in leaf preference depending on the genotypes offered. By contrast, there was significant genotypic variation in R. idaeus suitability for A. idaei (10‐fold variation in aphid abundance), but, contrary to our prediction, aphid preference and infestation levels were unrelated to leaf trichome density. Instead, A. idaei performed best on vigorous genotypes, indicating that plant tolerance traits contributed to R. idaeus suitability for aphids. Leaf trichomes had little effect on the behaviour of the beneficial control agent C. carnea larvae. We conclude that physical anti‐herbivore defences, specifically leaf trichomes, could be deployed to deter particular arthropod pests. However, the mechanistic approach adopted here is necessary to avoid antagonistic effects on other pests or on natural enemies.     

Prey consumption and development of the indigenous lacewing Chrysoperla externa feeding on two exotic Eucalyptus pests

ABSTRACT

The green lacewing Chrysoperla externa is a widespread species in the Neotropical region that occurs in different habitats. Its presence in Eucalyptus plantations infested with Glycaspis brimblecombei (Hemiptera: Aphalaridae) and Thaumastocoris peregrinus (Hemiptera: Thaumastocoridae) suggests that this lacewing might feed on one or both exotic pest species. In order to evaluate C. externa as a potential biocontrol agent of the eucalyptus pests, the prey consumption, development, survival and reproduction of the predator were evaluated under laboratory conditions. C. externa larvae consumed nymphs of both pest species. Developmental time and reproduction parameters of C. externa fed G. brimblecombei were similar to those obtained with the factitious prey Sitotroga cerealella. When fed on T. peregrinus, C. externa showed a delay in its developmental time and the emerged adults were malformed. The results of this study suggest that the green lacewing is a good candidate to be used in augmentative or conservative biological control programmes against G. brimblecombei. Further research is necessary to analyse the potential of this predator as a biocontrol agent under field conditions.     

Manipulation of oviposition and overwintering site choice of common green lacewings with synthetic lure (Neuroptera: Chrysopidae)

Common green lacewings (Chrysoperla carnea species complex) are important predators of several insect pests, particularly aphids. Due to their potential in biological control, several efforts have been made to find means to retain common green lacewing adults or even to increase their numbers at a given site. In the course of field experiments conducted in Hungary and Norway, we tested the effect of a known ternary bait (phenylacetaldehyde, methyl salicylate, acetic acid) on oviposition and overwintering site choice of common green lacewings. In an orchard in Hungary, overwintering chambers were set up with and without baits. For the experiment on oviposition in Norway, a number of lacewing eggs were compared on trees with and without baits in selected sectors of the canopy. With the ternary bait, more common green lacewings could be attracted to overwintering chambers, and also significantly more eggs were found in the vicinity of baits than in other selected parts of the canopy, suggesting that this bait has the potential to manipulate both overwintering site choice and oviposition site choice of these important beneficial insects.     

龙眼角颊木虱生物学特性及防治研究

龙眼角颊木虱是龙眼的主要害虫,以成虫和若虫为害龙眼新梢嫩叶。在厦门市同安区一年发生六代,主害代为经一代于３月下旬至４月中旬和第五代于９月中旬至１０月上旬。本报道了该虫在不同温度下各虫态的发育历期,发现各个世代若虫都有滞育的现象,研究分析了若虫滞育对越冬虫源,主害代虫源等种群动态的影响,并探讨了龙眼角颊木虱的为害损失测定及药剂防治试验。     

缺磷条件下不同水稻品种磷素吸收特性的研究

缺磷条件下,供试粳稻品种植株的单株鲜重、干重、全磷含量和单株磷累积量等具有较大差异,从中筛选出磷高效品种TP309和优质8号,其中TP309较磷低效品种早88-1的全磷含量和单株磷累积量分别增加37.50%~40.00%和82.76%~102.00%。单株根数、平均根长和根系体积与单株磷素吸收量的相关程度较小,光合速率(Pn)、叶片可溶蛋白含量和叶片可溶性糖含量均表现为随着吸磷量的增加而不断增大。     

星球藻属一新种——中国星球藻

<正> 中国星球藻 新种 图版Ⅰ、图1—6;图版Ⅱ、图1—8。 Asterocapsa sinica Chu et S. G. Chen, sp. nov. Massa plantae grumosa, gelatinosa, olivaceo-viridis; cellululae sp(?)aericae veloblongae, aut per compressionem mutam angulatae; singulae, 2—4—8 vel plures in involucreo crasso, vaginato, Iamellato aut non lamellato, non confluente;vagina coloniae crassissima, rigida, lamellae confluentes in involucri margine habens, incolorata aut flava aut punicea, pleuromque adulta fuscescens; superficies vaginae cellularum singularum atque involucri coloniae protectionieus verruciformibus. brevis longisve minutis crassive, perfusa; cellulae 3—4 μ diam., coloniae 300—500 μ diam. cellulae intus homogeneae aut grosse granulatae(pseudovaeuoleae?), olivaceo-viridea, nitide caeruleo-virides aut fusco-virides,in 2—3 plana divisae.     

