Pests of the Season

Apr 1, 2024

As spring unfolds its vibrant tapestry, so too emerges an array of garden pests threatening to disrupt the harmony. From insidious weeds to pesky insects and lurking diseases, our green sanctuaries face a seasonal onslaught. Lets look at three of the challenges you might find in the garden this season. 

Aphids are small plant-sucking, soft-bodied true bugs. They come in many sizes, shapes and colors (green, black, yellow, brown, and red) and are a common insect in the garden. They attack many vegetable plants, fruit trees, and ornamental vegetation. They are commonly found on roses in the spring. You can usually determine whether aphids are infesting your plants by noting curled, distorted leaves with sticky honeydew on them. Aphids excrete copious amounts of honeydew, rich in sugars. Ants will also be noticeable because they feed on the sweet honeydew. Honeydew encourages growth of sooty mold fungus – a black film on leaf surfaces. Aside from the damage aphids can do to a plant's appearance, aphids can transmit viruses from infected plants to healthy plants. In fact, aphids are the most important vectors of plant viruses, which they carry on their stylets or accumulate in their guts and transmit via their piercing and sucking mouthparts when they feed on young leaves and stems. If the infestation of aphids is low to moderate, they can usually be tolerated. Control aphids by hosing them off with jets of water or use soap solution or oil sprays. Naturally occurring predators such as lady beetles (adults and larvae), soldier beetles, lacewing, and syrphid fly larvae and parasitic wasps, also serve to control aphids. However, the ability of predators and parasites to control them can be thwarted by ants protecting their food source. Therefore, ants need to be excluded from aphid colonies by applying sticky material such as Tanglefoot to the bases of infested plants. Click here to view aphid-eating insects in action. For additional information see: IPM Aphid Pest Note

Phytophthora fungi cause a number of diseases with different names depending on the part of the plant affected: Roots (root rot), trunk (crown rot, collar rot or foot rot), and fruit (brown rot of citrus.) Phytophthora rot in general, can attack all herbaceous and woody plants, including deciduous fruit and nut trees as well as most ornamental trees and shrubs. Root rot destroys feeder roots that are weakened by excess soil moisture. Crown rot presents as beads of sap oozing from lower trunk lesions; the bark will be dark and slimy or rose-colored. However, the bark discoloration does not extend into the wood. The leaves of a plant affected by Phytophthora rot appear drought stressed in that the tree or plant will often show signs of wilting. The leaves may turn a dull green, yellow, or purplish color and drop. The tree or plant may decline over a period of several years before eventually dying, or it may die within a year. To avoid Phytophthora root rot, purchase healthy trees with rootstocks tolerant to pests and diseases. Proper soil preparation and good drainage are essential. To avoid crown rot, keep mounded soil and water away from trunk. Avoid damaging bark with lawn mowers and weed whackers. If infection of the trunk occurs, scrape away all diseased bark and include a buffer strip of about one inch of healthy light brown to greenish bark around margins. To view a video in which Farm Advisor Chuck Ingels distinguishes the symptoms caused by Phytophthora root and crown rot from those caused by bacterial canker in stone fruit orchards, click here. Additional Information can be found here.

You bend down to pull a weed with your bare hand and feel a sharp pain – not in your back but on your hand! You've likely just encountered a stinging or burning nettle, a broadleaf member of the Nettle Family (Urticaceae) found in California landscapes and uncultivated areas. When direct skin contact is made with this plant's tiny hairs, a stinging or burning sensation is felt – sometimes for up to several hours. The leaves of both nettle species at maturity are oval with toothed edges, though the burning nettle's leaves are more rounded than those of the stinging nettle. Both plants have stinging hairs on their stems, leaf stalks and lower surface of their leaves. The burning nettle has a slender taproot along with numerous lateral roots. In contrast, the stinging nettle may, under favorable conditions, grow in large clumps from rhizomes. Mature stinging nettle plants typically reach up to 10 feet tall while the burning nettle plants are usually 5 to 24 inches tall. The burning nettle is a summer annual. Its seeds germinate in late fall to early spring and its small, greenish white flowers bloom from January through April. The stinging nettle is a perennial. Its seeds germinate in the spring and the flowers bloom from March to September. The stinging and burning nettle is best controlled using cultural methods (i.e. good soil management) and mechanical or physical methods (i.e. hoeing or hand pulling with gloves). In removing stinging nettle, care should be taken to remove the rhizomes as well as the surface plant or the weed may return. For additional information, click here.