Table 1. Local and landscape features of hypothesized to exert important influences on Andean potato weevil infestations (Premnotrypes spp.).
| Variable category | Variable description | Mean ± SD or mode |
| Chemical control | Carbofuran at planting (yes/no) | no = 106/138 |
| Insecticide treatments December | 0.51±0.61 | |
| Insecticide treatments January | 1.12±0.74 | |
| Insecticide treatments February | 0.34±0.52 | |
| Insecticide treatments March | 0.02±0.15 | |
| Cultural | Ash application at plantinga (yes/no) | no = 134/138 |
| Chemical fertilization at plantingb (g/plant) | 8.13±7.03 | |
| Day of first potato hillingc (days after Oct 1st) | 104.10±8.57 | |
| Harvest dayd (days after Oct 1st) | 201.34±9.50 | |
| Height of first potato hillingc (cm) | 18.30±3.79 | |
| Height of row at harvestc (cm) | 29.02±5.17 | |
| Manure fertilization at plantingb (g/plant) | 75.87±21.80 | |
| Number of hillingsc | 2 = 131/138 | |
| Perimeter/area ratioe (m−1) | 0.26±0.10 | |
| Planting dayf (days after Oct 1st) | 48.96±8.39 | |
| Plants/5 meters rowg | 14.81±1.74 | |
| Rotation 2006h (potato/other) | other = 114/138 | |
| Rotation 2007h (potato/other) | other = 136/138 | |
| Row distanceg (cm) | 95.35±11.72 | |
| Weed removali (yes/no) | yes = 75/138 | |
| Geographic | Elevationj (m) | 3747±148.40 |
| Field slopek (cm) | 23.04±10.79 | |
| Host related | Potato cultivarl (Yungay/Larga) | Yungay = 87/138 |
| Soil | Claym (%) | 21.08±5.71 |
| Loamm(%) | 34.01±8.01 | |
| Sandm (%) | 44.91±9.62 | |
| Km (ppm) | 331.58±201.75 | |
| Pm (ppm) | 28.22±21.94 | |
| Organic matterm(%) | 5.87±2.38 | |
| pHm | 4.97±0.98 | |
| Landscape | Neighboring current potato (%)n | 8.79±9.71 |
| Neighboring previous potato (%)o | 4.08±4.32 | |
| Neighboring storage unitsp | 1.01±1.01 |
Farmers apply a layer of ash directly below the potato seed at the time of planting; this practice is intended to kill potato weevils.
Fertilization can influence crop defenses against herbivores [17].
Many agronomists recommend hilling the plants (piling dirt up around the stem of the plant) higher to lengthen the distance weevil larvae must travel to find tubers.
Early harvest shortens the exposure of tubers to neonate larvae [18].
Larger fields have lower perimeter to area ratios and have been suggested to have lower infestations [19].
Early emerging plants may experience greater infestations [20].
Planting density may influence the abundance of many insect pests [21].
Planting potatoes following a potato planting should lead to very high infestations [19], but implementing a single host free period should eliminate this risk. Rotation 2007 indicates if potatoes were sown in the field the previous season while Rotation 2006 indicates if potatoes were sown there two seasons before the study.
The study hypothesized that weeds may serve as refuges for adult weevils before potato plants emerge.
Weevils are poorly adapted to elevations above 3,700 meters [18].
The study hypothesized that greater soil erosion in steeper slopes may increase tuber exposure to weevils.
Modern cultivars like Yungay may be more susceptible to insect pests [22].
The study was interested in exploring any soil influences on weevil infestations without any strong a priori expectations.
A measure of potato fields sown the within 100 m of the focal potato field; these current fields dilute the effect of immigrating weevils [15].