Cultural Management Practices Can Help Reduce Pest and Disease Problems
Cultural management of California avocado groves can play an impactful role concerning disease management and pesticide use. As Dr. Ben Faber notes in a recent blog post, even the selection of rootstocks and scions is critical. In his blog, Dr. Faber notes irrigation, nutrient management timing, pruning, cover crops and harvest timing all play an important role in mitigating pests and disease. The California Avocado Commission has a library of cultural management articles dedicated to these topics and we have shared highlights from these articles, as well as links to them, below.
According to Dr. Faber, irrigation is “probably the most important cultural factor in managing tree disease” because the mismanagement of the amount of water applied and the timing of applications can often create the less-than-ideal conditions that lead to tree stress and susceptibility to diseases such as crown rot, black streak, stem blight, bacterial branch or trunk canker and root rot.
Irrigation plays an especially critical role in avocado tree root health. When irrigating, it’s important to divert excess water away from the base of trees, ensure you have proper soil drainage to avoid wet soil, and avoid over watering as well as wetting the trunks.
Nitrogen, potassium, boron and zinc are considered the most important minerals for avocado trees. But nitrogen management, in particular, can affect the number of insects on a tree as this nutrient plays an important role in canopy growth. As Dr. Faber points out, avocado thrips tend to build their populations in spring and then skip from leaf to fruit, which they then scar. By timing nitrogen fertilization to encourage leaf growth at flowering, insects are more likely to remain on the leaves and thus fruit scarring is reduced. Ultimately, leaf analysis remains a key means of assessing trees’ nutritional needs.
Pruning is beneficial for California avocado trees for many reasons — ranging from improving tree vigor and reducing fertilizer needs to improved profitability and fruit quality. It also plays a key role in pest control as pruning can modify humidity, light and canopy climate to make the canopy region less ideal for pests. The timing of pruning is critical, with the majority of it taking place during the winter months. However, periodic pruning during the season can be effectively used to promote shoot-flush during fruit set or to reduce the number of leaves available to hungry thrips populations.
Cover crops can play an important role in disease and pest management because they can improve soil drainage (which aids irrigation), improve soil health (which means less stress on trees) and can attract beneficial insects that may feast on pests. A new online Cover Crop Selection Tool is beneficial to growers considering this option.
Even when and how growers harvest their fruit can play a role in pest management. Greenhouse thrip populations can be reduced by picking the clusters of fruit available to them (which they tend to favor).