(F): Towards Sustainable Indigenous Mahogany Production in Ghana

PD 528/08 Re

PD 528/08 Rev.1 (F): Towards sustainable indigenous Mahogany production in Ghana: Phase II, refining the silviculture “tool kit” and practical training for industrial-foresters and community farmers

Effect of different densities of Azadirachta indica on the groth and incidence of Hypsipyla robusta and on Khaya grandifoliola in a mixed stand

Opuni-Frimpong, E.,1 Bampoh, A. A.2 and Baffour, A. A.2 1) Forestry Research Institute of Ghana 2) Kwame Nkrumah University of Science and Technology

SUMMARY

Khaya grandifoliola is among the most valuable tropical timber tree species in Africa. Sustainable utilization of this species is threatened by overexploitation from natural forest. The African mahogany in plantations is often assailed by a number of pests of which Hypsipyla robusta (Moore) is the most destructive. The shoot borer attacks succulent growing tissues which results into the proliferation of shoots and reduces the economic value of the timber. Mixed species plantation is likely to be effective in managing H. robusta infestation by hindering the host finding ability of the pest and possible abundance in natural enemies in mixed stands. In this study, growth performance of K. grandifoliola and evaluation of resistance to the shoot borer were made when planted in densities of 30%, 40%, 50% (line and random) and 60% in the matrix of Azadirachta indica. The results showed no significant (p < 0.05) differences among the different planting densities regarding shoot borer attack levels. While overall impact of mixtures on shoot borer damage was weak, the 30% Kg (30% Khaya and 70% Neem) plot showed promise for protecting Khaya grandifoliola from severe attacks. The results for growth performance also showed no significant (p < 0.05) differences among the different planting densities. However, the 30% Kg stand again, showed prospects for having the best growth compared to the other densities. This suggests that of the four treatments, the 30% Kg (30% Khaya and 70% Neem) is the most promising for mitigating shoot borer damage as well as enhancing the growth of K. grandifoliola when planted in mixture with A. indica.

1.0 INTRODUCTION

1.1 Background Khaya grandifoliola like other Khaya species are famous for their timber, accounting for a significant proportion of world trade in tropical hardwood. Despite having several uses which include medicinal (Opuni-Frimpong, 2008), they are principally used for furniture and veneers as they are easily worked and are strong for their weights (Lamb, 1966).

Like most sub-Saharan countries, Ghana consumes a greater volume of wood from Khaya species internally although they contribute substantially to the total Ghanaian export earnings (FPIB, 1995). The contribution of Khaya species to the total export earnings of Ghana with the passage of time has declined. The reduction in volume of about 100,000m3 of exported Khaya species in 1950 to 17,000m3 in 2005 is a clear evidence of its steady decline (Opuni-Frimpong, 2008). This is attributed to the fact that vast majority of mahogany timber are derived from the exploitation of natural forests (Atuahene, 2001; Hawthorne, 1993; Alder, 1989).

Supply from natural forests, however, is limited and at current rates of extraction, the resource is likely to be exhausted as the forests alone are inadequate to sustain a viable timber industry and meet the growing domestic demand for timber (Alder, 1989). This has led to concerns being raised about the conservation status of Khaya species (Newton et al., 1993; Rodan et al., 1992), as reflected in the listing of Khaya grandifoliola as a Red Star species (IUCN, 2009). Consequently, the only available strategy that could be used to increase the production of Khaya grandifoliola and ensure its sustainability is the establishment of plantations using this important species.

1.2 The Problem Statement Efforts to establish Khaya grandifoliola plantations in Ghana have persistently been hampered by the mahogany shoot borer, Hypsipyla robusta (Moore) (Lepidoptera: Pyralidae) (Roberts, 1966; Grijpma, 1976; Newton et al., 1993; Atuahene, 2001). The moth larvae destroys the terminal bud of the young mahogany tree which then frequently branches or forks reducing the economic value of the timber considerably and might even lead to the trees’ mortality (Newton et al., 1993; Opuni-Frimpong, 2000).

1.3 Justification Various experiments have been conducted in attempt to reduce the incidence of Hypsipyla robusta attacks on young mahogany plantations (Newton et al., 1993). Chemical (Floyd and Hauxwell, 2001), IPM methods such as the use of different shade levels (Opuni-Frimpong et al., 2008a) and pruning (Cornelius, 2000), have not been successful in reducing H. robusta damage to commercially acceptable levels. Silvicultural techniques however, have been recognised as having considerable potential for reducing the intensity of shoot borer damage (Mayhew, 1997). According to Ciesla (2001), planting high-risk indigenous species in mixtures

2 with companion species can lead to a substantial reduction in pest damages caused to the species. This is explained by two complementary mechanisms, i) reduced host plant accessibility and ii) increased populations of natural enemies (Sobek et al., 2009; Bosu et al., 2006).

