COMMUNITY STRUCTURE AND PEST STATUS OF PHYTOPHAGOUS

WHITEGRUB SPECIES IN SOUTH AFRICAN FORESTRY

by

DERIAN ECHEVERRI-MOLINA

RESEARCH DISSERTATION

Submitted in fulfilment of the requirements for the degree of

MASTER OF SCIENCE

in

BIOLOGY

in the

FACULTY OF HEALTH SCIENCES

(School of Pathology and Pre-Clinical Sciences, Department of Biology)

at the

UNIVERSITY OF LIMPOPO

(MEDUNSA Campus)

Supervisor: Prof. P. GOVENDER (Ph.D.)

2012 Table of Contents

Page

Declaration iv

Acknowledgements v

Preface vii

Chapter 1 1

Community structure and species composition of whitegrubs attacking

Acacia mearnsii seedlings in the Natal Midlands of South Africa

Abstract 2

Introduction 3

Materials and Methods 6

Species identification 6

Community analysis 7

Results 8

Discussion 11

Community structure pattern 11

References 15

Table 1 21

Table 2 22

Figure 1 23

Figure 2 24

Figure 3 25

Figure 4 26

ii

Table of Contents (Continued)

Page

Chapter 2 27

Pest status of whitegrubs attacking Acacia mearnsii seedlings

in the Natal Midlands of South Africa

Abstract 28

Introduction 29

Materials and Methods 32

Data analysis 33

Results 35

Whitegrub morphospecies: abundance and distribution 35

Whitegrub morphospecies: group contribution to the community

structure pattern 37

Whitegrub morphospecies: individual contribution to the community

structure pattern (analysis of typification and discrimination) 37

Discussion 39

Group contribution of whitegrub morphospecies to the community

structure pattern 40

Contribution of individual whitegrub morphospecies to the community

structure pattern 41

References 43

Table 1 46

Figure 1 47

Summary of Results 49

iii

Declaration

I, Derian ECHEVERRI-MOLINA, declare that the research dissertation hereby submitted to the University of Limpopo – MEDUNSA Campus, for the degree of

Master of Science in Biology has not previously been submitted by me for a degree at this or any other university; that it is my work in design and in execution, and that all material contained herein has been duly acknowledged.

Derian Echeverri M. 16 May 2013

D. ECHEVERRI-MOLINA (Mr.) Date

Student Number: 201118049

iv

Acknowledgements

I do believe that faith in God gives meaning and purpose to human life; a life given to me by my dear parents, Gilberto de Jesús Echeverry Cano and María Victoria Molina

Hurtado. I thank you both for giving me life, support, love and the best education with the strongest family values. You also gave me a brother, Carlos Gilberto Echeverry

Molina who has been there for me unconditionally. Carlos, I have never told you before but you were my very first dearly-wished gift. You also gave me a nephew,

Emanuel Echeverry Gómez. The feeling of being an uncle makes me super happy and forever grateful. One of the characteristics of being a Latino and Colombian is that families are usually big and close; characteristics that I treasure because the family is always there for you and makes you never feel alone. Therefore, to all of you, in the Echeverry Cano, Molina Hurtado and extended families, thank you.

Marija Kvas, you caught my attention without intention. Your love, company, encouragement and support make me proud and lucky of having found a beautiful diamond like you in South Africa. I love you! Remember that I also love an important person in your life, our lives, your mother, Irena Kvas.

Thanks to all my international friends and colleagues wherever you are, especially to and in no particular order: Leonardo López, Claudia Hurtado, Claudia Vélez, Gabriela

Jiménez, Gonzalo Agudelo, Sandra Serrano, Carlos Suárez, Razia Cassim,

Dr. María Noël Cortinas, Dr. Sari Mohali, Dr. Serena Santolamazza Carbone, John

Jairo Escobar, Tanja, Berislav and Lazar Savi čevi ć, Saša Suboti ć, Rebeka

Gluhbegovi ć, Roshantha Kolapen, Pranitha Dawlal, Dylan Pillay, Lilias Makashini and

Vusi Masiba, Tshepo Thlaku, Vladimir Krsti ć, Gifty Naa Ayeley Hammond,

v

Dr. Draginja Pavli ć Zupanc, Darko Zupanc, Vinka and Branko Bunjevac, Horacio

Mones Ruiz and his family. Also, thanks to my Junior Chamber International (JCI),

Linkedin and Facebook friends.

The success of this M.Sc. dissertation would not have been a reality without the professional support of Prof. Pramanathan (Prem) Govender. I do not have enough words to thank you for your friendship, supervision, mentorship, empowerment, endless and rich science discussions, and for giving me the opportunity to begin my path in science. Please know that it has been a real pleasure and privilege working with you. Just to let you know that you are my hero. I extend my gratitude to your family as well because I know that you function as one.

Thanks are extended to the various forestry companies and private growers for funding and supporting this study and especially the forestry staff that assisted with the sowing and maintenance of the trials.

The use of the map of KwaZulu-Natal showing the location of the trials in this study

(Chapter 1) was made with permission.

This research project (No. MREC/P/140/2012: PG) was scientifically and ethically approved by the MEDUNSA Research Ethics Committee of the University of

Limpopo. I thank the University of Limpopo, MEDUNSA Campus, for financial support and hosting me as a student, the Electron Microscope Unit of the Medunsa Campus for the arrangement to use the stereo microscope facilities. I promise to fulfil my duties as an ambassador and alumni of this University to the best of my abilities, wherever I will be in the future.

vi

Preface

Acacia mearnsii De Wildman (Mimosaceae) is known in South Africa as black wattle.

This tree species is native to Australia. Wattles were introduced into South Africa around the late eighteen hundreds. Since then, wattle has become the third most important commercial tree species used by the South African forestry industry after pines and eucalypts. Wattles are used for, amongst others, tannin extracts, production of pulpwood, mining poles and charcoal. The wattle industry employs numerous people due to its labour intensive silvicultural activities, hence the creation of jobs in South Africa. Since its introduction the expansion of wattle production has encounter different challenges such as: limited access to land due to the strong competition with agricultural crops; appearance of stricter planting permits, policies and regulations (e.g. Forestry Stewardship Council – FSC) to be able to plant in new areas and export and the appearance of pests and diseases that limit the production or make it less profitable. Today, the industry has no other choice but to become more efficient in increasing productivity.

There are new technologies available to increase productivity, for example, the development and improvement of plant breeding techniques with the use of genetically modified organisms. The improvement of silvicultural practices such as: land preparation; fertilization; correct matching tree species with the locality; implementation of integrated weed and pest management (IPM).

One of the most expensive and labour intensive activity in forestry is the preparation and planting of the site. There are many factors that limit the establishment of wattle seedlings. It has been reported that soil invertebrates, whitegrubs (Coleoptera:

vii

Scarabaeidae) in particular, are the most important pests that affect the survival rate of newly planted wattle seedlings and young saplings. This increases establishment costs because foresters have to implement control measures or incur expenses with the uncertainty of success. One of the preferred control measures is the prophylactic use of pesticides. However, most pesticide use is restricted by the FSC.

A particular challenge with whitegrubs is the limited knowledge about them.

Whitegrubs are generally associated with pest species. The family Scarabaeidae is one of the most prolific families in terms of diversity and abundance of species.

These scarabs are very important for the environment and they also contain the group of dung beetles which are very beneficial.

