Integrated pest management for
mango orchards using green ants
as a major component
Renkang Peng and Keith Christian
School of Science and Primary Industries
Charles Darwin University
Darwin NT 0909, AUSTRALIA
June 2005
A manual for conventional and organic
mango growers in Australia
ALL RIGHTS RESERVED
This booklet has been produced by the authors for the Australian
Centre for International Agricultural Research and may only be used
by Australian mango growers. No parts of this booklet may be
produced in any form or by any means, electronically, mechanically,
by photocopying, recording or otherwise, without the prior
permission of the author.
Authors’ email addresses:
and
.
Project funded by ACIAR:
Distributed by the Crops, Forestry and Horticulture Division of
DPIFM:
Introduction
Mango is the most important commercial crop in the Northern Territory (NT). The conventional mango growers currently rely on chemical insecticides to control insect pests. The heavy use of insecticides has resulted in increased costs, environmental pollution, disputes among neighbours, and the reduction in natural enemies of insect pests and pollinators. Organic growers generally have few resources to deal with insect pests, resulting in reduced yield and fruit qua lity. To reduce dependency on insecticides, a suitable integrated pest management (IPM) program is needed. Our research showed that green ants can control the major mango insect pests, while at the same time, they protect soft scales, damage fruits by their formic acid and annoy workers during fruit harvest. Further study addressing these constraints demonstrated that certain environmentally friendly soft chemicals reduce soft scale numbers without devastating green ants, the isolation of ant colonies reduces fruit damage by formic acid, and water spray reduces ant activity during harvest. Two IPM programs for conventional and organic growers in the NT have been developed. These IPM programs use green ants together with conventional agricultural methods and soft chemicals to manage the mango insect pest complex. The IPM programs can significantly benefit mango growers, including the potential for the production of ‘organic’ produce. These IPM programs are also friendly to the environment. To promote the use of the IPM programs, a booklet, a video (DVD) and a series of posters have been produced to describe how to use these programs step by step. The purpose of this booklet is to help farmers:
(1) recognise and protect the natural enemies of pests commonly found in mango orchards,
(2) understand the extent to which the green ant can control the main mango insect pests,
(3) implement the IPM programs using green ants as a key element, (4) manage green ant colonies, and
(5) recognise the potential problems associated with using green ants and how to apply the straight forward solutions to the problems.
This booklet also gives a detailed account of the way green ant colonies work, and how this can be used to the advantage of growers.
The booklet is based on the results of a four-year study undertaken between 2001 and 2005 at the Charles Darwin University, and supported by the Australian Centre for International Agricultural Research. The data presented in the booklet were collected from a series of field experiments at six study sites in the Darwin area of the Northern Territory. This IPM program has been developed in the context of the biological and environmental conditions in the Top End, but the techniques developed here can be extended to northern Queensland because of the similarity of insect pest complex and mango growing conditions. This booklet can also be used as an important reference for other tropical tree growers who are engaged in the production of cashew, macadamia, avocado, citrus, coconut, cocoa and lychee due to overlap in the major insect pests between these crops and mango.
Acknowledgements
The study was supported by the Australian Centre for International Agricultural Research and the Charles Darwin University. We are grateful to Mr Les Brigden, Ms Liz Marshall, Ms Dallas Johns, Mr Malcolm Green, Mr Peter Gilson, Mr Philip Stuart and Mrs Diane Lucas for providing us with the study sites and the necessary farm facilities. We thank Mr Matthew Shortus, Mr Pieter Bekkers, Mr Les Brigden and Ms Lanni Zhang for their technical assistance. We also thank Mr Les Brigden, Mr Ian Duncan, Mr Pieter Bekkers and Mr John Greatorex for their helpful comments on the manual.
Contents
Introduction .. .. .. .. .. .. .. .. .. .. .. .. 2 Acknowledgements .. .. .. .. .. .. .. .. .. .. .. 3 Part 1. Common beneficial predators and parasitoids in mango orchards .. 5 1.1 Predators .. .. .. .. .. .. .. .. .. .. .. 6 1.2 Parasitoids .. .. .. .. .. .. .. .. .. .. 11 Part 2. Effective control of mango insect pests by green ants .. .. .. 12
2.1 Major insect pests .. .. .. .. .. .. .. .. .. 13 2.2 Minor insect pests .. .. .. .. .. .. .. .. .. 23 Part 3. Problems using green ants in mango orchards and their solutions .. 24 3.1 Problems related to using green ants .. .. .. .. .. .. 25 3.2 Solutions to the problems caused by green ants .. .. .. .. 27 Part 4. Results from field experiments using the IPM program .. .. 29 4.1 Les’s orchard .. .. .. .. .. .. .. .. .. .. 30 4.2 Dallas’s orchard .. .. .. .. .. .. .. .. .. 30 4.3 Malcolm’s orchard .. .. .. .. .. .. .. .. .. 31 4.4 Liz’s orchard .. .. .. .. .. .. .. .. .. .. 31 Part 5. Suggested IPM programs in mango orchards .. .. .. .. .. 32 Part 6. Management of green ant colonies in mango orchards .. .. .. 34 6.1 Determination of ant species on each tree in a mango orchard .. 35 6.2 Bait other ant species and determie green ant colonies .. .. 35 6.3 Management of existing green ant colonies .. .. .. .. 37 6.4 Transplantation of new green ant colonies .. .. .. .. .. 39 6.5 Monitoring and maintenance .. .. .. .. .. .. .. 42 Part 7. Development of new mango orchards .. .. .. .. .. .. 45 Practical examples .. .. .. .. .. .. .. .. .. .. .. 47
IPM diagram .. .. .. .. .. .. .. .. .. .. .. .. 49 Bibliography of relevant scientific and technical publications .. .. .. 50
Part 1. Common beneficial predators and parasitoids in mango
orchards
In the Northern Territory, there are a number of beneficial predators and parasitoids which help reduce mango insect pest damage. The following pages show the common species found in mango orchards and provide a brief description of their contribution to the NT mango industry.
