Abstract
The adjuvants involved in pesticide formulation have a vital role in enhancing the physical properties of active ingredient delivered to the target site in plant-parasitic nematodes. The present study elucidates the potential effect of combinations of the nematicide oxamyl (Vaydate® 24 % SL) and surfactants on the root-knot nematode Meloidogyne incognita infecting tomato plants. Three surfactants namely, Agrimax-3H®, Silwet L-77®, and Sylgard 309® were used at their recommended rats (15 ml/100 L, 5 ml /100 L, and 250 ml/100 L, respectively) as well as the combinations of their respective ¼ R, ½ R, ¾ R with oxamyl at three rates i.e. the recommended (R, 48 mg a.i /plant); ¾ R, 36 mg a.i./plant and ½ R, 24 mg a.i./plant. The results revealed that surfactants caused approximately 50 and 25% hatching inhibition in egg masses and eggs, respectively while oxamyl exhibited the highest egg hatching inhibition by 90% throughout the trial period. The combination of oxamyl and Agrimax-3H showed significantly (P ≤ 0.01) more effectiveness against egg masses (71.17%) or free eggs (55.45% ) hatching as exposure time increase. Moreover, oxamyl potency increased to kill 95% of IJ2 whereas, other surfactants caused a 30% reduction. The mixtures of all tested adjuvants with oxamyl at the recommended rate raised oxamyl potency to kill 100 % IJ2 accompanied by a shortage of oxamyl latent period (LP). Whereas, Agrimax-3H surpassed other surfactants and shorted the LT50 of oxamyl to 0.82 days increasing its nematicidal effect. The addition of surfactants to oxamyl as protective treatment displayed a significant increase in tomato plant growth and suppressed galling of M. incognita while the combination between oxamyl and surfactants as curative treatments showed a vigor control efficacy within oxamyl and Agrimax-3H only and surpassed oxamyl formulation without significant difference.
Highlights
Root-knot nematodes (Meloidogyne spp.) are the main soil-borne disease especially in hot climates or short winters and considered the most damaging nematodes in agriculture, causing an estimated $100 billion loss/year worldwide (Oka et al, 2000)
Preparation of Egg Masses, Eggs and Second-Stage Juveniles: Infected tomato roots were cut into pieces of 2 cm long and placed in a 600 ml flask with 200 ml of 0.5% sodium hypochlorite (180 ml water + 20 ml Clorox)
Incognita as A Curative Treatment: One month after nematode inoculation, tomato plants infected with 1000 IJs of M. incognita were treated with 10 ml of the combination of the recommended rates of each tested surfactant (Agrimax-3H, Silwet L-77, and Sylgard 309) and the recommended rate of oxamyl as a curative treatment to assess their effect on nematode reproduction under greenhouse conditions
Summary
Root-knot nematodes (Meloidogyne spp.) are the main soil-borne disease especially in hot climates or short winters and considered the most damaging nematodes in agriculture, causing an estimated $100 billion loss/year worldwide (Oka et al, 2000). The thinking tuned directly to soil drenching application with chemical nematicides and may be ends with soil sterilization with fumigants to achieve fast–acting and considerable results in plant-parasitic nematodes control. The root-knot nematodes disease development requires taking a quick curative action to stop epidemic infection for crops using chemical nematicides e.g. carbofuran, fenamiphos, fensulfothion, and oxamyl (Taylor, 2003). There are many reports concerned with contamination of groundwater and different food types with aldicarb residues (Tchounwou et al, 2002) Taking this risk is necessary to keep the plants almost intact until the end of the crop season. The present study aimed to determine the effect of three tank-mix adjuvants on oxamyl (Vydate® 24 % SL) application rate as well as their efficiency against the development and reproduction of root-knot nematode, M. incognita infecting tomato plants under greenhouse conditions in vivo
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