This dissertation aimed to plug the knowledge gap on the management factors that could allow a better understanding of the composition and community structure of these various whitegrub species on previous wattle sites in the Natal Midlands (South

Africa) (Chapter 1). The abundance and distribution of whitegrubs that attacked black wattle seedlings during their establishment in the Natal Midlands of South Africa was assessed in Chapter 2, where their pest status and their contribution to the whitegrub community structure patterns were established. The results of this study can contribute towards the improvement and development of new whitegrub control strategies. This, in the end, will contribute to the success of wattle seedlings survival in the field. However, the impact of this study does not end in the forestry domain.

This knowledge will impact the agricultural sector because these insects are also pests in other important crops like sugarcane and potatoes. Other agricultural crops are often rotated with wattle plantations in the Natal Midlands of South Africa and these crops can also benefit from the findings of this research.

viii

Chapter 1

Community structure and species composition of whitegrubs attacking

Acacia mearnsii seedlings in the Natal Midlands of South Africa

Manuscript prepared for submission to Southern Forests: a Journal of Forest Science

1

Abstract

Whitegrubs (Coleoptera: Scarabaeidae) are the most important establishment pests attacking Acacia mearnsii De Wildman (black wattle) seedlings in South Africa. This study determined the composition and community structure of these various whitegrub species on previous wattle sites in the Natal Midlands (Seven Oaks, Umvoti, Melmoth,

Pietermaritzburg, Richmond and Hilton), South Africa. Whitegrub collections were done during the first year of growth from ten trials planted over three seasons (1990/91 to

1992/93). Very stressed, dying or dead black wattle saplings were dug together with their roots and surrounding soil to search for the causative pests. These whitegrubs were identified to morphospecies based on their unique raster patterns. The proportions of morphospecies at the different sites were evaluated by clustering and ordination methods. A ranked similarity matrix evaluated differences between whitegrub communities under different weeding and plantation residue management practices. In total, 2 660 whitegrub specimens belonging to 13 morphospecies were collected. The community of whitegrubs that attacked black wattle seedlings had three different patterns of distribution. The whitegrub community under the silvicultural practices of windrowing and burning had the greatest species richness (13 morphospecies) and abundance

(95%) of whitegrubs. The other two whitegrub communities (fallow sites that were mowed or manually weeded, and sites windrowed, burnt and ripped or planted in an old arable site) were in combination less diverse (7 morphospecies) and abundant (5%).

These three whitegrub community patterns were explained by their strong relation to the silvicultural weeding and plantation residue management practices of the forestry industry in South Africa between 1990 and 1993.

Keywords: Scarabs, black wattle, slash management, establishment pest, fallow, windrow-burn, silviculture, forestry

2

Introduction

Acacia mearnsii De Wildman (Mimosaceae) is commonly known in South Africa as black wattle. This tree species originated from eastern Australia and was introduced into South Africa around 1864 (Hepburn 1973, Annecke and Moran 1982). After pines (51%) and eucalypts (40.4%), wattle (8.2%) is the most important tree species used by the South African forestry industry in an area of approximately 1 275 000ha

(Godsmark 2010). The majority of wattle plantations (83%) are found in the KwaZulu-

Natal Province (Godsmark 2010). Wattles are mainly used for woodchips, pulpwood and bark extracts (tannins) (Feely 2012). Intensive labour hand use makes wattle an important source of income for the South African economy in terms of job creation

(Feely 2012).

‘Whitegrubs’ is the broadly used terminology for beetle larvae belonging to the family

Scarabaeidae, especially those considered to be pests (Ritcher 1966). The subfamilies Melolonthinae, Rutelinae, Dynastinae and Cetoniinae contain many pest species (Hayes 1929, Ritcher 1966). Whitegrub adults are commonly referred to as scarab beetles, dung beetles, chafers, amongst other names (Picker et al. 2004,

Visser 2011). Whitegrubs are generally white to off-white in colour, typically

C-shaped when disturbed, have stout bodies and three pairs of visible legs (Ritcher

1966). Their heads are sclerotized and their colour varies from reddish to brown

(Govender 1995). They have a grey-bluish colour appearance at the end of their abdomens due to internal black excrement (Visser 2011). These grubs are soil inhabitants and feed on decaying organic matter and plant roots (Visser 2011). Plant damage appears to depend on the larval instar (Petty 1977). First instars of whitegrubs feed mainly on organic matter (Andrewartha 1945, Carnegie 1988,

3

Mansfield 2004), while root (plug and secondary roots) and root collar feeding were commonly associated with the second and third instars (Sweeney 1967, Petty 1990,

Rajabalee 1994, Goebel 1996, Mansfield 2004, Govender 2007). Whitegrubs were generally grouped collectively as one pest and were not differentiated into species because their life-histories were considered to be sufficiently similar for practical and economic reasons (Forbes 1894, Hayes 1929). However, these authors encouraged the need to differentiate the species, or at least the recognition of groups of species of whitegrubs.

Research on the biology, taxonomy and morphology of whitegrubs has been sporadic and limited to a few species in South Africa. Bradford (1948, 1949) studied the biology and the external features of Anomala vetula . Oberholzer (1959a, 1959b) made morphological comparisons and descriptions of the third instar of eight whitegrub species (Oryctes boas , Hypopholis sommeri , Astenopholis subfasciata,

Camenta innocua , Anomala similis , Pachnoda impressa , Hypselogenia geotrupina and Diplognatha gagates var. silicea ). Prins (1965) studied the biology and morphology of three wattle chafers, Monochelus calcaratus , H. sommeri and

Adoretus ictericus because of their pest status. Murray (1996) considered the morphology of two undescribed whitegrub pest species of wattle. Govender (1995,

2007) determined the pest status of whitegrubs and various other establishment pests of forestry. In South Africa, two compilations have reported 26 and 31 scarabaeid species as being associated with black wattle respectively (Hepburn

1966, Swain and Prinsloo 1986). Some of the knowledge on South African whitegrubs also comes from studies done on sugarcane (Sweeney 1967, Carnegie

1974, 1988, Carnegie and Heathcote 1986, Carnegie and Leslie 1991, Mansfield

2004, Dittrich-Schröder 2009, Dittrich-Schröder et al. 2006, 2009) and pineapple

4

(Smith et al. 1995) where these insects have caused substantial damage. The phytophagous and polyphagous nature of these whitegrubs makes them important pest species. It is common in KwaZulu-Natal to find black wattle plantations converted into sugarcane fields and vice versa or planted close to each other

(Carnegie 1974, Govender 1995). Hence whitegrub species, for example, H. sommeri and Schizonycha affinis have been recorded to attack both wattle and sugarcane plantations (Hepburn 1966, Sherry 1971, Carnegie 1974, Govender 1995,

Mansfield 2004).

Whitegrubs were considered the most important establishment pest of black wattle trees (Govender 2007). Generally the establishment of black wattle seedlings can fail at an average rate of about 13% (range 9.2-18.9%) due to the incidence of whitegrub damage compared to an average total loss of seedling establishment of about 34% from all mortality factors (Govender 2007). Knowledge on the species composition of these economically important whitegrub pests in black wattle plantations is necessary for the development of effective management plans. Therefore, the aim of this study was to determine the composition and community structure of the various whitegrub species that attacked A. mearnsii seedlings during its establishment period on previous wattle sites in the Natal Midlands, South Africa.

