During this entire winter, the Spanish Association of Tropical Fruit Producers has found that the leaves of most avocado plants have been losing the green hue that characterises them and have turned brown, which is unusual, given that avocados are evergreen plants.
This anomaly has been caused by a massive attack of a mite, the Oligonichus punicae (Hirst). The presence of this mite has been recurrent in recent years, especially in autumn, but the incidence was only testimonial and went unnoticed every year, since it disappeared from the plantations with the arrival of winter. But this year it has not been the case and its presence has been growing, causing serious damage to avocado plants and fruits, with a reduction in sizes, production volumes and quality.
The bug, just like other spider mites, feeds from the plant's cell content, causing up to a 60% reduction of chloroplasts and changing the transpiration rate. This causes the leaves to dehydrate and fall. Trees attacked with high populations of mites are likely to let fruit fall, which leads to reduced yields.
In general, the spread of the pest starts from the trees on the roadsides and in the foliage near the ground, especially nearby dirt roads. The dust from the roads provides protection to the mite colonies against the action of biological control agents. Dust is an agent that interferes with the search, egg laying and feeding of predators, thereby reducing their efficiency.
"We are struggling to get the companies that manufacture other miticides to streamline the provision of documentation to facilitate their authorization for their use with avocados, but the small acreage devoted to avocados right now in Spain doesn't make it profitable for these companies to invest in official records," explains the Spanish Association of Tropical Fruit Producers in a statement.
Also, "given the seriousness of the problem that we, avocado growers, are facing, especially in the early and late summer, the Association has been working to make sure the Ministry of Agriculture grants the necessary authorizations for the exceptional use of other miticides in avocados. As a result of this work, some authorizations were obtained two years ago, but last year they were denied, and this may partly be the reason for the problem we are suffering at the moment," they affirm.
"We, at the Association of Producers, are aware of the issues that can arise from the widespread use of insecticides in our products; that is the reason why we are very selective when requesting exceptional authorizations."
The attack of these spider mites is not limited to avocado plantations; this year, the pest has already been detected also in some mango farms.
Source - freshplaza.com