1.1 Predators
1.1.1 Ladybird beetles
There are a number of ladybird beetles in mango orchards. The adults and larvae feed on aphids, red-banded thrips, leafhoppers, scales, mealybugs and lepidopteran eggs. Adult 7.9 – 8.2 mm 4.0 – 5.0 mm 4.3 – 4.6 mm 3.0 – 3.1 mm 8.2 – 8.4 mm 4.9 – 5.0 mm 4.9 – 5.2 mm 2.2 – 2.5 mm 6.3 – 6.5 mm 4.4 – 4.7 mm 4.5 – 4.8 mm 1.2 – 1.5 mm Larva 1.8 mm, Feed on red-banded thrips
1.1.2 Lacewings
Lacewing larvae play a very important role in controlling red banded thrips, mango leafhoppers, aphids, mites, immature scales, mealybugs and small caterpillars.
Adult 10.0 – 11.0 mm 5.5 mm
Eggs
Larva A larva feeds on mango
leafhoper
Larva carries skins of insects whose body fluids were sucked by the larva
1.1.3 Hoverflies
Hoverflies look like bees, but they only have one pair of wings, and maintain a stationary position in flight. Hoverfly adults are efficient pollinators, and their larvae feed on mealybugs, aphids and red-banded thrips.
1.1.4 Spiders
There are many species of spiders in mango orchards. Spiders are general predators, feeding on a range of insects including mango insect pests such as mango leafhoppers, mango tip borers, red-banded thrips, planthoppers, moths, bugs and flower
caterpillars, etc. They also attack beneficial insects like flies and bees. A few species of ant- mimicry spider feed on efficient predators like green ants, but their populations are too low to have an obvious influence on the ant populations.
A lynx spider catches a caterpillar
A jumping spider catches a Alydidae bug
A spider catches an adult red-banded thrips
A lynx spider catches a wasp
A jumping spider feeds on
1.1.5 Predatory bugs
There are several species of predatory bugs that feed on caterpillars, leafhoppers, pest bugs, aphids and insect eggs.
Platynopus bug 13 mm Geocoris bug 4.2 mm Reduviidae bug 18 mm
Reduviidae bug 10.0 mm
Flower bug: Nymphs <1.3 mm Adult 1.3 – 1.4 mm They are major predators of mango dimpling bugs
1.1.6 Preying mantids and mantispids
Preying mantids and mantispids feed on many insect pests such as grasshoppers, leafhoppers, planthoppers, fruit spotting bugs, tea mosquito bugs and moths. They also attack pollinators such as hoverflies and bush flies.
Adult 45.0 mm Old nymph Egg sack Preying mantids
Adult 6.5 mm Mantispids
1.1.7 Ants
There are a number of species of ants in mango orchards. Among them, green ants and meat ants are effective predators of a range of arthropods including the major mango insect pests.
Green ants live in leaf nests Major workers 7.2 – 8.0 mm Green ants catch a in mango trees Green ants protect fruitlets leafhopper
Meat ants nest under the ground Meat ants forage on flower Meat ants catch a
Workers 6.8 – 7.2 mm. panicles mango tip borer
1.2 Parasitoids
There are many species of parasitic wasps that parasite eggs, pupae and larvae of insect pests. They play an important role in the NT mango orchards in controlling the main insect pests such as planthoppers, mango tip borers, fruit spotting bugs, scale insects and flower caterpillars.
Parasitoids (1.1 – 1.2 mm) parasite mango planthopper egg rafts
Parasitoids (6.1 – 6.2 mm) parasite mango tip borer pupae
1.3 – 1.5 mm 1.9 – 2.0 mm 0.8 – 1.1 mm Parasitoids of fruit spotting bug eggs
Part 2. Effective control of mango insect pests by green ants
There are many species of natural enemies for mango insect pests. Among these, the green ant is the most effective both as a predator and a deterrent of a range of mango insect pests. These include the main pests such as mango leafhoppers, red-banded thrips, fruit spotting bugs, seed weevils, fruitflies, leaf rollers, mango tip borers, dimpling bugs, flower caterpillars and mango planthoppers, and minor pests such as case caterpillars, leaf beetles, grasptothus bugs, tea mosquito bugs, etc.. The following pages show the importance of each of the major insect pests and the effectiveness of control by green ants.
2.1Major insect pests
2.1.1 Green ants control the mango leafhopper
The mango leafhopper lives in ma ngo trees all year round. They cause severe damage between March and August. This pest damages mango foliar and floral buds by nymphs and adults sucking sap from flushing terminals and by adults laying eggs in tender tissues and fruitlets. Damaged buds grow slowly with curved leaves or buds. In severe cases, damaged buds stop growing and die back. Nymphs and adults suck the sap from flushing and flowering shoots, and deposit honey dew on the surface of lower flowering or leaf shoots, which promotes the growth of sooty mould, resulting in the death of flowers and leaf shoots. Therefore, it is important to control leaf hoppers during the period of pre-flowering, flowering and fruiting. Three years of field experiments demonstrated that green ants are equal to, or better than chemical insecticides in controlling the leafhopper.
