Whiteflies hitch a ride on transplants

Dear Helen: Now that the planting season has finally arrived, a major garden problem I had last summer is on my mind. Clouds of little white flies arose from many plants whenever they were disturbed, and on the leaf undersides were what looked like tiny white spots. Was this leaf miner?

A.S. Your issue was not leaf miner. Tiny grey leaf miner flies lay eggs on the undersides of leaves. The larvae that hatch burrow in between the tissue layers of the leaves and feed there, causing tan to brown blotches. Commonly infested plants are beets, spinach, and chard.

Light infestations can be controlled by picking off affected leaves and destroying them. Where infestations have been heavy in the past, create a barrier between pests and plants by securing a floating row cover over the plantings.

Leaf miner flies are rarely spotted. More noticeable are whiteflies — the pest you describe. The tiny, white, moth-like insects lay eggs on the undersides of leaves. The resulting larvae look like tiny pearl coloured scales. They suck sap from the leaves.

The whiteflies that are often seen on tomato, fuchsia, pepper and cucumber plants are not supposed to survive winters outdoors here. They are more commonly a pest of greenhouses; however, they are sometimes introduced into gardens via purchased transplants.

Last summer, my mail included several questions about these little white flies. Late in the summer, my seed-grown potted cherry tomatoes, for the first time, harboured whiteflies. I’m wondering whether the previous two mild winters allowed some of the flies to overwinter. It seems unlikely that there will be outdoor survivors this spring after such a long, cold winter.

I often hear from gardeners who spray for whitefly with insecticidal soap and report the flies return soon after. That’s because the spray does not affect all stages of the insect. To target newly hatched larvae, it’s best to spray every three days until the plants are free of the pest. Be sure to cover the leaf undersides.

Whiteflies outdoors rarely do significant damage to plants, but it’s wise to inspect transplants before purchase for signs of the insect. Adults flying away from disturbed plants can be sucked in by a hand-held vacuum — one with a gently action to avoid shredding the leaves.

Dear Helen: I was emptying some of last year’s pots recently and found a big, mushroom-like growth in one of them. It was 10 cm across, flattened and brown. What was it?

J.W.

Last year, a reader sent along a photo of a weird growth similar to yours. It is probably a slime mould, or slime fungus, a group of organisms that grow in very damp places. They usually appear on top of the soil, but they move about also in water. One of them is the organism that causes clubroot in cabbage family plants. Clubroot thrives in wet, acidic soils.

GARDEN EVENTS

Cactus and succulent sale. The Victoria Cactus and Succulent Society will host a plant sale on Friday and Saturday in the lower level of Tillicum Centre during mall hours. There will be a display of club members’ plants and sales of a wide variety of cacti and other succulents, including some hardy outdoor types. Potting soil suitable for these plants will be available. Members will be on hand to answer questions. Plant sales on Saturday: • Newcombe Singers fundraiser to support the choir, 8:30 a.m. to 2 p.m. at 1750 Hampshire Rd. in Oak Bay. Vegetables, herbs, perennials, shrubs and more. • Ladysmith Saltair Garden Club, 9 a.m. until sold out, in the Aggie Hall at Symonds and 1st Ave, at the roundabout in Ladysmith. Parking on 2nd Ave. Annuals, perennials, shrubs, herbs, vegetable transplants, house plants, floral baskets, used garden aids and books. • Nanaimo Horticultural Society, 10 a.m. to 2:30 p.m. in Nanaimo North Town Centre, 4750 Rutherford Rd. Large selection of herbs, vegetables, perennials, shrubs, tropicals. Master gardeners will answer questions. Proceeds support the society and a student bursary. • Morrell Nature Sanctuary, 8:30 a.m. to 1 p.m. at the sanctuary, 787 Nanaimo Lakes Rd. Rhododendron display. The Victoria Rhododendron Society will stage a display of flower trusses in Sidney’s Mary Winspear Centre on Friday, 4 p.m. to 9 p.m., Saturday, 10 a.m. to 9 p.m. and Sunday, 9 a.m. to 12 p.m. The display is an opportunity for the public to see the wide variety of rhododendrons grown by society members.

Whiteflies were seen to be more active than usual in gardens last summer. Tomatoes, including potted patio types, were common targets.

JONATHAN R. Weird looking, mushroom-like formations called slime moulds are sometimes seen in very wet places in gardens.