5

Materials and Methods

Whitegrubs were collected from ten multi-purpose trials planted on previous wattle sites, over three growing seasons (1990-1991 to 1992-1993). Trials were located on sites that were representative of the main black wattle growing areas in the Natal

Midlands of South Africa (Figure 1) and were also selected according to their various silvicultural, weeding and plantation residue management practices (Table 1). Trial site assessments were done monthly during the first year of growth. Very stressed, dying or dead black wattle saplings were dug out together with their roots and surrounding soil (approximately 1.2 ℓ) to look for the causative pests. Recovered whitegrub specimens were kept in glass vials and preserved in a Petersons K.A.A.

(paraffin-glacial acetic acid-ethanol) mixture (Peterson 1955), and ethanol (70-96%) was added to the vials during storage when needed. This study was a subset of the research that dealt with soil invertebrate pests during the re-establishment of forestry plantations in South Africa (Govender 1995, 2002, 2007).

Species identification

Whitegrub specimens collected from these trials were examined in the laboratory, to determine their species composition and abundance. Ritcher’s (1966) larval identification keys were followed to identify whitegrub specimens to a subfamily level.

Other relevant papers and taxonomic keys based on morphological characters

(Omer-Cooper et al. 1941, 1942, 1948, Bradford 1949, Obelholzer 1959a, 1959b,

1963, Prins 1965, Sweeney 1967, Petty 1976, 1977, 1990, Smith et al. 1995,

Mansfield 2004) were consulted to identify some whitegrub specimens. Many of the species that remained unidentified were referred to as morphospecies and given

6 specific numbers. Whitegrubs were grouped according to the raster pattern that was located ventrally on the last abdominal segment. Raster morphological features of the collected whitegrub specimens were then viewed by using a Zeiss Discovery v20 stereo microscope (Jena, Germany) at the Electron Microscope Unit and photographed by using an AxioCam MRc5 (Carl Zeiss).

Community analysis

A multivariate analysis was performed using the PRIMER software (Plymouth

Routines in Multivariate Ecological Research) version 5.2.9, as a statistical package

(Clarke and Warwick 2001). The different whitegrub morphospecies (their abundance within the trial expressed as a percentage) were the variables and the trial sites were treated as samples. Neither standardisation nor transformation was performed before data analyses. A similarity matrix that used a Bray-Curtis index to calculate similarity distance measurements was obtained. A hierarchical clustering into species group analysis (CLUSTER) was performed on the similarity matrix and a dendrogram was obtained. The ordination between trial sites was also evaluated by using the non- metric multi-dimensional scaling (MDS) and a two-dimensional (2D) plot was obtained. A one-way analysis of similarity (ANOSIM - permutation-based hypothesis testing) was performed on the rank similarity matrix to evaluate differences between whitegrub communities under different weeding and plantation residue management practices (Table 1).

7

Results

In total, 2 660 whitegrubs were grouped into 13 morphospecies of the family

Scarabaeidae (Coleoptera) from the ten trial sites in the Natal Midlands of South

Africa (Table 2). Photographs of the raster patterns of the 13 whitegrub morphospecies are presented in Figure 2. Of the total whitegrub abundance, morphospecies M1, M3, M5, M8, M4, M9 and M7 accounted for 98.3% and the other six morphospecies (M6, M11, M16, M24, M25 and M26) represented 1.7% of the whitegrubs that affected the establishment of black wattle seedlings in the Natal

Midlands of South Africa (Table 2).

The hierarchical agglomerative clustering analysis of the ten trial sites, based on the

Bray-Curtis similarity matrix and confirmed later by an ANOSIM test, produced three distinguishable clusters (A, B and C, sample statistic Global R = 0.748) with highly significant differences ( P = 0.003) between them (Figure 3). These clusters reflected the weeding and plantation residue management practices of the trial sites (Figure 3) viz., windrowed-burnt-weeded or with closer spacing (WBWS), fallow sites weeded manually or mowed (FMOW) and windrowed-burnt-ripped or planted in an old arable land (WBRO). The ANOSIM tests performed on other potential factors that could have explained the community patterns, i.e. the year of planting (Global R = -0.227,

P = 0.967), month of planting (Global R = -0.047, P = 0.58) and trial site localities

(Global R = -0.222, P = 0.189), indicated that clusters were not significantly distinguishable or separated based on these factors.

The analysis of similarity based on comparisons of pairwise tests showed that clusters WBWS (13 whitegrub morphospecies and 94.9% abundance) and WBRO

8

(6 morphospecies and 3.1% abundance) were significantly separated (ANOSIM,

R = 0.896, P = 0.036) (Table 2). Clusters WBWS and FMOW (5 morphospecies and

2% abundance) overlapped but were still different at the 10% level of significance

(ANOSIM, R = 0.542, P = 0.071). The WBRO and FMOW clusters (ANOSIM, R = 1,

P = 0.333) were well separated despite its significance level. Clarke and Gorley

(2001) considered that the R values carry more weight than the significance level because of its absolute measure of the separation of the clusters. Pairwise R values varied from zero (identical) to one; differences between clusters are more distinct when R approaches one (Clarke 1993). Six trial sites grouped within cluster WBWS.

Cluster WBWS represented the common practice where the harvest residues were windrowed, piled and burnt, followed by manually weeding the planting lines or around the pits before planting (four trial sites: WG1 from Seven Oaks, and WG4,

WG8, WG9 from Pietermaritzburg) plus the less practiced closer spacing of seedlings

(more trees planted per hectare, two trials: WG3 in Melmoth and WG7 in Seven

Oaks) (Figure 3). Leaving the sites fallow for a year or more after harvest, accompanied by mowing (trial WG5 in Richmond) or manually removing weeds (trial

WG6 in Hilton) before planting wattle seedlings characterized the plantation residue management contained in cluster FMOW (Figure 3). In cluster WBRO, the plantation residue was either windrowed, burnt and the planting lines ripped (trial WG2 in

Umvoti) or windrowed and burnt but on an old arable site neighbouring a cultivated sugarcane area (trial WG10 in Seven Oaks) (Figure 3).

Clarke and Warwick (2001) recommended that hierarchical agglomerative clustering analysis should be used together with ordination models even for samples that group tightly. Therefore, a MDS ordination model (Figure 4) was produced to test the results obtained with the clustering analysis (Figure 3) by using the same similarity matrix.

9

The best 2D model (Figure 4) had a good ordination (stress value: 0.07) with a small chance of misinterpretation, whilst the best 3D configuration (not shown) had an excellent representation (stress value: 0.03) of the trial site relationships.

10

Discussion

Several different whitegrub pest morphospecies were encountered during the establishment of black wattle seedlings in the Natal Midlands, South Africa. This was an expected outcome because of the great success of the Scarabaeid family to proliferate in the different areas of southern Africa (Scholtz and Holm 1985) and the fact that numerous whitegrub species have previously been reported to attack black wattle (Hepburn 1966, Swain and Prinsloo 1986, Govender 2007). However, the accurate identification of some whitegrub species was not possible because such species still remain undescribed. There was also a lack of scarabaeid larval taxonomic keys that would have allowed one to link the larval lifestages with described adults. Limited attempts have been made to match the adults with sugarcane whitegrubs in the Natal Midlands, South Africa, by using mitochondrial

DNA (Dittrich-Schröder et al. 2009) but further definitive studies are still required; especially with wattle whitegrub species.