Adults (4.4 – 5.0 mm) Nymphs Damage on flower buds Damage on fruitlets
Green ants catch a mango
leafhopper Trees with green ants are less damaged compared to trees protected by chemical insecticides
Leaf hopper damage in 3 treatments
0 10 20 30 40 50 Chemical insecticide Green ants only No green ants or chemicals
2.1.2 Green ants control red-banded thrips
Red-banded thrips live on mango trees all year round. They cause severe damage from March to September. This pest damages both flushing leaves and fruits. The feeding site for the thrips is the tissue next to the midrib on the undersurface of leaves. The first sign of damage is a silvering of leaves and fruit. The silvering then develops a pale-yellow to brown discolouration, speckled darkly with dried droppings. Severe infestations cause tree leaves to fall off and a reduction of flower panicles, resulting in poor yield and fruit quality. Therefore, it is very important to control this pest in the period of leaf flush, pre-flowering flush and fruiting. Field monitoring conducted over three years showed that green ants are efficient bio-control agents of red-banded thrips.
Adult (1.1 mm, Damaged area turns above) and to silver in colour nymph (below)
Damage on flushing shoots and fruitlets
Green ants catch red-banded thrips Trees with abundant green ants suffer little damage by red-banded thrips.
Thrips damage on trees with
0 20 40 60 80 Abundant green ants Fewer green ants No green ants
2.1.3 Green ants control fruit spotting bugs
The fruit spotting bug has a range of hosts. It lives on mango trees all year round. Nymphs and adults of the fruit spotting bug feed by piecing and sucking young fruits and flushing shoots, causing considerable damage, even if they are seen in small numbers in orchards. Rapid wilting and death follow an attack on young shoots. Damaged young fruits develop a dark stain at the puncture site before being shed. In the NT, there are two infestation periods: leaf flushing period (March – May) and early fruiting period ( July – August). Heavy infestation results in great reduction of yield and fruit quality. Field experiments demonstrated that green ants are more effective in controlling this pest than insecticides.
Adult Nymph Egg on Damaged flushing shoots and fruitlets (11.5 –12.5 mm) dried shoot
(1.9 mm)
Green ants catch a fruit spotting bug
Fruits on trees protected by green ants and soft chemicals are significantly less damaged than fruits protected by insecticides
Spotting bug damage in 2 treatments
0 5 10 15 20
Chemical insecticide Green ants & soft chemicals
No of fruitlets damaged
2.1.4 Green ants control the seed weevil
The seed weevil damages mango seeds. It is a major quarantine pest. Females of the mango seed weevil prefer to lay eggs on median-sized or full- sized unripened fruits. After the female makes a shallow depression on the skin, it lays an egg. It then covers the egg with exudate and cuts a crescent shaped slit just above the egg which causes a flow of sap to cover the egg laying area. Later, the sap dries to form a hard, amber-coloured, protective resin over the oviposition site. When pest populations are high, oviposition sites on the mature fruits are very obvious, and the spots of hardened sap on the skin surface are difficult to remove on the packing line, resulting in fruits being downgraded. Although seed weevils do not damage the flesh of fruits, the seed is often completely destroyed by the feeding activity of larvae, which affects nurseries wishing to grow seedlings for future grafting. The oviposition site can provide entry for saprophytic or pathogenic fungi, which can damage or abort developing fruit. In our study, we found that the use of green ants and the destruction of affected fruits in orchards are effective in controlling this pest.
Adult (7.5 – 8.1 mm) Larva and pupae Egg deposition damage on fruit skin
Green ants catch a seed weevil
Fruits from trees protected by green ants and soft chemicals are significantly less damaged than fruits from trees
protected by insecticides
Seed weevil damage in 3 treatments
0 2 4 6 8 Chemical insecticide
Green ants & soft chemicals
No green ants or chemicals
2.1.5 Green ants control fruit fly
In the NT, there are two species of fruit flies that damage mangos: Bactrocera jarvisi and B. aquilonis. Both species have a range of hosts. They are major quarantine pests of mangos. In general, fruit flies only attack fruit approaching maturity. Larvae or maggots of fruit flies burrow into mango fruit tissue, causing fruit spoilage. This activity introduces bacteria that hastens the spoiling process and leads to fruit rotting and to complete breakdown of the whole fruit. Fruit flies have little effect on mango yield, but they have great influence on fruit quality, which is the major concern of growers. Our study show that fruitfly control can be successfully achieved by using green ants, harvesting fruits when they are green-mature and applying fruit fly
baits or fruit fly pheromone traps.
Adult (6.2 – 6.9 Symptom of egg Eggs (0.8 – 1.0 mm) deposition mm) under the skin
Larva
Green ants repel fruit Green ants fly from fruits catch a fruit fly adult
Fruits in plots protected by green ants and soft chemicals are significantly less damaged than fruits protected by insecticides
Fruit fly damage in 3 treatments
0 2 4 6 8 10 Chemical insecticide
Green ants & soft chemicals
No green ants or chemicals
2.1.6 Green ants control the mango leafroller
The mango leafroller lives on mango trees all year round with many generations. Larvae of the mango leafroller mainly damage growing tips and young leaves, usually feeding from within the confine of a scroll of a leaf that the larvae web together. First instar larvae do not necessarily form a leaf scroll, but feed along the leaf margin. Leaf rollers have the ability to damage a whole tree under conditions of high density, and so it is an important pest during the period of mango leaf flushing (December – June). Data collected from three years of field experiments show that green ants are
effective in controlling the leafroller.
