Influence of Posttreatment Temperature on the Toxicity of Insecticides Against <I>Diaphorina citri</I> (Hemiptera: Psyllidae)

Abstract

The psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is one of the most important pests of citrus worldwide because it efficiently vectors three bacteria in the genus Candidatus Liberibacter that cause the devastating citrus greening disease (huanglongbing). Current management practices for this insect pest rely on multiple sprays of foliar insecticides and one or two applications of soil systemic insecticides per season. Effective psyllid and disease management in Florida requires insecticide applications throughout the entire season over wide ranging temperature and environmental conditions. Using a petri dish bioassay technique, the effect of posttreatment temperature (range, 17-37 degrees C) on the toxicity of selected organophosphate (chlorpyrifos and dimethoate), carbamate (carbaryl), avermectin (abamectin), pyrethroid (bifenthrin, zeta-cypermethrin, fenpropathrin, and lambda-cyhalothrin), and neonicotinoid (acetamiprid, imidacloprid, and thiamethoxam) insecticides was evaluated against adult D. citri. The toxicity of both organophosphates showed a positive temperature correlation within the 17-37 degrees C range. Similarly, carbaryl (carbamate) and abamectin (avermectin) exhibited increased toxicity with increasing temperature from 17 to 37 degrees C, with abamectin showing higher overall temperature-dependent toxicity against D. citri adults than carbaryl. With the exception of bifenthrin, which showed a positive temperature-dependent toxicity correlation between 27 and 37 degrees C, all other pyrethroids tested exhibited a negative correlation over the temperature range examined. The toxicity of fenpropathrin and lambda-cyhalothrin dramatically decreased with increasing temperature from 17 to 37 degrees C. The neonicotinoids imidacloprid and thiamethoxam exhibited a mixed response to increasing temperature, whereas acetamiprid showed a positive temperature correlation. However, all three neonicotinoids showed positive temperature-dependent toxicity correlations against D. citri adults over the temperature range tested. These data will enable citrus growers to choose the most effective insecticides for D. citri control from the various classes currently available depending on the prevailing temperature conditions.

Chemicals, Climate, and Control: Increasing the Effectiveness of Malaria Vector Control Tools by Considering Relevant Temperatures

“…Investigating the performance of our vector control tools under different temperature conditions will augment our ability to select the most efficacious tool for a given environment. For insecticidal control of pests in crop systems, it has been acknowledged that knowing a product's temperature coefficient enables pest managers to select a product that is efficacious under the prevailing environmental conditions [26]–[28].…”

Environmental temperatures significantly change the impact of insecticides measured using WHOPES protocols

“…According to WHO criteria, the ultimate level of survival would justify additional testing to evaluate this ‘potentially-resistant’ population [6]. Post-exposure temperatures have been shown to decrease or increase insecticidal activity in other insects [14–17, 33–36], but this appears not to have been investigated extensively with malaria vectors. More generally, the functional significance of ‘knockdown’ remains unclear.…”

“…For example, in Diaphorina citri (Hemiptera: Psyllidae), a pest and vector of greening disease in citrus, Boina et al saw that two organophosphates and a carbamate were more toxic at higher temperatures, while three out of four of the tested pyrethroid insecticides (zeta-cypermethrin, fenpropathrin, lambda-cyhalothrin) were more toxic at lower temperatures [17]. Bifenthrin, the fourth pyrethroid tested, was more toxic at higher temperatures [17], which shows that even within the same class of chemical, against the same species of insect, the interaction between the toxicity of a given compound and temperature can be difficult to predict a priori (see also in tobacco budworm [18]).…”

Effective Use of Neonicotinoids for Protection of Citrus Seedlings From Invasion by <I>Diaphorina citri</I> (Hemiptera: Psyllidae)

“…Furthermore, the efÞcacy on pests is different between insecticides; for example, in soybean, Glycine max (L.) Merr., thiamethoxam is more effective than imidacloprid (Magalhaes et al 2009). The longevity and efÞcacy of insecticides are also affected by climatic conditions, especially temperature (Boina et al 2009a).…”

“…The t 1 and t 2 of imidacloprid and thiamethoxam in M. paniculata (L.) are reported to be shorter than 6 d and longer than 34 d, respectively (Mannion and Peñ a 2006). Furthermore, because temperature is an important factor to inßuence the efÞcacy of insecticides (Boina et al 2009a), these two variables, t 1 and t 2 , may vary both between varieties and between sites located in different climate zones. King mandarin, C. nobilis Loureiro, is dominantly cultivated in southern Vietnam, where the climate is characterized by hot and wet conditions.…”