Community structure pattern

Whitegrub interaction with other invertebrates, pathogens, silvicultural practices, soil conditions, surrounding vegetation, natural enemies, climatic conditions, amongst others, and their complex interactions, are possible factors that could additionally be considered when analysing the community structure of whitegrubs attacking wattle plantations in the Natal Midlands of South Africa. For example, the month of planting failed to explain the community structure because the whitegrub incidence was measured over the entire wattle growing season. Another factor, for example, trial site localities did not explain the whitegrub community structure despite the

11 expectation (Picker et al. 2004) that specific whitegrub species could be distributed only in certain locations. However, the black wattle silvicultural practices of weeding and plantation residue management were found to be the most plausible explanation of the whitegrub community patterns observed in the Natal Midlands of South Africa.

The community assemblage with the greatest species richness and abundance of whitegrubs that attacked seedlings during wattle re-establishment in the Natal

Midlands was the community under the silvicultural practices of windrowing

(collecting plantation residues and piling them up along the planting rows) and burning (manipulated fire). These were common practices at the time of the study in the South African wattle forestry industry (Norris 1993, 1995, Govender 2002) and the results of this study showed that these practices appeared to be associated with an increased abundance and species richness of whitegrub pests. This contradicts the results of other studies that expressed the view that manipulated fires could reduce the abundance of pests (Huhta et al. 1967, Bird et al. 2000, Decaëns et al.

2001) or that the abundance and diversity of invertebrates were unaffected by such fires (Andrew et al. 2000, Collet 2003, Nadel et al. 2007). Increasing the planting density of crops per hectare is an acknowledged cultural pest control strategy (Dent

1991). This concept was supported when the incidence of soil invertebrate pests under different wattle plantation residue management regimes were compared by

Govender (2002). However, in this study closer espacement of wattle seedlings did not significantly decrease the incidence of whitegrub pest morphospecies. Prior to the introduction of improved wattle seeds to produce transplants, it was common practice to line sow wattle seeds and then to progressively thin the resulting regeneration to the required density per hectare (Sherry 1971). This outdated practice that could be equated to closer espacement, often translated to a reduced net incidence of

12 seedling mortality (Sherry 1971). However, in many instances this may not have meant that there was a lower incidence of invertebrate pests or other mortality factors but rather that sufficient seedlings remained to ensure optimal stocking despite the various mortality factors. This study indicated that trials windrowed, burnt and with higher plant density per hectare showed a greater abundance and species richness of whitegrubs.

The community of whitegrubs were less abundant and diverse when the sites were left fallow for a year or more before planting (FMOW). This was consistent with the findings of Govender (2002) who demonstrated that fallow sites showed lower incidences of whitegrub damage. There was also a high mortality in these study trials caused by frost, nursery pathogens and cattle browsing on wattle seedlings during establishment (Govender 1995). These mortality factors could have reduced the availability of seedlings to whitegrub damage as well. Given the scarcity of arable land for forestry production, the practice of deliberately leaving the sites fallow for several seasons, sometimes for years, after harvesting black wattle is rather unusual for the South African forestry industry (Govender 2002).

The low whitegrub species richness and abundance observed in the community

WBRO (windrowing, burning and ripping or planting in an old arable site next to a sugarcane plantation) was congruent with that of Govender (2002). However,

Govender (2002) reported that the incidence of pests on these two silvicultural practices (windrowed-burnt-ripped and windrowed-burnt but planted in an old arable land), as separate soil invertebrate clusters, whilst in this study the whitegrub communities assembled as one.

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This study demonstrated that the community of whitegrubs found attacking black wattle seedlings in the Natal Midlands of South Africa had three different patterns of distribution. These whitegrub community patterns could be explained by their strong relation to the silvicultural weeding and plantation residue management practices used by the forestry industry in South Africa at the time. The whitegrub community

WBWS showed the greatest species richness (13 morphospecies) and abundance

(95%) of whitegrub species. Research is needed in assessing the individual pest status of the different whitegrubs found attacking black wattle seedlings in the Natal

Midlands and other regions of South Africa. Further efforts are needed to describe the biology and population dynamics of the different whitegrubs present in this region.

14

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Town: Struik Publishers.

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Institute.

20

Table 1: Trial site information and silvicultural details of Acacia mearnsii weeding and plantation residue management in the Natal Midlands, South Africa.

Black wattle weeding and Trial Date of Latitude/ Location plantation residue Sites Planting Longitude management practices* WG1 23-Oct-1990 Seven Oaks 29 °12’S/30 °38’E WBW WG2 03-Dec-1990 Umvoti 29 °11’S/30 °27’E WBR WG3 10-Dec-1990 Melmoth 28 °31’S/31 °17’E WBS WG4 14-Jan-1991 Pietermaritzburg 29 °32’S/30 °27’E WBW WG5 11-Feb-1991 Richmond 29 °49’S/30 °17’E FMO WG6 14-Mar-1991 Hilton 29 °34’S/30 °16’E FMW WG7 04-Dec-1991 Seven Oaks 29 °11’S/30 °40’E WBS WG8 13-Jan-1992 Pietermaritzburg 29 °33’S/30 °27’E WBW WG9 19-Oct-1992 Pietermaritzburg 29 °33’S/30 °27’E WBW WG10 26-Oct-1992 Seven Oaks 29 °10’S/30 °39’E WBO

*WBW: Windrowed-Burnt-Weeded. WBS: Windrowed-Burnt-Closer Spaced.

WBO: Windrowed-Burnt-Old Arable Land. WBR: Windrowed-Burnt-Ripped.

FMO: Fallow-Mowed. FMW: Fallow-Manually Weeded.

21

Table 2: Abundance of whitegrubs collected at various wattle trial sites in the Natal

Midlands (South Africa).

Whitegrub abundance according to black wattle weeding and Whitegrub No. plantation residue management practices morphospecies Cluster A Cluster B Cluster C Total WBWS* FMOW** WBRO*** Abundance 1 M1 718 28 5 751 2 M3 525 0 44 569 3 M4 202 12 11 225 4 M5 477 3 0 480 5 M6 2 0 0 2 6 M7 58 0 0 58 7 M8 387 7 5 399 8 M9 115 3 15 133 9 M11 12 0 0 12 10 M16 5 0 0 5 11 M24 21 0 0 21 12 M25 1 0 3 4 13 M26 1 0 0 1 Total Abundance of Individuals 2524 53 83 2660 Total Abundance (%) 94.89 1.99 3.12 100.00 Total of Morphospecies 13 5 6 13

*Windrowed-burnt-weeded together with closer spacing ( WBWS ).

**Fallow sites weeded manually or mowed ( FMOW ).

***Land windrowed-burnt-ripped or planted in an old arable land ( WBRO ).

22

Figure 1: A map of KwaZulu-Natal (South Africa) indicating the location of Acacia mearnsii trial sites.

23

Figure 2: Photographs of the last abdominal (10 th ) sternite (raster pattern) of whitegrub morphospecies (M) collected from trials in the Natal Midlands (South

Africa). Scale bars = 1mm. 24

Figure 3: Dendrogram for hierarchical clustering (group-average linking). Model computed for the whitegrub morphospecies abundance (%) from each of the ten trial sites (WG1 to WG10) from the Natal Midlands (South Africa); clusters formed at an arbitrary level of 50% similarity. Clusters A, B and C are the clustering result of the

Bray-Curtis similarity matrix.

