Anantanarayanan Raman

Biological Control of Tropical Weeds using Arthropods

1. Biological control of weeds in the tropics and sustainability R. Muniappan, G. V. P. Reddy and A. Raman 2. Acacia nilotica ssp. Indica (L.) Willd. ex Del. (Mimosaceae) K. Dhileepan 3. Australian Acacia species (Mimosaceae) in South Africa F. Impson, J. H. Hoffmann and C. Kleinjan 4. Ageratina adenophora (Sprengel) R. King and H. Robinson (Asteraceae) R. Muniappan, A. Raman and G. V. P. Reddy 5. Azolla filiculoides Lamarck (Nostocaceae) M. P. Hill and A. J. McConnachie 6. Cabomba caroliniana Gray (Cabombaceae) S. Schooler, W. Cabrera-Walsh and M. H. Julien 7. Invasive cactus species (Cactaceae) H. Zimmermann, C. Moran and J. H. Hoffmann 8. Chromolaena odorata (L.) R. King and H. Robinson (Asteraceae) C. Zachariades, M. Day, R. Muniappan and G. V. P. Reddy 9. Clidemia hirta (L.) D. Don (Melastomataceae) P. Conant 10. Coccinia grandis (L.) Voigt (Cucurbitaceae) R. Muniappan, G. V. P. Reddy and A. Raman 11. Eichhornia crassipes (Mart.) Solms-Laub. (Pontederiaceae) J. A. Coetzee, M. P. Hill, M. H. Julien, T. D. Center and H. A. Cordo 12. Lantana camara Linn. (Verbenaceae) M. D. Day and M. P. Zalucki 13. Mimosa diplotricha C. Wright ex Sauvalle (Mimosaceae) L. S. Kuniata 14. Mimosa pigra L. (Leguminosae) T. A. Heard and Q. Paynter 15. Parthenium hysterophorus L. (Asteraceae) K. Dhileepan and L. Strathie 16. Passiflora mollissima (HBK) Bailey (Passifloraceae) G. P. Markin 17. Pistia stratiotes L. (Araceae) P. Neuenschwander, M. H. Julien, T. D. Center and M. P. Hill 18. Prosopis species (Leguminosae) R. D. van Klinken, J. H. Hoffmann, H. G. Zimmermann and A. P. Roberts 19. Salvinia molesta D. S. Mitchell (Salviniaceae) M. H. Julien, M. P. Hill and P. W. Tipping 20. Solanum mauritianum Scopoli (Solanaceae) T. Olckers 21. Application of natural antagonists including arthropods to resist weedy Striga (Scrophulariaceae) in tropical agroecosystems J. Sauerborn and D. Muller-Stover 22. Biological control of weeds in India J. Rabindra and B. S. Bhumannavar 23. The role of International Institute of Tropical Agriculture in weed biological control F. Beed and T. Dubois 24. The role of Secretariat of the Pacific Community in the biological control of weeds in the Pacific Islands region - past, present and future activities W. Orapa Index.

Effects of gall induction by Epiblema strenuana on gas exchange, nutrients, and energetics in Parthenium hysterophorus

Gall induction by arthropods results in a range of morphological and physiological changes in their host plants. We examined changes in gas exchange, nutrients, and energetics related to the presence of stem galls on Parthenium hysterophorus L. (Asteraceae) induced by the moth, Epiblema strenuana Walker (Lepidoptera: Tortricidae). We compared the effects of galls on P. hysterophorus in the rosette (young), pre-flowering (mature), and flowering (old) stages. Gall induction reduced the leaf-water potential, especially in flowering stage plants. In young and mature stage plants, galling reduced photosynthetic rates considerably. Gall induction reduced the transpiration rate mostly in mature plants, and this also diminished stomatal conductance. Energy levels in most galls and in shoot tissue immediately below the galls were significantly higher than the energy levels in stem tissue immediately above the galls, indicating that the gall acts as a mobilizing sink for the moth. Galling had significant effects on concentrations of minerals such as boron, chloride, magnesium, and zinc. In galled plants, reduced leaf-water potential and reduced rates of photosynthesis, transpiration, and stomatal conductance may have altered mineral element levels. These observed effects demonstrate that E. strenuana has the potential to regulate P. hysterophorus.