Neem (Azadirachta indica) has a widespread use as an insecticide in companion planting as it contains a chemical compound azadirachtin, which is the predominant biologically active chemical in most insect-based bioassays (Ishaaya et al., 2007).

A method which used azadirachtin was found to be successful in controlling mahogany webworm in Florida (Howard, 1990). This inspired another experiment using mahogany shoot borer insect and results of the experiment revealed higher percentages of trees attacked in the control group than in the azadirachtin-treated group (Howard, 1995). Hypsipyla uses infochemical cues to identify flushing mahogany trees as well as mates (Howard 1991). Neem with its insecticidal properties may release masking chemical stimuli to interfere with odours released by mahogany tree, disrupting the efficiency of Hypsipyla identifying the tree and more so, their mating behaviour (Moore, 2007).

Neem grows in many areas of Ghana and so prospects for neem-mahogany plantations exist. This experiment seeks to take a look at how A. indica can influence the growth and incidence of H. robusta on K. grandifoliola in a mixed stand.

1.4 Research Objectives The objectives for this research project were:

1. To determine the effect of different planting densities of Azadirachta indica on Hypsipyla robusta attacks on Khaya grandifoliola in a mixed stand. 2. To examine the impact of Azadirachta indica on the growth performance of Khaya grandifoliola among the different mixed composition stands.

2.0 MATERIALS AND METHODS

2.1 Study Area The study was carried out on the Forestry Research Institute of Ghana (FORIG) experimental plot at Mesewam which is sited off the main Kumasi-Accra road and about 4 km from Aperade Junction. Mesewam (6º 44’N, 1º30’) (Bosu et al., 2006) falls within the Moist-Semi Deciduous South East Zone. The area experiences a bi-modal rainfall regime. The peak period (1650mm) being June and September. The area also experiences dry season from November-March.

2.2 Experimental Design The experimental plot was laid out in a randomized complete block design, with three blocks. Each block was divided into five plots, making a total of fifteen plots. A mixed species plantation consisting of Khaya grandifoliola and Azadirachta indica in various densities or ratios were established on the plots. Each plot consisted of 30 tree species both of A. indica and K. grandifoliola planted at a spacing of 2x2 m. K. grandifoliola was planted at densities of 60%, 40%, 30% and 50% (Line and Random) in the matrix of A. indica.

2.3 Data collection Data collection was concentrated on Khaya grandifoliola since that was the key species the experiment focused on. Assessment of damage by H. robusta was done by recording the total number of shoots that have developed as a result of H. robusta attack, number of fresh attacks, number of shoots attacked, number of dead shoots, and length of dead shoot. Growth parameters such as total tree height, diameter at 10 cm above ground, height at first fork were measured and recorded.

2.4 Data analysis The means and standard errors from each replicate for growth indices (total tree height, diameter and height at first fork) as well as the total number of shoots that have developed as a result of H. robusta attack, number of fresh attacks, number of shoots attacked, number of dead shoots and length of dead shoot were determined with SPSS statistical package. Data were analyzed using analysis of variance (ANOVA) and to test for significance of treatments, p-value of 0.05 was used. Graphs were drawn using Microsoft Office Excel.

2.5 Presentation of Results Results of the study were presented using bar charts.

3.0 RESULTS

3.1 Hypsipyla robusta attack on K. grandifoliola among the different densities of mixed- species plantation. The mixed-species stand with 50% Khaya grandifoliola (Kg) and 50% Neem planted randomly, had the lowest mean shoots at a value of 3.20 compared to the other mixed composition stands. The highest mean total shoots of 4.12, was recorded in the stand with 50% K. grandifoliola and 50% Neem planted in line (Figure 4.1). The number of shoots of K. grandifoliola attacked by Hypsipyla robusta was higher in the 60% K. grandifoliola stand, recording a mean value of 2.21 whilst the 30% Kg stand recorded the lowest mean shoots attacked at a value of 1.6 (Figure 4.2). Again, the results indicate a higher number of fresh attacks in the 40% K. grandifoliola stand at a mean value of 2.50 followed by the 60% Kg with 2.08, 50% Kg (random) with 2.00, and then 50% Kg (line) with a mean value of 1.75. The 30% Kg stand recorded the least mean number of fresh attacks at 1.00 (Figure 4.3). Statistically, there was no significant differences between densities with respect to the total number of shoots, number of shoots attacked and number of fresh attacks for K. grandifoliola (p < 0.05). 5 4.5 4 3.5

3 2.5 2 Total Shoots 1.5 1 0.5 0 Kg60 Kg50L Kg50R Kg40 Kg30 Density of Khaya grandifoliola (%)

Figure 3.1: Mean number of total shoots in Khaya grandifoliola (Kg) among the different mixed planting densities.