Nymph Adult (7.6 – 8.2 mm) Damaged leaf shoot
Green ants catch a leaf roller
Trees protected by green ants are less damaged by the leaf roller than trees protected by insecticides
Leafroller damage in 3 treatments
0 10 20 30 40 Chemical insecticide
Green ants No green ants
or chemicals
2.1.7 Green ants control the mango tip borer
The mango tip borer lives on mango trees all year round with over 10 generations per year. Larvae feed predominantly at night with activity commencing late afternoon and continuing through to early morning, and they prefer the tender leaves of new flush. Early instar larvae confine their feeding to the leaf margins, causing a window effect. As larvae grow, they take a large proportion of leaf, often leaving only the midribs. In severe cases, larvae remove all the leaves from the tree, and they also feed on fruitlets.
Green ants are an efficient bio-control agent of this pest.
Larvae Adult (12.0 – 14.0 mm)
Damage on leaf shoots and fruitlets
Green ants catch a mango
tip borer Trees with green ants are significantly less damaged compared to trees witho ut the ants Mango tip borer damage in 2 treatments
0 2 4 6 8 10 12 14 16
Green ants No green ants
2.1.8 Green ants control the dimpling bug
The dimpling bug is now a common pest in all mango orchards in the NT. Its recognition as a serious pest came to the attention of growers in 2002 following a significant noticeable damage to fruitlets. The bugs suck sap from the ovary of flowers with their needle-like proboscis. As the ovary grows, each puncture leaves a black spot on the skin of tiny fruitlets (3 – 5 mm). If a fruitlet has many puncture wounds, it falls. If a fruitlet has a few, it is able to grow to maturity, and the black spots gradually fade and finally disappear. The dimpling bug only damages mango flowers between late July and early August. To control this pest, green ants plus
soft chemicals are better than chemical insecticides.
Young larva Old larvae Adult (1.5 – 1.8 mm)
Damage symptoms (black spots) on fruitlets
Fruitlets are much less damaged in plots with green ants plus soft chemicals than in plots with insecticide spray
Dimpling bug damage in 3 treatments
0 10 20 30 40 50 60 Chemical insecticide
Green ants & soft chemicals
No green ants or chemicals
2.1.9 Green ants control flower caterpillars
There are at leat eight species of caterpillars that damage both flowers and developing fruits in mango orchards. The larvae often web clusters of flowers together when they feed, forming matted silk and debris, in which the larvae often pupate. This feeding activity causes a huge reduction of yield and fruit quality. Therefore, it is essential to control this group of pests during the period of mango flowering and fruiting (July – September). Our field experiments suggested that green ants together with soft chemicals are better than insecticide spray to control flower caterpillars.
Flower caterpillar damage in 3 treatments
0 2 4 6 8 10 12 14 16 Chemical insecticide
Green ants & soft chemicals
No green ants or chemicals
2.1.10 Green ants manage mango planthoppers
There are several species of mango planthoppers. They live on mango trees all year round. Adults lay oval-shaped egg rafts on the surface of leaves or fruits. Adults and nymphs prefer to stay and feed on the fruit peduncles at the bottom level of the tree canopy, and their secretion drops on the base of fruits, which promotes the growth of sooty mould. This indirect damage has a great effect on fruit quality. Our study shows that while green ants have a mutual relationship with the planthopper, they do not affect parasitoids of planthopper egg rafts. This results in higher levels of parasitism in plots using green ants and soft chemicals than in plots using insecticide spray, leading to low numbers of planthoppers in plots with green ants and soft chemicals. These small numbers of the pest secrete limited honeydew on the base of fruit, which is continuously taken away by green ants, leaving fruits free from sooty mould. We also find that thinning the tree canopy and pruning at the bottom
level help reduce planthopper populations.
7.0 – 8.0 mm 5.0 – 5.5 mm 5.2 – 5.5 mm
A parasitoid lays eggs in a planhopper egg raft A planthopper egg raft is parasitised
No. of mango planthopper adults in 2 treatments 0 0.2 0.4 0.6 0.8 1
Chemical insecticide Green ants & soft chemicals
No. of adults/tree
Parasitic level of mango planthopper egg rafts in 2 treatments
0 20 40 60 80 100 120
Chemical insecticide Green ants & soft chemicals
2.2Minor insect pests
2.2.1 Green ants control minor insect pests
There are many other minor insect pests in mango orchards such as case caterpillars, leaf beetles, grasptothus bugs, tea mosquito bugs, etc.. These pests can be
successfully controlled by green ants.
Case caterpillars damage fruits and leaves Green ants chase a case caterpillar
Part 3. Problems related to using green ants in mango orchards and
their solutions
Although green ants are very effective in controlling a range of mango insect pests, they have been regarded as a pest by many mango growers. This is because of:
(1) the mutual relationship between the ants and scales and mealybugs; (2) black spots on fruits caused by the ant formic acid; and
(3) disturbance to people while picking fruits.
Through our extensive research, we have found satisfactory solutions for each of the problems.
3.1 Problems of using green ants
3.1.1 Green ants protect scales and mealybugs
Our field experiments show that the number of scales and mealybugs is higher in plots with green ants than plots protected by insecticides. Normally, flat scales and fluted scales do not cause significant damage on fruits. However, in large numbers, mealybug damage on fruits can be as high as 30%, and on average the damage on fruits is 6%.
The ants protect mango flat scales on fruit stalk
The ants protect flat scales on fruit
The ants protect fluted scales
The ants protect mealybugs on flower stems and fruits
Fruit damage level is 6% higher in trees with green ants than in trees with insecticide spray
Mealybug damage in 2 treatments
0 2 4 6 8 10 12 14
Green ants Chemicla insecticide
3.1.2 Fruits damaged by green ant formic acid
Green ant formic acid causes black marks on fruit skin, and on average, 5% of fruit are damaged in this way based on our three years of experimental data.