25

Figure 4: Non-metric multi-dimensional scaling (MDS) ordination plot in two dimensions; model computed for the whitegrub morphospecies abundance (%) from each of the ten trial sites (WG1 to WG10) from the Natal Midlands (South Africa).

Superimposed circles indicate Clusters windrowed-burnt-weeded together with closer spacing ( WBWS ), fallow sites weeded manually or mowed ( FMOW ) and windrowed- burnt-ripped or planted in an old arable land ( WBRO ). Stress level = 0.07, indicates good ordination with small risk of misinterpretation.

26

Chapter 2

Pest status of whitegrubs attacking Acacia mearnsii seedlings in

the Natal Midlands of South Africa

Manuscript prepared for submission to Southern Forests: a Journal of Forest Science

27

Abstract

The abundance and distribution of whitegrubs that attacked black wattle seedlings during their establishment in the Natal Midlands of South Africa were assessed to establish their pest status and their contribution to the whitegrub community structure patterns. Ten trials, located on previous wattle sites were planted over three growing seasons

(1990-1991 to 1992-1993). Monthly collections of whitegrubs that attacked seedlings occurred during the first year of seedling growth. Very stressed or dying wattle saplings and their surrounding roots were dug and the soil was assessed to collect any pests that were responsible for saplings damage or mortality. A multivariate analysis enabled the ranking of the average abundance of the various whitegrub morphospecies that attacked black wattle. The individual contribution of whitegrub morphospecies to the average similarity within a community and the dissimilarity between communities were tested with similarity percentages comparisons. The best 2D model obtained for each morphospecies pattern of distribution and relative abundance had a good ordination

(stress value: 0.07). A complex of 13 whitegrub pests was found. Five whitegrub species

(M1 Hypopholis sommeri , M3 Schizonycha affinis , M4 Adoretus ictericus , M5

Schizonycha fimbriata and M8 undescribed Maladera sp.2), with average abundance of

87.2%, were confirmed to have a high pest status. They accounted for the community structure pattern in the black wattle growing areas of the Natal Midlands (BVSTEP,

ρ = 0.971). The remaining combined eight morphospecies, M7 (undescribed Maladera sp. 1), M11 ( Heteronychus licas ), and M6, M9, M16, M24, M25 and M26 (unknown species), contributed only 12.8% and were considered to be lesser pests due to their low abundance.

Keywords: Black wattle, slash management, establishment pest, Coleoptera,

Scarabaeidae, Rutelidae, Dynastidae, Melolonthidae, silviculture, forestry 28

Introduction

Acacia mearnsii De Wildman (Mimosaceae) (black wattle) was introduced into South

Africa around 1864 from Australia (Hepburn 1973). Since then, 329 species of invertebrates (mainly insects, mites and spiders) have been associated with wattle in

South Africa (Hepburn 1966). Swain and Prinsloo (1986) produced a list of 221 species of phytophagous insects and mites that they reported to attack wattle. All the insects that attack black wattle trees in South Africa were reported to be indigenous

(Govender 2002). Newly introduced exotic plants can become susceptible to resident pests in their new environment; this is often caused by the disruption of the balance of host-herbivore-natural enemy interactions and/or may be due to crops grown extensively over large areas (Rao et al. 2000). Exotic black wattle plantations have, therefore, provided a rich food source to many insects that previously had an unknown pest status (Govender 2002).

Govender (2002) grouped wattle pests into two broad categories viz., establishment and post-establishment pests. Wattle bagworm caterpillars ( Chaliopsis junodi

Heylaerts – Lepidoptera: Psychidae) and the wattle mirid ( Lygidolon laevigatum

Reuter – Hemiptera: Miridae) are important pests that attack established black wattle trees (Govender 2002). Four checklists on pests species associated with wattle in

South Africa have been developed and these provide scanty and general information on their damage (Ossowski and Wortmann 1960, Hepburn 1966, Sherry 1971, Swain and Prinsloo 1986). Govender (1995, 2007) reported that whitegrubs (Coleoptera:

Scarabaeidae), cutworms (Lepidoptera: Noctuidae), grasshoppers (Orthoptera:

Acrididae), millipedes (Diplopoda: Juliformia), termites (Isoptera: Termitidae and

Hodotermitidae), tipulid larvae (Diptera: Tipulidae), wireworms (Coleoptera:

29

Elateridae), false wireworms (Coleoptera: Tenebrionidae), crickets (Orthoptera:

Gryllidae), ants (Hymenoptera: Formicidae) and nematodes (Nematoda:

Heteroderidae) are pests that were found to affect the establishment of wattle seedlings. Whitegrubs were determined to be the most important pests during wattle establishment because of their abundance, frequency of occurrence and type of damage (Govender 1995, 2002, 2007).

The larval stages of certain scarab beetles (Coleoptera: Scarabaeidae) are commonly known as whitegrubs (Ritcher 1966). In South Africa, some scarabs that have been reported as pests belong mainly to the sub-families Cetoniinae,

Melolonthinae, Rutelinae and Dynastinae (Prins 1965, Hepburn 1966, Annecke and

Moran 1982). For example, the wattle pest species Hypopholis sommeri Burmeister

(large wattle chafer), Schizonycha affinis Boheman, both Melolonthinae, and

Adoretus ictericus Burmeister (Rutelidae) have also been reported as sugarcane pests on areas previously planted with wattle (Prins 1965, Hepburn 1966, Carnegie

1974). In KwaZulu-Natal, especially on small scale farms, it often happened that black wattle crops were rotated with sugarcane and vice versa or to find these crops grown in close proximity to each other (Carnegie 1974, Govender 1995). This situation facilitated the build-up of residual scarab pests that were polyphagous in their feeding habits. For example, there have been reports of H. sommeri attacking fruit trees (litchi and plum) (Carnegie 1974), turfgrass (Omer-Cooper et al. 1942,

1948, Prins 1965), pines (Hepburn 1966, Swain and Prinsloo 1986), eucalypts

(Swain and Prinsloo 1986), roses, potatoes and previous pasture or grazing fields

(Visser 2011).

30

Thirty one scarab pest species of wattle have been reported in South Africa (Hepburn

1966, Swain and Prinsloo 1986) and they attack aerial organs, roots or both

(Govender 1995). The pest status of whitegrubs was determined by Govender (2007) and they were found to be the most important pests during wattle re-establishment when compared to other invertebrate pests of seedlings in South Africa. Furthermore,

13 whitegrub pests were found to be associated with black wattle during its establishment and their community structure patterns were explained by the plantation weeding and residue management in wattle plantations (Chapter 1).

However, the pest status of these different whitegrub species is still unknown. This study assessed the pest status of the whitegrubs that attacked A. mearnsii seedlings during its re-establishment, ranked the economically important whitegrub morphospecies, and sought to explain their individual contribution to the whitegrub community structure in the Natal Midlands of South Africa.