Gall induction by hemipteroid insects

The Thysanoptera and sternorrhynchous Hemiptera induce galls through feeding action, a behavior similar to that in the Cecidomyiidae. Salivary glands of gall-founding female thrips include greater quantities of hydrolyzing enzymes and soluble proteins than those in either males or pupae, which possibly alter the host-tissue metabolism, enabling galls to develop. Piercing-and-sucking mouthparts of the Hemiptera are adapted for an exclusively liquid diet – either the plant sap from vascular elements or the fluids from living nonvascular cells. Hemipteran-salivary chemistry alters the hormonal balance in the host, triggering gall development. Soluble proteins in the saliva of nymphs are critical. Gall-inducing Hemiptera vigorously take oxygen from the ‘gall’ tissue, which triggers auxin activity. Gall-inducing behaviors in the Thysanoptera and Sternorrhyncha are similar in that gall induction occurs by the feeding action of a single female, and gall-founding females disperse over short distances seeking young host-plant organs. Besides providing a comparative overview of gall induction by hemipteroids, this paper highlights the subtle but noteworthy differences in behaviors among these insects, thus offering pointers to their evolution within the specialist guild of herbivory. 1To Warren Gene Abrahamson III (Bucknell University, Lewisburg, PA, USA), who blazed new trails in interpreting the evolutionary ecology of galls and inducing insects. Memories of my stay in his laboratory in 1990–1991 are pleasant.

Metabolite mobilization in the stem galls of Parthenium hysterophorus induced by Epiblema strenuana inferred from the signatures of isotopic carbon and nitrogen and concentrations of total non-structural carbohydrates

Parthenium hysterophorus L. (Asteraceae) is a weed of national significance in Australia. Among the several arthropod agents introduced into Australia to control populations of P. hysterophorus biologically, Epiblema strenuana Walker (Lepidoptera: Tortricidae) is the most widespread and abundant agent. By intercepting the normal transport mechanisms of P. hysterophorus, the larvae of E. strenuana drain nutrients, other metabolic products, and energy, and place the host plant under intense metabolic stress. In this study, determinations of total non‐structural carbohydrates (TNC) levels and carbon and nitrogen isotope ratios of fixed products in different parts of the plant tissue, including the gall, have been made to establish the function of gall as a sink for the nutrients.

Cecidogenetic Behavior of some gall-inducing thrips, psyllids, coccids, and gall midges, and morphogenesis of their galls

Abstract Several plant species, belonging to diverse and unrelated families of Angiospemae respond to insect action by developing a gall. Development of a gall is a complex phenomenon that involves subtle alterations initiated at critical and specific points of time during plant differentiation. Galls are truly modified plant tissues; however, galls arise as a sequel to insect attack only, ensuring a suite of adaptations to the inducing insect. Natural selection seems to favor those insects that are able to introduce a perturbation in the plants growth and developmental process. Unlike the free-living insects, gall-inducing insects display an imperative demand of a particular plant species to complete their life-cycles; such a relationship includes specialized feeding and reproductive behaviors, high levels of specificity to host plants, and contribution to the dynamics of the evolution of the gall-inducing guild. Against this background, this review summarizes and analyzes morphogenesis of some galls induced by thrips, psyllids, coccids, and gall midges in the context of the behavior of the inducing agents, studied mostly from subtropical peninsular India. The review concludes with a comparative synthesis of the available information on insect-induced galls in general, and in the particular context of galls induced by thrips, psyllids, coccids, and gall midges from other biogeographical regions, and the biologies of those insects.

