Increase in mortality of prepupae and pupae of Liriomyza trifolii (Diptera: Agromyzidae) by manipulation of relative humidity and substrate
1989
Keularts, J.L. | Lindquist, R.K.
Relative humidity, substrate particle size, and polyethylene soil coverings were evaluated for their effects on the survival of prepupae and pupae of Liriomyza trifolii (Burgess) in greenhouse and laboratory experiments. At 100% RH, pupae developed normally but did not survive because of fungal infection. At other humidities, mortality decreased as humidities increased, with effects greater on prepupae. At humidities less than 50%, prepupal mortalities ranged from 70 to 85%. Pupal mortality reached a maximum of about 50% at 20% RH. The depth of pupation increased from less than 20 mm in particles of 1 mm diameter or less to deeper than 2 mm in coarse sand (less than 2 mm diameter). Pupation appeared to occur normally in all case, but adult emergence was significantly reduced when the depth of the coarsest sand was greater than 200 mm. Experiments were conducted to evaluate effects of white polyethylene soil coverings, on prepupal and pupal survival. Leaf miner populations on tomato were significantly lower in treatments with polyethylene sheeting wetted periodically by overhead irrigation than in treatments with uncovered soil. Drowning of prepupae on the plastic was the principal reason for this difference. Pavement ants, Tetramorium caespitum (L.), may cause considerable pupal mortality on polyethylene that is not wetted. All of the above-described procedures could be used in a management program for L. trifolii on certain greenhouse crops. At present, the most practical procedure appears to be the use of polyethylene sheeting combined with irrigation.
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