The Effects of aLow Toxicity Pesticide on Potato Late Blight, Tomato Leafminer, Potato Tuber Moth and its Major Parasitoid in Potato and Tomato Intercrops
| dc.contributor.advisor | Mulatu, Bayeh (PhD) | |
| dc.contributor.author | Mulugeta, Tewodros | |
| dc.date.accessioned | 2018-07-23T13:46:35Z | |
| dc.date.accessioned | 2023-11-09T04:20:34Z | |
| dc.date.available | 2018-07-23T13:46:35Z | |
| dc.date.available | 2023-11-09T04:20:34Z | |
| dc.date.issued | 2017-04 | |
| dc.description.abstract | Potato late blight caused by the oomycete Phytophthora infestans (Mont.) de Bary is the most important potato disease worldwide. It causes losses of several billion dollars annually and it is a global threat to potato growers. The pathogen is also equally important in tomato. Even though various resistant cultivars are being released, potato late blight is mainly controlled with intensive application of fungicides. In Ethiopia the pathogen is distributed throughout the potato producing areas. The main rainy season is quite favorable for the growth and development of the disease and loss could reach 100%. Tomato is the second most affected crop by late blight in the country. The potato tuber moth (PTM), Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), is one of the most important potato pests worldwide. Tuber damage in storage facilities is the major problem related to PTM infestation. Even though foliar damage is the source of infestation for the damage in stores, it usually causes insignificant yield losses. In Ethiopia field tuber infestation could reach 42%. In addition to potato PTM attacks tomato, eggplant, tobacco and wild solanum species. Tuta absoluta (Meyrick), commonly called tomato leafminer, is a devastating pest of tomatoes. Up to 100% losses have been reported in tomato crops. Even in a condition where control measures have been taken, losses could still exceed 5%. In Ethiopia the pest has been causing severe damage in tomato since 2011. Control of both PTM and tomato leafminer has been mainly with the use of synthetic insecticides. Due to the non-judicious and continuous use of fungicides/pesticides, insects and pathogens are developing resistance, the environment is polluted and non-target organisms are damaged. Furthermore, lack of knowledge in chemical use and low use of personal protective devices during application, mainly in developing countries, is imposing health problem to poor farmers. xix Therefore due to the harmful impacts of pesticides/fungicides use to the environment and human health there is a need to search for a safe alternative to manage pests and pathogens. Phosphite has been identified as a potential alternative to pesticides/fungicides in controlling some herbivorous insects, fungal diseases and oomycetes. The present study investigated the effect of phosphite against PTM, tomato leafminer and potato late blight. Field trails were conducted for three consecutive years to investigate the efficiency of potassium phosphite, a low toxic inorganic salt with direct and indirect toxicity on oomycetes, and its combinations with the Ridomil fungicide against potato and tomato late blight. Two potato, Belete and Jalene, and one tomato, Melka shola, cultivars with different susceptibility to late blight were used. We demonstrated that phosphite combined with reduced dose of fungicides led to an effective suppression of potato foliar blight same as the full recommended dose of the recommended fungicide. In the moderate resistant potato cultivar Belete phosphite alone had adequate foliar protection against foliar late blight. In tomato, phosphite alone was as effective as the recommended dose of fungicide and combination of phosphite and fungicide. Yield was also affected with phosphite and phosphite and fungicide synergism. Treated plants provided far better yield than untreated control plants. Similarly, three years field trials were conducted to investigate the efficacy of phosphite against PTM and tomato leafminer. The study showed that the phosphite treatment did not affect the population density of tomato leaf miner larvae; however, it reduced PTM larvae population density. Furthermore, the direct toxicity of phosphite on mycelial growth, sporangia production and sporangia germination was investigated in a rye-agar and pea broth plate assays, in vitro, in different P. infestans isolates. The isolates responded differently to phosphite treatment with LC50 value between 1.4-4.3mM and their response was dose dependent. xx These findings show that phosphite can be used efficiently against potato and tomato late blight either alone or combined with reduced dose of fungicides. Phosphite has concentration based direct toxic effect on P. infestans, but the toxicity varies between isolates. Therefore phosphite could be a possible a component in the IPM of PTM and late blight. Key words: Fungicide, isolate, pesticide, plant resistance inducers, PTM, synergism, toxicity, | en_US |
| dc.identifier.uri | http://etd.aau.edu.et/handle/123456789/9865 | |
| dc.language.iso | en | en_US |
| dc.publisher | Addis Ababa University | en_US |
| dc.subject | Fungicide | en_US |
| dc.subject | Isolate | en_US |
| dc.subject | Pesticide | en_US |
| dc.subject | Plant Resistance Inducers | en_US |
| dc.subject | PTM | en_US |
| dc.subject | Synergism | en_US |
| dc.subject | Toxicity | en_US |
| dc.title | The Effects of aLow Toxicity Pesticide on Potato Late Blight, Tomato Leafminer, Potato Tuber Moth and its Major Parasitoid in Potato and Tomato Intercrops | en_US |
| dc.type | Thesis | en_US |