Lady beetle: pray on both nymph and adult stages of aphids, also feed on mealy bugs, scale insect, spider, and mite. Dramatic example; control of cottony cushion scale insect of citrus plants in California in 1988 in two years.
Green lacewings: both adult and larva are voracious feeder ( as predator ) on aphids. Adult is 15 mm long , lay eggs on foliage.
Big- eyes bug : bug feed on eggs, first instar caterpillars, lygus nymphs and mites, and on aphids. Generation completed in 17 days in summer. Overwinter in eggs or adult stages in different species.
Blister beetles : larvae feed on grasshopper adult feed on foliage of potatoes, sugarbeet, cabbage, canola, fababeans, and turnip in Alberta.
Parasitic wasps : in USA Ichneumons ( size 4 to 38 mm, 3100 spp ), Braconids ( 1700 spp ) have parasitic larval stages and free living adults.
Parasitic flies : size 5-15 mm, larvae parasites of the larvae of butterflies, moths, beetles, and sawflies.
Insect pathogens : insects are infested by many diseases causing organisms ( pathogens ) including fungi, viruses, bacteria, and protozoa. Some pathogens are quite common and frequently cause widespread infection in insect population. Bacillus thuringiensis ( BT ) produced since 1958 provide control of butterflies, moths ; cabbage looper, cabag worm, alfalfa looper, and diamondback moth. Nuclear polyhedrosis virus ( NPV ) has also been effectively used against the larvae of butterflies and moths. Alfalfa looper is susceptible to virus infection and outbreak of this insect are brought under control. Fungus do not attack insect indiscriminately but are specific to a selective group of insects. Entomaphaga grylli attack certain grasshopper. Another Entomophaga spp attack pest aphids. Atrongwellsea castrans attack Canada root flies.
Protozoan ; Nosema locustae control grasshopper. Very large doses kill grasshoppers and lower
doses reduce the ability to reproduce and feed.
Beneficial Management Practices
I P M
Crop pests include : plants, insects, birds, mammals, and diseases that reduce yield and/ quality. IPM involves using a combination of control methods. It is overall management of a pest psecies.
Objective of IPM : is to prevent pest outbreak not to eradicate but to keep population below threshold level.
Advantage of IPM:
Fewer pesticide applications; save insecticide, time,labour,and time.
Less ill effects on soil, water, beneficial insects etc.
More stability in pest complex.
No loss of quality/ yield in the long term.
IPM steps:
Identify the pest and use appropriate pest control method.
Monitor pest and beneficial species population. Use Threshold to implement control.
Choose control options implement them when Threshold indicate control is needed.
Keep records of all pertinent date and result.
Economic threshold: damage equal to control cost.
Action threshold : time for treatment.
Pest Control Methods
Cultural Control
Crop vigorous.
Resistant varieties.
Rotation.
Planting dates.
Eliminate materials where pest live. a. Use clean treated seed. b. Clean tillage seeding, equipment. c. Contaminated crop residue. d. Remove alternate host.
Use trap strips.
Leave strip for forage.
Biological Control
Introduce biological agents.
Avoid pesticide use.
Biological control when pest established.
Mechanical Methods
Moving, telling, grazing, hand pulling weeds
Silage weed fields before seed formation.
Wheat midge Sitodiplosis mosellana
Wheat midge is found in most of the areas in the world. It is reported in Alberta, Saskatchewan, Manitoba, and British Columbia area.
Damage:
It reduces crop yield and lower the grade of grains. After egg hatching, the larvae feed on the developing wheat kernel, causing it to shrivel, crack and become deformed. Damage can only be detected by inspecting the developing seed within the glumes.
Adult:
Adult very small, 2-3mm long, fragile orange fly. Two black eyes cover much of its head. It has three pairs of legs that are long relatively to its body size. It’s wings are oval shaped transparent and fringed with fine hairs. Adult emerge from pupal stage in late June or early July. During the day, adult remain within the crop canopy where conditioned are humid. In the evening female becomes active at the top of the wheat canopy, laying eggs on the newly emerged wheat heads. Female lives for 5-7 days and lay about 80 eggs.
Eggs:
Egg laying take place generally after 8.30 PM when wind sped is less than 10 Km/ hour and air temperature greater than 15 C. Eggs are laid , either singly or in cluster of 3-4 eggs, on florets, on the external surface of glumes or in outer groves of florets. Eggs hatch 4-7 days depending on temperature.
Larvae:
Upon egg hatching, the small orange larvae move from the outer surface into the head to feed on the surface of developing kernels. Frequently 3-4 larvae per floret have been observed, but in severe infestation there may be 26 larvae feeding on a single kernel. Larvae feed and develop in 2-3 weeks, growing 2-3mm in length, then find their way to the ground and burry themselves in the soil. Under dry conditions larvae remain in the head stop developing and enclosed within a envelope ( last instar ). If moisture conditions improve larvae move into the soil. However, larvae may also remain in the wheat heads until trashed out during harvest . Most larvae remain within the top 5 cm of soil, but same way burrow 10 cm below the soil surface. The larvae spin round cocoon. Overwintering larvae may remain dormant until conditions are favourable for development whether that the fallowing spring several years later. Once the temperature and soil conditions end the overwintering period, the larvae became active and move to the soil surface to pupate. Depending on conditions the larvae will pupate with or without a cocoon. Temperature, soil moisture, and geographic location will effect the emergence of the adult flies, which begin in June or early July. Emergence can continue for up to 6 weeks.
