Mijuskovic, M., 1953.
Quelques maladies et insectes nuisibles aux agrumes au Montenegro. Zastita Bilja, 19: 47-60.
Abstract
Citrus was introduced to Montenegro around 150 years ago. At first, their cultivation was not very widespread. It was only recently, and especially after the last war, that state intervention led to a system of plantations. The climatic conditions of the Monténegro coastal zone are quite favorable for citrus growing, and their numbers can be considerably increased. Since citrus fruits have been introduced from different parts of the world (Italy, Japan, California etc.), we now have almost every citrus species represented. At the same time, a large number of diseases and insect pests were introduced, so that today some of them require regular treatment, while others do not require compulsory control, either because they have been reduced by the action of natural enemies, or because these diseases and insects do not find conditions favorable to their development and therefore do not cause significant damage. One of the most serious diseases (which is becoming less and less important with the practice of grafting citrus cultivated on bitter orange and Poncirus trifoliata) is gum blight, caused by Phytophthora sp. Crown rot is the most common form of this disease. Anthracnose (Colletotrichum gloeosporioides - Penz.) is not uncommon on citrus weakened by adverse weather conditions or the action of other diseases and insects. Of the other diseases found in this region, Phytomonas syringae Van Hall is the most widespread. However, the damage caused is not very significant.
The time of appearance and origin of most of the harmful insects on our citrus fruits is unknown to us. An exception to this is the red spider mite (Paratetranychus citri McG.), which was first observed on Topolica in Bar at the end of April 1950 *). Since its appearance that year was massive, and in a limited area, and since, as far as we know, it had not been observed at all before, it can be said with a lot of confidence that it was brought from Italy the previous year with the first batch of citrus seedlings, which were purchased there. Otherwise, it is known in other citrus production areas, but it seems to cause the greatest damage in Florida and California.
It is a very small spider, dark red in color. On the back of the body it has bristle-like growths, each of which is located on a warty protrusion. These protrusions make it the easiest to distinguish from other spider mites found on citrus trees (Tetranychus sexmaculatus Riley, Tetranychus bimaculatus Harv, etc.). It is found on leaves and fruits, and when it appears in masses, also on citrus branches. By sucking the sap, it weakens the fruit tree, and the attacked leaves and fruits acquire a characteristic pale silvery sheen. In severe attacks, such as the one we had in 1950, the leaves fall off en masse, and the branches dry up.
The eggs of this spider are almost spherical; they have a single vertical stalk, from the top of which radially arranged cobwebby threads extend, with which the egg is attached to the substrate, most often on the back of the leaf.
The female lays an average of 30 eggs, usually 2-3 per day. According to Batchelor and Webber (3), incubation lasts 8-10 days in summer, and up to three weeks during winter.
The red spider usually appears in larger numbers in spring and autumn, especially if the weather is dry. In winter, as well as during high summer temperatures, it is less numerous. We found it in all stages of development in the middle of February, but it seems that in our country the mass appearance occurs at the end of April and the beginning of May.
Although it is not yet spread along the entire coast, and although it has not caused as much damage in the last two years as it did in 1950, the red spider is without a doubt still the most dangerous pest of our citrus fruits.
The best-known and earliest used means against the red spider were based on sulfur (powdered sulfur, sulfur-lime broth, etc.). However, in some parts of California, it has been noticed that it becomes resistant to the effect of sulfur, and today other, more efficient means for its suppression have been found. Thus, emulsions of medium-heavy oils are recommended, and in recent times, preparations based on dinitro-O-cyclohexylphenol (DNOCHP), which destroy eggs, as well as parathion agents.
In a small orientation experiment that we carried out in Bar in 1952, we used Albolineum No 1, Fosferno 20 and Fosferno 15. All three agents worked on adult spiders, but it seems that they did not work on eggs, so that after ten days we had the same large number of spiders as before treatment, although the control of the first days after the spraying showed a high mortality of adult spiders. There was also the possibility of transferring spiders from the surrounding untreated trees, but in any case, two consecutive sprayings should be carried out at an interval of 10-15 days, in order to destroy the newly hatched spiders, which were in the egg stage at the time of the first treatment. Such spraying should be done periodically, every time spiders appear in large numbers.