Predators mediate host plant resistance to a phytophagous pest in cabbage with glossy leaf wax

This study examined the role of generalist predators in producing higher mortality ofPlutella xylostella L. (Plutellidae) larvae on glossy vs. normal-wax cabbage,Brassica oleracea var.capitata L. To test this, survival and feeding ofP. xylostella were measured on individually caged glossy and normal-wax plants with and without each of three generalist predators,Chrysoperla carnea (Stephens) (Chrysopidae),Orius insidiosus (Say) (Anthocoridae), andHippodamia convergens Guerin-Meneville (Coccinellidae). In the greenhouse, predators always significantly reduced survival ofP. xylostella larvae on glossy plants, but never on normal-wax plants. In the field, predators significantly reducedP. xylostella survival on glossy plants, but onlyC. carnea was effective on normal-wax plants. In similar experiments with excised leaves,O. insidiosus andC. carnea were more effective predators on the glossy leaves, whileH. convergens was equally effective on both kinds of leaves. Patterns for feeding were similar, but significance levels differed from those forP. xylostella survival. The greater effectiveness of predators on glossy plants is apparently due to the reported improved mobility of these animals on glossy leaf surfaces. The data also suggest that reduced mining byP. xylostella exposes the larvae to more predation on glossy plants and contributes some to the resistance. Regardless of the mechanism, resistance toP. xylostella on glossyB. oleracea appears to depend on the action of generalist predators for its full expression. This dependence on predation must be considered in the development and deployment of glossy insect-resistantB. oleracea.     

The effects of different components of an artificial food on adult green lacewing (Chrysoperla carnea) fecundity and longevity

Artificial foods comprising yeast products, sugar and water are often sprayed in the field to increase numbers of naturally occurring lacewing populations. The relative importance of the components of these foods for green lacewing (Chrysoperla carnea Stephens) fecundity and longevity is investigated in this paper. In laboratory experiments insects receiving only sugar solution lived significantly longer than those receiving diets containing both sugar and yeast (P<0.05). The inclusion of yeast is required for egg production, but few eggs are produced on yeast solution alone. For maximum egg production, food containing yeast and sugar must be offered on more than one occasion. Compared with insects given a diet comprising yeast autolysate, sugar, and water in the ratios 4∶7∶10, small but significant reductions in egg production rate were noted when the amount of either the yeast, or both the yeast and the sugar, was halved. The implication of these findings for the field is that viscous foods must be offered on a regular basis for maximum effectivity.     

Potential for intraguild predation and competition among predatory Coccinellidae and Chrysopidae

In a laboratory study two coccinellid species, Coleomegilla maculata (DeGeer) and Harmonia axyridis Pallas, completed preimaginal development on lacewing eggs, Chrysoperla carnea Stephens or pea aphids, Acyrthosiphon pisum (Harris) in similar times. Preimaginal survival on C. carnea eggs was similar to survival on A. pisum for all stages of C. maculata and H. axyridis. Coccinellid adults that developed on C. carnea eggs were smaller than adults reared on A. pisum. Coccinella septempunctata L. did not complete preimaginal development on C. carnea eggs. Chrysoperla carnea preimaginal developmental time was approximately 20 days when fed either C. maculata eggs or A. pisum. Chrysoperla carnea fed C. maculata eggs developed into smaller adults, compared to adults reared as larvae on A. pisum, Ostrinia nubilalis (Hübner) eggs, or A. pisum alternated daily with O. nubilalis eggs. C. carnea did not complete preimaginal development on H. axyridis eggs. Cannibalism occurred more frequently between C. carnea third instars than between C. maculata fourth instars. When a C. carnea third instar was paired with a C. maculata fourth instar, more C. maculata were preyed upon by C. carnea, regardless of the herbivorous prey density. In the field these two predator species may negatively affect each other and reduce their suppression of pest densities.