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TECHNICAL REPORT ON THE EFFICACY OF A NEW PESTICIDE (BLACK OFF) AGAINST THE

BLACK COFFEE TWIG BORER, XYLOSANDRUS COMPACTUS (EICHHOFF)

1.0 Introduction

The Black Coffee Twig Borer (BCTB), Xylosandrous compactus (Eichhoff) (Coleoptera:

Scolytidae) is a relatively new pest in Uganda attacking coffee and a number of other plant

species. It was first reported in Bundibugyo in 1993 but now spreading rapidly to other areas

particularly in the Robusta growing regions. Being a new pest, there are limited control

strategies for the pest. Secondly, the pest spends most of its life cycle inside the host plant

galleries, making control rather difficult. Farmers in Uganda and elsewhere usually use

cultural and sometimes combined with inorganic pesticides to control BCTB. However,

cultural methods are labor intensive and may be uneconomical whereas, inorganic

pesticides are being discouraged because of their hazardous effects on humans, animals and

environment. Therefore, less expensive natural (organic) biopesticide could be an

alternative to inorganic pesticides. These biopesticides are biodegradable and

environmentally-friendly and less likely for insects to develop resistance against them. Black

Off is an example of such pesticides which has been developed by Reticia Products for

managing BCTB. This report therefore outlines the findings by the National Coffee Research

Institute (NaCORI) Entomology team in regard to the efficacy of Black off against BCTB.

2.0 Objectives

The objectives of the study were: -

(i) To determine the efficacy of this biopesticide against adult twig borer under laboratory

(in vitro) conditions

(ii) To assess farmers’ perception on the efficacy of Black Off against BCTB in Rakai and

Masaka districts

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3.0. In vitro evaluation of efficacy of Black off on adult BCTB

3.1. Methodology

3.1.1. Black Off

Black Off is a relatively new biopesticide manufactured and being promoted by Reticia

Products for managing the twig borer. Reticia Products is owned by Mr. Andrew

Ssewanyana, Mr. Daniel Muwonge and Mrs. Alexandra Mawanda Bagenda. It is based in

Kyengera, Kampala-Masaka road. The biopesticide is made by mixing plant extracts

(oranges, lemons, Aloe vera etc) with water and Sodium laureth sulfate and incubating the

mixture at room temperature for 30 days.

3.1.2 Insect used

Adult black coffee twig borers were extracted from the infested primary branches collected

from on-station coffee plantations at the National Coffee Research Institute (NaCORI),

Kituza, Mukono.

3.1.3 Bioassay 1

Two biopesticides, Black Off – dilute (BOD) and Black Off – concentrated (BOC) and an

inorganic pesticide, imidochloroprid (Imaxi) were tested against the adult black coffee twig

borer. Before use, the pesticides were diluted basing on the manufacturer’s recommended

rates i.e. 14 mls per liter of water for Black off (dilute), 7 mls per liter of water for Black off

(concentrated) and 4 mls per liter of water of Imidochlorprid (Imaxi). Filter papers

moistened with the pesticides and water (control) were placed in petri dishes. Four (4)

freshly collected adult beetles were released in each petri dish. The petri dishes were

labeled according to treatment and replication. The experiment was laid in a completely

randomized design (CRD) replicated three times (Fig. 1) and maintained in the laboratory at

room temperature. After 3 days, dead beetles were counted and used to compute the

percentage mortality.

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Figure 1: Experimental layout for the effect of Imaxi, Black Off – dilute (BOD),‘Black Off

– concentrated (BOC) on the black coffee twig borer

3.1.3.1 Results

The results are shown in the table 1 below.

Both the synthetic and botanical pesticides were able to kill more than 50% of the

adult black coffee twig borers exposed to them

The Synthetic pesticide (maxi) performed best, killing 75% of the adult BCTB

However, the biopesticides were also able to kill 67% of the BCTB (Black off – dilute)

and 59% (Black Off - concentrated; 58%)

Water was also able to cause at least 25% mortality of the beetles

Table 1: Percentage mortality of adult BCTB when exposed to a synthetic pesticide

(Imaxi) and two biopesticides, Black off (dilute) and Black off (concentrated)

TREATMENT MORTALITY (%)

IMAX 75.0

BLACK OFF2 (DILUTE) 66.7

BLACK OFF1 (CONCENTRATED) 58.3

WATER (CONTROL) 25.0

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3.1.4 Bioassay 2

The experiment was repeated using the manufacturers’ recommended rate (X) and double

the manufacturers’ recommended rate (2X). Also, 10 beetles were used per petri dish

instead of 5.