Influence of Botrytis cinerea (Helotiales: Sclerotiniaceae) infected leaves of Vitis vinifera (Vitales: Vitaceae) on the preference of Epiphyas postvittana (Lepidoptera: Tortricidae)

Herbivorous insects use sensory cues to choose their host plants for feeding and/or oviposition by assessing host quality. Olfactory, contact and visual cues of the host mediate such choices. The right‐host choice for oviposition by a lepidopteran is essential for the performance of its progeny. In natural conditions, plants are often and concurrently attacked by both herbivorous insects and pathogenic fungi. In such a three‐way relationship, the interaction between the plant and insect is usually influenced by the fungal population, and such an influence can be either mutualistic or antagonistic. In the present study, we tested the three‐way relationship using the system, Epiphyas postvittana–Vitis vinifera–Botrytis cinerea. We sought answers to the questions: (1) whether the females of E. postvittana prefer to oviposit on V. vinifera leaves infected by B. cinerea; and (2) whether the larvae of E. postvittana prefer to feed on V. vinifera leaves infected by B. cinerea. We found that the host‐seeking gravid females of E. postvittana ‘tested’ the infection status of the host plant using olfactory, visual, and tactile cues; in consequence, they laid significantly fewer eggs on the moderately (30–60%) and intensely (90–100%) infected leaves of V. vinifera. The neonate larvae preferred to feed on mildly (5–10%) and moderately (30–60%) infected leaves, as against the uninfected (control) leaves, and showed no preference for intensely (90–100%) infected leaves. External and internal examination of the larvae established that the larvae fed on B. cinerea‐infected leaf because viable conidia of B. cinerea occurred on the body surface and within the gut of the neonate larvae.

Effects of flowering groundcover vegetation on diversity and activity of wasps in a farm shelterbelt in temperate Australia

Significant worldwide interest in conservation biological control in agricultural systems currently exists but little information is available on the usefulness of this approach in farm forestry. In a field experiment conducted in a native vegetated shelterbelt in central-west New South Wales, we measured the diversity of wasps in plots comprising Eucalyptus blakelyi Maiden (Myrtaceae) trees with and without a groundcover of Lobularia maritima (L.) Desv. (Brassicaceae). Vacuum samples revealed a greater abundance and species richness of parasitic wasps in the plots comprising trees surrounded by the L. maritima groundcover. Cotesia sp. (Hymenoptera: Braconidae), Pteromalus sp. (Hymenoptera: Pteromalidae), Anagyrus sp. (Hymenoptera: Encyrtidae), Entedoninae sp. and Eulophidae sp. 1 (Hymenoptera: Eulophidae) were the most common taxa. These were more abundant also in the trees with the L. maritima groundcover. Ardozyga stratifera (Meyrick) (Lepidoptera: Gelechiidae) larvae, that were naturally infesting the E. blakelyi trees, were significantly more parasitized in the trees with the L. maritima groundcover. Results indicate that parasitic wasps associated with a native-tree shelterbelt in Australia were amenable to manipulation via groundcover vegetation.

Visual Cues Are Relevant in Behavioral Control Measures for Cosmopolites sordidus (Coleoptera: Curculionidae)

ABSTRACT Trap designs for banana root borer, Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae), have been done essentially on the understanding that C. sordidus rely primarily on chemical cues. Our present results indicate that these borers also rely on visual cues. Previous studies have demonstrated that among the eight differently colored traps tested in the field, brown traps were the most effective compared with the performances of yellow, red, gray, blue, black, white, and green traps; mahogany-brown was more effective than other shades of brown. In the current study, efficiency of ground traps with different colors was evaluated in the laboratory for the capture of C. sordidius. Response of C. sordidus to pheromone-baited ground traps of several different colors (used either individually or as 1:1 mixtures of two different colors) were compared with the standardized mahogany-brown traps. Traps with mahogany-brown mixed with different colors had no significant effect. In contrast, a laboratory color-choice tests indicated C. sordidus preferred black traps over other color traps, with no specific preferences for different shades of black. Here again, traps with black mixed with other colors (1:1) had no influence on the catches. Therefore, any other color that mixes with mahogany-brown or black does not cause color-specific dilution of attractiveness. By exploiting these results, it may be possible to produce efficacious trapping systems that could be used in a behavioral approach to banana root borer control.

