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 SURPRISE OBSERVATION OF BSF IN HARVESTED FRUITS IN TANZANIA 
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Joined: Fri Sep 05, 2014 8:52 am
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Location: Dar es Salaam Tanzania
Post SURPRISE OBSERVATION OF BSF IN HARVESTED FRUITS IN TANZANIA
I am fruit fly researcher at Mikocheni Agriculture Research Institute (MARI) in Dar es Salaam Tanzania. During a trial with small-scale farmers on community IPM against Bactrocera invadens fruit fly in three villages in Muheza district north eastern Tanzania, hundreds of unexpected maggots were recovered from oranges of different developmental stages. The maggots and hatched adults were later identified by world-renowned experts as the black soldier fly (BSF), Hermetia illucens (Linnaeus). Follow the following article:

In 2011/12 while working with farmers in a community-based IPM trial to control the exotic fruit fly B. invadens in three orange-growing villages of Muheza district, BSF maggots were observed in some of the oranges from all three villages distanced between 15 and 35 km apart.

Methods

Oranges were collected from diffrent farmers at three developmental stages: when they were at early stages (approximately 5 cm in diameter) in June 2011; in September 2011 when they were midway to maturity (10 cm in diameter) and in March 2012 at ripening (13 cm in diameter). Most of the oranges were early and late Valencia variety. At each sampling, 550 oranges were collected from each trial village by randomly harvesting 55 fruits from each of 10 experimental orchards. Fewer oranges could be collected at times due to unavoidable circumstances then prevailing.

Fruits were transported soon after harvest in labeled and closed manila or jute bags to Mikocheni Agricultural Research Institutes’ Pest Control Laboratory. They were weighed and incubated, according to site, for 14 days in 4-litre plastic food containers one third filled with moderately moist sand heat-sterilized at 60-65 degrees Celsius. Mouths of the food containers were securely covered by a piece of cotton cloth or fine-pored mosquito netting to prevent accidental laboratory infestation, escape of maggots or of hatched adult flies.

After incubation, fruits were individually dissected using sharp knives or scalpels and searched for fruit fly maggots. Recovered maggots were incubated in 4-litre plastic containers with heat-sterilized sand as in the fruit incubation arrangement until emergence of adult flies.

Observations

1. Only 0.2% of the dissected oranges (n = 4210) were infested by the targetted B. invadens at orange ripening stage.

2. To our surprise, a large number of maggots of a non-tephritid Diptera emerged from oranges as follows:

(i) First village

In June 2011, 3% of 5 cm diameter oranges (n=550) from 30% of orchards (n= 10) yielded 345 BSF maggots. At the middle of the season in September 2011, 13% of oranges (10 cm in diameter n= 550), from 90% of sampled orchards (n=10) were infested by 1700 maggots, while at end of season in March 2012 (13 cm diameter oranges) only 1% of the orchards had infested oranges, involving 4% of the fruits (n = 233) and only 2 recovered maggots.

(ii) Second village

In June 2011 BSF-infested oranges were collected from 55% of experimental orchards (n = 10) with 13% fruit infestation (n=550) and 840 maggots; in September 2011, 20% of orchards with 2% orange (n=530) infestation and 170 maggots while in March 2012 at the ripening stage none of the oranges were infested (n=238).

(iii) Third village

In June 2011, 77% of orchards (n = 10) had oranges observed with BSF maggots with 20% orange infestation (n= 550) and 1920 maggots; in september 2011, 78% of orchards (n=10) had oranges infested by BSF maggots involving 11% of oranges (n=488) and 430 maggots; while in March 2012 only on 20% of orchards (n=10) and in 1% of oranges (n=523) were BSF (270) maggots observed.

Discusion and conclusion

Simultaneous observation of H. illucens (BSF) in oranges in three distantly located villages and in different orchards in Muheza district suggests the ability of the female fly to penetrate eggs into the pulp of developing oranges. This is also supported by recovery of similar maggots in tree-harvested mangoes and guava from three different areas near Dar es Salaam. If this is the case, then this is the first record of the fly behaving as a pest of intact fruit in the investigated areas?. This contradicts with literature on BSF.

Could this be an incidental observation? Could BSF pose as a potential fruit pest? Does it poccess ability to penetrate intact fruit? Further research is needed to provide conclusive evidence that the fly is consistently able to oviposit in intact fruit even on trees and the potential implications. This may sounds quite strange to many BSF experts and enthusiasts.

I am sorry for unusually long article, kindly react to it.

Dr Zuberi Seguni
Department of Crop Protection
Pest Control Unit MARI
Dar es Salaam Tanzania


Wed Oct 01, 2014 5:07 am
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Post Re: SURPRISE OBSERVATION OF BSF IN HARVESTED FRUITS IN TANZA
Zuberi wrote:
... Simultaneous observation of H. illucens (BSF) in oranges in three distantly located villages and in different orchards in Muheza district suggests the ability of the female fly to penetrate eggs into the pulp of developing oranges. This is also supported by recovery of similar maggots in tree-harvested mangoes and guava from three different areas near Dar es Salaam. If this is the case, then this is the first record of the fly behaving as a pest of intact fruit in the investigated areas?. This contradicts with literature on BSF.


Dr Seguni thank you for posting your research results. As you mention it is commonly thought that BSF are detritivores (link) so finding them in fresh developing oranges is a surprise.

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I Believe The Black Soldier Fly Has The Potential To Be A Beneficial Insect Second Only To Pollinating Bees


Wed Oct 01, 2014 10:33 am
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Post Re: SURPRISE OBSERVATION OF BSF IN HARVESTED FRUITS IN TANZA
Hello Zuberi. Thank you for joining our forum and sharing this work.

Quote:
Simultaneous observation of H. illucens (BSF) in oranges in three distantly located villages and in different orchards in Muheza district suggests the ability of the female fly to penetrate eggs into the pulp of developing oranges. This is also supported by recovery of similar maggots in tree-harvested mangoes and guava from three different areas near Dar es Salaam. If this is the case, then this is the first record of the fly behaving as a pest of intact fruit in the investigated areas?. This contradicts with literature on BSF.


Not only does this contradict the literature on BSF, if also contradicts the empirical evidence based on the global fruit industry. I haven't heard of a single issue with BSF infesting fresh fruit, and given the amount of fruit produced, it seems unlikely to me that BSF infestation would go unnoticed. Have you found reports of BSF infestation from any other source?

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*I'm not an entomologist, and much of what I write about BSF is an educated guess.


Fri Oct 03, 2014 9:27 am
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Joined: Fri Sep 05, 2014 8:52 am
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Location: Dar es Salaam Tanzania
Post Re: SURPRISE OBSERVATION OF BSF IN HARVESTED FRUITS IN TANZA
Forum colleagues

Thanks to those reacting on BSF in fruits.

I have never heard before, this surprises me alot. I even had little prior information regarding SBF and only got interested when these surprising results emerged. I will continue to make a close followup of this topic and you will be informing you. But you may wish to give it a thought


Thanks once more


Z. Seguni


Mon Oct 06, 2014 3:57 am
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