Table 3.
Summary of findings of meta-analyses of the effect of rice cultivation practices on Anopheles larval density (the number of larvae and pupae per dip or area sampler), arranged by the type of control, study design and geographical region.
| Study | Country | Predominant vector | Comparison | Plot size (no. of replications) | Relative percent difference (95% CI) |
|---|---|---|---|---|---|
| Intermittent irrigation | |||||
| Palchick and Washino (1986) | USA | An. freeborni | Drained 5 DAS1, water depth raised to 3–5 inches until 60 DAS, then to 6–8 inches for rest of season | 2800–3800 m2 (3) | + 24.1 (+ 16.7, + 32.0) |
| Hill and Cambournac (1941) | Portugal | Anopheles | 10 day wet, 7 day dry cycle* | 100 m2 (4) | − 35.1 (− 60.4, + 6.6) |
| Hill and Cambournac 1941 | Portugal | Anopheles | 10 day wet, 7 day dry cycle* | 2000 m2 (4) | + 4.6 (− 63.4, + 199.2) |
| Djegbe et al. (2020) | Benin | Anopheles | 7 day wet, 2 day dry cycle* | 16.5 m2 (3) | − 56.0 (− 82.5, + 10.9) |
| Mutero et al. (2000) | Kenya | An. arabiensis | Flooded before TP, drained during TP2, flooded after TP | 750 m2 (4) | + 6.3 (− 44.4, + 103.3) |
| Mutero et al. (2000) | Kenya | An. arabiensis | Flooded before TP, drained during TP, alternately flooded and drained after TP | 750 m2 (4) | + 455.6 (+ 21.2, + 2448.0) |
| Krishnasamy et al. (2003) | India | An. subpictus | 4d wet, 3d dry cycle* (rotational water supply) | Varying sizes (5) | + 59.6 (− 66.3, + 654.2) |
| Krishnasamy et al. (2003) | India | An. subpictus | Irrigation to 5 cm one day after disappearance of ponded water in fields | Varying sizes (5) | + 105.1 (− 61.7, + 997.4) |
| Rajendran et al. (1995) | India | An. subpictus | 2.5 cm depth maintained for the first 10–14 DAT3. Fields subsequently dried out and re-irrigated to 5 cm depth immediately after all standing water had disappeared (3-5d after irrigation stopped) | 16.2–22.3 ha (2) | − 26.9 (− 81.3, + 185.5) |
| Rao et al. (1995) | India | An. subpictus | Water allowed to stand 2.5–3.5 cm in the week following TP + from the second week, plots were dried for 2–3 days before re-irrigation | 400 m2 (3) | − 43.7 (− 90.7, + 240.7) |
| RE model for all studies | + 0.6 (− 27.3, + 39.4) | ||||
| Control of water depth | |||||
| Palchick and Washino (1986) | USA | An. freeborni | Medium: water level 3–5 inches during first 60d then raised to 6–8 inches vs shallow: water level 1–2 inches during first 60d then to 6–8 inches | 2800–3800 m2 (3) | + 89.7 (+ 77.7, + 102.4) |
| Palchick and Washino (1986) | USA | An. freeborni | Deep: 6–8 inches all season vs shallow: water level 1–2 inches during first 60d then to 6–8 inches | 2800–3800 m2 (3) | + 103.4 (+ 89.1, + 118.9) |
| + 96.0 (+ 83.0, + 110.0) | |||||
| Water management system | |||||
| Sogoba et al. (2007) | Mali | An. gambiae s.l | Hors-casier plot sector (no technical assistance in irrigation system and therefore lack efficient drainage systems) vs. casier plot sector (renovated irrigation systems) | 1000 m2 (4) | + 113.4 (− 50.9, + 827.1) |
| Rice variety | |||||
| Takagi et al. (1996) | Japan | An. sinensis | Tall rice (98.5 cm) vs short rice (45 cm) | 1500 m2 (2) | + 150.0 (− 66.1, + 1745.1) |
| Rice variety and plant spacing | |||||
| Victor and Reuben (2000) | India | An. subpictus & An. vagus | ADT36 (short duration variety of 110 days) at 60 hills/m2 (20 × 15 cm) vs. 80 hills/m2 (15 × 10 cm) | 40 m2 (4) | − 49.1 (− 94.8, + 396.5) |
| Victor and Reuben (2000) | India | An. subpictus & An. vagus | IR50 (short duration variety of 110 days) at 60 hills/m2 (20 × 15 cm) vs. 80 hills/m2 (15 × 10 cm) | 40 m2 (4) | − 77.9 (− 97.0, + 60.8) |
| Victor and Reuben (2000) | India | An. subpictus & An. vagus | IR20 (medium duration variety of 120 days) at 60 hills/m2 (20 × 15 cm) vs. 80 hills/m2 (15 × 10 cm) | 40 m2 (4) | − 62.0 (− 95.2, + 202.5) |
| RE model for all studies | − 66.3 (− 90.0, + 13.4) | ||||
| Weed control | |||||
| Palchick and Washino (1986) | USA | An. freeborni | Weed controlled by herbiciding vs. no weed control | 2800–3800 m2 (3) | + 77.4 (+ 65.7, + 89.9) |
| Agricultural insecticide | |||||
| Martono (1988) | Indonesia | An. aconitus | Organophosphorous compound (Basudin 60 EC) used to control paddy pests (such as Trvporvza spp., Leptocorsica acuta and Nilaparvata Lugens) at 960 ppm | 250 m2 (2) | − 76.4 (− 88.8, − 50.2) |
| Land preparation | |||||
| Djegbe et al. (2020) | Benin | Anopheles spp. | Minimal tillage (tillage depth < 15 cm) vs. deep tillage | 16.5 m2 (3) | − 64.7 (− 85.5, − 14.1) |
| Djegbe et al. (2020) | Benin | Anopheles spp. | Normal levelling vs. abnormal levelling | 16.5 m2 (3) | − 12.8 (− 65.2, + 118.5) |
Significant values are in bold.
*Water is applied to the field so that it is wet for X days and left for X days to dry before being irrigated again.
1DAS: Days after seeding.
2TP: Transplanting.
3DAT: Days after transplanting.
4EC: Emulsifiable concentrate.