Volatiles in perennial ryegrass infected with strains of endophytic fungus: impact on African black beetle host selection

Perennial ryegrass (Lolium perenne) is often infected with the fungal‐endophyte Neotyphodium lolii. In addition to the ‘wild‐type’ strain (EWT), several ‘selected’ strains of N. lolii are now being marketed as AR1 (EAR1) and AR37 (EAR37). Each of these strains impact positively on L. perennes resistance against many insects, including the African black beetles (Heteronychus arator). The impact of volatile oils produced specifically by each strain in the endophyte–grass association in enhancing the grasss resistance to insects is still largely unknown. Keeping these in view, we determined the volatile oil profiles produced by L. perenne infected with either EWT or EAR1 or EAR37 and determined the impacts of these volatiles on the host‐selection behaviour of H. arator adults. In the absence of endophyte infection (E–), L. perenne produced 18 different volatile oils. In L. perenne EWT, quantities of 2‐ethyl‐1‐hexanol acetate (Rt = 14.5 min), (Z)‐2‐octen‐1‐ol (Rt = 22.2 min), and butylated hydroxyl toluene (Rt = 23.2 min) were 24, 16 and 26%, respectively, greater than L. perenne E–. The strains EAR1 and EAR37 affected differently the quantities of the volatile compounds but not their identity. In the four‐choice bioassay, males and females of H. arator were equally attracted to each strain. In Y‐tube olfactometer, compared against E–, H. arator adults were less attracted to L. perenne EWT and EAR1. The attractiveness of EAR37 was similar in effect to E– to H. arator. The results indicate that each strain of N. lolii alters the profile of volatile oils in L. perenne differently and that alteration can influence H. arator adult‐host selection.

Biology and host specificity of gall-inducing Acythopeus burkhartorum (Coleoptera: Curculionidae), a biological-control agent for the invasive weed Coccinia grandis (Cucurbitaceae) in Guam and Saipan

An introduced cucurbit Coccinia grandis (Linnaeus) Voigt has grown into problem proportions in Hawaii and the Pacific islands of Guam and Saipan. The biology of Acythopeus burkhartorum O’Brien, 1998, a potential biological-control agent of C. grandis, has been described. By inducing the gall – a sink for nutrients – and by deriving nutrition, A. burkhartorum places C. grandis under stress. Especially during the late larval stage, the weevil displays an unusual behaviour of shredding dry gall tissues with its mandibles to ‘prepare’ the ‘pupal case’ and using the shredded sclerenchyma fibres to fill the open and cut ends of the pupal case. This ability to ‘create’ such a pupal case is unique among weevils. Because A. burkhartorum is able to sever tender shoots of C. grandis at points where galls are induced, we consider that this weevil will be highly relevant in C. grandis management. Although nongall-inducing species of baridine weevils have a wide host range, the known gallinducing species are specific to their respective hosts, similar to the majority of gall-inducing insects. A. burkhartorum prefer consistently either petioles or stems, behave identically by tunnelling through soft tissues within the host organs, and induce galls. Because of the potential of A. burkhartorum in biological control of C. grandis, we tested its specificity against C. grandis and Zehneria guamensis (an endemic cucurbit of Guam and Mariana Islands), following ‘choice’ and ‘no choice’ test modes. No feeding hole or gall development occurred on Z. guamensis indicating a categorical response that A. burkhartorum is specific to C. grandis. This result encouraged field release of A. burkhartorum in Guam and Saipan.