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the millet head miner in tree-crop agroforestry systems Agroforestry 2019

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(1)

Vertebrates contribute to natural control of

the millet head miner in tree-crop agroforestry systems

Ahmadou Sow, Djiby Seye, Emile Faye,

Laure Benoit, Maxime Galan, Julien Haran, Thierry Brévault

Session 1.2

Agroforestry

8―10 october 2019

Hotel Ngor Diarama Dakar, Sénégal

2

ème

Conférence

Intensification Durable

(2)

Presentation plan

Biodiversity services in

agroecosystems

Tree-crop agroforestry

systems promote natural pest

control

On the role of birds and bats

as insect predators

Take-home message

(3)

Crop pests

3

(4)

What about natural pest control?

4

Simplification of agricultural landscapes

Cultivated ecosystems more

susceptible to pests

Intensification of agriculture

Loss of biodiversity and associated ecosystem services

such as natural pest control

(5)

Pests

Trees can promote natural pest control

5

Cropping system

Natural enemies

By providing habitats to natural enemies in agroecosystems

Refuges

Food resources

Alternative preys

Microclimate

Barrier to pest

colonization

Etc.

(6)

What did meta-analyses say?

6

(Pumariño et al. 2015)

Agroforestry practices generally result in…

Natural enemies

Pests in perennial crops (coffee, cocoa and plantain)

in annual crops

(e.g. maize, rice and beans)

(7)

Tree-crop systems as a case study

7

(8)

Pearl millet as a staple crop

(9)

Wanted

: The millet head miner

9

Heliocheilus albipunctella (Lepidoptera, Noctuidae)

B

 Monophagous, only one generation a year

 30-95% infested panicles - 2-20% grain yield loss (Sow et al. 2017)

larva (23-29 d) diapause In the soil (11 months) adult eggs (3-4 d) Dry season Rainy season

(10)

Tree-crop agroforestry systems promote

natural pest control in millet fields

10

• Natural pest control increases with the abundance of trees in the landscape

(11)

Food webs and natural pest control

11

• High throughput molecular tools (metabarcoding) were used to document

food web structures (parasitism and predation)

(Sow et al. 2018, 2019) Predators Parasitoids Aranea e (sp.1) Bradybaenu s scalaris Heliocheilus albipunctella Schoelandella sp. Copidosoma primulum Trichogrammat oïdae armigera

(12)

12

Case study:

Trees, vertebrates and natural pest control

10 Sites : high vs low tree density in a 1000 m-buffer (landscape) 2 fields per site : open vs closed in a 100 m-buffer (local)

Tree abundance (1000m buffer) HV: high

BV: low

(13)

13

In each site, trees were geolocalised and identified at the species level using drone imagery and remote sensing.

Case study:

(14)

14

Material and methods

1- Exclusion of natural

enemies

2- Field monitoring of birds

and bats

3- Evaluation of pest

incidence (abundance and

grain loss)

And collection of fecal samples for diet assessment

metabarcoding

Eggs on panicles Grain loss

Mesh bag Naturally egg-infested panicles exposed to natural enemies (T) Naturally egg-infested panicles protected from all natural enemies (M) Naturally egg-infested panicles protected from vertebrates (C) Millet panicle

(15)

Test of research hypothesis

15 • Abundance and diversity • Egg infestation • Damage

• Abundance and diversity

(16)

Abundance and diversity of tree cover

(17)

17

Insectivorous birds and bats

Taphozous mauritianus 0 5 10 15 20 25 30 35 40 45 50

Passer griseus Ploceus cucullatus

Ploceus luteolus Lamprotornis caudatus

Pycnonotus barbatus

Ptilostomus afer Lamprotornis chloropterus

Lamprotornis pulcher

(18)

18

Detection of pest DNA in feces

Taphozous mauritianus Ploceus cucullatus

Predation of the millet head miner was confirmed by molecular analysis of feces or direct observations 0 10 20 30 40 50 60

Moths and eggs Moths and early instar larvae Late instar larvae

Pr es en ce o f th e M H M in t h e fecal s amp les

(%) Bat (Taphozous mauritianus) Bird (Ploceus cucculatus)

(19)

19

Natural pest control by arthropods and birds

Grain losses were reduced when panicles were accessible to arthropods only, and even more when they were accessible to both arthropods and birds (-35%).

(20)

20

Effect of trees on insectivorous birds

The abundance of insectivorous birds was positively correlated to the diversity of trees at a local scale (SHDI_100 m).

+

0,0 0,5 1,0 Saopberry trees Palmyra palms Apple-ring acacias Neems All trees Baobabs SHDI trees

(21)

21

Effect of trees on insectivorous birds

Village weavers

The abundance of village weavers was positively correlated to the diversity of trees

+

0,0 0,5 1,0 Baobabs Saopberry trees Neems All trees Apple-ring acacias Palmyra palms SHDI trees

(22)

22

Effect of trees on insectivorous birds

-The abundance of the grey-headed sparrow was negatively correlated to the number of trees at a local scale.

Grey-headed sparrow 0,0 0,5 1,0 Saopberry trees Apple-ring acacias Baobabs SHDI trees Palmyra palms Neems All trees

(23)

23

Effect of trees on insectivorous bats

(24)

24

Effect of trees on insectivorous birds

At a lansdcape scale, no effect of trees on the abundance of insectivorous birds.

0,0 0,5 1,0

Tree cover at 1000m-radius

Tree cover at 1750m-radius

Relative importance Σwi Birds abundance

(25)

0,0 0,5 1,0 SHDI trees Apple-ring acacias Palmyra palms All trees Neems Saopberry trees Baobabs 25

Effect of trees on pest incidence

Eggs on panicles Grain loss

+

-Positive effect of baobab trees on egg infestation of panicles but negative effect of neems and balanites. No significant relation between trees and grain loss.

-0,0 0,5 1,0 Apple-ring acacias SHDI trees Neems All trees Palmyra palms Saopberry trees Baobabs

(26)

Take-home message

26

Vertebrates, including birds and bats, are

effective predators of the millet head miner.

They contribute to natural pest control and

reduction of millet grain loss.

The abundance of insectivorous village weaver

birds increased with tree diversity whereas

that of grey-headed sparrows decreased with

the abundance of trees, at a local scale.

The contribution of trees for natural pest

control is species-dependent. Trees can serve

as refuges for pest (eg. baobab/moths) and

predators (eg. palm tree/bats or neem/village

weavers).

(27)

Thank you for your attention !

Session 1.2.

Agroforestry

8―10 october 2019

Hotel Ngor Diarama Dakar, Sénégal

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