31

Materials and Methods

Whitegrubs that attacked black wattle seedlings during their establishment from ten different study sites (WG1 to WG10) in the Natal Midlands of South Africa were collected. Study trials WG1 (29 °12’S, 30 °38’E), WG7 (29 °11’S, 30 °40’E) and WG10

(29 °10’S, 30 °39’E) were located in Seven Oaks. Trial WG2 (29 °11’S, 30 °27’E) was located in Umvoti. Trial WG3 (28 °31’S, 31 °17’E) was in Melmoth. Study trials WG4

(29 °32’S, 30 °27’E), WG8 (29 °33’S, 30 °27’E) and WG9 (29 °33’S, 30 °27’E) were in

Pietermaritzburg. Trials WG5 (29 °49’S, 30 °17’E) and WG6 (29 °34’S, 30 °16’E) were situated in Richmond and Hilton, respectively. This study complimented a multi- purpose experimental design of research on soil invertebrate pests of forestry crops in South Africa done by Govender (1995, 2002, 2007). The ten trials used here were situated on sites previously planted with wattle and were also representative of the different wattle plantation residue management practices at the time (Govender

1995). Trials were planted over three growing seasons, that is, from 1990-1991 to

1992-1993. Monthly collections of whitegrubs that attacked seedlings took place during the first year of seedling growth. Very stressed or dying wattle saplings and their surrounding roots were dug out and soil was assessed to collect any pests, especially whitegrubs that were responsible or related with saplings damage or mortality. These whitegrubs were preserved in a mixture of paraffin-glacial acetic acid-ethanol (Peterson K.A.A. (Peterson 1955)) and during their storage ethanol

(70% and/or 96%) was added when required. The different whitegrub morphospecies used in this study were previously identified in Chapter 1.

32

Data analysis

A statistical package PRIMER (Plymouth Routines in Multivariate Ecological

Research) version 5.2.9 (Clarke and Warwick 2001) was used in this study. Variables used here were the abundance of the different whitegrub morphospecies expressed as a percentage and the trial sites were the samples. A similarity matrix, without data transformation or standardisation, was obtained. A two-dimensional (2D) plot was obtained via a non-metric multi-dimensional scaling (MDS) of the most important whitegrub morphospecies found in this study. This was used to assess and visualize the distribution of the abundance pattern of the morphospecies within the ten study trials. Data interpretation was made by contrasting the abundance pattern to the three whitegrub communities found on wattle plantations in the Natal Midlands

(Chapter 1).

Ranking was based on the average abundance of the various whitegrub morphospecies found attacking saplings of black wattle in the Natal Midlands. A

BVSTEP (biota and/or environment matching, a stepwise search procedure) analysis with PRIMER was selected. The analysis established the smallest possible subset of whitegrub morphospecies that in combination are capable of explaining the majority of the pattern ( ρ > 0.95) of all trial sites (Clarke and Gorley 2001). By default, the standard Spearman rank correlation coefficient ρ was chosen (Clarke and Gorley

2001). This routine analysed between the ten trial sites (samples) and measured a

Bray-Curtis similarity coefficient that required neither transformation nor standardisation of the data. Default criteria were also used for this routine (Clarke and Gorley 2001).

33

Based on the three whitegrub community patterns in black wattle previously identified in Chapter 1, the individual contribution of whitegrub morphospecies to the average similarity (typical morphospecies) within a community and the average dissimilarity

(discriminatory morphospecies) between communities were tested by using SIMPER

(similarity percentages) (Clarke and Warwick 2001). This test examined the individual morphospecies percentage contribution to the Bray-Curtis dis/similarity measurement. To limit the number of morphospecies, in decreasing order of importance, which contributed to the average dis/similarity, a level equal to or greater than 5% was used. The formula of similarity/dissimilarity divided by the standard deviation (SD) where the value was equal or greater than two was used to determine which morphospecies, from all trial sites, contributed the most to the similarity within communities and those that provided the strongest discrimination between communities (Dollin et al. 2008). Where possible, the ranking of the first three morphospecies responsible for the dis/similarity was made.

34

Results

Whitegrub morphospecies: abundance and distribution

A total of 2 660 whitegrub specimens were collected during the first year of wattle growth from the ten trial sites that represented the black wattle growing areas in the

Natal Midlands of South Africa. The spatial distribution and average abundance of the seven most abundant whitegrub morphospecies over the ten study sites was presented in Figure 1 (a-g). The best 2D model obtained for each morphospecies pattern of distribution and relative abundance had a good ordination (stress value: 0.07) with a small chance of misinterpretation, and the best 3D (plot not shown) configuration had an excellent representation (stress value: 0.03)

(Figure 1 a-h). The three different communities (Windrowed-Burnt-Weeded-Closer

Spaced - WBWS, fallow sites weeded manually or mowed - FMOW and Windrowed-

Burnt-Ripped-Old arable land - WBRO) that explained the abundance of these whitegrub pests in the Natal Midlands (Chapter 1) was used comparatively (Figure

1 h).

Morphospecies 1, represented by Hypopholis sommeri Burmeister (Prins 1965) was present in all six localities (Seven Oaks, Pietermaritzburg, Hilton, Melmoth, Richmond and Umvoti) but was absent in the trial WG10 (Seven Oaks). This morphospecies was the most abundant in this study; with an average abundance of 29.86%. It was particularly abundant within the community FMOW (averaging 57.2%) while it was less abundant within the community WBRO (averaging 4.17%) (Figure 1 a).

Morphospecies 3, representing Schizonycha affinis Boheman (Prins 1965) was absent in the community FMOW, which represented the localities of Richmond and 35

Hilton (Figure 1 b), but was particularly abundant within the community WBRO

(averaging 60.8%). Morphospecies 3 was the second most abundant whitegrub species encountered in this study (averaging 23.88%). Morphospecies 8, representing the undescribed Maladera sp.2 (averaging 12.33%) was the third most abundant species. It was common in the WBWS community but absent in trials

WG10 (Seven Oaks) and WG6 (Hilton) (Figure 1 c). Morphospecies 5, representing the whitegrub provisionally identified as Schizonycha fimbriata Bryke (averaging

10.85%), was the fourth most abundant morphospecies in this study. It was evidently absent or scarce in the communities FMOW and WBRO but was fairly common within the WBWS community (Figure 1 d). In fifth place was M4, representing

Adoretus ictericus Burmeister (Prins 1965) (averaging 10.29%), which was absent in trial WG10 (Seven Oaks) but present in all other localities sampled. Its abundance in community FMOW was noticeable (Figure 1 e). Morphospecies 9 (Unknown sp., averaging 9.19%) was placed sixth and was present in all localities except in Hilton

(WG6) (Figure 1 f). Morphospecies 7, representing the undescribed Maladera sp.1

(averaging 1.93%), in seventh place, was absent in the communities of WBRO and

FMOW but was common in the WBWS community with the exception of trial WG3

(Melmoth) (Figure 1 g). Morphospecies 24 (Unknown sp.) was placed eighth with an average abundance of 0.77% and it was only found in Melmoth (WG3). The ninth abundant species was M25 (Unknown sp., averaging 0.52%) and it was only found in

Umvoti (WG2). Morphospecies 11, representing Heteronychus licas Klug (Sweeney

1967) (averaging 0.26%) was only found in two trials in Seven Oaks (WG1 and WG7) and was placed tenth. Morphospecies 16 (Unknown sp., averaging 0.09%), in eleventh place, was only found in WG9 (Pietermaritzburg). Morphospecies 6

(Unknown sp., averaging 0.03%) was placed in twelfth position and was sporadically found in the WG4 trial locality (Pietermaritzburg). Morphospecies 26 (Unknown sp.,

36 averaging 0.01%) was ranked in thirteenth place and was also only found in WG4

(Pietermaritzburg).

