Egyptian tomato leaf miner Tuta absoluta prediction of tomato cultivation over the years
Egyptian agriculture is characterized by the production of many export vegetable crops, such as tomatoes. The annual production of this crop in Egypt is 9,204,097 tons, covering an area of about 9000 hectares. As a result, it is considered the fifth largest producer in the world.
Due to the shortage and regeneration of its cultivation, more than once a year, it represents the main host plant of different insect species that affect crop quality and productivity, such as tomato leaf miner Tuta absoluta. This pest infects nightshade crops at all stages of development, mainly tomatoes, potatoes, pepper and eggplants.
The female deposits the eggs in all parts of the host plant: leaves, leaf necks, stems, sepals and especially fruits, except for mining leaves. After the eggs hatch, the larvae penetrate the tomato leaves and feed on the leaf parenchymal tissue, forming irregular mines that become longer and wider as the larvae continue to feed, which affects the plant's ability to photosynthesize, resulting in a massive loss of productivity.
Surveys assessing the impact of climate variables on absolute grasses are important to provide comprehensive data on their population parameters in order to better design and develop management strategies for tomato crops against this pest.
According to Salama et al., larvae collected from infected tomato cultivation in Al Ayyat, Giza were raised for three generations. Salama et al. studied the duration of different developmental stages of this insect and estimated the life table parameters in an experimental farm attached to the laboratory. Follow-up of eggs hatched by adults to larvae and then to pupae was estimated, and duration of larvae and pupal was determined.
where y is the thermal constant, x is the thermal threshold, and n is the average duration of development at temperature t.
Meteorological data has been recorded to estimate the unit of degree, and daily temperature records have been obtained from the Agroclimate Center laboratory.
Since the appearance of moths will herald the beginning of a new generation, the complete development of the larval stage to produce normal pupae and its duration will be the main goal of this study.
To explicitly investigate the role of mathematical calculations in predicting the generation of Tuta absoluta, a tomato leaf miner in Egyptian tomato cultivation, three different provinces, namely Giza, Qena and Melsa-Matru, were selected, applying the above Jasic formula. The choice of these provinces depends on changes in climatic conditions, and Qena province is known as one of the best tomato producing provinces in Egypt, also because it is located in Upper Egypt and has a higher average temperature throughout the year compared to other regions. Melsa-Matrouh province, on the other hand, is a coastal city, so the average temperature throughout the year is low compared to the rest of Egypt. In addition, T. absoluta was first recorded in Merssa-Matrouh province in 2009 and then reached other parts of Egypt in 2010.
The data showed that the pupal duration of absolute pupae was 1.05±15.32 d at 17.95 °C, and 1.3±26.03 d when the temperature dropped to 8.45 °C. The calculated value of developmental zero x is 5.79 °C, and the thermal constant y is 171 degrees day.
Based on this data, Jasic's formula can be used to determine the frequency of adult occurrence and the number of generations of field pests anywhere in Egypt.
Judging by the data, the cycle of insect emergence seems to occur throughout the year, and determining the development of pupae at any time represents the expected time of moth emergence.
Therefore, the number of cycles in which wild pupal development terminates can be calculated by dividing the heat required for a certain period by the thermal constant. The results showed that the average annual temperature recorded in 2012 was 22.8 °C, and the development rate of pupation could be repeated 36 times. This means that adults must appear continuously, but vary in temperature in different months.
Our data clearly show that the cycle of insect emergence occurs throughout the year, with the first cycle of adult emergence lasting 20 days in 82.8 days. The second cycle starts with 18 days remaining in January and extends to the first 3.98 days of the following month to complete the second cycle.
Similarly, the 36th cycle is extended within the same month. This phenomenon continued until the end of '41 in 22. Thus, the thermal constant of the pupal stage can be traced many times as a method of controlling this pest to estimate the role of the thermal unit in predicting the sequence in which adult pests appear in the wild. This method is recommended for mathematical prediction of pest production. This is consistent with Hamdy, when this method is used to determine the appropriate time for chemical control of pale lepidoptera in field crawler abundance.
As mentioned earlier, changes in climatic conditions in different provinces will definitely affect the development of insects, so the generations of insects will also vary. The results showed that the insect formation time was 38.49 d at 26.03 °C and 15.32 d at 79.5 °C. Thus, the calculated zero degree of development is 5.268 °C and the thermal constant is 799.1 DDs. As a result, the expected annual generation frequency was established in the three provinces of Giza, Qena and Melsa-Matru.
The ecological study reported that changes in climatic conditions recorded in all provinces tested affected biological aspects of insects. Therefore, the use of Christie's formula is a very important strategy for predicting and calculating the frequency of insect formation, for choosing the best time, and for designing effective insect management methods. This method has been adopted by previous authors for a variety of insect species, for example, Farag et al. noted that cumulative thermal units have been used to predict the seasonal development and emergence of various insects.
Vercher et al. report that South America has 10-12 generations per year. And Varges found 7-8 generations in Chile. In the Mediterranean basin, as many as 9 generations were observed in southern Italy, and in open field conditions in Egypt, 13-13 generations were predicted by applying the day accumulation model mentioned by Abolmaaty et al. Hamdy noted that the expected date of the oleander scale, Aspidiootus hederae, can be easily detected and can help design pest management protocols.