3.1.4.1 Results

The results for bioassay 2 are shown in table 2 below

Black Off (Concentrated) at double the manufacturer’s rate performed best, killing

73% of the adult beetles

Black Off (concentrated) at manufacturer’s rate and Black Off (dilute) at double the

manufacturer’s rate caused a mortality of 47% of the adult BCTB

All other pesticides and water caused a mortality of less than 45% of the adult BCTB

Water (control) performed better (27%) than Imax at double the manufacturer’s rate

(23%)

Table 2: Percentage mortality of adult BCTB when exposed to a synthetic pesticide

(Imaxi) and two biopesticides, Black off (dilute) and Black off (concentrated)

at manufacturer’ rate and double

TREATMENT Mortality of adult BCTB (%)

BLACK OFF CONCENTRATED (2X) 73.3

BLACK OFF CONCENTRATED (X) 46.7

BLACK OFF DILUTE (2X) 46.7

BLACK OFF DILUTE (X) 33.3

IMAXI (X) 30.0

WATER (CONTROL) 26.7

IMAXI (2X) 23.3

3.1.5 Conclusions

Both biopesticides were able to cause mortality to adult BCTB in vitro conditions with

their efficacy comparable to the recommended synthetic pesticide (Imax)

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3.1.6 Recommendations

Since BCTB spends most of its life cycle inside the host plant galleries, a systemic

chemical needs to be used to kill it. Therefore, the mode of action (whether systemic

or contact) and the delivery mechanisms need to be determined.

The effect of these biopesticides on the various life stages of the beetle (eggs, larvae

and pupae) should be investigated.

The effect of the biopesticides on the coffee and other susceptible plants

(phytotoxicity) should be determined.

The biopesticides should also be tried on other insect pests of coffee particularly in

areas where organic farming is being promoted e.g. on Arabia coffee in Mt. Elgon

region and weaver ants in northern Uganda

4.0. Farmers’ perceptions of the efficacy of Black Off for managing BCTB

4.1. Methodology

Two farmers who had used Black Off –dilute (BOD) for managing BCTB on their coffee were

visited in April 2015 by the NaCORI Entomology team and the proprietors of Reticia Products

which manufactures and promotes Black Off. The research team consisted of: - Dr. Godfrey

H. Kagezi, Mr. Patrick Kucel, Mr. Joseph Sseruyange and Mr. John Ssemuwemba, and the

Reticia team had, Mr. Andrew Ssewanyana and Mr. Daniel Muwonge. The purpose of the

visit was to conduct a situational analysis on the farmers’ perception on the efficacy of Black

Off on BCTB on coffee.

4.1.1. Mr. Joseph Rogers Kateregga

Mr. Kateregga’s farm is located in Nabyajjwe II village, Nabyajjwe parish, Lwankoni sub-

county, Rakai district. He has about 5 acres of coffee. His coffee field was well managed with

trenches, grass bands. It was also moderately self mulched and intercropped with bananas

and shade trees including Ficus natalensis, Jack fruit, musizi and mangoes. His major

constraints hindering coffee production were: - the black coffee twig borer (BCTB), thieves,

drought and lack of labor. He reported that observes more BCTB infestation on older than

young coffee plants and clonal compared to other coffee types. He reported that he usually

manages BCTB by trimming off and burning the infested twigs and recently by spraying with

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BOD which was given to him by Mr. Andrew Ssewanyana. The farmer informed the team

that he applied BOD between April and June 2014 at a rate of 50 milliliters in 15 liters of

water after trimming off the infested plant materials. He testified that he observed a

tremendous reduction in infestation after applying Black Off. However, BCTB infestation was

still evident on his farm with 50% of the coffee trees and 5.4% of the primary branches

assessed were infested by the twig borer. He informed the team that this was because Mr.

Andrew Ssewanyana did not replenish the BOD stocks.

4.1.2. Miss Pelagia Nakiwala

Miss Nakiwala’s farm is located in Mweluka village, Bugere parish, Kyesiga sub-county,

Masaka district. The farmer owns about 1 acre under coffee and the main constraints

hindering coffee production were: - BCTB, management, lack of manure and chemicals to

manage the twig borer. The coffee was generally well managed apart from change of cycle.

The farmer informed the team that she first observed the twig borer on her farm 5 years

ago. Also that bushiness and a lot of shade promote infestation by the twig borer. She also

reported that older trees are more prone to infestation and that all coffee lines are equally

attacked by the pest. She controls BCTB by spraying with Black Off at a rate of 20 mls in 15

liters of water every month. She testified that the infestation generally reduced when Black

Off was used. However, as with Mr. Kateregga, Mr. Andrew Ssewanyana did not replenish

the stock which has led to resurgence of the pest.

4.2. Conclusions

According to the interviewed farmers, BOD reduces BCTB infestation on coffee.

However, the sample size is very small for an authoritative conclusion to be drawn.

4.3. Recommendations

Both BOD and BOC should be tested on a larger sample size and the concentration as

well as the frequency of application should be varied.

On-farm tests of BOD and BOC on other insect pests such leaf eating beetles, tailed

caterpillars, leaf skeletonizers, weaver ants should be conducted.