Ingrid H. Williams

Bees and the Pollination of Crops and Wild Flowers in the European Community

(1991). Bees and the Pollination of Crops and Wild Flowers in the European Community. Bee World: Vol. 72, No. 2, pp. 47-59.

Are honey bees' foraging preferences affected by pollen amino acid composition?

Abstract.  1. Although pollen is a vital nutritional resource for honey bees, Apis mellifera, the influence of pollen quality on their foraging behaviour is little understood.

(Z)-11-eicosen-1-ol, an important new pheromonal component from the sting of the honey bee,Apis mellifera L. (Hymenoptera, Apidae.)

Abstract(Z)-11-Eicosen-1-ol was identified by GC-MS and microchemical methods as a major volatile component, ca. 5 μg per insect, secreted by the sting apparatus of the worker honey bee. When presented on moving lures at the hive entrance, (Z)-11-eicosen-1-ol, like isopentyl acetate already known as an alarm pheromone, elicited stinging, and together these two compounds were as active as the natural pheromone from the sting. On stationary lures, (Z)-11-eicosen-1-ol prolonged the effectiveness of isopentyl acetate.

Nasonov pheromone of the honey bee, Apis mellifera L. (Hymenoptera, Apidae) Part I. Chemical characterization.

Composition of the Nasonov pheromone of the honey bee has been reexamined using new procedures, including analysis of pheromone from single live insects by capillary column GC-MS. Two new components have been identified, nerol and (E,E)-farnesol, and the presence of components proposed previously has been confirmed. Absolute amounts or relative proportions of components in the pheromonal secretion have been determined.

Exploitation of host plant preferences in pest management strategies for oilseed rape (Brassica napus)

New control strategies for insect pests of arable agriculture are needed to reduce current dependence on synthetic insecticides, the use of which is unsustainable. We investigated the potential of a simple control strategy to protect spring‐sown oilseed rape, Brassica napus L. (Brassicaceae), from two major inflorescence pests: the pollen beetle, Meligethes aeneus (Fabricius) (Coleoptera: Nitidulidae), and the seed weevil, Ceutorhynchus assimilis (Paykull) (Coleoptera: Curculionidae), through exploitation of their host plant preferences. The strategy comprised, for the main crop, Starlight [an oilseed rape cultivar with relatively low proportions of alkenyl glucosinolates in the leaves (thereby releasing lower levels of attractive isothiocyanates than conventional cultivars)] and turnip rape, Brassica rapa (L.) (Brassicaceae), as a trap crop. We tested the system in laboratory, polytunnel semifield arena, and field experiments. The odours of Starlight were less attractive in olfactometer tests to both pests than those from a conventional cultivar, Canyon, and the plants were less heavily colonized in both polytunnel and field experiments. Turnip rape showed good potential as a trap crop for oilseed rape pests, particularly the pollen beetle as its odour was more attractive to both pests than that of oilseed rape. Polytunnel and field experiments showed the importance of relative growth stage in the system. As turnip rape flowers earlier than oilseed rape, beetles would be maintained on turnip rape past the damage‐susceptible growth stage of oilseed rape. The development of a pest control regime based on this strategy is discussed.

Spatial distribution of pest insects in oilseed rape: implications for integrated pest management

Abstract Insect pests, plant growth and plant yield in a crop of winter oilseed rape ( Brassica napus L.) were studied to assess the potential value of spatial information in integrated pest management for this crop. Ceutorhynchus assimilis Payk., Ceutorhynchus pallidactylus (Marsh.), Meligethes aeneus (Fab.) and Dasineura brassicae Winn. were sampled from the nodes of a rectangular grid across the crop. Their spatial distributions were mapped, analysed and compared using Spatial Analysis by Distance IndicEs (SADIE). The relationships between the distributions of insects, plant growth and yield were assessed using regression techniques. The distributions of C. assimilis , C. pallidactylus and M. aeneus were complex with differing irregular patterns of aggregation, whereas D. brassicae was edge-distributed. Stem injury, chiefly caused by larval Psylliodes chrysocephala L., was associated with significant yield loss and the spatial distribution of stem injury was reflected in the distribution of oil yield. The distribution of larval M. aeneus was dissociated from that of pods which shed their seed before harvest. Spatial heterogeneity in plant maturation as a result of infestation could delay the choice of harvest date beyond the optimum to prevent seed loss from less injured plants. Some of the variability (21–31%) in insect numbers within the crop was explained by variation in plant density and in growth stage at mid-flowering. The spatial ecology of these pests is discussed in terms of the roles of environmental factors, behavioural responses and the implications of spatial patterns for yield loss and for developing sustainable integrated crop protection. The data indicate that decision support systems should use sampling strategies which incorporate spatial information to model crop loss more accurately and that there may be potential for spatially targeted applications of insecticide to optimise the influence of biocontrol agents in oilseed rape.

