Evaluation of Host Stinging Behavior of the Larval Ectoparasitoid Diglyphus isaea on Some Selected Host Plants

Background: In parasitoid insects, beside parasitism, there are two other behaviors that may increase leaf miner mortality: Feeding on the host (host feeding) and, host penalization without oviposition or feeding (host stinging).

Objectives: The present study aimed to evaluate (host stinging) behavior of the larval ectoparasitoid D. isaea in field on some selected host plants.

Methods: The present study was carried out in Alejelat region. Four selected host plants were studied, chick pea (Cicer arietinum) and broad bean (Vecia faba) as a Winter host plants and, Cow pea (Vigna unguiculate) and kidney bean (Phaseolus vulgaris) were selected as summer host plants during the growing seasons 2018 and 2019. Samples were kept in plastic bags and transferred to be examined in the laboratory. Number of living L. trifolii larvae, and number of killed larvae according to feeding (no oviposition) by D. isaea were counted and recorded.

Results: On cow pea host stung larvae recorded (156 individuals/ 100 infested leaflets) occurred in 10th of August, with (r = +0.69**) between host stung larvae and the population of L. trifolii recorded). On kidney bean host stung larvae recorded (101 individuals/ 100 infested leaflets) occurred in 24th of August, with (r = + 0.85**) value between host stung larvae and the population of L. trifolii recorded. On the other hand, the percentage of host stung larvae ranged between (5.67% and 28.22%) and (15.88% and 42.30%) for cow pea and kidney bean respectively. On broad bean host stung larvae recorded (159 individuals/ 100 infested leaflets), with (r = +0.59*) between host stung larvae and the population of L. trifolii .On chick pea host stung larvae recorded (82 individuals/ 100 infested leaflets) with (r = +0.20ns) between host stung larvae and the population of L. trifolii. On the other hand, percentages of host stung larvae ranged between (8.45% and 36.60%) and (21.80% and 87.65%) for broad bean and chick pea respectively.

Conclusion: The highest percentage of host stung larvae recorded on chick pea 44.65% followed by kidney bean 24.21%, broad bean 18.45% and cow pea 12.97% respectively. On the other hand, the correlation coefficient value (r) between numbers of L. trifolii larvae and, host stung larvae recorded the highest on kidney bean +0.85** followed by cow pea +0.69**, Broad bean +0.59* and Chick pea +0.20ns respectively.