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Table 57. Larval parasitism on Heliothis armigera (Hubner) in sprayed versus pesticide-free areas,<br />
ICRISAT Center (Sep-Mar 1976-1977).<br />
Larval parasitism<br />
Parasites Pesticide-free a Sprayed area<br />
Diptera<br />
Eucarcelia (Carcelia) illota Curran<br />
Goniopthalmus halli Mes.<br />
Others (three species)<br />
(%) (%)<br />
8.3<br />
3.1<br />
9.9<br />
1.4<br />
1.0<br />
0.6<br />
Total<br />
Hymenoptera<br />
Diadegma sp.<br />
Eriborus argenteopilosus Cameron<br />
Campoletis chlorideae Uchida<br />
Others (five species)<br />
Total<br />
Overall parasitism (%)<br />
Larvae collected (total)<br />
19.2<br />
5.3<br />
3.1<br />
0.6<br />
0.2<br />
9.2<br />
28.4<br />
3828<br />
5.1<br />
4.1<br />
0.3<br />
0.8<br />
0.1<br />
5.3<br />
10.4<br />
7877<br />
a Area BA-25 at ICRISAT Center has been set aside as a perpetual pesticide-free area.<br />
The final yield-loss data were obtained using<br />
the actual weights of damaged and undamaged<br />
pods and seeds and calculating the potential<br />
yields if all pods had been undamaged. Loss in<br />
seed yield caused by insect pests was lowest in<br />
sole-drop blocks of cv HY-2 in Vertisol and of cv<br />
HY-3A in Alfisol (Table 58). Increased damage<br />
to pigeonpea in Vertisol resulted in reduced<br />
shelling percentages in both the cultivars.<br />
The yield of both cultivars was higher on<br />
Alfisol in intercropped blocks but cv HY-2 in the<br />
sole-crop block yielded more on Vertisol (Table<br />
58).<br />
Crop proportion (pigeonpea/sorghum) studies.<br />
On sorghum (CSH-5) and pigeonpea (ICP-1)<br />
sown in various crop proportions in late June in<br />
Vertisol, the percentage larval parasitism on H.<br />
armigera on sorghum declined with the increase<br />
in plant population, but the levels were only<br />
significantly different (P< 0.05) during the peak<br />
parasite activity on pigeonpea (Table 59). Data<br />
from similar trials during 1975-1976 on both soil<br />
types revealed that fewer egg and larval numbers<br />
were present on blocks with fewer plants per ha.<br />
Pest numbers, pest-parasite ratios, and plantdensity<br />
relationships will affect the efficiency of<br />
selection procedures for resistance to H. armigera<br />
in the pigeonpea screening program.<br />
Pest monitoring on sorghum in intercrop/crop<br />
proportion trials. It was confirmed that shootfly,<br />
Atherigona soccata Rond., attack was more<br />
severe on later sowings. Damage levels were<br />
higher on sorghum grown on Alfisols with up to<br />
43 percent compared with a maximum of 20<br />
165
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