Academic literature on the topic 'Guava rust'

A newly emerging disease affecting proprietary hybrids of Neoregelia bromeliads was found in nursery production throughout south Florida. Initial symptoms appeared as small, reddish leaf spots with signs of fungal-like growth on the abaxial leaf surface closely resembling a rust. Closer examination of diseased tissue revealed the growth to be an alga with morphological and molecular characteristics of Cephaleuros parasiticus. This genus of plant parasitic thalloid green algae occurs worldwide in tropical and subtropical regions. Isolates of C. parasiticus collected from Neoregelia hybrid bromeliads were compared with two common Cephaleuros spp. (C. parasiticus and C. virescens) causing leaf spots on guava (Psidium guajava) in south Florida. Further, pathogenicity tests were conducted on healthy Neoregelia hybrids using C. parasiticus isolates collected from diseased leaves of bromeliads and guava. Isolates from both sources produced symptoms consistent with those originally described as “red rust” on Neoregelia hybrids. Florida has 165 plant species belonging to 53 families that have been reported as hosts of Cephaleuros spp., but this is the first report on Neoregelia hybrid bromeliads.

Abstract:Biological invasions can have negative consequences for resident biota, particularly when disease-causing organisms are involved. Austropuccinia psidii, or guava rust, has rapidly spread through the tropics affecting both native and non-native Myrtaceae. In Puerto Rico, the rust has become common on Syzygium jambos, an invasive tree native to South-East Asia. What are the drivers of infection, and do refugia exist across a heterogeneous landscape? We address these questions using species distribution modelling and beta regressions. The realized and potential distribution of Syzygium jambos is extensive. The model produced an AUC of 0.88, with land-use categories and precipitation accounting for 61.1% of the variation. Predictability of S. jambos is highest in disturbed habitats, especially in mountainous regions with high precipitation. All 101 trees surveyed and measured across Puerto Rico showed signs of infection to varying extents. Infection severity was consistently associated with annual mean temperature in all top beta regression models, but was also commonly associated with tree size and precipitation variables. We found no safe sites for S. jambos. Many trees were extremely unhealthy and some were dead, suggesting that S. jambos may soon become extinct on the island or reduced to persistent stump sprouts. Native vegetation may benefit from the local demise of S. jambos. While the rust has not jumped to native Myrtaceae, vigilance is required, as host-shifts have occurred in other tropical regions.

Pests and diseases that attack Crystal Guava are the main obstacles in increasing agricultural productivity, as well as disrupting plant physiology and growth. The purpose of this study was to identify pests and diseases of crystal guava (Psidium guajava L). The study was conducted for 3 months, (June-August) 2022 in three crystal guava gardens in Gemawang Village, Dukuh, Ngargoyoso District, Karangayar. Data were obtained from observations of guava plant samples crystals and fruit attacked by pests and diseases, as well as interviews with owners and managers to obtain information about cultivation from planting to harvest. The results of the research found several pests of Crystal Guava (Psidium guajava L.), including: Frogs (Cynopterus spp.), Fruit flies (Bactrocera dorsalis), caterpillars (Setora nitens), ladybugs (Helopeltis sp.), sac caterpillars (Lepidopthera: Psychide), shoot caterpillars (Lepidoptera: Pyralidae), and mealybugs (Paracoccus marginatus). morphology due to nutrient deficiency (potassium/magnesium); black spot and fruit rot by the fungus Collectrichum gleosporioides Penz, fruit canker (scab) Pestalotiopsis psidii (pat) Mordue, red rust by the algae Chephaleurus virescens, wilt disease by the algae Fusarium sp, and the fungus Cercospora psidii. Treatment was carried out once a week, by applying NPK and gandasil fertilizers and spraying with regent 50 insecticides, Yasithrin and Fostin. as well as wrapping young fruit. Pests and diseases found in Crystal Guava plantations in this study can reduce production, therefore the results of this study can be used as information material for novice farmers who want to develop Crystal Guava picking tours both on plantations and in their yards.

A higher percentage of crops are affected by diseases, posing a challenge to agricultural production. It is possible to increase productivity by detecting and forecasting diseases early. Guava is a fruit grown in tropical and subtropical countries such as Chad, Pakistan, India, and South American nations. Guava trees can suffer from a variety of ailments, including Canker, Dot, Mummification, and Rust. A diagnosis based only on visual observation is unreliable and time-consuming. To help farmers identify plant diseases in their early stages, an automated diagnosis and prediction system is necessary. Therefore, we developed a deep learning method for classifying and forecasting guava leaf diseases. We investigated a dataset composed of 1834 leaf examples, separated into five categories. We trained the dataset using four different and generally preferred pre-trained CNN architectures. The EfficinetNet-B3 architecture outperformed the other three architectures, achieving 94.93% accuracy on the test data. The results ensure that deep learning methods are more successful and reliable than traditional methods.