Generally, insects are not considered much of a problem in field pea crops in Alberta. Pea leaf weevils, grasshoppers and pea aphids are the main insects that could potentially cause economic damage. Blister beetle can occasionally be found in pea crops, but have not caused economic damage.
- pea is not considered a preferred food of grasshopper, so they will normally attack other crops before moving into a pea field – with direct seeding of pea into a perennial forage stand, however, grasshopper can become a problem
- grasshopper can attack at any growth stage, but cause the most damage in the seedling stage – grasshopper nymphs will attack seedlings on the edge of a field as they emerge from ditches and fence rows in the spring
- economic threshold in pea is 10 grasshoppers per square metre
- early seeding can help pea plants outgrow the susceptible stage before grasshoppers emerge
- no insecticides are registered for the control of grasshopper in pea
- aphids overwinter as eggs in alfalfa and clovers, but more commonly blow in on warm southerly winds from the United States in June and early July
- aphids suck the sap from pea plants and weaken them and can also spread viruses from infected plants to healthy ones
- aphids reproduce more slowly under cooler conditions, where pea is generally grown in Alberta, so rarely cause problems
- economic threshold for spraying in pea is 10 aphids per plant in tenth node to early flowering stages
- there are products registered to control pea aphids (refer to The Blue Book for appropriate insecticide options)
- heavy winds and rain can minimize the damaging effects
Pea Leaf Weevil
Pea leaf weevil is a tiny insect that punches far above its weight in terms of potential impact on crop yield. The size of a grain of rice, this non-native invasive insect has emerged in recent years as a threat to Alberta’s most-planted pulse crop. Complicating growers’ pea leaf weevil defense is the fact that this insect appears intermittently. Some years it’s a significant problem, while in others it’s just a minor inconvenience. APG is funding several research projects related to preventing pea leaf weevil damage to crops.