Tuber Moth Research Articles

Grower perceptions of biotic and abiotic risks of potato production in South Africa

Growers' surveys took place in all sixteen potato growing regions of South Africa in 2013 and 2014. The agro-ecological climate of these regions is diverse and potato is produced in rainy or dry seasons, in winter or summer seasons, or year round. Growers were asked how often in ten years crops suffered more than 25% yield losses due to extreme weather events related to precipitation events such as hail, floods and droughts, and to temperature-related events such as frost and heat waves. Simultaneously they were asked their opinion about occurrence and severity of diseases caused by potato viruses, fungi and bacteria and pests such as nematodes, tuber moths, aphids and leaf miners. Weather related hazards resulted in losses over 25% virtually each year in the Gauteng growing region due to hail, frosts and floods; losses occurred less than once every five years, for example due to extremely high temperatures, in the Sandveld area where growers take a risk by producing potatoes in hot summers. Regarding the biotic factors, every pest or pathogen assessed was reported to occur on at least one farm in each growing region. Countrywide the lowest frequency of 50% was recorded for powdery scab whereas the insects tuber moths, leaf miners and aphids were reported most frequently, by between 88% and 98% of the growers. The complex of silver scurf and black dot resulted in the greatest yield losses in all growing regions, followed closely by tuber moth, early blight and the blackleg/soft rot disease complex. Yield losses due to potato virus Y, potato leaf roll virus and aphids were not reported as being very severe. When the growers' perceptions of severity of biotic factors were accumulated, significant differences between the regions appeared, with the Eastern Cape most prone with an accumulated score of 700 due to an array of pests and diseases, and the North–West with a score of only 50 mainly attributed to root knot nematodes. Growers were also asked how frequently biocides were applied to potato to control soil-borne organisms (nematicide and seed treatment), foliar fungi or insects. There were no significant correlations between frequency of biocide applications and severity of the disease as reflected in yield losses, most likely because growers use biocide applications as insurance against pests and diseases. This is common among crop farmers around the world. Although potato production in South Africa appears to carry more risks than production elsewhere, South African commercial potato growers are economically competitive when compared to growers in other areas of the globe, with comparable planting conditions and risks.

Ecogeography and breeding potential of the wild Peruvian tuber-bearing species ofSolanum

About 225 wild tuber-bearing species of Solanum occur on the American continent. Seventy-five percent of these are distributed in South America, with the largest concentration (approximately 100 species) occurring in Peru. Located on the western side of South America, Peru has five main regions: the Pacific Ocean Territory, the Coast, the Sierra, the Ceja de Selva, and the Selva. Wild potatoes are found only along the Coast, the Sierra, and the Ceja de Selva. The Coast (Fig. 1), a vast desert territory 2500 km long and 150 km wide, varies in elevation from sea level to 1000 m. The central and southern part of this region is usually covered with low clouds from April or May until October or November. When these clouds touch the mountains to the east, they produce a very fine condensation or mist called garua. This mist gives rise to a special ephemeral plant formation called the loma, which is notably lacking in species diversity. Within this coastal fog zone, the precipitation is extremely low, ranging from 4 to 80 mm of rainfall per year. Temperatures range from 13 to 23?C, and the humidity varies from 65 to 95 percent. During the winter season, some tuber-bearing species of Solanum occur in the lomas formation, including S. immite, S. medians, S. mochiquense, S. chancayense, S. neoweberbaueri and S. wittmackii. Not only are these species remarkable for their drought tolerance, but some are also quite resistant to viruses, fungi and bacteria. Solanum immite, for example, the first tuber-bearing species described for Peru by Dunal in 1852, is resistant to the spindle tuber viroid (PSTVd) and to the fungal wilt caused by a Verticillium species. Solanum medians, a coastal mountain species, has perhaps the widest distribution in the loma formations of the Peruvian coast. It is found from the Lomas de Manchay (350 m asl.) near La Molina, Lima (12?05' S and 76056' W) all along the southern Peruvian coast to the Lomas de Ilo (400 m asl.) and the Lomas de Sama (550 m asl.) in the departments of Moquegua and Tacna (or approximately 17?48' S and 70030' W). At Manchay-La Molina, the average annual precipitation is only 18 mm, while at Sama Grande it is 40 mm. The monthly median temperature for both places is 24?C and the minimum is nearly 13.5?C. Solanum medians represents a valuable source of genes for potato breeding programs. It is resistant to the attack of several potato viruses, including potato virus X (PVX), leaf roll (PLRV), potato viruses S (PVS) and M (PVM) and the potato spindle tuber viroid (PSTVd). It is also resistant to the tuber canker fungus, Synchytrium endobioticum; to the potato ring rot disease caused by the bacterium, Corynebacterium; the cyst nematode Globodera rostochiensis; and the tuber moth, Phthorimaea operculella. The most northern loma formation along the Peruvian coast is found at Cerro Campana (400 m asl.) in the vicinity of Trujillo (08005' S and 79?06' W). Here, thrives Solanum mochiquense, a species resistant to the potato black leg bacterium, Erwinia carotovora; the fungal organism, Synchytrium endobioticum; potato viruses PVS, and PVM; and, the nematode Meloidogyne. The Sierra divides the Coast from the Selva

The need for international research programmes on some potato pathogens

Growers are being faced with a conflic between the effects of specialization on increasing pest and disease problems (particularly late blight, Colorado beetle, cyst nematodes and tuber moth), and public opinion that will force them to reduce the use of pesticides. For this disease and these pests international research programmes are needed to develop parental lines and cultivars with durable resistance that can be used world-wide.

Protection of stored potatoes against tuber moth

Protection of stored potatoes against tuber moth

Pest Control in French North Africa

A RECENT publication ("Les Nouvelles Méthodes Insecticides et Les Épidémies." By Dr. A. L. Lepigre. Centre Nationale de la Recherche Scientinque, Algiers) describes what is being done to reduce losses at the ports, in the marshalling yards and in the agricultural depots in French North Africa, resulting from infestation by insects and rats. The loss of potatoes caused by the tuber moth is stated to exceed 50 per cent within three months of harvesting, most of which loss is preventable by fumigation. Dr. A. L. Lepigre, whose pioneer work on the fumigants ethylene oxide and methyl bromide is well known, describes the fumigants and methods now in use in the eight large official stations for désinsectisation in Algiers, and the possibility of using vacuum and mobile chambers. Ethylene oxide, hydrogen cyanide and methyl bromide are recommended; but it seems that ethylene oxide is not available in Algiers at present. Chlorpicrin, once highly favoured by the French authorities, is described as being too unpleasant. A brief account of these fumigants is given, and special interest is attached to the statement that ethylene oxide is bactericidal as well as insecticidal, and as such is probably more effective than formalin or sulphur dioxide.