Black spots caused by ant formic acid Enlargement of black spots
Trees with green ants have an average of 5% of fruits damaged by ant formic acid
3.1.3 Aggressiveness of green ants
Green ants are well known for their aggressive behaviour, which annoys people during fruit harvest.
F r u i t s d a m a g e d b y f o r m i c a c i d o f g r e e n a n t s 0 5 1 0 1 5 2 0 I n s e c t i c i d e s G r e e n a n t s N o g r e e n a n t s
3.2 Solutions to the problems caused by green ants
We have successfully developed the following methods to solve these three problems.
3.2.1 Use of soft chemicals
Scale insects or mealybugs are significantly reduced by spraying one of several
environmentally friendly soft chemicals that do not disrupt green ants. White oil (2%), D.C.Tron oil (1%) or Neem oil (0.1%) reduces flat scale numbers by up to 90%. Potassium soap (1.5%), white oil (2%) or Applaud® (0.03%) reduces mealybugs numbers by 40%, 40% and 70% respectively. In organic orchards, the use of
Potassium soap and white oil is approved, while the use of Neem oil and D.C.Tron oil is restricted.
Our field experiments show that the use of green ants plus soft chemicals can greatly reduce mealybug damage on fruits (from 6% to 3%).
Control efficiency of soft chemicals on mealybugs 0 20 40 60 80 100
Potassium soap White oil Applaud
% corrected mortality
Control efficiency of soft chemicals on mango flat scales
0 20 40 60 80 100 120
White oil D.C. Tron oil Neem oil
% corrected mortality
Mealybug damage in 3 treatments
0
2
4
6
8
10
12
14
Green ants only
Green ants +
soft chemicals
Chemicla
insecticide
3.2.2 Isolation of green ant colonies
Field trials demonstrate that green ant marks on fruit skin were mainly due to green ant fights between different colonies. Separation of the ant colonies can
substantially reduce fruit damage from 5% to 2.5%.
Green ants fight between colonies Separation of ant colonies greatly reduces fruit damage by ant formic acid
3.2.3 Water spray
Ant aggressiveness is greatly reduced by spraying water on trees prior to harvest. Our observations suggest that green ants either go back to their nests or stay on the
underside of twigs and leaves when it is raining. In a field experiment, the activity of green ants was reduced by 88% for the first 20 minutes after spraying water onto trees at a rate of 2000 L/ha and by 61% after a further 30 minutes. Mango fruits and tree leaves dried within 20 minutes, thus the added water was unlikely to cause fruit lenticels or post- harvest diseases.
A water spray reduces green ant activity
Effect of colony isolation on fruits with ant marks
0 5 10 15 20
Seperation of colonies No seperation of colonies
% damaged fruits / tree
0 20 40 60 80 100
5 min 20 min 30 min 40 min 50 min 60 min
Part 4. Results from field experiments using the IPM program
In part 3, solutions were identified for the three problems related to the use of green ants. Field experiments were conducted over three years (2001 – 2003) in both conventional and organic orchards using green ants together with soft chemicals and farming strategies (IPM). Each year, mango yields were measured by counting total numbers of fruits per tree. The first class fruit was used as a fruit quality
measurement. For each harvest, every green mature fruit was picked from a tree and sorted on site according to the Mango Quality Standards for the Mango Growers of Australia.
Management expenses for different treatments were recorded. In insecticide plots, the expenses included the insecticides, labour, machinery costs and fuel. In IPM plots, the expenses included labour for transplanting and managing green ant colonies, soft chemicals, machinery costs and fuel. Income per tree was calculated as: the number of first class fruit produced per tree / 17 fruits (average number of fruits per box) x A$15.77 (average price per box). The net profit = income per tree – management expenses per tree.
IPM plot
Overview of fruits in IPM plots Reject 2nd
class 1st class Insecticide plot
This is a conventional orchard. Two treatments were used: plots protected by insecticides and plots protected by IPM program. Compared to the profit in
insecticide plots, IPM plots created A$6.12 /tree/year more net profit, which is a 73% increase in profit.
IPM plots create
73% higher profit than Insecticide plots
4.2Dallas’s orchard
No chemical insecticides have been used in this orchard for many years. Three treatments were used: trees protected by the IPM program, trees protected by green ants only and trees without green ants or soft chemicals (control). Compared to the profit in the control plot, the IPM plot and green ant plot produced 152% and 110% more profit respectively. Compared to the profit in the green ant plot, the IPM plot produced 20% more profit.
IPM plot had 152% increase in profit, and green ant plot had 110% increase in profit
compared to the control plot 0 10 20 30 40 50 60 70
IPM plot Green ant plot Control plot
Profits /tree/year (A$)
0 4 8 12 16 20
Insecticide plot IPM plot
4.3Malcolm’s orchard
This is an organic orchard, and two treatments were used: trees with green ants and trees without green ants. Compared to trees without green ants, trees with green ants produced 41% more in profit per year.
Trees with green ants created 41% higher profit than trees without green ants
4.4Liz’s orchard
No chemical insecticides have been used in this orchard since 1997. Two treatments were used: trees with green ants and trees without green ants. Trees with green ants produced 46% more profit than trees without green ants.
Trees with green ants
had $6 dollars more
profit compared to trees without green ants, which is 46% increase in profit
In conclusion, the IPM programs are profitable for both conventional and organic mango orchards, resulting in a 70% increase in profit in the conventional orchard and a 40% increase in profit in organic orchards.
