Weather conditions in Latvia are very favourable for the development of potato late blight caused by Phytophthora infestans (Mont) de Bary. The control of potato late blight can be performed using different approaches: standardised technology, prognoses of the first infection and prognoses of the progress of disease development. The negative prognosis model Negfry is based on the last two mentioned above. For the control of potato late blight in Latvia mainly has been used - standardised technology. The first field treatment was made during the row closing or according to prognoses. Regular treatments were made each 8-14 days. The use of NegFry model started in Latvia in 1998. Local varieties and weather data have been used for the trial. For the control of potato late blight in field trials standartised fungicide application was compared with the NegFry model and the untreated variant. The major task of the use of the model is possibility to reduce the number of fungicide treatments. The NegFry model helps to realise an integrated plant protection system, which decreases fungicide application and increases economical efficiency.

One of the most serious diseases of the potato crop worldwide is late blight caused by Phytophthora infestans (Mont.) de Bary. Most growers control the disease by applying fungicides at regular intervals of 8-10 days from the time of row closing until the end of the growing season. The NEGFRY model is used for timing the chemical control of potato late blight. The NEGFRY model is based on two existing models, the "negative prognosis", for forecasting the risk of primary attacks, and a model for timing subsequent fungicide applications during the season. The main objective of NEGFRY is to get high yield and quality with minimum use of fungicides. Present work underlies the experiments that were arranged in 2000 and 2001 at the Jogeva Plant Breeding Institute. Two potato varieties with different resistance to late blight were taken to the experiment in both years: susceptible 'Adora' and modarately resistant 'Anti' in the year 2000 and susceptible 'Berber' and 'Anti' in 2001. NEGFRY gave highest economical effect among six tested treatment regimes.

Potato is the second important crop in Latvia. The area covered with potato is about 50 thousand hectares. Potato late blight caused by Phytophthora infestans (Mont.) de Bary is the most serious potato disease. Weather conditions in Latvia are very favourable for the development of potato late blight and it is occuring almost every year. The biology of P.infestans was the subject of a number of authors - plant pathologists. Research results about P.infestans population biology and epidemiology are presented in this review, especially focusing on the changes of pathogen biology.

Late blight (Phytophthora infestans) is one of the most serious potato diseases. The light blight forecasting is a very important factor for the protection of potato plants. NEGFRY is a decision support system for scheduling the chemical control of potato late blight. Trials were carried out in 2000-2001 at the Lithuanian Institute of Agriculture (LIA) in Dotnuva in medium early and moderately susceptible to late blight varieties. Ordinary plant protection systems against late blight and different NEGFRY models were compared. Results of two years' investigations show that by using NEGFRY models we can obtain satisfactory protection of potato crop and get higher yield using fewer spray applications.

Second to Black Sigatoka (Mycosphaerella fijiensis), Moko (Pseudomonas solanacearum race 2) is the most threatening disease to plantains and bananas. No resistance has been found on commercial varieties. It is present throughout Central America, as well as in Trinidad, Grenada, Brazil, Surinam, Venezuela, Colombia, Ecuador and Peru and suspected in the Dominican Republic. Its detailed distribution in Mexico, Nicaragua, Costa Rica, Venezuela, Colombia, Ecuador and Peru is described. Symptoms, pathogenesis and survival of race 2, which is pathogenic and divided into SFR, the major disease agent on bluggoe, and A and B are described. Disease control by elimination of diseased plants by glyphosate injections is detailed. Good control was achieved in 70 % of infected farms with a 90 day fallow after injection

Important features of the disease Pseudomonas solanacearum or Moko, affecting banana and plantain are reviewed. The history and distribution, host range, symptoms, causal organisms and dissemination, pathogen cycle, disease resistance and control based on sanitation methods are briefly described

Phytosanitary practices are recommended to reduce the incidence in the Windward Islands of banana pests and diseases: leaf spot (Mycosphaerella musicola), crown rot (Fusarium roseum), virus diseases (bunchy top), moko disease (Pseudomonas solanacearum), banana borer (Cosmopolites sordidus), rust thrips (Chaetonophothrips signipennis), flower thrips (Frankliniella parvula), Lachnopus beetle and nematodes

Outlines the history and objectives of the California Citrus Clonal Protection Program (CCPP) which conducts research and is a primary source of disease-free budwood of desirable true-to-type citrus scion and rootstock varieties designed to exclude graft transmissible diseases (virus and virus-like)

Poor phytosanitation affects banana quality through physical defects, harbouring of pests and diseases. The implications on marketing are briefly discussed

A diseased mat eradication programme in which mats are injected with Round up, followed by cygon spray and the area sprayed with Gramoxone has been successful. 216,812 mats were destroyed between 1978 and July 1985. Findings of research funded by the EDF include early detection of infected mats by examination for corm discolouration, possibility of Ricinus comunis, begonia jumbie tomato (Solanum sp.) and Xanthosoma sp. as alternative hosts, a recommended fallow period between injection of mats and re-planting of 9-12 months, optimum weed killer and application rate (Round up at 20 mls 2 % soln) and a buffer zone of more than 8 in. in radius