Whitegrub morphospecies: group contribution to the community structure pattern

Mostly five whitegrub morphospecies (M1, M3, M4, M5 and M8) accounted for the community structure pattern that was present in the black wattle growing areas of the

Natal Midlands (BVSTEP, ρ = 0.971). These five morphospecies contributed to

87.2% of the average abundance of the whitegrub community attacking wattle seedlings during their period of establishment. The remaining 12.8% (average abundance) was represented by the remaining eight morphospecies (M6, M7, M9,

M11, M16, M24, M25 and M26).

Whitegrub morphospecies: individual contribution to the community structure pattern (analysis of typification and discrimination)

SIMPER analysis showed that six whitegrub morphospecies typified (cumulative contribution of 97.98%) the community under the WBWS plantation residue management practice. These were M1 (36.74%), M3 (23.47%), M8 (14.51%), M5

(13.67%), M4 (5.15%) and M9 (4.44%) in decreasing order of average abundance

(Table 1 a). However, morphospecies M1 (Sim/SD = 4.29), M9 (Sim/SD = 2.39) and

M3 (Sim/SD = 2.33) (in decreasing ranking order) were the species that best characterized (contributed most to the similarities) this community (Table 1 a). Two morphospecies, M1 and M4 (contribution of 65% and 35%, respectively) typified the

37

FMOW community. Morphospecies, M3 and M9, (contribution of 72.22% and

27.78%, respectively) typified the WBRO community (Table 1 a).

When the communities WBWS and WBRO were compared, three morphospecies,

M9 (Diss/SD = 3.54), M1 (Diss/SD = 2.14) and M3 (Diss/SD = 2.08), in ranking order) best differentiated between these two communities (Table 1 b). When the communities WBRO and FMOW were compared, the same three morphospecies discriminated between these two clusters but the order was different; ranked as M3

(Diss/SD = 3.01), M1 (Diss/SD = 2.51) and M9 (Diss/SD = 2.44). The WBWS and

FMOW comparison showed that two morphospecies, M4 (Diss/SD = 3.08) and M3

(Diss/SD = 2.51), differentiated between these two whitegrub communities under specific residue management strategies (Table 1 b).

38

Discussion

In this study, the abundance and distribution of whitegrubs that attacked black wattle saplings during their establishment in the Natal Midlands of South Africa was assessed to establish their pest status and their contribution to the whitegrub community structure patterns. It was demonstrated previously that the assemblage of whitegrub communities could be explained by the type of weeding and plantation residue management practice of the forestry industry (Chapter 1).

Hypopholis sommeri (Coleoptera: Scarabaeidae: Melolonthinae) (large wattle chafer) has a wide distribution (Picker et al. 2004) over the black wattle (around 105 000ha)

(Godsmark 2010) and sugarcane (round estimation of 378 000ha) (Anonymous

2012) growing areas of South Africa. Hypopholis sommeri , therefore, has numerous host sites to complete its lifecycle and maintain its pest status. Its adults can also cause great damage to wattle trees but its larvae are capable of weakening or causing the mortality of wattle seedlings and often necessitate control measures and the need to replant (Govender 2007). The Melolonthinae hosts several species in

South Africa, within which the genus Schizonycha has the most species and several are recognised as pests (Scholtz and Holm 1985). Schizonycha affinis (wattle whitegrub) and S. fimbriata (tentative undescribed species name) were recorded to be abundant in the sampled wattle areas of the Natal Midlands as was the case in sugarcane (Carnegie 1974). This is an interesting deviation of its recorded distribution in the south-western and south-eastern Cape (Picker et al. 2004). Other melolonthids that were found in this study included the genus Maladera , with two undescribed species, of which Maladera sp.1 was found to be important in sugarcane

(equivalent to sp.2 in Mansfield (2004)). Adoretus ictericus (Coleoptera:

39

Scarabaeidae: Rutelinae) has been reported to attack wattle and sugarcane plantations in the Natal Midlands (Prins 1965, Mansfield 2004, Govender 2007) and has an extended distribution along the coastal and inland areas of South Africa and its habitats can be very diverse (Picker et al. 2004). Heteronychus licas (black sugarcane beetle) (Coleoptera: Scarabaeidae: Dynastinae), a recognised dynastid pest in South Africa and Swaziland (Annecke and Moran 1982), had a very low abundance and distribution in the wattle regions of the Natal Midlands despite its potential of being an important pest. However, besides the status of individual whitegrub pest species found in this study, there was a complex of whitegrub species that attacked black wattle seedlings and cumulatively this elevates the status of whitegrubs in general.

Group contribution of whitegrub morphospecies to the community structure pattern

There was a complex of whitegrub species that attacked black wattle seedlings during its establishment. Wattle saplings were attacked by 13 species of whitegrub root feeders but five were confirmed to be the economically important pests in the

Natal Midlands. These whitegrub pests were, in decreasing order of abundance, the morphospecies M1 ( Hypopholis sommeri , large wattle chafer), M3 ( Schizonycha affinis ), M8 (undescribed Maladera sp.2), M5 ( Schizonycha fimbriata , tentative species name) and M4 ( Adoretus ictericus ). These whitegrub morphospecies therefore have a high pest status during the establishment of black wattle in the Natal

Midlands of South Africa. Morphospecies 9 (Unknown sp.) and 7 (undescribed

Maladera sp.1) together with the other six whitegrub morphospecies (M6, M11, M16,

M24, M25 and M26) can be considered as lesser pests based on their low

40 abundance. The wattle whitegrub morphospecies collected in this study were similar to the morphospecies found in sugarcane in similar localities of KwaZulu-Natal by

Mansfield (2004). Hence, the risk of pest attack is greater in mixed cropping systems, for example wattle trees and sugarcane, when there is a high level of common insect pests between them (Rao et al. 2000).

Contribution of individual whitegrub morphospecies to the community structure

Wattle plantation residue is commonly windrowed and burnt after clearfelling

(Govender, 2002) and this breaks the dormancy of the bank of wattle seeds in the soil from the previous wattle crop. Spring rains during the start of the growing season results in a carpet of wattle regeneration in these fire disturbed windrows. This wattle regeneration is particularly attractive to ovipositing chafer beetles and results in a build-up of whitegrub species that later switch to feeding on the roots of young wattle transplants when the site is weeded; hence the high prevalence and abundance of whitegrubs of the whitegrub community WBWS (Chapter 1). Early instar whitegrubs feed on organic matter and, as they grow, they tend to feed on roots (Govender,

1995). Prescribed fires are somewhat superficial because of the characteristics of the suggested conditions for plantation residue burning. For example, low wind speeds, temperatures less than 23 °C, relative humidity greater than 40% and burning can only be carried out after three days of at least 30mm of rain to avoid humus depletion and soil degradation (van Wyk et al. 2012). Overwintering species of whitegrubs that are located deeper in the soil profile (>30cm and pupation of some scarabs at 95cm

(Carnegie 1974) are often unaffected by prescribed fires. These species of whitegrubs later migrate to feed on the tender roots of wattle transplants during the

41 growing season. Sweeney (1967) also observed this in sugarcane infested with H. licas . Two morphospecies ( H. sommeri and S. affinis ) out of the three most typical whitegrubs of the communities found in the Natal Midlands have a 2-year lifecycle

(Annecke and Moran 1982) and the overlapping of their generations could explain their more or less continuous infestation of wattle plantations during its establishment period (Govender 2007). Hypopholis sommeri and S. affinis can coexist but when H. sommeri is prevalent S. affinis is uncommon and vice versa. Mansfield (2004) observed this phenomenon in sugarcane as well; where S. affinis proliferates when

H. sommeri is less abundant. Hypopholis sommeri and A. ictericus could coexist in modest numbers when there was an availability of organic matter and roots as a food source (weeds, grass plants, wattle regrowth) present in the community FMOW.