0 5 10 15 20 25 30 35
Trees with green ants Trees without green ants
Profits /tree/year (A$)
0 2 4 6 8 10 12 14 16 18 20
Trees with green ants Trees without green ants
Part 5. Suggested IPM programs in mango orchards
According to the results from three years of field experiments, we recommend the following IPM programs for both conventional and organic mango growers.
5.1 Two IPM programs for mango growers in northern Australia.
Month
Dec. - Apr.
May - Aug.
Aug. - Nov.
Tree phenology
Leaf flush or dormancy
Pre-flowering flush, flowering & fruit setting
Fruiting & harvesting
Main insect pests Leaf hopper, Leaf roller, Mango tip borer, Leaf beetle, Red-banded thrips
Leaf hopper, Red-banded thrips, Fruit spotting bug, Mango tip borer, Leaf beetle Dimpling bug, Flower caterpillars Flower caterpillars, Seed weevil, Fruit fly, Mealybugs, Red-banded thrips Management strategy
For organic
growers
1. Use green ant colonies and 2. Use Mixed-cropping (eg. Mango + citrus) or 3. In monoculture, provide 5% sugar solution and cat food in 2 - 4 locations for each colony when trees in dormancy.
Use green ant colonies only.
1. Use green ant colonies,
2. Spray with
Potassium soap (1%) or White oil (2%) 2 - 3 times when >5% fruits have > 10 mealybugs,
3. Use fruit fly pheromone traps in late fruiting stage, 4 traps/ha, and
4. Pick fruits when they are green mature,
5. Spray water 2000L/ha on trees prior to harvest. Management strategy
For
conventional
growers
1. Use green ant colonies and
2. Provide 5% sugar solution and cat food in 2 - 4 locations for each colony when trees in dormancy.
Use green ant colonies only.
1. Use green ant colonies,
2. Spray with Applaud (0.03%) 2 times when >5% fruits have > 10 mealybugs,
3. Spray fruit fly bait (once a week for 4 weeks before harvest) on a 30 x 30 cm board for every 5 trees,
4. Pick fruits when they are green mature,
5. Spray water 2000L/ha on trees prior to harvest.
Part 6. Management of green ant colonies in mango orchards
The most important issue of these IPM programs is to keep green ant populations at a high level all year round. This can be achieved by following 5 steps: (1) identify what ants are in the orchard, (2) determine green ant colonies and bait other ants, (3) separate and manage existing green ant colonies, (4) transplant new colonies if needed, and (5) manage ant colonies for the longer term. Instructions for these steps are on the following pages.
6.1 Determine what ants you have on each tree in your orchard
You will probably find it helpful to make a map or diagram of your orchard, showing (and numbering) each tree (see example 1, page 48). You need to inspect each of the trees in your orchard and record the dominant species of ant on the tree. You can do
this quickly by slightly tapping the tree trunk with a stick, and then look to see what ants are moving around on the branches and twigs you can easily observe.
6.2 Determine green ant colonies and bait other ant species
Under natural conditions, green ant populations are not distributed evenly across trees. They often fluctuate over the year in mango orchards. This is because ? Some species of ants compete with green ants in the field, and
? Green ants are strongly territorial between colonies, and wars often start immediately after two colonies meet each other.
For the former, it is advisable to use ant baits to control other competitive ant species, and for the latter, green ant colonies need to be determined.
6.2.1 Baiting of other ant species
There are three main species of ants that compete with green ants in the Northern Territory, and their populations can be greatly reduced using the ant baits listed in the following table.
Ant species Ant bait
Big headed ant or Ginger ant AMDRO (1 – 2 g/tree)
Black ants 10% sugar solution with borax or cat
food mixed with AMDRO
AMDRO is a slow-acting poison which is easily effective against the queen ant.
Big headed ants take Amdro granules to their nest
Worker ants will find the bait granules and carry them back to the nest and pass them along to the queen and other nestmates. For each tree, 1 – 2 grams of AMDRO granules (depending on the abundance of ants) are evenly sprinkled at the base of the tree in late afternoon when ants are active. Do not irrigate the treated trees within 24 hours or do not apply AMDRO if rain is likely within 24 hours of application. Meat ants are often seen in mango orchards, especially young orchards. These ants prey on a range of mango insect pests. They sometimes compete with green ants in young orchards, but hardly ever in mature orchards. Therefore, meat ants should be protected.
6.2.2 Determination of green ant colonies
Green ants fiercely fight between colonies, but within a colony they are friendly to each other, and they collectively forage, communicate between the nests and trees and defend the colony. There are two methods you can use to determine whether green ants living in different trees belong to the same colony.
? Method 1. Testing ants between trees,
Pick a small nest from one tree and place If resident ants fight the introduced it on an adjacent tree ants, they belong to different colonies
(return the small nest to original tree) ? Method 2. Following ant trails on tree branches or on the ground until no-ant-
area is found.
An ant trail on a branch An ant trail on the orchard floor between trees
When existing colonies of green ants are identified, florescent tapes or paint can be used to mark the colony boundary. Having completed this step, the orchard map should be modified as in example 2 (page 48).
6.3 Management of existing green ant colonies
There are two procedures you need to follow when you have identified existing green ant colony boundaries.
6.3.1 Separation of the ant boundaries
If two colonies are connected to each other by interlocking tree branches, they must be separated by removing the interlocking branches. A gap of at least one meter between the colonies is suggested.
Trees marked with different colour tape belong to different colonies, and they should be separated by removing interlocking branches.
