SUBTROP

DU TOIT ET AL. (1993) reported

that the avocado bug causes le-

sions under the skin of avocado fruit,

making it unsuitable for export. These

lesions are called “Vosknoppe” and

have a bumpy appearance (Fig. 1).

The pimple-like lesions do not have

any scarred tissue below the skin but

do make fruit unsightly. Bruising of the

pimples might lead to early fruit decay

during transit or ripening. The bump-

like lesions do have scarred tissue below

the epidermis, suggesting that the Tay-

loryligus spp. injects a more powerful

enzyme into the fruit than the insects

causing the pimple-like lesions (Alberts,

2011).

Investigations have shown that many

minute sucking bugs belonging to the

sub-orders Sternorrhyncha and Auche-

norrhyncha, as well as from the group

Heteroptera, are captured on avocado

trees during the flowering and fruit set

periods (Alberts, 2004).

Avocado flowering in the South

African avocado growing regions oc-

cur in the May to September period.

Figure 1. ‘Vosknoppe’ – lesions under

the skin of avocado fruit caused by the

avocado bug.

Most of the larger insect sucking bugs

(Pentatomidae and Coreidae) hibernate

during the colder winter period. The

minute avocado sucking bug complex

(Miridae) is very active during this colder

period (Alberts, 2011).

Life cycleTwo field generations are present

during blossom and early fruit devel-

opment. The early flowering cultivars,

such as ‘Fuerte’ and ‘Pinkerton’, lure

the adults of the first generation. Their

eggs are inserted as single eggs be-

neath the epidermis of new leaves and

flowers in slits made by the female’s

ovipositor (Stones, 2014).

After five days the eggs hatch and

the immature wingless nymph stages

(5) lasts ± 28,6 days. These new winged

adults colonise the later flowering

cultivars, ‘Hass’, ‘Ryan’ and ‘Edranol’.

This is then the second field generation.

The duration of the life cycle is about

33 days and an adult avocado bug lives

± 45,2 days (Stones, 2014).

Damage caused by the avocado bugAccording to Alberts (2011), losses

of up to 60% have been reported by

various pack houses and farmers in the

past. In most years, however, the losses

are less than 5%. Forecast models to

pre-warn farmers in advance are there-

fore very important.

Damage on the early cultivars is

usually lower than on later flowering

cultivars, except if there is a prolonged

flower on the early cultivars. The five

wingless nymph stages cause fruit le-

sions, malformed fruit and fruit drop.

They are forced to feed on the newly

set fruit, as they do not have wings

to fly to other avocado flowers in the

orchard. They reach maturity 5 – 6

weeks after fruit set before they can fly

away to re-infest other flowers. ‘Hass’

damaged fruit tends not to drop off like

‘Fuerte’ and ‘Pinkerton’ fruit (Stones,

2014).

Scout thresholdsOn year: > 13 avocado bugs / block

Off year: > 7 avocado bugs / block

10% flower infestation = 3% fruit

damage per tree

20% flower infestation = 5% fruit

damage per tree.

ControlControl measures must take place

before petal fall, therefore, when 80%

– 100% flowering on cooler side of

tree is finished. Therefore, scouting is

of utmost importance, as timing of the

chemical spray is crucial to the success

of control. The following procedures

must be followed:

• Scout very early in the morning

(06:00)

• Scout 10 trees/block and 10 flower-

ing panicles/tree

• Scout the cool side of the tree at

80% – 100% flower

• When the avocado fruit is > 30 mm,

there is no risk for damage in the

orchard

• Fruit damage on fruit smaller than

5 mm will drop.

Chemical treatments: Three pesticides:

Acephate (trade name Ace 750 SP),

Beta-cyfluthrin (trade name Bulldock

Beta 125 SC), and Pymetrozine (trade

names Chess, and Trivia 500 WDG).

There is resistance in the EU mar-

ket to Acephate, as the chemical is

metabolised by insects into Methami-

dophos (classified by the World Health

Organisation as Toxicity Class 1b, Highly

hazardous) and is a hard chemical i.e.

also kills predatory insects.

Beta-cyfluthrin should only be

sprayed during flowering and up to

fruit set and is not intended to be

sprayed on fruit.

ConclusionAs part of control, allow weed growth

in the orchard. The additional flowers

Figure 2. Life cycle of the avocado bug (Tayloryligus sp., Family Miridae).

Nymph stage Nymph stage with wings Adult stage

Figure 3a. The first two nymph instars

are green. Adults and nymphs feed on

flowers, young fruit and young leaves.

Figure 3b. Damage to avocado fruit is

caused within the first few weeks after

fruit set. This leads to the development

of protrusions on larger fruit which are

only visible a month after feeding.

Figure 3c. The protrusions are known

as “Vosknoppe” and can be very severe

especially on ‘Hass’ fruit of old orchards.

This may lead to culling of 30% or more.

in the orchard will also lure the adult

avocado bugs to feed on, rather than

the avocado flowers. Flower infesta-

tions of ± 10% will result in 3% fruit

damage and 20% will result in 5% fruit

damage.

It is important to keep record of

the number of avocado bugs in the

orchard, even when they do not exceed

the threshold number. In this way you

will build up a history of that orchard

and when the crucial time will be, with

regards to spraying.

Remember, it is the nymph stages of

the avocado bug that cause damage,

not the adult avocado bug.

REFERENCES

ALBERTS, A.J. 2004. First report on the

identification of possible causes of

pimple-like skin protuberances on

avocado fruit in the Soutpansberg

area. South African Avocado Grow-

ers’ Association Yearbook 27: 21-31.

ALBERTS, A.J. 2011, Avocado fruit

sucking bugs - Development of a

forecasting model for an areawide

monitoring system. South African

Avocado Growers’ Association Year-

book 34: 42-46.

DU TOIT, W.J., STEYN, W.P. & DE BEER,

M.S. 1993. Occurrence of protrusions

on avocado fruit and the causative

agent. South African Avocado Grow-

ers’ Association Yearbook 16: 100-102.

STONES, W. 2014. The Avocado Bug.

Factsheet. https://www.avocado.

co.za/wp-content/uploads/2018/09/

Avocado-bug-factsheet-2014.pdf.

Accessed 05/08/2019.