Prospects of monosodium glutamate use for enhancement of spinosad toxicity against codling moth neonates

Abstract

It was demonstrated that neonates of the codling moth, Cydia pomonella (L.), feed on 'Red Delicious' apple leaves and successfully molt to the second instar. Next, using a nonchoice bioassay, we targeted codling moth neonates feeding on apple leaves, with standard concentrations of a culinary taste enhancer, monosodium glutamate (MSG), and Success ® , which contains 22.8% spinosad as its active ingredient. The addition of 25 ppm MSG increased feeding by 20-30%. Stimulatory properties of MSG were preserved in the presence of 12.5 ppm Success, and mortality from a 12.5 ppm Success + 25 ppm MSG combination increased by factors of 3.1-1.6 compared with Success alone. In a field experiment without rain, MSG maintained its stimulatory properties for 24 h, increasing feeding by 37%. Consistently, without rain, MSG increased the toxicity of Success in the field by a factor of ¡ 3.5. However, the stimulatory properties of MSG dropped to 19% with 4.3 mm of rain, and to zero with 9.6 mm of rain. Increased Success toxicity by MSG was reduced to ¡ 1.6 with 4.3 mm of rain, and dropped to zero after 9.6 mm of rain. It is concluded that MSG seems to be a promising feeding stimulant, enhancing the toxic properties of Success which itself is a good candidate for codling moth control. However, field persistence of MSG needs to be improved, either by formulating the Success + MSG combination into some field-stable matrix, or by employing a sparingly water-soluble substance mimicking MSG's action as a feeding stimulant in codling moth neonates.

Enhancement of Bacillus thuringiensis with monosodium glutamate against larvae of obliquebanded leafroller (Lep.:Tortricidae)

“…There is another explanation why stimulatory effect of MSG lasted for so long in obliquebanded leafrollers. As we have shown elsewhere ( Pszczolkowski and Brown , 2002), with time MSG residues on leaves tend to loose their stimulatory properties after 7 days. In our present study we used about 10 times higher dose of MSG than the minimum stimulatory dose both for the codling moth ( Pszczolkowski et al., 2002) and for obliquebanded leafroller (this study).…”

“…Our data showed that MSG stimulates feeding of obliquebanded leafroller within a broad range of concentrations 50–700 μ g/l. The obliquebanded leafroller responds to MSG by increasing leaf tissue consumption at 50 μ g/l concentration, which resembles the minimum effective MSG concentrations that stimulate feeding in the codling moth too ( Pszczolkowski and Brown , 2002; Pszczolkowski et al., 2002). This fact suggests that threshold MSG concentrations are similar in neonates of the obligueband leafroller and the codling moth.…”

“…Concentration‐dependent effects of MSG on apple leaf consumption by obliquebanded leafroller were examined using the feeding bioassay previously described in detail by Pszczolkowski and Brown (2002). In brief, circular sections of uniform size (12 mm of diameter) were removed from Red Delicious foliage, avoiding the rib area.…”

“…Recently, Pszczolkowski et al. (2002) showed that MSG, at concentrations as low as 25–50 μ g/l, increases intake of feeding substrate in codling moth neonates, and its presence in formulation with spinosad substantially increases mortality from a standard dose of this insecticide ( Pszczolkowski and Brown , 2002).…”

Pharmacological analysis of the feeding response of codling moth (Cydia pomonella; Lepidoptera: Tortricidae) neonates to bitter compounds

“…Most the microscope slides were kept in Petri dishes with wet fi lter paper placed on the bottom of each dish. Additional details of this procedure are given elsewhere (Pszczolkowski & Brown, 2002).…”