Govender (1995) reported on various other mortality factors that occurred concurrently with whitegrubs in the same localities and in such instances whitegrubs and their associated damage were less abundant. The reduced incidence of whitegrubs in sites that were left fallow for a year or more could also be explained by the emigration of 1-year lifecycle emerging beetles (for example, A. ictericus) towards neighbouring wattle crops (Govender 2002).

The most important whitegrub pest species that attacked black wattle during its establishment in the Natal Midlands of South Africa were the morphospecies

M1 ( H. sommeri ), M3 ( S. affinis ), M8 ( Maladera sp.2), M5 ( S. fimbriata ) and

M4 ( A. ictericus ). This identification of the important whitegrub pests can improve the design and implementation of more efficient pest management programmes of whitegrubs in this region. However, the identities of some of the whitegrub species found in this study are unknown and need to be formally described using traditional taxonomic tools and molecular techniques.

42

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Table 1: a) Analysis of typification and b) discrimination of whitegrub morphospecies based on the percentage contribution to three whitegrub community patterns associated with black wattle weeding and plantation residue management practices in the Natal Midlands of South Africa.

a) Analysis of Typification b) Analysis of Discrimination WBWS WBWS vs. WBRO Av. Av. Contrib. Cum. M Abund. Sim. Sim/SD WBWS WBRO % % Av. Contrib. Cum. % % M Diss/SD Diss % % 1 Av. Av. M1 29.31 22.76 4.29 36.74 36.74 Abund Abund M3 19.53 14.54 2.33 3 23.47 60.22 M3 19.53 60.80 20.63 2.08 3 32.34 32.34 M8 15.63 8.99 1.12 14.51 74.73 M1 29.31 4.17 12.57 2.14 2 19.71 52.05 M5 16.56 8.46 0.92 13.67 88.39 M5 16.56 0.00 8.28 1.31 12.98 65.03 M4 6.39 3.19 0.86 5.15 93.54 M9 7.41 19.21 7.30 3.54 1 11.44 76.48 M9 7.41 2.75 2.39 2 4.44 97.98 M8 15.63 4.17 6.60 1.48 10.34 86.82 Av. Sim 61.93% M4 6.39 9.17 4.58 1.57 7.18 94.00 M7 3.21 0.00 1.61 0.84 2.52 96.52 FMOW Av. Diss 63.79% M1 57.20 39.39 # 65.00 65.00 WBWS vs. FMOW M4 23.11 21.21 # 35.00 100.00 WBWS FMOW Av. Sim 60.60% M1 29.31 57.20 14.63 1.50 27.77 27.78 WBRO 2 M3 19.53 0.00 9.76 2.51 18.54 46.30 M3 60.80 43.33 # 72.22 72.22 M4 6.39 23.11 8.36 3.08 1 15.87 62.17 M9 19.21 16.67 # 27.78 100.00 M5 16.56 4.55 7.26 1.39 13.78 75.95 Av. Sim 60.00% M8 15.63 10.61 6.26 1.35 11.89 87.84 WBWS : Windrowed-Burnt-Weeded-Closer Spaced. M9 7.41 4.55 3.82 1.00 7.24 95.08 FMOW : Fallow-Mowed or Manually Weeded. Av. Diss 52.67% WBRO : Windrowed-Burnt-Ripped-Old arable land. Contrib. : Whitegrub individual contribution to community. WBRO vs. FMOW Cum. : Accumulated contribution to community (up to 95%). Av. : Average. WBRO FMOW Sim. : Similarity. Diss. : Dissimilarity. 1 #: Undefined result or value. M3 60.80 0.00 30.40 3.01 37.98 37.98 1, 2 and 3: Bold superscripts denote species with the three highest consistency ratios for each whitegrub community. M1 4.17 57.20 26.52 2.51 2 33.13 71.11 Ranking levels based on formula similarity or dissimilarity divided by the standard deviation (SD) where the value/ratio 3 obtained was greater or equal than two. M9 19.21 4.55 7.33 2.44 9.16 80.27 M: Morphospecies. M1 (Hypopholis sommeri ), M4 9.17 23.11 6.97 1.29 8.71 88.97 M3 (Schizonycha affinis ), M8 4.17 10.61 5.30 1.20 6.63 95.60 M4 (Adoretus ictericus ), M5 (Schizonycha fimbriata ), M7 (Maladera sp.1), M8 (Maladera sp.2), Av. Diss 80.04% M9 (Unknown sp.). 46

Figure 1 (a-h): Figure 1a-g) MDS ordination of the different whitegrub morphospecies (M) found attacking black wattle in each of the ten different study trials (WG1 to 10) located in the Natal Midlands of South Africa. The three superimposed circles in Figure 1h, represent the different communities of whitegrubs based on the black wattle weeding and plantation residue management practices found in Chapter 1. Windrowed-burnt-weeded together with closer spacing (WBWS).

Fallow sites weeded manually or mowed (FMOW). Land windrowed-burnt-ripped or planted in an old arable land (WBRO). Gray circles represent the relative abundance

(weight and importance) of the respective morphospecies in a particular trial site.

Numbers represent the abundance (%) of the morphospecies in their respective community. Number within the gray circle (100%) represents the percentage of the morphospecies of the total whitegrub abundance in that particular study site. M:

Morphospecies. M1 ( Hypopholis sommeri ), M3 ( Schizonycha affinis ), M4 ( Adoretus ictericus ), M5 ( Schizonycha fimbriata ), M7 ( Maladera sp.1), M8 ( Maladera sp.2), M9

(Unknown sp.). Stress level = 0.07, indicates good ordination with small risk of misinterpretation.

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48

Summary of Results

In total, 2 660 whitegrub specimens belonging to 13 morphospecies were collected.

The community of whitegrubs that attacked black wattle seedlings had three different patterns of distribution. The whitegrub community under the silvicultural practices of windrowing and burning had the greatest species richness (13 morphospecies) and abundance (95%) of whitegrub species. The other two whitegrub communities (fallow sites that were mowed or manually weeded, and sites windrowed, burnt and ripped or planted in an old arable site) were in combination less abundant (5%) and diverse (7 morphospecies). These three whitegrub community patterns were explained by their strong relation to the silvicultural weeding and plantation residue management practices of the forestry industry in South Africa between 1990 and 1993.

The best 2D model obtained for each morphospecies pattern of distribution and relative abundance had a good ordination (stress value: 0.07). A complex of 13 whitegrub pests was found. Five whitegrub species (M1 Hypopholis sommeri , M3

Schizonycha affinis , M4 Adoretus ictericus , M5 Schizonycha fimbriata and M8 undescribed Maladera sp.2) with average abundance of 87.2%, were confirmed to have a high pest status. They accounted for the community structure pattern in the black wattle growing areas of the Natal Midlands (BVSTEP, ρ = 0.971). The remaining combined eight morphospecies, M7 (undescribed Maladera sp. 1), M11

(Heteronychus licas ), and M6, M9, M16, M24, M25 and M26 (unknown species), contributed only 12.8% and were considered to be lesser pests due to their low abundance.

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