2.5

1.5

Shoots attacked 1

0.5

0 Kg60 Kg50L Kg50R Kg40 Kg30 Density of Khaya grandifoliola (%)

Figure 3.2: Mean number of total shoots attacked in Khaya grandifoliola (Kg) among the different mixed planting densities. 4

3.5

2.5

1.5

1 Number ofNumber fresh attack 0.5

0 Kg60 Kg50L Kg50R Kg40 Kg30 Density of Khaya grandifoliola (%)

Figure 3.3: Mean number of fresh attacks in Khaya grandifoliola (Kg) among the different mixed planting densities.

In general, the 40% Kg stand recorded the lowest mean number of dead shoots at 1.92 with the 50% Kg planted in line stand, recording the highest mean number of dead shoots at a value of 2.66 (Figure 4.4). Statistically, there were no significant differences between densities on the number of dead shoots as well as the length of dead shoot recorded for K. grandifoliola (p <

0.05. However, the 30% Kg density recorded the lowest mean length of dead shoot at a value of 3.78 cm. K. grandifoliola had the longest mean length of dead shoot at 16.42 cm (40% density), followed by 14.52 cm (60% density), 9.26 cm (50% Kg planted randomly) and then 6.88 cm (50% Kg planted in line) respectively (Figure 4.5). 3.5

2.5

1.5

1 Number of dead shoots 0.5

0 Kg60 Kg50L Kg50R Kg40 Kg30 Density of Khaya grandifoliola (%)

Figure 3.4: Mean number of dead shoots in Khaya grandifoliola (Kg) among the different mixed planting densities.

20 18

16 14 12 10 8 6 4 Length ofdead shoot (cm) 2 0 Kg60 Kg50L Kg50R Kg40 Kg30 Density of Khaya grandifoliola (%)

Figure 3.5: Mean length of longest dead shoot in Khaya grandifoliola (Kg) among the different mixed planting densities.

3.2 Growth of K. grandifoliola among the different densities of mixed-species plantation.

Figures 4.6 and 4.7 represent growth performance in diameter and height among the different planting densities respectively. The highest mean diameter (4.28 cm) and height (1.98 m) for K. grandifoliola among the mixed-species stand was recorded in the 30% K. grandifoliola stand. The smallest mean diameter growth (3.93 cm) was recorded for the 50% K. grandifoliola (random planting) plot with the 40% K. grandifoliola stand, recording the least mean growth in height (1.59 m). There were no significant differences between densities on the diameter and height growth performance of K. grandifoliola (p < 0.05).

5 4.5 4

) 3.5 3 2.5 2

Diameter (cm Diameter 1.5 1 0.5 0 Kg60 Kg50L Kg50R Kg40 Kg30 Density of Khaya grandifoliola (%)

Figure 3.6: Mean diameter of Khaya grandifoliola (Kg) among the different mixed planting densities.

2.5

1.5

1 Height (m) Height

0.5

0 Kg60 Kg50L Kg50R Kg40 Kg30 Density of Khaya grandifoliola (%)

Figure 3.7: Mean height of Khaya grandifoliola (Kg) among the different mixed planting densities.

On the whole, the 30% K. grandifoliola plot showed early branching/forking than the remaining stands (Figure 4.8) with the 40% K. grandifoliola stand showing the most contrast. Density between and within groups had no significant effect on the height at which K. grandifoliola branched (p < 0.05).

1.6

1.4

1.2

0.8

0.6

0.4

Height at at (m) fork firstHeight 0.2

0 Kg60 Kg50L Kg50R Kg40 Kg30 Density of Khaya grandifoliola (%)

Figure 3.8: Mean height at first fork of Khaya grandifoliola (Kg) among the different mixed planting densities.

4.0 DISCUSSION

4.1 Hypsipyla robusta attack on K. grandifoliola among the different densities of mixed- species plantation. Forking of Khaya grandifoliola in this study was as a result of H. robusta attacks. This is in line with observations by Opuni-Frimpong et al., (2008b) who concluded that frequent attacks on young K. grandifoliola plants generally led to poor quality timber. Branching of K. granidoliola occurred in all densities planted.

Results of the experiment indicate that the neem did not have any significant impact (p < 0.05) on the incidence of Hypsipyla robusta on K. grandifoliola in all the mixed-species stand established. This could be attributed to the young nature of the plantation as data was collected in the second year of its establishment and at that time, the neem tree had not matured enough to fruit as recounted by NRC (1992), Gunasena and Marambe (1998) and Chandra (1997), that neem begins bearing fruit after 3-5 years of establishment and becomes fully productive in 10 years. Azadirachtin, the complex tetranortriterpenoid liminoid (Capinera, 2008) is found in the highest concentration in the seeds of neem. This azadirachtin, the predominant biologically active chemical in most insect-based bioassays and known as the “most potent insect anti-feed ant discovered to date” (Ishaaya et al., 2007) might have been absent due to the age of the neem tree and thus, the neem could not measure up to its full insect repellent property in this experiment. Results of this study agrees with Bosu and Nkrumah (2011) and Matsumoto and Kotulai (2002) whose works ascertained that planting neem in mixture with K. ivorensis did not lead to a significant reduction of Hypipyla damage to K. ivorensis. They concluded that their hypothesis, volatiles in neem could repel Hypsipyla when planted in mixtures with African mahoganies was not supported.

