How to detect it

PREVENTION

How can we detect it?

SYMPTOMS AND DETECTION

How can we prevent the spread of HLB?

The appropriate time to look for symptoms of the presence of the vectors transmitting HLB is when there is budbreak, which covers almost the whole year (from the end of February to the beginning of May there is spring budbreak, between July and August, summer budbreak, and from September to the end of November the third budbreak or autumn budbreak).

Visual inspection would consist of selecting young shoots, looking for the presence of symptoms or the vectors themselves. The main symptoms of both psyllids are described below.

DETECTION OF

Trioza erytreae

NIMPHS

When feeding on the leaves, the nymphs inject toxic substances which induce the formation of concave bumps on the underside of the leaf, inside which they nest individually. These nests correspond to bumps or protuberances on the upper side of the leaves.

leaves

When populations are high, the leaf and shoot may look totally deformed.

HONEYDEW

Both nymphs and adults excrete honeydew which crystallises and settles on the lower leaves, encouraging the development of black mould.

DETECTION OF

Diaphorina citri

NIMPHS

Nymphs do not protect themselves by forming gills and are mobile in all stages.

leaves

Adults and nymphs twist young leaves and shoots and excrete copious amounts of honeydew that takes on a characteristic coiled filament shape.

HONEYDEW

Presence of whitish waxy excretions generated by both nymphs and adults.

COMMON FEATURES FOR DETECTION OF THE

HLB disease

fruits

The exterior of the fruit has a deformed structure that isn’t even similar to its natural shape. They are small in size and the skin is thicker. Furthermore, the colouring is neither natural nor homogeneous.

Inside, the fruit has black, aborted seeds and the stalk (the central white part) is orange in colour. In addition, there is less juice content and it is more acidic and bitter.

tree

When a tree is affected by the HLB disease, it starts to have a yellowish colouration as shown in this picture of a Florida crop field (right on the second tree). The root system of the trees is also heavily affected by Asian HLB infections although it is not visible to the naked eye. When the tree is infected, it produces much fewer secondary roots and thus has a lot of difficulties to take up nutrients from the soil.

Over time, the tree loses nutrients and loses both leaves and fruit, which fall to the ground, lowering productivity. In as little as one year, this disease can affect an entire field and eradicate it, as happened in Florida. One way of detecting HLB in roots is root sampling. Because roots are the only organ of the tree where there is a more or less regular distribution of the bacterium, they can be tested by PCR and, if infected, almost all of them will be positive.

DETECTION OF

Trioza erytreae

NIMPHS

leaves

When populations are high, the leaf and shoot may look totally deformed.

HONEYDEW

Both nymphs and adults excrete honeydew which crystallises and settles on the lower leaves, encouraging the development of black mould.

DETECTION OF

Diaphorina citri

NIMPHS

Nymphs do not protect themselves by forming gills and are mobile in all stages.

leaves

Adults and nymphs twist young leaves and shoots and excrete copious amounts of honeydew that takes on a characteristic coiled filament shape.

HONEYDEW

Presence of whitish waxy excretions generated by both nymphs and adults.

COMMON FEATURES FOR DETECTION OF THE

HLB disease

fruits

Inside, the fruit has black, aborted seeds and the stalk (the central white

TREE

Gallery of images of

HLB symptoms

Yellowed branches

Yellowed trees

Yellowed branches

Orange colored pendulum and aborted seeds of the fruit

Aborted seeds of the fruit

Asymmetric fruit growth

Inverted coloration of the fruit

Fruit deformation

Asymmetric mottling of leaves

Leaf vein thickening

PSYLLA

How to detect its presence?

Adhesive traps

These are yellow plastic cards with adhesive on both sides. Yellow traps are recommended over other colours. It is recommended to place them in the sprouting area of the tree, approximately 1.5 metres away.

Samples by hitting the branches

It consists of hitting a randomly selected branch three times with a PVC tube. Psyllid adults are counted as they fall onto a slat with a white sheet or a white tray placed horizontally under the branch.