Normally in Gardenprue we write about pests related to a crop. Not in this case. Due to the great importance of the big-headed worm, we are going to dedicate a full post to it. We are going to know its biological cycle, its dangerousness in cultivation, the ways in which it acts and the means to combat it.
THE FEARSOME PLAGUE OF THE BIG-HEADED WORM IN FRUIT TREES
In recent years, the big-headed worm has increased its population and its dangerousness. In the Region of Murcia, the Valencian Community, Extremadura and Aragon is where it is having the most importance. What is the reason for this increase?
On the one hand, the continued excessive use of herbicides and pesticides systemically reduces the predatory populations of the big-headed worm . On the other hand, with the modernization of irrigation systems, the land that is not close to the tree is dry, and since the big-headed worm inhabits part of its stages in the soil, the proliferation is timely.
LIFE CYCLE OF THE BIG-HEADED WORM
The adults of this pest remain sheltered (one of those shelters is the ground) until the end of winter. From this stage (late February, early March), they emerge, coinciding with the budding of the fruit trees.
The adult leaves very hungry (after all the winter, imagine), and they devour shoots, buds and petioles that they find in their path. After 40 days feeding, it is time to reproduce (May to September), with temperatures that are mild for the plague. Each female lays between 350 and 400 eggs on the ground and less than 1 meter from the trunk, with a depth on the ground between 0.5 and 2 cm. In just 10 days, the egg hatches and the larvae of the big-headed worm head for the roots of the tree. Inside this it will grow to 7 and 10 cm.
BIGHEAD WORM IDENTIFICATION
The adult of the big-headed worm is a black beetle with a size between 2 and 2.5 cm. You will find this beetle in the branches of the fruit tree. As soon as it detects your presence, it will hide under the branch (how curious is it?) And will fly away if it thinks you have identified it.
The big-headed worm affects all stone fruit trees. In addition, it has also been proven that it affects other fruit trees such as chestnut, pear, apple and quince. The adult, which lives in the aerial part of the tree, feeds on the shoots and buds of the tree that emerge. But the most important damage is caused by the larva, creating galleries on the roots, destroying the cortical tissue, damaging the sap ducts and consequently, malnourishing the tree, which ends up weakened and dies.
TRADITIONAL METHODS TO AVOID THE INVASION OF THE PEST IN THE FRUIT TREE
Irrigation: If the ground around the trunk of the fruit tree is humid, the females do not carry out the laying on the ground. One recommendation is that the drip is placed close to the trunk, to increase the humidity radius.
Plastic: it would act as a defense, surrounding the tree with a radius of approximately 1 meter. It has to be buried far enough so that the big-headed worm cannot get through it underground. The plastic will be collected when the worm invasion season is over. In my opinion, it is an effective but not ecological operation, being able to generate plastic waste on the ground (it is only my opinion). Also, the moisture around the tree cannot extend beyond the plastic and can cause excess moisture.
Elimination of the affected tree: only in cases of great affectation of the tree, will it be started and burned, in order to avoid the spread to other fruit trees.
It cannot in itself be called control since the measures are still insufficient and sporadic, and are still being investigated. Found fungi (Entomococcus) as a natural enemy of the bigheaded worm, Coleoptera ( Melanotus rufipes) a Hymenoptera (Spathius erythrocephalus), Diptera ( latifrons Sarcophylla and Billaea subrotundata) and entomopathogenic nematodes ( Sreinernematidae and Heterorhabditidae) .
BIGHEAD WORM TREATMENTS
To date, the control, both ecologically and conventionally, is not 100% safe. The best way to treat is to adapt to the different stages of the pest, and act according to the phase in which it is. These are the recommendations.
In larval stage: using a phytosanitary product when the headed worm is in the roots is complicated, because its penetration will not be entirely effective. In addition, these agrochemicals are quite expensive and do not guarantee complete results at all. Sometimes a by-product of the oil (neem cake) is used which is added in July and August on the ground around the trunk. BioControl magazine has published results of a product (Biorend R) on the worm with efficiencies between 70 and 90%, yes, in the best application conditions.
Adult state: treatment against adults is more effective since they are found in the aerial part of the tree. They are treated with contact phytosanitary products (spraying on the tree) in spring (April and May). The application of the product on the fruit trees has to be done at the same time on all the trees, including those around our farm, because otherwise it is useless. In a matter of hours, the neighbor’s pest can re-colonize our trees.