PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Delayed effects, Spread, Conditions favouring
DELAYED
EFFECTS
The number is infinite.
Symptoms of non-target drift from glyphosate applications to control weeds
in autumn around deciduous shrubs and climbers only become apparent when new
spring growth commences in spring.
Too many oil sprays may affect fruiting in citrus.
Alkalinity problems associated with certain improperly aged or composted
materials may only slowly become apparent over months or years. Mushroom
compost is usually alkaline.
Frost damage to early flowering fruit trees in colder areas may only be obvious
in spring when fewer fruit develop. In plums, flowers not totally killed by frost
develop russet patches as damaged areas enlarge.
Years of below average rainfall which deplete soil moisture cause a gradual
decline of established trees and shrubs over many years.
Lack of flowering in bulbs due to prolonged water stress, flowers laid
down the previous season.
Wind damage to young leaves and developing fruit becomes more obvious as
they grow in size.
Pollutants.
SPREAD Herbicides may leach through the soil or be washed over the surface of soil on
sloping areas, to sensitive sites.
Seed sources may not be reliable; varieties may not be suitable for the particular
season.
Soil deliveries which include mushroom compost, etc.
Soil deliveries which are hygroscopic.
CONDITIONS
FAVOURING
New varieties may not live up to their promise, eg may not grow so well under
certain conditions.
Planting the wrong variety for the district or season, planting too early or too late.
Rootstocks which are incompatible with scions, understand why rootstocks may
flourish at the expense of the scion.
Poor culture, eg incorrect pruning may lead to lack of flowers or fruit, excess
applications of phosphorus and nitrogen contribute to development of algal blooms.
Lack of appropriate environmental monitoring, eg the degree of frost injury may
depend on the suddenness in the drop in temperature rather than the absolute
temperature.
Applying certain pesticides when conditions favour pesticide injury to crops and
o
non-target plants, eg sulphur sprays at temperatures >30 C, excessive wind.
Application of pesticides in enclosed areas with poor ventilation and high humidity.
CROPS
PESTS
DISEASES
WEEDS
BENEFICIALS
NON-PARASITIC
Temperature, moisture
Climate change
Deficiencies, toxicities
Salinity, genetic, etc
Fig. 245. Non-parasitic disease triangle
398 Non-parasitic pests and diseases