6.3.2 Connecting trees within the same colony
Within the same colony, a few of the trees are often not attached to the other trees, and the ants are forced to walk on the ground in order to communicate with each other. An artificial bridge (twisted polystrings of more than 3 mm in diameter) should
The two trees marked with same colour of tapes belong to the same colony and they are linked with a polystring.
be strung to facilitate ant communication, and reduce disturbance to the ants due to orchard management such as weeding and irrigation. Make it easy for ants to travel between trees within the colony because they are working for you when they are in
An individual tree without green ants should be linked by a polystring to a strong colony nearby, eg. Trees 1 and 3 are linked to colony 1 and trees 2 and 4 to colony 2 in example 3 (page 49).
6.3.3 Grouping of trees without ants
Those trees without ants should be linked with polystrings if they are not attached to each other by side branches (about 10 - 15 trees in a group). Now this group of trees is ready to receive a new green ant colony (group 1, example 3).
6.4 Transplantation of new green ant colonies
There are seven steps you need to follow to transplant new green ant colonies. They are described in detail below.
6.4.1 Permit for picking green ant colonies
Ideally, you may have green ant colonies on other parts of your property. Ask your neighbours if they have green ants you can take. If you want to collect green ant colonies in public places or parks in the Northern Territory, you need a permit from the Parks and Wildlife Commission of the Northern Territory. The detailed contact is Permits and Licences, Golder Suilding, Chung Wah Terrace, Palmerston, PO Box 496, Palmerston NT 0831; Telephone: 08 89994795; Fax: 08 89994524.
6.4.2 Identification of the ant colonies
Methods to identify ant colonies in other areas of your property or elsewhere have been described above (see 6.2.2 for detail).
6.4.3 The best time to transfer ant colonies
The best time of the day to transfer ant colonies is between 10:00 to 15:00 hrs
because during this period, the ants are least active and most of them stay in their nests. The best time of a year to transfer ant colonies is between March and May
(late in the wet season and the beginning of the dry season).
6.4.4 Collecting equipment
To collect green ant colonies, you need a ve hicle with cover, ant protective clothing, picking poles, a step ladder, buckets, large plastic bags, rubber bands and fluorescent
tape. Each bucket is put into a plastic bag to hold ant nests and to reduce mechanical mortality by handing and transportation.
Protective clothing, picking pole, buckets with bags A step ladder
6.4.5 Identification of the tree with the queen ant nest
An established green ant colony often has several dozen or more than 100 leaf nests, which are spread over several or many trees. It is important to note that only one nest contains queens (in the NT, the queen ant nest usually contains multiple queens). Queens are essential to maintain colonies, and colonies without queens will die in about 6 months. Thus, it is essential to determine the tree with the queen ant nest (see the colony below).
Normally, in a green ant colony, the tree with the queen ant nest has the greatest number of ant trails connecting to other trees, and it has more nests than the other
Tree with the queen ant nest.
Each circle refers to a tree and the size of circle refers to tree size varied from 2 – 7 m height.
The number next to each circle refers to the number of ant nests in that tree.
3
3 5
18 21 4
6.4.6 Collecting ant nests
It is important to collect every nest in the queen ant tree. Each bucket can be filled with 2 - 6 nests depending on the size of the bucket and ant nests. Bags containing the same colony of the ants must be marked clearly on the bags when they are
transported.
Bags containing the same colony are marked with the same number, and they should be placed in the shade before transportation (Remember! the temperature inside the bags should not be > 35o C)
6.4.7 Releasing ant colonies
The final step is to release the ants. It is important to make sure that each group of trees only receives ants from a single colony. Each tree in a group receives 5 - 10 nests depending on the size of trees and the size of ant nests. When releasing, each bag is hung on a tree branch, and then opened. Worker ants will immediately walk out to look for suitable leaves to build their new nests before they start to move brood from the old nests in the bag to the new nests. To reduce the mortality of larvae, pupae and eggs caused by desiccation, it is essential to keep ant nests inside the plastic bags, and the bags should be hung in the shade of trees for at least three days. As soon as you put green ant colonies in place, you need to provide some food such as 5% sugar solution and cat food (see below) to promote their settlement. Try to avoid disturbing the ants (by pruning or weeding nearby) while the ants settle into their new environment.
Each group of trees receives only one colony, and bags are hung in the shade of trees
6.5 Monitoring and maintenance
At this point, every tree in the orchard should have green ants as in example 4 (page 49). The next procedure is to keep the ants happy on the trees.
6.5.1 Frequency of monitoring and the monitoring method
A program of monitoring must be set up to monitor the changes in ant populations in each colony. Suggested frequency for such monitoring is once every month. During each monitoring session, you need to inspect every tree in a colony. The re-growth of the trees along the ant boundary should be continuously checked, and pruned. Ant bridges within colonies should be fixed as soon as possible if they are broken. You can assess the ant abundance by either counting the number of ant nests in the tree canopy or by counting the number of ant trails on the main branches of the tree. We found that counting ant trails is more reliable and quicker than counting the number of nests. To do this, you need to slightly tap on the base of the tree with a stick, and then count ant trails on the major branches of the tree.
6.5.2 Judgement of strong or weak colonies
If trees in an ant colony have an average of more than two ant trails per tre e (about 4 – 5 m high), the colony is strong. If trees in the colony have an average of one or less than one ant trail per tree or if the ants have disappeared on some of the trees in the colony, the colony is weak. Through consistent monitoring, the causes responsible for the ant population changes can be determined.
? dispersal;
? competition with other ant species; and ? inadequate management.
