Influence of soil temperature and moisture on the infectivity of entomopathogenic nematodes (Rhabditida: Heterorhabditidae, Steinernematidae) against larvae of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae)

Abstract

-The Mediterranean fruit fl y, Ceratitis capitata (Wiedemann), is considered one of the main pests that affect fruit production in the world. This insect spends part of its life cycle in the soil, making it a target for entomopathogenic nematodes. This work aimed at evaluating the infl uence of soil temperature and moisture on the infectivity of Heterorhabditis sp. RSC01 and Steinernema carpocapsae ALL to third-instars of C. capitata, and to compare the effi ciency of these isolates at fi ve different soil temperatures (19, 22, 25, 28, and 31°C) and three levels of relative soil moisture (100, 75, and 50% of fi eld capacity). Ten C. capitata larvae were transferred to plastic jars (12 cm × 6 cm) containing 100 g soil, followed by the application of an aqueous suspension containing 125 infective juveniles (IJ)/cm 2 . In the control treatment, 3 ml of distilled water was applied. Mortality evaluations were made fi ve days later and were confi rmed by observations of the characteristic symptoms and cadaver dissection. The infectivity was directly proportional to temperature increase, with maximum percent mortality of 86.7% and 80.0% for S. carpocapsae and Heterorhabditis sp., respectively, at 31°C. At 25°C, the highest mortality for both species was obtained at 75% of fi eld capacity (96.7% and 26.7% for S. carpocapsae and Heterorhabditis sp., respectively).

Selection of entomopathogenic nematodes for the control of the fruit fly Ceratitis capitata (Diptera: Tephritidae)

“…This fact was also observed by Rohde et al (2010) while studying the susceptibility of C. capitata, larvae to the entomopathogen, and Yee & Lacey (2003), who investigated the pathogenicity of nematodes on Rhagoletis indifferens Curran, 1932 larvae.…”

“…In this respect, studies were conducted under laboratory and field conditions to determine the effectiveness of entomopathogenic nematodes on different C. capitata developmental stages; observations showed high susceptibility of this insect (Lindegren, 1990;Gazit et al, 2000;Laborda et al, 2003;Malan & Manrakhan, 2009;Rohde et al, 2010).…”

Virulence of nematodes against larvae of the south-American fruit fly in laboratory using soil from Porto Amazonas, Paraná, Brazil, as substrate

“…The passive dispersal of the nematodes by the water through the soil pore space and the small soil depth could have helped S. carpocapsae to spread in the soil. The temperature is another possible explanation, since Steinernema genus was observed to be more efficient at 25°C (temperature of this experiment) while Heterorhabditis showed higher efficiency at 30°C (ROHDE et al, 2010). Furthermore, Steinernematids seem to be more adaptable to different textures of soil than Heterorhabditis sp.…”

Susceptibility of Spodoptera frugiperda and Helicoverpa gelotopoeon (Lepidoptera: Noctuidae) to the entomopathogenicnematode Steinernema diaprepesi (Rhabditida: Steinernematidae)under laboratory conditions

“…Besides, the effect of the isolate needs to be evaluated in the field, considering other variables, such as nematode capacity to find the host, influence of temperature and humidity (Rohde et al, 2010), and interaction with other pathogens (García et al, 2008). In addition, the site of the host plant where each stage of the insect life cycle occurs should be taken into account to develop an effective EPN application strategy.…”