A study by Griffith (2001) revealed that, in spite of Hypsipyla spp. high capacity and ability to disperse, Hypsipyla moths do not readily leave an area of active infestation while new shoots are available, thus causing severe damage. This might be a contributing factor to the insignificance of the experimental treatments envisaging the relatively high Hypsipyla population in the experimental area. This is because the plantation was cited a few metres away from several older African mahogany plantations all of which were infested by Hypsipyla. Perhaps, the experimental plots were already subdued by high shoot borer population and thus, the overall poor response to the experimental treatments imposed. In support, Grijpma (1973) states that Hypsipyla shoot borers represents the main hindrance to the establishment of mahogany tree plantations in areas infested with the insect.

While overall impact of mixtures on shoot borer damage was weak, the 30% Kg plot showed promise for protecting Khaya grandifoliola from severe attacks.

4.2 Growth of K. grandifoliola among the different densities of mixed-species plantation.

The different densities of mixed-species plantations in this study agrees with Mayhew (1997), who stated that one of the silvicultural techniques that ensures the success of mahogany plantations is the planting of mahogany in a mixture with species certain desirable qualities. Mixed species plantations according to Kelty (2006) may improve growing conditions and lead to an increase in productivity of trees stand.

Results of the study indicated that after two years of planting, there was no significant difference (p < 0.05) between growth in diameter and height for all mixed-species stands of Khaya grandifoliola established. This result implies that the neem did not impact the growth performance of K. grandifoliola in the various mixed composition stands established. Khaya grandifoliola trees had less competition for water, light and soil nutrients and thus could photosynthesize effectively, leading to its growth as reiterated by Petit and Montagnini (2006). This phenomenon does not corroborate previous observations by Gorse (1986, cited in Benge, 1988), who ascertained that neem is very competitive for water, light and soil nutrients when planted in density with other species.

Favourable environmental conditions amongst which soil is a major factor (Grijpma 1976 as cited in Opuni-Frimpong et al. 2008b) may have also contributed to the growth performance of K. grandifoliola, although these factors were not examined directly. This is evident when one looks at the vegetation surrounding the experimental plot. Again, results of the 50% K. grandifoliola plot (50% Khaya and 50% Neem) for both line and random planting does not agree with the findings of Kelty (2006) whose study demonstrated that, mixture stands with equal percentage of species were more productive than other combinations. Overall, the 30% K. grandifoliola stand showed prospects for having the best growth compared to the other densities. There was however, no clear trend between growth observed and the number of shoots attacked by the mahogany shoot borer (Hypsipyla robusta).

5.0 CONCLUSIONS AND RECOMMENDATIONS

5.1 Conclusions Evidence in support of initial perception that repellent properties of neem would provide protection against shoot borer damage to K. grandifoliola was weak. However, of the four treatments, the 30% K. grandifoliola plot (30% Khaya and 70% Neem) appeared the most promising for reducing shoot borer damage to K. grandifoliola and the reduction in damage can fully be realized when the neem is cultivated three years earlier than the K. grandifoliola, so that its insecticidal properties can be harnessed. Also under conditions of lower Hypsipyla pressure, contrary to what was pertaining in the experimental area, the protection of neem against Hypsipyla attack could be higher.

The results from the growth performance observations indicated that the most suitable density for K. grandifoliola plantation establishment in mixture with Azadirachta indica should be 30% Khaya grandifoliola and 70% Neem (30% Kg plot).

5.2 Recommendations 1. Since this study was conducted after only two years of planting, more assessment should be undertaken at this study area after some years to evaluate the effect the neem has had on the Khaya grandifoliola. 2. Future experiments should be cited well away from areas subdued by the Hypsipyla moths already. 3. The effect of provenance (seed source) on the growth of African mahogany and its resistance to Hypsipyla spp. in a mixed-species plantation with neem should be examined to reveal which seed source would be most appropriate for such a mixed-species stand. 4. The experiment should be replicated across the different ecological zones of Ghana to reveal which one would best enhance the growth of K. grandifoliola and its resistance to H. robusta attacks. 5. An experiment using neem based insecticides to augment the repellence prowess of the trees in a mixed-species stand with Khaya grandifoliola should be undertaken to ascertain the extent of protection against Hypsipyla robusta incidence. 6. Results from such studies should not be limited to academic circles but made available to foresters and farmers who are involved in the restoration of mahogany.

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