# Research on Plant Disease and Pest Diagnosis Model Based on Generalized Stochastic Petri Net
## 2 Early Warning System for Plant Pests and Diseases  
### Influence of Environmental Factors  
The occurrence of plant diseases is closely related to environmental factors such as water availability, nutrient levels, temperature, humidity, light exposure, and PH value. Proper control of these environmental conditions is key to preventing diseases and ensuring healthy plant growth. The classification and definition of environmental factors related to diseases are shown in Table 1. Among them, C represents the coding of various environmental factors. The relationship between plant diseases and environmental factors can be described in the form of a function, where the disease \(\rm{D_{m}}\) is a function of various environmental factors. Taking the first pest and disease in Table 1 as an example, the relationship between downy mildew \(\rm{D_{1}}\) and environmental factors can be expressed in the following form:  
\[\rm{D_{11}} =f(E_{3},\ A_{1},\ TR_{1},\ H_{1},\ L_{1},\ PH_{1}) \tag{1}\] \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline
**C** & **Dissence** & **C** & **Missence** & **C** & **Forelliance** & **C** & **Temperature** & **C** & **Hanielity** & **C** & **Light** & **C** & **PH Value** \\ \hline \multirow{2}{*}{D1} & Dussery & E1 & Dry & A1 & \begin{tabular}{c} Escolutes \\ Nugers \\ \end{tabular} & T6A & 15-20\({}^{\circ}\)C & H1 & \begin{tabular}{c} High \\ humidity \\ \end{tabular} & L1 & Low Light & PH1 & Absolute \\ \hline \multirow{2}{*}{D2} & Dussery & E2 & \begin{tabular}{c} Imefficient \\ Milower \\ \end{tabular} & A2 & \begin{tabular}{c} Imefficient \\ Verification \\ \end{tabular} & T6A & 20-25\({}^{\circ}\)C & H2 & \begin{tabular}{c} Moderate \\ Immunity \\ \end{tabular} & L2 & \begin{tabular}{c} Moderate \\ Light \\ \end{tabular} & P1G & Neutral \\ \hline \multirow{2}{*}{D3} & Gray Model & E3 & Water Encours & A3 & \begin{tabular}{c} Proper \\ Avoidance \\ Application \\ \end{tabular} & T6B & 25-30\({}^{\circ}\)C & H0 & \begin{tabular}{c} Low \\ Immunity \\ \end{tabular} & L3 & High Light & P1G & Acidic \\ \hline \hline \multirow{2}{*}{Dm} & Dussery & Ea & \begin{tabular}{c} Moderate \\ Condition \# \\ \end{tabular} & Ab & \begin{tabular}{c} Ferllication \\ Station \# \\ \end{tabular} & T6C & \begin{tabular}{c} Temperature \\ Condition \# \\ \end{tabular} & H4 & \begin{tabular}{c} Healthy \\ Condition \# \\ \end{tabular} & Le & \
\begin{tabular}{c} Light \\ Condition \# \\ \end{tabular} & PH &
\begin{tabular}{c} PH Value \\ Condition \# \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Classification and definition of environmental factors for diseases. Formula (1) indicates that downy mildew is more likely to occur in areas with standing water (E1), especially when excessive nitrogen fertilizer (A1) increases the number of susceptible young leaves. The disease develops rapidly within a temperature range of 15-20 \({}^{\circ}\)C (TR1). High humidity (H1) promotes the spread and development of downy mildew, while excessive shading and low light (L1) also contribute to the expansion of the disease. Additionally, an alkaline soil environment (PH1) further exacerbates the occurrence of downy mildew. These environmental factors interact to create high-risk conditions for the disease. Similarly, the disease dynamics model can be expressed as follows:  
\[\text{D}_{21} =\text{f}(\text{E}_{1},\text{ A}_{1},\text{ TR}_{2},\text{ H}_{1},\text{ L}_{1},\text{ PH}_{1}) \tag{2}\] \[\text{D}_{31} =\text{f}(\text{E}_{3},\text{ A}_{1},\text{ TR}_{1},\text{ H}_{1},\text{ L}_{1},\text{ PH}_{3})\] (3) \[\ldots\] \[\text{D}_{\text{m1}} =\text{f}(\text{E}_{\text{a}},\text{ A}_{\text{b}},\text{ TR}_{\text{c}},\text{ H}_{\text{d}},\text{ L}_{\text{e}},\text{ PH}_{\text{f}}) \tag{4}\]  
In addition to plant diseases, the occurrence of pests is also greatly influenced by environmental factors. Table 2 presents six environmental factors related to pest occurrence.