Presented By:

Deshaun Martin- Clarke

Delano S. Lewis

Life history and feeding preference of Spodoptera exigua (Hübner) on two varieties of Allium fistulosum and one variety of Allium cepa under field conditions

Introduction The Beet Armyworm (Spodoptera exigua) is a well-known pest

species across the world. It is believed to have been introduced in Jamaica in the 1970s and two major outbreaks in 2009 and 2012 and the subsequent devastation of several hectares of onion and scallion as well as damage to other crops in South St. Elizabeth has brought it to national recognition.

BAW is described as a polyphagous insect pest which has a host range of more than 50 plant species in 10 plant families worldwide (Farahani, 2011; Greenberg et al., 2001; Karimi-Malati, 2012; Mehrkhou, 2013).

The outbreaks were exacerbated by the pest’s resistance to most chemical applications and cultural practices

Introduction Larval development is temperature dependent (Capinera,1999)

S.exigua reared under controlled conditions on scallion at two different temperatures at Bodles Research Station showed a clear 10 day difference in larval period with a temperature difference of approximately 6 degrees celcius (25 days at 23.7 oC and 15 days at 29.6oC) (Deidrick and Sherwood, 2014).

Fig 1: Map Showing Global Distribution of S. exigua. Source: Yu Takeuchi (FAO consultant)

This research is a direct result of the National beet armyworm programme, “Strengthening the National Beet Army worm Programme” which is a collaborative effort of the MOAF, Bodles, FAO, NCU and other stake holders, geared towards providing the much needed local based research to bolster the efficacy of the National Pest Forecasting System.

Introduction

The study seeks to bridge the information gap as it relates to local based

research on pest species specifically the life history and behaviour of

BAW in field conditions

To provide baseline data for the national pest forecasting system

Objectives

Methodology

A 30 day phenological study was carried out in three locations in South St. Elizabeth: Flaggaman, Seaview and Munro

Growth Studies were done in field conditions to assess the larval period on two varieties of Allium fistulosum (Red root and Evergreen Hardy Scallion) and one variety of Allium cepa (onion).

Preference studies were done to ascertain if BAW larvae fed indiscriminately on all the host plants tested or not.

Fig 2: Ground view of study plots. Top left is Flagaman, top right is Munro, Bottom left is Seaview

Fig 3 View of inside of life cages after set up (left), and final set up (right)

Fig 4: Set up for preference study

Results: Phenological study

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 300

100

200

300

400

500

600

Graph comparing the total number of individuals found in each area per day

FLAGAMANSEAVIEWMUNRO

# of

indi

vidu

als

days

Fig 5: Comparison of total number of individuals found per day per plot over the study period

Results: Growth StudyTable 1: The following table shows the average growth per day of BAW on three Allium varietiesday Ave Temp. oC ONION RED ROOT EGH

28.73585 head(mm)body (mm)

head (mm) body (mm)head (mm) body(mm)

1 29.36 0.315 3.085 0.336 2.736 0.254 1.4852 29.796 0.462 3.83 0.35 3.556 0.274 2.0523 29.312 0.479 5.243 0.433 4.468 0.296 2.5534 29.634 0.752 7.42 0.593 6.451 0.274 2.7365 28.929 0.872 9.575 0.752 7.979 0.41 3.426 29.109 1.14 17.5 1.231 19 0.41 4.4237 28.599 1.55 18.625 1.47 18 0.41 5.8828 28.453 1.505 20 1.505 22.667 0.42 5.99 28.409 1.573 24 1.368 18 0.547 12

10 29.18 Pupation 1.641 20 0.547 1211 26.973 1.641 26 1.368 1512 27.973 Pupation 1.505 1513 27.839 1.168 15.656

Std. Dev +/-

0.802361 0.5 7.911 0.538 8.543 0.438 5.506

Results: Preference StudyTable 2 : Showing the extent of consumption of the leafs t the close of the preference trials. A rating of 1-5 was assigned based on the amount of leaf matter consumed where 1 is the least and 5 is total consumption Instar 3-4 Treatment EGH RR O C  1 5 4 3 2  2 3 2 5 3  3 4 3 5 2  4 3 3 3 2  5 2 5 4 3  Average 3.4 3.4 4 2.4           Instar 4-5 treatment EGH RR O C  1 2 4 3 5  2 3 5 1 4  3 4 5 3.5 2  4 1 5 4.5 2  5 4 2 3 5  Average 2.8 4.2 3 3.6

Lessons Learnt

There is a significant difference in larval period of BAW in the field as opposed to the lab at similar temperatures

The larval period of BAW is affected by host plants even of the same species in that Evergreen Hardy is a poor host for BAW development

Local Research is imperative in determining the Management of pest species

While BAW is polyphagous it does not feed indiscriminately on every available plant material

Recommendations

More investments needs to be made to increase local research as a means of solving local issues rather than depend on internationally based research.

In light of climate change, it should be expected that changes and fluctuations in general climatic conditions will lead to more unpredictable pest behaviour, hence the need for a constant and consistent monitoring of pest populations within the parameters of temperature and humidity.

Way Forward

Continue local based research on the Beet Army worm and expand methods to other pest species on an island wide basis.

Lobby for more government and private sector funds to be invested in developing the capacity for high quality local based research to increase improve our decision making processes.