Biological control:
Macroglenes penetrans ( Kirly ) 1-2 mm long parasitic wasp. Prairies.
Euxestonotus error ( Fitch ) South BC
A small wasp emerge from its pupa about the same time as its host and lay its eggs inside those of wheat midge. The wasp eggs and the midge eggs hatch about the same time, and the tiny wasp grows slowly inside the midge larva.
Barley Thrip Limothrips denticomis
Barley thrip 2 mm long. Female has feathery wings while male are wingless. They have two pupal stages. The prepupal stage last for few hours to one day. Pupal stage 2-6 days. It is present throughout Canada where barley is grown.
Host plant : Kentucky bluegrass and brome plants.
Overwintering : Female migrate from the crop into overwintering sites. Males and late maturing larvae remain on the crop and are killed by starvation and early frost. Only adult female overwinter in debris or under bark. Female mate in the fall but require 6 weeks in the spring for the eggs to mature.
Spring appearance : Thrips migrate from grass to crop with wind currents. Eggs are laid either scattered or in rows. Upon hatching larvae feed for 7 days, shedding their skin twice.
Feeding damage: Both immature and adult thrips feed by rasping or scraping away the leaf surface and suck out the cell contents.
Diseases of Crops Alberta
Club root of canola , Plasmodiophora brassicae
Clubroot of canola is a serious soil born disease of cruciferous crops ( cabbage, brocooli, cauliflower, canola, and mustard etc. ) It’s pathogens persist for many years in the soil.
Loss : 50 percent loss in case of 100 percent infestation.
Symptoms : Infected roots causing irregular club-like galls that restricted the flow of water and nutrients to stem and leaves. It cause wilting, stunted growth, yelling, premature ripening and shriveled seed. Plants look like heat or drought stressed.
Control:
Prevention is best management strategy.
A long rotation canola crop ( 1-4 years ) but disease may live for 17 years.
Use resistant canola hybrid.
Equipment senitation.
Avoid straw purchase from infested area.
Remove alternate hosts.
Minimize soil erosion.
Soil Ph 7 or higher reduce longevity of spores.
2. Fusarium wilt of canola, Fusarium oxysporum
It causes part or all of the plant to wilt, reduce yield up to 30 percent or more on badly sffected fields.
Control:
Rotation
Brassica weed control in cereal crops.
Control annual weeds in crops boarder to headlands.
Select resistant varieties.
3. Fusarium head blight, Fusarium graminearum
It causes significant losses in grain yield and grain quality, while also resulting in the production of mycotoxins that affect live stock feed, the baking and milling quality of wheat. It also reduce germination.
Host range : It has a wide host range that includes all small grain crops, corn and many wild and tame grass species.
Life cycle : It overwinter in crop and grass residues or in soil, as well as in seed. Seedling can infected at emergence, wind-born spores are formed in fruiting structure formed on the old infested crop residues and are then spread by wind to infect florets when the grain is at flowering stage. Warm, and moist weather worsens the infection.
Symptoms :
1. Premature bleaching or blighting of heads.
2. Florets may have a pinkish appearance.
3. Seeds appear shriveled and bleached.
Spread of disease : Short distance spread via dispersal of fungal spores by the wind. Long distance spread occurs through the transportation of infected seed or crop residue.
Control:
Rotation
Fungicide applications only provide disease suppression ie Caramba, Folicur, Proline, Prosaro.
4. Seedling blight, or damping off, Pythium spp ( prefer humid ) , Fusarium spp ( prefer dry ) Rhizoctonia spp.
Symptoms : Patches in the fields that fail to germinate. If the seedling do manage to germinate, they may not emerge, or they may emerge and then become brown, pinched, and die. Other symptoms include stunted and yellow growth, or reduced roots growth with brown parts on the roots and coleoptile. All crops can be affected.
Control:
Seed treatment
Plant shallow so that it germinate.
5. Late blight of potatoes tomatoes, Phytopthora infestans.
This disease results in significant yield and quality losses annually. In Alberta late blight occurs infrequently, but can have devastating impacts in the year when it reaches epidemic level.
History : Irish potato famine in the 1840s which resulted in the death and mass immigration of millions of people. Major outbreak in Alberta 1993 then 2010 there have been reports of late blight.
Alternate host : eggplant, pepper, petunias and solanaceous weeds. Some varieties are less susceptible, none is immune.
Causes of late blight : Phytopthora infestans also called Ooycetes which are water moulds . Pathogen is highly aggressive and can potentially infect all the plant parts, causing rapid die back and death. Late blight organism produces two main spore types.
Sporangia are formed on infected foliage and are dispersed by wind and water.
Zoospores can form within a single sporium and are able swim in film of water on the plant and in the soil to infect plant parts.
An overwintering, sexual spore type called an oospore can also be produce by pathogen are present in an area ; however, only one mating type presently occurs in western Canada. Therefore sexual apores are not known to be produced in Alberta and overwintering is only possible on living host tissues. There are different strains, some are more virulent on potato and some on tomato. In Alberta Phytopthora is more common.
Spread : In winter Canada late blight does not create the overwintering spore type and require living tissues to survive the following season.
Symptoms : Dark water- soaked lesions on leaves, after moving in from leaf tips/ margins toward centre.
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