6.5.3.1 Natural death
The average age of green ant colonies is about 7 years. Because the age of green ant colonies is difficult to determine at the time they are separated or introduced into the orchards, some colonies will die earlier than the others. Therefore, replacement of weak colonies is essential.
6.5.3.2 Big rainfall
During the wet season, in addition to cyclones which are disastrous to green ants, rainfall of > 60 mm per event is responsible for the reduction of ant populations because big rains break the ant nests that are built around the tree canopy, where they are exposed to rain. A large proportion of the brood in the nests can be mechanically destroyed by heavy rainfall. You do not need to do anything if the ant populations gradually recover in a short period of 3 – 4 weeks. This is because the queen or queens in the colony survived the heavy rainfall events. However, if the ant populations continue declining after the fifth week, which means that the queen or queens were killed, the colony will die in a few months (3 – 6 months). In this case,
the replacement of the weak colonies is necessary.
6.5.3.3 Dispersal
When mango trees are dormant during the period of December – April, the trees are not attractive to a range of insects. At this time, the trees cannot provide green ants with sufficient food, and so, the ants often walk down to the orchard floor to forage. When food becomes increasingly scarce, ants start to walk long distances to forage on other mango trees that may already be occupied by another colony. As a result, boundary fights occur. If this happens, ground trails of the ant should immediately be cut by a heavy spray of water, and at the same time, a food station containing a
5% sugar solution and some cat food should be provided in the tree as ant food to
bring the ants back.
Ants feed on sugar solution
Three to four feeding stations are enough for each colony, and after a short period (2 – 3 weeks), feeding should be stopped and the stations should be collected from the orchard and put away, otherwise the ants will get lazy! During this time of year, grass and other broad- leaved weed species in mango orchards can be very useful to the ants as foraging areas, and should be protected.
Mixed-cropping between mango and other fruit trees is good to maintain high stable ant populations. This is because the ants can switch to other trees when mango are dormant. It is important that the trees selected should have different phenology from mangos, eg. mangos mixed with grapefruits. Native trees such as black wattle are also useful, but they must be managed the same as mango trees.
6.5.3.4 Competition with other ant species
Competition between green ants and other species of ants such as big- headed ants, ginger ants or small black ants, is often seen in mango orchards. If this happens, you must reduce competitive ant populations using the ant baits (see the section 6.2.1. for detail).
6.5.3.5 Inadequate management
Toxic insecticide spray and heavy pruning must be avoided. A decrease in the
green ant populations in your orchards may be due to toxic insecticide spray or heavy pruning. Green ants are very susceptible to a range of toxic insecticides such as Dimethoate, Lepidex, Carbaryl and Maldison etc.. Remember! when you use the ants, you do not need these toxic insecticides anyway. Apart from this, you also need to watch out for the drifting of the insecticides used by neighbouring orchards. Green ants live in leaf nests in tree canopy, and so, they need suitable tree canopy. normal pruning activity such as cutting twigs, thinning canopy by removing some unwanted small branches, has no effect on green ant colonies. However, heavy pruning to the main branches will reduce the ant nesting sites, and gradually disrupt them. This often results in great reduction of the ant populations and increase risk of ant fights between colonies.
7.1 Planting pattern with regard to the use of the IPM program
For those who plan new mango orchards in collaboration with the use of the IPM programs, mixed-cropping between mangos and another fruit tree species is highly recommended. It is important to select trees with different phenology from mangos. This is because in this cropping system, the green ant populations will be maintained high and stable throughout the year due to the alternative food supply. Two kinds of fruit trees can be considered for this purpose: grapefruit (Citrus spp) and soursop (Annona spp). Green ants can live on these tree species throughout the year. These trees have different flushing periods from mangos. To accommodate average size of green ant colonies, our recommendation is to plant 14 mangos with two trees of Citrus or soursop (see below), and we suggest that growers should manage these trees the same way as mango trees.
When mango trees are over 2 meters high (about 2 - 3 years old), they are ready to receive green ant colonies. The procedure of transplanting green ant colonies is the same as that described in the section 6.4.
Note:
‘o’ refers to a mango tree;
‘x’ refers to a grapefruit or soursop tree.
O O X O O O O O O O X O O O O O
O O O O O X O O O O O O O X O O
Example 1 (Step 1)
Trees with green ants (Oecophylla smaragdina) Trees with black ants (Iridomyrmex sp.)
Trees with big headed ants (Pheidole megacephala) Trees with meat ants (Iridomyrmexsanguineus) Trees with ginger ants (Solenopsis geminata)
Example 2 (Step 2)
Example 3 (Step 3)
Other ant species on the tree were removed by ant baits. _____ Green ant trail on a branch
--- Green ant trail on the gound
1
Colony 1
2
Colony 2
3
4
Group 1
Example 4 (Step 4)
* Individual trees which are linked to the nearest colony are soon colonised by the colony.
* Each group of trees only receives ants from a single colony. * A gap of at least one meter between the colonies should be l eft.
Colony 1 Colony 2
Mango orchards
With existing green ants Without green ants
Trees with green ants Put 10-15 trees in a group, and link the trees with polystrings if not attached
Identify ant colonies Identify green ant Transfer whole or part by following ant trails colonies in the colonies with queen ants. or testing nests. bush. The best The best time is
time to do this is 10:00 – 15:00.
Isolate the ant 15:00 – 20:00. Make sure each group colonies receives only one colony.
Monitor and separate ant
colonies once a month Trees with weak colonies
Natural death Big rainfall Dispersal Competition or inadequate (walk away) with other management ant species
Non-recovery Recovery
Trees with strong Replaced with Provision of Control colonies new colonies food (sugar + competitive
cat food) with ant baits
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