Factors determining the rearing and rejection of drones by the honeybee colony

Abstract Production of drone cells and drone brood and the eviction of adult drones by honeybee colonies have been investigated. Smaller colonies of honeybees either built no drone comb, or a smaller proportion of drone-to-worker comb than larger colonies. The proportion of drone cells built was greatest in May, June and July although colonies continued to build drone comb long after they had ceased to rear drones. The proportion of drone comb built by a colony also depended on the amount of drone comb already present. The amount of drone brood and the number of adult drones present in a colony was correlated positively with the number of workers. Removing drone brood from colonies encouraged its production, adding it diminished its production. A large percentage of eggs was sometimes laid in drone cells before the end of April, although few were reared. The proportion of drone brood was at its maximum in May and June. A colony could be caused to evict its drones by preventing it from foraging and in autumn eviction was greatly delayed by providing forage or removing the queen.

Growth stimulation of beetle larvae reared on a transgenic oilseed rape expressing a cysteine proteinase inhibitor.

The resistance of a transgenic line of oilseed rape expressing constitutively the cysteine proteinase inhibitor oryzacystatin I (OCI) was assessed against Psylliodes chrysocephala L. (Coleoptera: Chrysomelidae). The levels of OCI expression in the transformed line averaged 0.2% and 0.05% of total soluble protein in leaves and petioles respectively. In vitro analyses showed that P. chrysocephala larvae use both cysteine and serine proteinases for protein digestion, and that all the cysteine proteolytic activity is OCI-sensitive. However, bioassays showed that adults fed identically on leaf discs from control or transformed plants. When larvae were reared on transgenic plants expressing OCI, they showed an increase in weight gain compared to those reared on control plants. Furthermore, those larvae from transgenic plants exhibited a 2-fold increase in both cysteine and serine proteolytic activity as a reponse to the presence of OCI. The plasticity of insect digestive physiology and feeding behaviour are discussed, as well as the relevance of engineering a genotype expressing both types of proteinase inhibitors.

The economic value of bees in the UK

In the UK, as elsewhere in Europe, bees are valued not only for the honey and wax that they produce, but also for the pollination service that they provide to the majority of our crops and wild flowers. However, no estimate of their value in economic terms has been made in recent years.

The responses of the cabbage seed weevil Ceutorhynchus assimilis to volatile compounds from oilseed rape in a linear track olfactometer

The cabbage seed weevil, Ceutorhynchus assimilis Payk. [syn. Ceutorhynchus obstrictus (Marsham)] (Coleoptera: Curculionidae), a crucifer‐feeding insect, is a pest of oilseed rape (Brassica napus L.). It is known to be attracted by isothiocyanates, crucifer‐specific volatiles that are metabolites of the glucosinolates. The responses of this insect to other electrophysiologically‐active volatiles from rape were tested in a linear track olfactometer. Attraction was demonstrated to nitriles (phenylacetonitrile, 4‐pentenenitrile and 5‐hexenenitrile), which are also glucosinolate metabolites, and to volatiles emitted by a wider spectrum of plant families ((Z)‐3‐hexen‐1‐ol and methyl salicylate). Combination of an isothiocyanate mixture with phenylacetonitrile increased attraction, but there was no such increase when the isothiocyanate mixture was combined with methyl salicylate. A mixture of 23 volatiles, emulating an attractive air‐entrainment extract of oilseed rape, was not significantly attractive, although a high proportion of weevils (60%) turned towards it. The potential of these volatiles for inclusion into an isothiocyanate‐based monitoring system is discussed.